Peptide-Based Materials for Cartilage Tissue Regeneration.

PubMed

Hastar, Nurcan; Arslan, Elif; Guler, Mustafa O; Tekinay, Ayse B

2017-01-01

Cartilaginous tissue requires structural and metabolic support after traumatic or chronic injuries because of its limited capacity for regeneration. However, current techniques for cartilage regeneration are either invasive or ineffective for long-term repair. Developing alternative approaches to regenerate cartilage tissue is needed. Therefore, versatile scaffolds formed by biomaterials are promising tools for cartilage regeneration. Bioactive scaffolds further enhance the utility in a broad range of applications including the treatment of major cartilage defects. This chapter provides an overview of cartilage tissue, tissue defects, and the methods used for regeneration, with emphasis on peptide scaffold materials that can be used to supplement or replace current medical treatment options.

Lyophilized Silk Sponges: A Versatile Biomaterial Platform for Soft Tissue Engineering

PubMed Central

2015-01-01

We present a silk biomaterial platform with highly tunable mechanical and degradation properties for engineering and regeneration of soft tissues such as, skin, adipose, and neural tissue, with elasticity properties in the kilopascal range. Lyophilized silk sponges were prepared under different process conditions and the effect of silk molecular weight, concentration and crystallinity on 3D scaffold formation, structural integrity, morphology, mechanical and degradation properties, and cell interactions in vitro and in vivo were studied. Tuning the molecular weight distribution (via degumming time) of silk allowed the formation of stable, highly porous, 3D scaffolds that held form with silk concentrations as low as 0.5% wt/v. Mechanical properties were a function of silk concentration and scaffold degradation was driven by beta-sheet content. Lyophilized silk sponges supported the adhesion of mesenchymal stem cells throughout 3D scaffolds, cell proliferation in vitro, and cell infiltration and scaffold remodeling when implanted subcutaneously in vivo. PMID:25984573

Benzimidazoles: an ideal privileged drug scaffold for the design of multitargeted anti-inflammatory ligands.

PubMed

Kaur, Gaganpreet; Kaur, Maninder; Silakari, Om

2014-01-01

The recent research area endeavors to discover ultimate multi-target ligands, an increasingly feasible and attractive alternative to existing mono-targeted drugs for treatment of complex, multi-factorial inflammation process which underlays plethora of debilitated health conditions. In order to improvise this option, exploration of relevant chemical core scaffold will be an utmost need. Privileged benzimidazole scaffold being historically versatile structural motif could offer a viable starting point in the search for novel multi-target ligands against multi-factorial inflammation process since, when appropriately substituted, it can selectively modulate diverse receptors, pathways and enzymes associated with the pathogenesis of inflammation. Despite this remarkable capability, the multi-target capacity of the benzimidazole scaffold remains largely unexploited. With this in focus, the present review article attempts to provide synopsis of published research to exemplify the valuable use of benzimidazole nucleus and focus on their suitability as starting scaffold to develop multi-targeted anti-inflammatory ligands.

Multilayered Magnetic Gelatin Membrane Scaffolds

PubMed Central

Samal, Sangram K.; Goranov, Vitaly; Dash, Mamoni; Russo, Alessandro; Shelyakova, Tatiana; Graziosi, Patrizio; Lungaro, Lisa; Riminucci, Alberto; Uhlarz, Marc; Bañobre-López, Manuel; Rivas, Jose; Herrmannsdörfer, Thomas; Rajadas, Jayakumar; De Smedt, Stefaan; Braeckmans, Kevin; Kaplan, David L.; Dediu, V. Alek

2016-01-01

A versatile approach for the design and fabrication of multilayer magnetic scaffolds with tunable magnetic gradients is described. Multilayer magnetic gelatin membrane scaffolds with intrinsic magnetic gradients were designed to encapsulate magnetized bioagents under an externally applied magnetic field for use in magnetic-field-assisted tissue engineering. The temperature of the individual membranes increased up to 43.7 °C under an applied oscillating magnetic field for 70 s by magnetic hyperthermia, enabling the possibility of inducing a thermal gradient inside the final 3D multilayer magnetic scaffolds. On the basis of finite element method simulations, magnetic gelatin membranes with different concentrations of magnetic nanoparticles were assembled into 3D multilayered scaffolds. A magnetic-gradient-controlled distribution of magnetically labeled stem cells was demonstrated in vitro. This magnetic biomaterial–magnetic cell strategy can be expanded to a number of different magnetic biomaterials for various tissue engineering applications. PMID:26451743

Multilayered Magnetic Gelatin Membrane Scaffolds.

PubMed

Samal, Sangram K; Goranov, Vitaly; Dash, Mamoni; Russo, Alessandro; Shelyakova, Tatiana; Graziosi, Patrizio; Lungaro, Lisa; Riminucci, Alberto; Uhlarz, Marc; Bañobre-López, Manuel; Rivas, Jose; Herrmannsdörfer, Thomas; Rajadas, Jayakumar; De Smedt, Stefaan; Braeckmans, Kevin; Kaplan, David L; Dediu, V Alek

2015-10-21

A versatile approach for the design and fabrication of multilayer magnetic scaffolds with tunable magnetic gradients is described. Multilayer magnetic gelatin membrane scaffolds with intrinsic magnetic gradients were designed to encapsulate magnetized bioagents under an externally applied magnetic field for use in magnetic-field-assisted tissue engineering. The temperature of the individual membranes increased up to 43.7 °C under an applied oscillating magnetic field for 70 s by magnetic hyperthermia, enabling the possibility of inducing a thermal gradient inside the final 3D multilayer magnetic scaffolds. On the basis of finite element method simulations, magnetic gelatin membranes with different concentrations of magnetic nanoparticles were assembled into 3D multilayered scaffolds. A magnetic-gradient-controlled distribution of magnetically labeled stem cells was demonstrated in vitro. This magnetic biomaterial-magnetic cell strategy can be expanded to a number of different magnetic biomaterials for various tissue engineering applications.

Recent advancements in electrospinning design for tissue engineering applications: A review.

PubMed

Kishan, Alysha P; Cosgriff-Hernandez, Elizabeth M

2017-10-01

Electrospinning, a technique used to fabricate fibrous scaffolds, has gained popularity in recent years as a method to produce tissue engineered grafts with architectural similarities to the extracellular matrix. Beyond its versatility in material selection, electrospinning also provides many tools to tune the fiber morphology and scaffold geometry. Recent efforts have focused on extending the capabilities of electrospinning to produce scaffolds that better recapitulate tissue properties and enhance regeneration. This review highlights these advancements by providing an overview of the processing variables and setups used to modulate scaffold architecture, discussing strategies to improve cellular infiltration and guide cell behavior, and providing a summary of electrospinning applications in tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2892-2905, 2017. © 2017 Wiley Periodicals, Inc.

Optimization strategies for electrospun silk fibroin tissue engineering scaffolds

PubMed Central

Meinel, Anne J.; Kubow, Kristopher E.; Klotzsch, Enrico; Garcia-Fuentes, Marcos; Smith, Michael L.; Vogel, Viola; Merkle, Hans P.; Meinel, Lorenz

2013-01-01

As a contribution to the functionality of scaffolds in tissue engineering, here we report on advanced scaffold design through introduction and evaluation of topographical, mechanical and chemical cues. For scaffolding, we used silk fibroin (SF), a well established biomaterial. Biomimetic alignment of fibers was achieved as a function of the rotational speed of the cylindrical target during electrospinning of a SF solution blended with polyethylene oxide. Seeding fibrous SF scaffolds with human mesenchymal stem cells (hMSC) demonstrated that fiber alignment could guide hMSC morphology and orientation demonstrating the impact of scaffold topography on the engineering of oriented tissues. Beyond currently established methodologies to measure bulk properties, we assessed the mechanical properties of the fibers by conducting extension at breakage experiments on the level of single fibers. Chemical modification of the scaffolds was tested using donor/acceptor fluorophore labeled fibronectin. Fluorescence resonance energy transfer imaging allowed to assess the conformation of fibronectin when adsorbed on the SF scaffolds, and demonstrated an intermediate extension level of its subunits. Biological assays based on hMSC showed enhanced cellular adhesion and spreading as a result of fibronectin adsorbed on the scaffolds. Our studies demonstrate the versatility of SF as a biomaterial to engineer modified fibrous scaffolds and underscore the use of biofunctionally relevant analytical assays to optimize fibrous biomaterial scaffolds. PMID:19233463

Using Protein Dimers to Maximize the Protein Hybridization Efficiency with Multisite DNA Origami Scaffolds

PubMed Central

Verma, Vikash; Mallik, Leena; Hariadi, Rizal F.; Sivaramakrishnan, Sivaraj; Skiniotis, Georgios; Joglekar, Ajit P.

2015-01-01

DNA origami provides a versatile platform for conducting ‘architecture-function’ analysis to determine how the nanoscale organization of multiple copies of a protein component within a multi-protein machine affects its overall function. Such analysis requires that the copy number of protein molecules bound to the origami scaffold exactly matches the desired number, and that it is uniform over an entire scaffold population. This requirement is challenging to satisfy for origami scaffolds with many protein hybridization sites, because it requires the successful completion of multiple, independent hybridization reactions. Here, we show that a cleavable dimerization domain on the hybridizing protein can be used to multiplex hybridization reactions on an origami scaffold. This strategy yields nearly 100% hybridization efficiency on a 6-site scaffold even when using low protein concentration and short incubation time. It can also be developed further to enable reliable patterning of a large number of molecules on DNA origami for architecture-function analysis. PMID:26348722

Cascade rearrangement of furylcarbinols with hydroxylamines: practical access to densely functionalized cyclopentane derivatives.

PubMed

Veits, Gesine K; Wenz, Donald R; Palmer, Leoni I; St Amant, André H; Hein, Jason E; Read de Alaniz, Javier

2015-08-21

This article describes the aza-Piancatelli rearrangement with hydroxylamines to 4-aminocyclopentenones and subsequent transformations that highlight the versatility of the cyclopentene scaffold and the value of the hydroxylamine nucleophile in this transformation.

Peptide-directed self-assembly of functionalized polymeric nanoparticles. Part II: effects of nanoparticle composition on assembly behavior and multiple drug loading ability.

PubMed

Xiang, Xu; Ding, Xiaochu; Moser, Trevor; Gao, Qi; Shokuhfar, Tolou; Heiden, Patricia A

2015-04-01

Peptide-functionalized polymeric nanoparticles were designed and self-assembled into continuous nanoparticle fibers and three-dimensional scaffolds via ionic complementary peptide interaction. Different nanoparticle compositions can be designed to be appropriate for each desired drug, so that the release of each drug is individually controlled and the simultaneous sustainable release of multiple drugs is achieved in a single scaffold. A self-assembled scaffold membrane was incubated with NIH3T3 fibroblast cells in a culture dish that demonstrated non-toxicity and non-inhibition on cell proliferation. This type of nanoparticle scaffold combines the advantages of peptide self-assembly and the versatility of polymeric nanoparticle controlled release systems for tissue engineering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Parallel fabrication of macroporous scaffolds.

PubMed

Dobos, Andrew; Grandhi, Taraka Sai Pavan; Godeshala, Sudhakar; Meldrum, Deirdre R; Rege, Kaushal

2018-07-01

Scaffolds generated from naturally occurring and synthetic polymers have been investigated in several applications because of their biocompatibility and tunable chemo-mechanical properties. Existing methods for generation of 3D polymeric scaffolds typically cannot be parallelized, suffer from low throughputs, and do not allow for quick and easy removal of the fragile structures that are formed. Current molds used in hydrogel and scaffold fabrication using solvent casting and porogen leaching are often single-use and do not facilitate 3D scaffold formation in parallel. Here, we describe a simple device and related approaches for the parallel fabrication of macroporous scaffolds. This approach was employed for the generation of macroporous and non-macroporous materials in parallel, in higher throughput and allowed for easy retrieval of these 3D scaffolds once formed. In addition, macroporous scaffolds with interconnected as well as non-interconnected pores were generated, and the versatility of this approach was employed for the generation of 3D scaffolds from diverse materials including an aminoglycoside-derived cationic hydrogel ("Amikagel"), poly(lactic-co-glycolic acid) or PLGA, and collagen. Macroporous scaffolds generated using the device were investigated for plasmid DNA binding and cell loading, indicating the use of this approach for developing materials for different applications in biotechnology. Our results demonstrate that the device-based approach is a simple technology for generating scaffolds in parallel, which can enhance the toolbox of current fabrication techniques. © 2018 Wiley Periodicals, Inc.

3D Powder Printed Bioglass and β-Tricalcium Phosphate Bone Scaffolds.

PubMed

Seidenstuecker, Michael; Kerr, Laura; Bernstein, Anke; Mayr, Hermann O; Suedkamp, Norbert P; Gadow, Rainer; Krieg, Peter; Hernandez Latorre, Sergio; Thomann, Ralf; Syrowatka, Frank; Esslinger, Steffen

2017-12-22

The use of both bioglass (BG) and β tricalcium phosphate (β-TCP) for bone replacement applications has been studied extensively due to the materials' high biocompatibility and ability to resorb when implanted in the body. 3D printing has been explored as a fast and versatile technique for the fabrication of porous bone scaffolds. This project investigates the effects of using different combinations of a composite BG and β-TCP powder for 3D printing of porous bone scaffolds. Porous 3D powder printed bone scaffolds of BG, β-TCP, 50/50 BG/β-TCP and 70/30 BG/β-TCP compositions were subject to a variety of characterization and biocompatibility tests. The porosity characteristics, surface roughness, mechanical strength, viability for cell proliferation, material cytotoxicity and in vitro bioactivity were assessed. The results show that the scaffolds can support osteoblast-like MG-63 cells growth both on the surface of and within the scaffold material and do not show alarming cytotoxicity; the porosity and surface characteristics of the scaffolds are appropriate. Of the two tested composite materials, the 70/30 BG/β-TCP scaffold proved to be superior in terms of biocompatibility and mechanical strength. The mechanical strength of the scaffolds makes them unsuitable for load bearing applications. However, they can be useful for other applications such as bone fillers.

Directing self-assembly of gold nanoparticles in diblock copolymer scaffold

NASA Astrophysics Data System (ADS)

Li, Qifang; He, Jinbo; Glogowski, Elizabeth; Emrick, Todd; Russell, Thomas

2007-03-01

A versatile hierarchical approach for directing self -assembly of gold nanostructures with size 2-3nm in diblock copolymer scaffolds is found. Diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) is used to form a regular scaffold of highly anisotropic, stripe-like domains, and controlled differential wetting by dichloromethane and thermal annealing guides gold nanoparticles with half hydrophilic ligand to aggregate selectively along the scaffold, producing highly organized metal nanostructures. In as-cast block-copolymer and gold nanoparticles thin films, micelle structure and gold nanoparticles random distribution on scaffold are typically observed. However, samples annealed in dichloromethane exhibit well-defined short-range ordered nanostructure with gold nanoparticles located at the interface of PS and P2VP nanoscale domain. After annealing at 170 C, the gold nanoparticles at interface migrated into the middle of P2VP phase and exhibited long-range ordered hierarchical structures. Synergistic interactions between the gold nanoparticles and the PS-b-P2VP caused an orientation of the microdomains normal to the film surface.

New developments in 3D liquid crystal elastomers scaffolds for tissue engineering: from physical template to responsive substrate

NASA Astrophysics Data System (ADS)

Prévôt, Marianne E.; Bergquist, Leah E.; Sharma, Anshul; Mori, Taizo; Gao, Yungxiang; Bera, Tanmay; Zhu, Chenhui; Leslie, Michelle T.; Cukelj, Richard; Korley, LaShanda T. J.; Freeman, Ernest J.; McDonough, Jennifer A.; Clements, Robert J.; Hegmann, Elda

2017-08-01

We report here on cell growth and proliferation within a 3D architecture created using smectic liquid crystal elastomers (LCEs) leading to a responsive scaffold for tissue engineering. The investigated LCE scaffolds exhibit biocompatibility, controlled degradability, with mechanical properties and morphologies that can match development of the extracellular matrix. Moreover, the synthetic pathway and scaffold design offer a versatility of processing, allowing modifications of the surface such as adjusting the hydrophilic/hydrophobic balance and the mobility of the LC moieties to enhance the biomaterial performance. First, we succeeded in generating LCEs whose mechanical properties mimic muscle tissue. In films, our LCEs showed cell adhesion, proliferation, and alignment. We also achieved creating 3D LCE structures using either metallic template or microsphere scaffolds. Finally, we recorded a four times higher cell proliferation capability in comparison to conventional porous films and, most importantly, anisotropic cell growth that highlights the tremendous effect of liquid crystal moieties within LCEs on the cell environment.

Ketenimines Generated from Ynamides: Versatile Building Blocks for Nitrogen-Containing Scaffolds.

PubMed

Dodd, Robert H; Cariou, Kevin

2018-02-16

Using ynamides as readily available starting materials, a single step can generate highly reactive ketenimines, which can then undergo a variety of transformations. The choice of the method for generating the ketenimine dictates the outcome of the reaction that can, moreover, be precisely steered through minor variations of the starting material. This Concept gives an overview of the different existing methodologies for this objective, showcasing the diverse nitrogen-containing frameworks that can be obtained by this highly versatile strategy. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Natural polypeptide scaffolds: beta-sheets, beta-turns, and beta-hairpins.

PubMed

Rotondi, Kenneth S; Gierasch, Lila M

2006-01-01

This paper provides an introduction to fundamental conformational states of polypeptides in the beta-region of phi,psi space, in which the backbone is extended near to its maximal length, and to more complex architectures in which extended segments are linked by turns and loops. There are several variants on these conformations, and they comprise versatile scaffolds for presentation of side chains and backbone amides for molecular recognition and designed catalysts. In addition, the geometry of these fundamental folds can be readily mimicked in peptidomimetics. Copyright 2005 Wiley Periodicals, Inc.

Synthesis and 3D printing of biodegradable polyurethane elastomer by a water-based process for cartilage tissue engineering applications.

PubMed

Hung, Kun-Che; Tseng, Ching-Shiow; Hsu, Shan-Hui

2014-10-01

Biodegradable materials that can undergo degradation in vivo are commonly employed to manufacture tissue engineering scaffolds, by techniques including the customized 3D printing. Traditional 3D printing methods involve the use of heat, toxic organic solvents, or toxic photoinitiators for fabrication of synthetic scaffolds. So far, there is no investigation on water-based 3D printing for synthetic materials. In this study, the water dispersion of elastic and biodegradable polyurethane (PU) nanoparticles is synthesized, which is further employed to fabricate scaffolds by 3D printing using polyethylene oxide (PEO) as a viscosity enhancer. The surface morphology, degradation rate, and mechanical properties of the water-based 3D-printed PU scaffolds are evaluated and compared with those of polylactic-co-glycolic acid (PLGA) scaffolds made from the solution in organic solvent. These scaffolds are seeded with chondrocytes for evaluation of their potential as cartilage scaffolds. Chondrocytes in 3D-printed PU scaffolds have excellent seeding efficiency, proliferation, and matrix production. Since PU is a category of versatile materials, the aqueous 3D printing process developed in this study is a platform technology that can be used to fabricate devices for biomedical applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and characterization of toughness-enhanced scaffolds comprising β-TCP/POC using the freeform fabrication system with micro-droplet jetting.

PubMed

Gao, Li; Li, Cuidi; Chen, Fangping; Liu, Changsheng

2015-06-24

A novel elastomeric material, poly(1,8-octanediol-co-citrate) (POC), has demonstrated tremendous versatility because of its advantageous toughness, tunable degradation properties, and efficient drug release capability. In this study, POC was used to improve the mechanical performance of β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP). (3D) β-TCP/POC composite scaffolds were fabricated by a 3D printing technique based on the freeform fabrication system with micro-droplet jetting (FFS-MDJ). The physiochemical properties, compressive modulus, drug release behavior, and cell response of β-TCP/POC composite scaffolds were systematically investigated. The results showed that β-TCP/POC scaffolds had uniform macropores of 300-400 μm, porosity of approximately 45%, biodegradability in phosphate-buffered saline, and high compressive modulus of 50-75 MPa. With the incorporation of POC into β-TCP, the toughness of the composite scaffolds was improved significantly. Moreover, β-TCP/POC scaffolds exhibited sustained drug (ibuprofen (IBU)) release capability. Additionally, β-TCP/POC scaffolds facilitated C2C12 cell attachment and proliferation. It was indicated that the 3D-printed porous β-TCP/POC scaffolds with high compressive modulus and good drug delivery performance might be a promising candidate for bone defect repair.

Cyclodextrins as versatile building blocks for regenerative medicine.

PubMed

Alvarez-Lorenzo, Carmen; García-González, Carlos A; Concheiro, Angel

2017-12-28

Cyclodextrins (CDs) are one of the most versatile substances produced by nature, and it is in the aqueous biological environment where the multifaceted potential of CDs can be completely unveiled. CDs form inclusion complexes with a variety of guest molecules, including polymers, producing very diverse biocompatible supramolecular structures. Additionally, CDs themselves can trigger cell differentiation to distinct lineages depending on the substituent groups and also promote salt nucleation. These features together with the affinity-driven regulated release of therapeutic molecules, growth factors and gene vectors explain the rising interest for CDs as building blocks in regenerative medicine. Supramolecular poly(pseudo)rotaxane structures and zipper-like assemblies exhibit outstanding viscoelastic properties, performing as syringeable implants. The sharp shear-responsiveness of the supramolecular assemblies is opening new avenues for the design of bioinks for 3D printing and also of electrospun fibers. CDs can also be transformed into polymerizable monomers to prepare alternative nanostructured materials. The aim of this review is to analyze the role that CDs may play in regenerative medicine through the analysis of the last decade research. Most applications of CD-based scaffolds are focussed on non-healing bone fractures, cartilage reparation and skin recovery, but also on even more challenging demands such as neural grafts. For the sake of clarity, main sections of this review are organized according to the architecture of the CD-based scaffolds, mainly syringeable supramolecular hydrogels, 3D printed scaffolds, electrospun fibers, and composites, since the same scaffold type may find application in different tissues. Copyright © 2017 Elsevier B.V. All rights reserved.

Protected Amine Labels: A Versatile Molecular Scaffold for Multiplexed Nominal Mass and Sub-Da Isotopologue Quantitative Proteomic Reagents

PubMed Central

Ficarro, Scott B.; Biagi, Jessica M.; Wang, Jinhua; Scotcher, Jenna; Koleva, Rositsa I.; Card, Joseph D.; Adelmant, Guillaume; He, Huan; Askenazi, Manor; Marshall, Alan G.; Young, Nicolas L.; Gray, Nathanael S.; Marto, Jarrod A.

2014-01-01

We assemble a versatile molecular scaffold from simple building blocks to create binary and multiplexed stable isotope reagents for quantitative mass spectrometry. Termed Protected Amine Labels (PAL), these reagents offer multiple analytical figures of merit including, (i) robust targeting of peptide N-termini and lysyl side chains, (ii) optimal mass spectrometry ionization efficiency through regeneration of primary amines on labeled peptides, (iii) an amino acid-based mass tag that incorporates heavy isotopes of carbon, nitrogen, and oxygen to ensure matched physicochemical and MS/MS fragmentation behavior among labeled peptides, and (iv) a molecularly efficient architecture, in which the majority of hetero-atom centers can be used to synthesize a variety of nominal mass and sub-Da isotopologue stable isotope reagents. We demonstrate the performance of these reagents in well-established strategies whereby up to four channels of peptide isotopomers, each separated by 4 Da are quantified in MS-level scans with accuracies comparable to current commercial reagents. In addition we utilize the PAL scaffold to create isotopologue reagents in which labeled peptide analogs differ in mass based on the binding energy in carbon and nitrogen nuclei, thereby allowing quantification based on MS or MS/MS spectra. We demonstrate accurate quantification for reagents that support 6-plex labeling and propose extension of this scheme to 9-channels based on a similar PAL scaffold. Finally we provide exemplar data that extends the application of isotopologe-based quantification reagents to medium resolution, quadrupole time-of-flight mass spectrometers. PMID:24496597

Hierarchical bioceramic scaffolds with 3D-plotted macropores and mussel-inspired surface nanolayers for stimulating osteogenesis

NASA Astrophysics Data System (ADS)

Xu, Mengchi; Zhai, Dong; Xia, Lunguo; Li, Hong; Chen, Shiyi; Fang, Bing; Chang, Jiang; Wu, Chengtie

2016-07-01

The hierarchical structure of biomaterials plays an important role in the process of tissue reconstruction and regeneration. 3D-plotted scaffolds have been widely used for bone tissue engineering due to their controlled macropore structure and mechanical properties. However, the lack of micro- or nano-structures on the strut surface of 3D-plotted scaffolds, especially for bioceramic scaffolds, limits their biological activity. Inspired by the adhesive versatility of mussels and the active ion-chelating capacity of polydopamine, we set out to prepare a hierarchical bioceramic scaffold with controlled macropores and mussel-inspired surface nanolayers by combining the 3D-plotting technique with the polydopamine/apatite hybrid strategy in order to synergistically accelerate the osteogenesis and angiogenesis. β-Tricalcium phosphate (TCP) scaffolds were firstly 3D-plotted and then treated in dopamine-Tris/HCl and dopamine-SBF solutions to obtain TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds, respectively. It was found that polydopamine/apatite hybrid nanolayers were formed on the surface of both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds and TCP-DOPA-SBF scaffolds induced apatite mineralization for the second time during the cell culture. As compared to TCP scaffolds, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly promoted the osteogenesis of bone marrow stromal cells (BMSCs) as well as the angiogenesis of human umbilical vein endothelial cells (HUVECs), and the TCP-DOPA-SBF group presented the highest in vitro osteogenic/angiogenic activity among the three groups. Furthermore, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly improved the formation of new bone in vivo as compared to TCP scaffolds without a nanostructured surface. Our results suggest that the utilization of a mussel-inspired Ca, P-chelated polydopamine nanolayer on 3D-plotted bioceramic scaffolds is a viable and effective strategy to construct a hierarchical structure for synergistically accelerating osteogenesis.The hierarchical structure of biomaterials plays an important role in the process of tissue reconstruction and regeneration. 3D-plotted scaffolds have been widely used for bone tissue engineering due to their controlled macropore structure and mechanical properties. However, the lack of micro- or nano-structures on the strut surface of 3D-plotted scaffolds, especially for bioceramic scaffolds, limits their biological activity. Inspired by the adhesive versatility of mussels and the active ion-chelating capacity of polydopamine, we set out to prepare a hierarchical bioceramic scaffold with controlled macropores and mussel-inspired surface nanolayers by combining the 3D-plotting technique with the polydopamine/apatite hybrid strategy in order to synergistically accelerate the osteogenesis and angiogenesis. β-Tricalcium phosphate (TCP) scaffolds were firstly 3D-plotted and then treated in dopamine-Tris/HCl and dopamine-SBF solutions to obtain TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds, respectively. It was found that polydopamine/apatite hybrid nanolayers were formed on the surface of both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds and TCP-DOPA-SBF scaffolds induced apatite mineralization for the second time during the cell culture. As compared to TCP scaffolds, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly promoted the osteogenesis of bone marrow stromal cells (BMSCs) as well as the angiogenesis of human umbilical vein endothelial cells (HUVECs), and the TCP-DOPA-SBF group presented the highest in vitro osteogenic/angiogenic activity among the three groups. Furthermore, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly improved the formation of new bone in vivo as compared to TCP scaffolds without a nanostructured surface. Our results suggest that the utilization of a mussel-inspired Ca, P-chelated polydopamine nanolayer on 3D-plotted bioceramic scaffolds is a viable and effective strategy to construct a hierarchical structure for synergistically accelerating osteogenesis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01952h

In vitro characterization of a collagen scaffold enzymatically cross-linked with a tailored elastin-like polymer.

PubMed

Garcia, Yolanda; Hemantkumar, Naik; Collighan, Russell; Griffin, Martin; Rodriguez-Cabello, Jose Carlos; Pandit, Abhay

2009-04-01

Collagen, the main structural component of the extracellular matrix (ECM), provides tensile stiffness to different structures and organs against rupture. However, collagen tissue-engineered implants are hereto still lacking in mechanical strength. Attempts to create stiffer scaffolds have resulted in increased brittleness of the material, reducing the versatility of the original component. The hypothesis behind this research is that the introduction of an elastic element in the scaffold will enhance the mechanical properties of the collagen-based scaffolds, as elastin does in the ECM to prevent irreversible deformation. In this study, an elastin-like polymer (ELP) designed and synthesized using recombinant DNA methodology is used with the view to providing increased proteolytic resistance and increased functionality to the scaffolds by carrying specific sequences for microbial transglutaminase cross-linking, endothelial cell adhesion, and drug delivery. Evaluation of the effects that cross-linking ELP-collagen has on the physicochemical properties of the scaffold such as porosity, presence of cross-linking, thermal behavior, and mechanical strength demonstrated that the introduction of enzymatically resistant covalent bonds between collagen and ELP increases the mechanical strength of the scaffolds in a dose-dependent manner without significantly affecting the porosity or thermal properties of the original scaffold. Importantly, the scaffolds also showed selective behavior, in a dose (ELP)-dependent manner toward human umbilical vein endothelial cells and smooth muscle cells when compared to fibroblasts.

Tailoring of processing parameters for sintering microsphere-based scaffolds with dense-phase carbon dioxide

PubMed Central

Jeon, Ju Hyeong; Bhamidipati, Manjari; Sridharan, BanuPriya; Scurto, Aaron M.; Berkland, Cory J.; Detamore, Michael S.

2015-01-01

Microsphere-based polymeric tissue-engineered scaffolds offer the advantage of shape-specific constructs with excellent spatiotemporal control and interconnected porous structures. The use of these highly versatile scaffolds requires a method to sinter the discrete microspheres together into a cohesive network, typically with the use of heat or organic solvents. We previously introduced subcritical CO2 as a sintering method for microsphere-based scaffolds; here we further explored the effect of processing parameters. Gaseous or subcritical CO2 was used for making the scaffolds, and various pressures, ratios of lactic acid to glycolic acid in poly(lactic acid-co-glycolic acid), and amounts of NaCl particles were explored. By changing these parameters, scaffolds with different mechanical properties and morphologies were prepared. The preferred range of applied subcritical CO2 was 15–25 bar. Scaffolds prepared at 25 bar with lower lactic acid ratios and without NaCl particles had a higher stiffness, while the constructs made at 15 bar, lower glycolic acid content, and with salt granules had lower elastic moduli. Human umbilical cord mesenchymal stromal cells (hUCMSCs) seeded on the scaffolds demonstrated that cells penetrate the scaffolds and remain viable. Overall, the study demonstrated the dependence of the optimal CO2 sintering parameters on the polymer and conditions, and identified desirable CO2 processing parameters to employ in the sintering of microsphere-based scaffolds as a more benign alternative to heat-sintering or solvent-based sintering methods. PMID:23115065

Solvent/non-solvent sintering: a novel route to create porous microsphere scaffolds for tissue regeneration.

PubMed

Brown, Justin L; Nair, Lakshmi S; Laurencin, Cato T

2008-08-01

Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from -8 to 41 degrees C and poly (lactide-co-glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 mum, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. (c) 2007 Wiley Periodicals, Inc.

Solvent/Non-Solvent Sintering: A Novel Route to Create Porous Microsphere Scaffolds For Tissue Regeneration

PubMed Central

Brown, Justin L.; Nair, Lakshmi S.; Laurencin, Cato T.

2009-01-01

Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from −8°C to 41oC and poly(lactide-co-glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1µm respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. PMID:18161819

Development of a multipurpose scaffold for the display of peptide loops

PubMed Central

Rossmann, Maxim; J. Greive, Sandra; Moschetti, Tommaso; Dinan, Michael

2017-01-01

Abstract Protein–protein interactions (PPIs) determine a wide range of biological processes and analysis of these dynamic networks is increasingly becoming a mandatory tool for studying protein function. Using the globular ATPase domain of recombinase RadA as a scaffold, we have developed a peptide display system (RAD display), which allows for the presentation of target peptides, protein domains or full-length proteins and their rapid recombinant production in bacteria. The design of the RAD display system includes differently tagged versions of the scaffold, which allows for flexibility in the protein purification method, and chemical coupling for small molecule labeling or surface immobilization. When combined with the significant thermal stability of the RadA protein, these features create a versatile multipurpose scaffold system. Using various orthogonal biophysical techniques, we show that peptides displayed on the scaffold bind to their natural targets in a fashion similar to linear parent peptides. We use the examples of CK2β/CK2α kinase and TPX2/Aurora A kinase protein complexes to demonstrate that the peptide displayed by the RAD scaffold can be used in PPI studies with the same binding efficacy but at lower costs compared with their linear synthetic counterparts. PMID:28444399

Characterization of Electrospun Nanofibrous Scaffolds for Nanobiomedical Applications

NASA Astrophysics Data System (ADS)

Emul, E.; Saglam, S.; Ates, H.; Korkusuz, F.; Saglam, N.

2016-08-01

The electrospinning method is employed in the production of porous fiber scaffolds, and the usage of electrospun scaffolds especially as drug carrier and bone reconstructive material such as implants is promising for future applications in tissue engineering. The number of publications has grown very rapidly in this field through the fabrication of complex scaffolds, novel approaches in nanotechnology, and improvements of imaging methods. Hence, characterization of these materials has also grown significantly important for getting satisfied and accurate results. This advantageous and versatile method is ideal for mimicking bone extracellular matrix, and many biodegradable and biocompatible polymers are preferred in the field of bone reconstruction. In this study, gelatin, gelatin/nanohydroxyapatite (nHAp) and gelatin/PLLA/nHAp scaffolds were fabricated by the electrospinning process. These composite fibers showed clear and continuous morphology according to observation through a scanning electron microscope and their component analyses were also determined by Fourier transform infrared spectrometer analyses. These characterization experiments revealed the great effects of the electrospinning method for biomedical applications and have an especially important role in bone reconstruction and production of implant coating material.

3D-printed PCL scaffolds for the cultivation of mesenchymal stem cells.

PubMed

Steffens, Daniela; Rezende, Rodrigo Alvarenga; Santi, Bruna; Pereira, Frederico David Alencar de Sena; Inforçatti Neto, Paulo; da Silva, Jorge Vicente Lopes; Pranke, Patricia

2016-04-06

Tissue engineering is a field which is currently under a great deal of investigation for the development and/or restoration of tissue and organs, through the combination of cell therapy with biomaterials. Rapid prototyping or additive manufacturing is a versatile technology which makes possible the fabrication of three dimensional (3D) structures from a wide range of materials with complex geometry and accuracy, such as scaffolds. The aim of this study has been to investigate the interaction between mesenchymal stem cells with poly (ε-caprolactone) (PCL) biomaterials used for obtaining scaffolds through additive manufacturing. Scanning electron microscopy, confocal microscopy and biological assays were performed to analyse the successful interaction between the cells and the biomaterials. As a result, the number of viable cells attached to the scaffolds was lower when compared to the control group; however, it was possible to observe cells in the scaffolds since day 1 of analysis, with regions of confluence after 21 days of seeding. To conclude, these biomaterials are interesting if used as medical artifacts, principally in tissue with prolonged regeneration time and which requires 3D supports with good mechanical properties.

Biomineralized poly (l-lactic-co-glycolic acid)-tussah silk fibroin nanofiber fabric with hierarchical architecture as a scaffold for bone tissue engineering.

PubMed

Gao, Yanfei; Shao, Weili; Qian, Wang; He, Jianxin; Zhou, Yuman; Qi, Kun; Wang, Lidan; Cui, Shizhong; Wang, Rui

2018-03-01

In bone tissue engineering, the fabrication of a scaffold with a hierarchical architecture, excellent mechanical properties, and good biocompatibility remains a challenge. Here, a solution of polylactic acid (PLA) and Tussah silk fibroin (TSF) was electrospun into nanofiber yarns and woven into multilayer fabrics. Then, composite scaffolds were obtained by mineralization in simulated body fluid (SBF) using the multilayer fabrics as a template. The structure and related properties of the composite scaffolds were characterized using different techniques. PLA/TSF (mass ratio, 9:1) nanofiber yarns with uniform diameters of 72±9μm were obtained by conjugated electrospinning; the presence of 10wt% TSF accelerated the nucleation and growth of hydroxyapatite on the surface of the composite scaffolds in SBF. Furthermore, the compressive mechanical properties of the PLA/TSF multilayer nanofiber fabrics were improved after mineralization; the compressive modulus and stress of the mineralized composite scaffolds were 32.8 and 3.0 times higher than that of the composite scaffolds without mineralization, respectively. Interestingly, these values were higher than those of scaffolds containing random nanofibers. Biological assay results showed that the mineralization and multilayer fabric structure of the composite nanofiber scaffolds significantly increased cell adhesion and proliferation and enhanced the mesenchymal stem cell differentiation toward osteoblasts. Our results indicated that the mineralized nanofiber scaffolds with multilayer fabrics possessed excellent cytocompatibility and good osteogenic activity, making them versatile biocompatible scaffolds for bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Fibrous scaffolds fabricated by emulsion electrospinning: from hosting capacity to in vivo biocompatibility

NASA Astrophysics Data System (ADS)

Spano, F.; Quarta, A.; Martelli, C.; Ottobrini, L.; Rossi, R. M.; Gigli, G.; Blasi, L.

2016-04-01

Electrospinning is a versatile method for preparing functional three-dimensional scaffolds. Synthetic and natural polymers have been used to produce micro- and nanofibers that mimic extracellular matrices. Here, we describe the use of emulsion electrospinning to prepare blended fibers capable of hosting aqueous species and releasing them in solution. The existence of an aqueous and a non-aqueous phase allows water-soluble molecules to be introduced without altering the structure and the degradation of the fibers, and means that their release properties under physiological conditions can be controlled. To demonstrate the loading capability and flexibility of the blend, various species were introduced, from magnetic nanoparticles and quantum rods to biological molecules. Cellular studies showed the spontaneous adhesion and alignment of cells along the fibers. Finally, in vivo experiments demonstrated the high biocompatibility and safety of the scaffolds up to 21 days post-implantation.Electrospinning is a versatile method for preparing functional three-dimensional scaffolds. Synthetic and natural polymers have been used to produce micro- and nanofibers that mimic extracellular matrices. Here, we describe the use of emulsion electrospinning to prepare blended fibers capable of hosting aqueous species and releasing them in solution. The existence of an aqueous and a non-aqueous phase allows water-soluble molecules to be introduced without altering the structure and the degradation of the fibers, and means that their release properties under physiological conditions can be controlled. To demonstrate the loading capability and flexibility of the blend, various species were introduced, from magnetic nanoparticles and quantum rods to biological molecules. Cellular studies showed the spontaneous adhesion and alignment of cells along the fibers. Finally, in vivo experiments demonstrated the high biocompatibility and safety of the scaffolds up to 21 days post-implantation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00782a

Genomic analysis reveals versatile heterotrophic capacity of a potentially symbiotic sulfur-oxidizing bacterium in sponge.

PubMed

Tian, Ren-Mao; Wang, Yong; Bougouffa, Salim; Gao, Zhao-Ming; Cai, Lin; Bajic, Vladimir; Qian, Pei-Yuan

2014-11-01

Sulfur-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) play essential roles in marine sponges. However, the detailed characteristics and physiology of the bacteria are largely unknown. Here, we present and analyse the first genome of sponge-associated SOB using a recently developed metagenomic binning strategy. The loss of transposase and virulence-associated genes and the maintenance of the ancient polyphosphate glucokinase gene suggested a stabilized SOB genome that might have coevolved with the ancient host during establishment of their association. Exclusive distribution in sponge, bacterial detoxification for the host (sulfide oxidation) and the enrichment for symbiotic characteristics (genes-encoding ankyrin) in the SOB genome supported the bacterial role as an intercellular symbiont. Despite possessing complete autotrophic sulfur oxidation pathways, the bacterium developed a much more versatile capacity for carbohydrate uptake and metabolism, in comparison with its closest relatives (Thioalkalivibrio) and to other representative autotrophs from the same order (Chromatiales). The ability to perform both autotrophic and heterotrophic metabolism likely results from the unstable supply of reduced sulfur in the sponge and is considered critical for the sponge-SOB consortium. Our study provides insights into SOB of sponge-specific clade with thioautotrophic and versatile heterotrophic metabolism relevant to its roles in the micro-environment of the sponge body. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Direct amination of γ-halo-β-ketoesters with anilines

PubMed Central

Zhang, Yinan; Silverman, Richard B.

2012-01-01

The direct amination of α-haloacetoacetates with anilines is described. Compared to existing methods, this simple protocol provides an attractive strategy to prepare diverse γ-anilino-β-ketoesters in one step. Good to excellent yields of the amination products were obtained under robust conditions, providing versatile and useful scaffolds. PMID:22390154

Enhanced bone formation in electrospun poly(L-lactic-co-glycolic acid)-tussah silk fibroin ultrafine nanofiber scaffolds incorporated with graphene oxide.

PubMed

Shao, Weili; He, Jianxin; Sang, Feng; Wang, Qian; Chen, Li; Cui, Shizhong; Ding, Bin

2016-05-01

To engineer bone tissue, it is necessary to provide a biocompatible, mechanically robust scaffold. In this study, we fabricated an ultrafine nanofiber scaffold by electrospinning a blend of poly(L-lactic-co-glycolic acid), tussah silk fibroin, and graphene oxide (GO) and characterized its morphology, biocompatibility, mechanical properties, and biological activity. The data indicate that incorporation of 10 wt.% tussah silk and 1 wt.% graphene oxide into poly(L-lactic-co-glycolic acid) nanofibers significantly decreased the fiber diameter from 280 to 130 nm. Furthermore, tussah silk and graphene oxide boosted the Young's modulus and tensile strength by nearly 4-fold and 3-fold, respectively, and significantly enhanced adhesion, proliferation in mouse mesenchymal stem cells and functionally promoted biomineralization-relevant alkaline phosphatase (ALP) and mineral deposition. The results indicate that composite nanofibers could be excellent and versatile scaffolds for bone tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

Branched poly(ethyleneimine): a versatile scaffold for patterning polymer brushes by means of remote photocatalytic lithography

NASA Astrophysics Data System (ADS)

Panzarasa, Guido; Dübner, Matthias; Soliveri, Guido; Edler, Matthias; Griesser, Thomas

2017-09-01

Patterning of functional surfaces is one of the cornerstones of nanotechnology as it allows the fabrication of sensors and lab-on-a-chip devices. Here, the patterning of self-assembled monolayers of branched poly(ethyleneimine) (bPEI) on silica was achieved by means of remote photocatalytic lithography. Moreover, when 2-bromoisobutyryl-modified bPEI was used, the resulting pattern could be amplified by grafting polymer brushes by means of surface-initiated atom transfer radical polymerization. In contrast to previous reports for the patterning of bPEI, the present approach can be conducted in minutes instead of hours, reducing the exposure time to UV radiation and enhancing the overall efficiency. Furthermore, our approach is much more user-friendly, allowing a facile fabrication of patterned initiator-modified surfaces and the use of inexpensive instrumentation such as a low-power UV source and a simple photomask. Considering the versatility of bPEI as a scaffold for the development of biosensors, patterning by means of remote photocatalytic lithography will open new opportunities in a broad field of applications.

Design and Fabrication of Complex Scaffolds for Bone Defect Healing: Combined 3D Plotting of a Calcium Phosphate Cement and a Growth Factor-Loaded Hydrogel.

PubMed

Ahlfeld, Tilman; Akkineni, Ashwini Rahul; Förster, Yvonne; Köhler, Tino; Knaack, Sven; Gelinsky, Michael; Lode, Anja

2017-01-01

Additive manufacturing enables the fabrication of scaffolds with defined architecture. Versatile printing technologies such as extrusion-based 3D plotting allow in addition the incorporation of biological components increasing the capability to restore functional tissues. We have recently described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of an oil-based CPC paste under mild conditions. In the present study, we have developed a strategy for growth factor loading based on multichannel plotting: a biphasic scaffold design was realised combining CPC with VEGF-laden, highly concentrated hydrogel strands. As hydrogel component, alginate and an alginate-gellan gum blend were evaluated; the blend exhibited a more favourable VEGF release profile and was chosen for biphasic scaffold fabrication. After plotting, two-step post-processing was performed for both, hydrogel crosslinking and CPC setting, which was shown to be compatible with both materials. Finally, a scaffold was designed and fabricated which can be applied for testing in a rat critical size femur defect. Optimization of CPC plotting enabled the fabrication of highly resolved structures with strand diameters of only 200 µm. Micro-computed tomography revealed a precise strand arrangement and an interconnected pore space within the biphasic scaffold even in swollen state of the hydrogel strands.

Biomimetic Layer-by-Layer Self-Assembly of Nanofilms, Nanocoatings, and 3D Scaffolds for Tissue Engineering.

PubMed

Zhang, Shichao; Xing, Malcolm; Li, Bingyun

2018-06-01

Achieving surface design and control of biomaterial scaffolds with nanometer- or micrometer-scaled functional films is critical to mimic the unique features of native extracellular matrices, which has significant technological implications for tissue engineering including cell-seeded scaffolds, microbioreactors, cell assembly, tissue regeneration, etc. Compared with other techniques available for surface design, layer-by-layer (LbL) self-assembly technology has attracted extensive attention because of its integrated features of simplicity, versatility, and nanoscale control. Here we present a brief overview of current state-of-the-art research related to the LbL self-assembly technique and its assembled biomaterials as scaffolds for tissue engineering. An overview of the LbL self-assembly technique, with a focus on issues associated with distinct routes and driving forces of self-assembly, is described briefly. Then, we highlight the controllable fabrication, properties, and applications of LbL self-assembly biomaterials in the forms of multilayer nanofilms, scaffold nanocoatings, and three-dimensional scaffolds to systematically demonstrate advances in LbL self-assembly in the field of tissue engineering. LbL self-assembly not only provides advances for molecular deposition but also opens avenues for the design and development of innovative biomaterials for tissue engineering.

X-ray phase-contrast computed tomography visualizes the microstructure and degradation profile of implanted biodegradable scaffolds after spinal cord injury

PubMed Central

Takashima, Kenta; Hoshino, Masato; Uesugi, Kentaro; Yagi, Naoto; Matsuda, Shojiro; Nakahira, Atsushi; Osumi, Noriko; Kohzuki, Masahiro; Onodera, Hiroshi

2015-01-01

Tissue engineering strategies for spinal cord repair are a primary focus of translational medicine after spinal cord injury (SCI). Many tissue engineering strategies employ three-dimensional scaffolds, which are made of biodegradable materials and have microstructure incorporated with viable cells and bioactive molecules to promote new tissue generation and functional recovery after SCI. It is therefore important to develop an imaging system that visualizes both the microstructure of three-dimensional scaffolds and their degradation process after SCI. Here, X-ray phase-contrast computed tomography imaging based on the Talbot grating interferometer is described and it is shown how it can visualize the polyglycolic acid scaffold, including its microfibres, after implantation into the injured spinal cord. Furthermore, X-ray phase-contrast computed tomography images revealed that degradation occurred from the end to the centre of the braided scaffold in the 28 days after implantation into the injured spinal cord. The present report provides the first demonstration of an imaging technique that visualizes both the microstructure and degradation of biodegradable scaffolds in SCI research. X-ray phase-contrast imaging based on the Talbot grating interferometer is a versatile technique that can be used for a broad range of preclinical applications in tissue engineering strategies. PMID:25537600

A bioscaffolding strategy for hierarchical zeolites with a nanotube-trimodal network.

PubMed

Li, Guannan; Huang, Haibo; Yu, Bowen; Wang, Yun; Tao, Jiawei; Wei, Yingxu; Li, Shougui; Liu, Zhongmin; Xu, Yan; Xu, Ruren

2016-02-01

Hierarchical zeolite monoliths with multimodal porosity are of paramount importance as they open up new horizons for advanced applications. So far, hierarchical zeolites based on nanotube scaffolds have never been reported. Inspired by the organization of biominerals, we have developed a novel precursor scaffolding-solid phase crystallization strategy for hierarchical zeolites with a unique nanotube scaffolding architecture and nanotube-trimodal network, where biomolecular self-assembly (BSA) provides a scaffolding blueprint. By vapor-treating Sil-1 seeded precursor scaffolds, zeolite MFI nanotube scaffolds are self-generated, during which evolution phenomena such as segmented voids and solid bridges are observed, in agreement with the Kirkendall effect in a solid-phase crystallization system. The nanotube walls are made of intergrown single crystals rendering good mechanical stability. The inner diameter of the nanotube is tunable between 30 and 90 nm by varying the thickness of the precursor layers. Macropores enclosed by cross-linked nanotubes can be modulated by the choice of BSA. Narrow mesopores are formed by intergrown nanocrystals. Hierarchical ZSM-5 monoliths with nanotube (90 nm), micropore (0.55 nm), mesopore (2 nm) and macropore (700 nm) exhibit superior catalytic performance in the methanol-to-hydrocarbon (MTH) conversion compared to conventional ZSM-5. BSA remains intact after crystallization, allowing a higher level of organization and functionalization of the zeolite nanotube scaffolds. The current work may afford a versatile strategy for hierarchical zeolite monoliths with nanotube scaffolding architectures and a nanotube-multimodal network leading to self-supporting and active zeolite catalysts, and for applications beyond.

Nano-particulate Aluminium Nitride/Al: An Efficient and Versatile Heterogeneous Catalyst for the Synthesis of Biginelli Scaffolds

NASA Astrophysics Data System (ADS)

Tekale, S. U.; Tekale, A. B.; Kanhe, N. S.; Bhoraskar, S. V.; Pawar, R. P.

2011-12-01

Nano-particulate aluminium nitride/Al (7:1) is reported as a new heterogeneous solid acid catalyst for the synthesis of 3, 4-dihydroxypyrimidi-2-(1H)-ones and their sulphur analogues using the Biginelli reaction. This method involves short reaction time, easy separation, high yields and purity of products.

Hydrogel-laden paper scaffold system for origami-based tissue engineering

PubMed Central

Kim, Su-Hwan; Lee, Hak Rae; Yu, Seung Jung; Han, Min-Eui; Lee, Doh Young; Kim, Soo Yeon; Ahn, Hee-Jin; Han, Mi-Jung; Lee, Tae-Ik; Kim, Taek-Soo; Kwon, Seong Keun; Im, Sung Gap; Hwang, Nathaniel S.

2015-01-01

In this study, we present a method for assembling biofunctionalized paper into a multiform structured scaffold system for reliable tissue regeneration using an origami-based approach. The surface of a paper was conformally modified with a poly(styrene-co-maleic anhydride) layer via initiated chemical vapor deposition followed by the immobilization of poly-l-lysine (PLL) and deposition of Ca2+. This procedure ensures the formation of alginate hydrogel on the paper due to Ca2+ diffusion. Furthermore, strong adhesion of the alginate hydrogel on the paper onto the paper substrate was achieved due to an electrostatic interaction between the alginate and PLL. The developed scaffold system was versatile and allowed area-selective cell seeding. Also, the hydrogel-laden paper could be folded freely into 3D tissue-like structures using a simple origami-based method. The cylindrically constructed paper scaffold system with chondrocytes was applied into a three-ring defect trachea in rabbits. The transplanted engineered tissues replaced the native trachea without stenosis after 4 wks. As for the custom-built scaffold system, the hydrogel-laden paper system will provide a robust and facile method for the formation of tissues mimicking native tissue constructs. PMID:26621717

Hydrogel-laden paper scaffold system for origami-based tissue engineering.

PubMed

Kim, Su-Hwan; Lee, Hak Rae; Yu, Seung Jung; Han, Min-Eui; Lee, Doh Young; Kim, Soo Yeon; Ahn, Hee-Jin; Han, Mi-Jung; Lee, Tae-Ik; Kim, Taek-Soo; Kwon, Seong Keun; Im, Sung Gap; Hwang, Nathaniel S

2015-12-15

In this study, we present a method for assembling biofunctionalized paper into a multiform structured scaffold system for reliable tissue regeneration using an origami-based approach. The surface of a paper was conformally modified with a poly(styrene-co-maleic anhydride) layer via initiated chemical vapor deposition followed by the immobilization of poly-l-lysine (PLL) and deposition of Ca(2+). This procedure ensures the formation of alginate hydrogel on the paper due to Ca(2+) diffusion. Furthermore, strong adhesion of the alginate hydrogel on the paper onto the paper substrate was achieved due to an electrostatic interaction between the alginate and PLL. The developed scaffold system was versatile and allowed area-selective cell seeding. Also, the hydrogel-laden paper could be folded freely into 3D tissue-like structures using a simple origami-based method. The cylindrically constructed paper scaffold system with chondrocytes was applied into a three-ring defect trachea in rabbits. The transplanted engineered tissues replaced the native trachea without stenosis after 4 wks. As for the custom-built scaffold system, the hydrogel-laden paper system will provide a robust and facile method for the formation of tissues mimicking native tissue constructs.

The Role of Electrospinning in the Emerging Field of Nanomedicine

PubMed Central

Chew, SY; Wen, Y; Dzenis, Y; Leong, KW

2008-01-01

The fact that in vivo the extracellular matrix or substratum with which cells interact often includes topography at the nanoscale underscores the importance of investigating cell-substrate interactions and performing cell culture at the submicron scale. An important and exciting direction of research in nanomedicine would be to gain an understanding and exploit the cellular response to nanostructures. Electrospinning is a simple and versatile technique that can produce a macroporous scaffold comprising randomly oriented or aligned nanofibers. It can also accommodate the incorporation of drug delivery function into the fibrous scaffold. Endowed with both topographical and biochemical signals such electrospun nanofibrous scaffolds may provide an optimal microenvironment for the seeded cells. This review covers the analysis and control of the electrospinning process, and describes the types of electrospun fibers fabricated for biomedical applications such as drug delivery and tissue engineering. PMID:17168776

Multilayered Electrospun Scaffolds for Tendon Tissue Engineering

PubMed Central

Chainani, Abby; Hippensteel, Kirk J.; Kishan, Alysha; Garrigues, N. William; Ruch, David S.; Guilak, Farshid

2013-01-01

Full-thickness rotator cuff tears are one of the most common causes of shoulder pain in people over the age of 65. High retear rates and poor functional outcomes are common after surgical repair, and currently available extracellular matrix scaffold patches have limited abilities to enhance new tendon formation. In this regard, tissue-engineered scaffolds may provide a means to improve repair of rotator cuff tears. Electrospinning provides a versatile method for creating nanofibrous scaffolds with controlled architectures, but several challenges remain in its application to tissue engineering, such as cell infiltration through the full thickness of the scaffold as well as control of cell growth and differentiation. Previous studies have shown that ligament-derived extracellular matrix may enhance differentiation toward a tendon or ligament phenotype by human adipose stem cells (hASCs). In this study, we investigated the use of tendon-derived extracellular matrix (TDM)-coated electrospun multilayered scaffolds compared to fibronectin (FN) or phosphate-buffered saline (PBS) coating for use in rotator cuff tendon tissue engineering. Multilayered poly(ɛ-caprolactone) scaffolds were prepared by sequentially collecting electrospun layers onto the surface of a grounded saline solution into a single scaffold. Scaffolds were then coated with TDM, FN, or PBS and seeded with hASCs. Scaffolds were maintained without exogenous growth factors for 28 days in culture and evaluated for protein content (by immunofluorescence and biochemical assay), markers of tendon differentiation, and tensile mechanical properties. The collagen content was greatest by day 28 in TDM-scaffolds. Gene expression of type I collagen, decorin, and tenascin C increased over time, with no effect of scaffold coating. Sulfated glycosaminoglycan and dsDNA contents increased over time in culture, but there was no effect of scaffold coating. The Young's modulus did not change over time, but yield strain increased with time in culture. Histology demonstrated cell infiltration through the full thickness of all scaffolds and immunofluorescence demonstrated greater expression of type I, but not type III collagen through the full thickness of the scaffold in TDM-scaffolds compared to other treatment groups. Together, these data suggest that nonaligned multilayered electrospun scaffolds permit tenogenic differentiation by hASCs and that TDM may promote some aspects of this differentiation. PMID:23808760

A PEGylated platelet free plasma hydrogel based composite scaffold enables stable vascularization and targeted cell delivery for volumetric muscle loss.

PubMed

Aurora, Amit; Wrice, Nicole; Walters, Thomas J; Christy, Robert J; Natesan, Shanmugasundaram

2018-01-01

Extracellular matrix (ECM) scaffolds are being used for the clinical repair of soft tissue injuries. Although improved functional outcomes have been reported, ECM scaffolds show limited tissue specific remodeling response with concomitant deposition of fibrotic tissue. One plausible explanation is the regression of blood vessels which may be limiting the diffusion of oxygen and nutrients across the scaffold. Herein we develop a composite scaffold as a vasculo-inductive platform by integrating PEGylated platelet free plasma (PFP) hydrogel with a muscle derived ECM scaffold (m-ECM). In vitro, adipose derived stem cells (ASCs) seeded onto the composite scaffold differentiated into two distinct morphologies, a tubular network in the hydrogel, and elongated structures along the m-ECM scaffold. The composite scaffold showed a high expression of ITGA5, ITGB1, and FN and a synergistic up-regulation of ang1 and tie-2 transcripts. The in vitro ability of the composite scaffold to provide extracellular milieu for cell adhesion and molecular cues to support vessel formation was investigated in a rodent volumetric muscle loss (VML) model. The composite scaffold delivered with ASCs supported robust and stable vascularization. Additionally, the composite scaffold supported increased localization of ASCs in the defect demonstrating its ability for localized cell delivery. Interestingly, ASCs were observed homing in the injured muscle and around the perivascular space possibly to stabilize the host vasculature. In conclusion, the composite scaffold delivered with ASCs presents a promising approach for scaffold vascularization. The versatile nature of the composite scaffold also makes it easily adaptable for the repair of soft tissue injuries. Decellularized extracellular matrix (ECM) scaffolds when used for soft tissue repair is often accompanied by deposition of fibrotic tissue possibly due to limited scaffold vascularization, which limits the diffusion of oxygen and nutrients across the scaffold. Although a variety of scaffold vascularization strategies has been investigated, their limitations preclude rapid clinical translation. In this study we have developed a composite scaffold by integrating bi-functional polyethylene glycol modified platelet free plasma (PEGylated PFP) with adipose derived stem cells (ASCs) along with a muscle derived ECM scaffold (m-ECM). The composite scaffold provides a vasculo-inductive and an effective cell delivery platform for volumetric muscle loss. Copyright © 2017 Acta Materialia Inc. All rights reserved.

3D printing of high-strength bioscaffolds for the synergistic treatment of bone cancer

NASA Astrophysics Data System (ADS)

Ma, Hongshi; Li, Tao; Huan, Zhiguang; Zhang, Meng; Yang, Zezheng; Wang, Jinwu; Chang, Jiang; Wu, Chengtie

2018-04-01

The challenges in bone tumor therapy are how to repair the large bone defects induced by surgery and kill all possible residual tumor cells. Compared to cancellous bone defect regeneration, cortical bone defect regeneration has a higher demand for bone substitute materials. To the best of our knowledge, there are currently few bifunctional biomaterials with an ultra-high strength for both tumor therapy and cortical bone regeneration. Here, we designed Fe-CaSiO3 composite scaffolds (30CS) via 3D printing technique. First, the 30CS composite scaffolds possessed a high compressive strength that provided sufficient mechanical support in bone cortical defects; second, synergistic photothermal and ROS therapies achieved an enhanced tumor therapeutic effect in vitro and in vivo. Finally, the presence of CaSiO3 in the composite scaffolds improved the degradation performance, stimulated the proliferation and differentiation of rBMSCs, and further promoted bone formation in vivo. Such 30CS scaffolds with a high compressive strength can function as versatile and efficient biomaterials for the future regeneration of cortical bone defects and the treatment of bone cancer.

Designing LibGuides as Instructional Tools for Critical Thinking and Effective Online Learning

ERIC Educational Resources Information Center

Baker, Ruth L.

2014-01-01

Did you ever wish for an easy-to-maintain tool to create course-level or assignment-level instruction for online or distance students? LibGuides can provide the solution! LibGuides provide a versatile and easy-to-maintain platform for delivering step-by-step, scaffolded tutorials that enhance learning outcomes through chunking, reduced strain on…

Nanofiber scaffold gradients for interfacial tissue engineering.

PubMed

Ramalingam, Murugan; Young, Marian F; Thomas, Vinoy; Sun, Limin; Chow, Laurence C; Tison, Christopher K; Chatterjee, Kaushik; Miles, William C; Simon, Carl G

2013-02-01

We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electrospun. A dye was used to characterize the 2-spinnerette approach and applicability to tissue engineering was demonstrated by fabricating nanofibers with gradients in amorphous calcium phosphate nanoparticles (nACP). Adhesion and proliferation of osteogenic cells (MC3T3-E1 murine pre-osteoblasts) on gradients was enhanced on the regions of the gradients that contained higher nACP content yielding a graded osteoblast response. Since increases in soluble calcium and phosphate ions stimulate osteoblast function, we measured their release and observed significant release from nanofibers containing nACP. The nanofiber-nACP gradients fabricated herein can be applied to generate tissues with osteoblast gradients such as ligaments or tendons. In conclusion, these results introduce a versatile approach for fabricating nanofiber gradients that can have application for engineering graded tissues.

Bioorthogonal Modification of the Major Sheath Protein of Bacteriophage M13: Extending the Versatility of Bionanomaterial Scaffolds.

PubMed

Urquhart, Taylor; Daub, Elisabeth; Honek, John Frank

2016-10-19

With a mass of ∼1.6 × 10 7 Daltons and composed of approximately 2700 proteins, bacteriophage M13 has been employed as a molecular scaffold in bionanomaterials fabrication. In order to extend the versatility of M13 in this area, residue-specific unnatural amino acid incorporation was employed to successfully display azide functionalities on specific solvent-exposed positions of the pVIII major sheath protein of this bacteriophage. Employing a combination of engineered mutants of the gene coding for the pVIII protein, the methionine (Met) analog, l-azidohomoalanine (Aha), and a suitable Escherichia coli Met auxotroph for phage production, conditions were developed to produce M13 bacteriophage labeled with over 350 active azides (estimated by fluorescent dye labeling utilizing a strain-promoted azide-alkyne cycloaddition) and capable of azide-selective attachment to 5 nm gold nanoparticles as visualized by transmission electron microscopy. The capability of this system to undergo dual labeling utilizing both chemical acylation and bioorthogonal cycloaddition reactions was also verified. The above stratagem should prove particularly advantageous in the preparation of assemblies of larger and more complex molecular architectures based on the M13 building block.

Evolution of an ancient protein function involved in organized multicellularity in animals.

PubMed

Anderson, Douglas P; Whitney, Dustin S; Hanson-Smith, Victor; Woznica, Arielle; Campodonico-Burnett, William; Volkman, Brian F; King, Nicole; Thornton, Joseph W; Prehoda, Kenneth E

2016-01-07

To form and maintain organized tissues, multicellular organisms orient their mitotic spindles relative to neighboring cells. A molecular complex scaffolded by the GK protein-interaction domain (GKPID) mediates spindle orientation in diverse animal taxa by linking microtubule motor proteins to a marker protein on the cell cortex localized by external cues. Here we illuminate how this complex evolved and commandeered control of spindle orientation from a more ancient mechanism. The complex was assembled through a series of molecular exploitation events, one of which - the evolution of GKPID's capacity to bind the cortical marker protein - can be recapitulated by reintroducing a single historical substitution into the reconstructed ancestral GKPID. This change revealed and repurposed an ancient molecular surface that previously had a radically different function. We show how the physical simplicity of this binding interface enabled the evolution of a new protein function now essential to the biological complexity of many animals.

Ball with hair: modular functionalization of highly stable G-quadruplex DNA nano-scaffolds through N2-guanine modification

PubMed Central

Lech, Christopher Jacques

2017-01-01

Abstract Functionalized nanoparticles have seen valuable applications, particularly in the delivery of therapeutic and diagnostic agents in biological systems. However, the manufacturing of such nano-scale systems with the consistency required for biological application can be challenging, as variation in size and shape have large influences in nanoparticle behavior in vivo. We report on the development of a versatile nano-scaffold based on the modular functionalization of a DNA G-quadruplex. DNA sequences are functionalized in a modular fashion using well-established phosphoramidite chemical synthesis with nucleotides containing modification of the amino (N2) position of the guanine base. In physiological conditions, these sequences fold into well-defined G-quadruplex structures. The resulting DNA nano-scaffolds are thermally stable, consistent in size, and functionalized in a manner that allows for control over the density and relative orientation of functional chemistries on the nano-scaffold surface. Various chemistries including small modifications (N2-methyl-guanine), bulky aromatic modifications (N2-benzyl-guanine), and long chain-like modifications (N2-6-amino-hexyl-guanine) are tested and are found to be generally compatible with G-quadruplex formation. Furthermore, these modifications stabilize the G-quadruplex scaffold by 2.0–13.3 °C per modification in the melting temperature, with concurrent modifications producing extremely stable nano-scaffolds. We demonstrate the potential of this approach by functionalizing nano-scaffolds for use within the biotin–avidin conjugation approach. PMID:28499037

A novel one-pot process for near-net-shape fabrication of open-porous resorbable hydroxyapatite/protein composites and in vivo assessment.

PubMed

Mueller, Berit; Koch, Dietmar; Lutz, Rainer; Schlegel, Karl A; Treccani, Laura; Rezwan, Kurosch

2014-09-01

We present a mild one-pot freeze gelation process for fabricating near-net, complex-shaped hydroxyapatite scaffolds and to directly incorporate active proteins during scaffold processing. In particular, the direct protein incorporation enables a simultaneous adjustment and control of scaffold microstructure, porosity, resorbability and enhancement of initial mechanical and handling stability. Two proteins, serum albumin and lysozyme, are selected and their effect on scaffold stability and microstructure investigated by biaxial strength tests, electron microscopy, and mercury intrusion porosimetry. The resulting hydroxyapatite/protein composites feature adjustable porosities from 50% to 70% and a mechanical strength ranging from 2 to 6 MPa comparable to that of human spongiosa without any sintering step. Scaffold degradation behaviour and protein release are assessed by in vitro studies. A preliminary in vivo assessment of scaffold biocompatibility and resorption behaviour in adult domestic pigs is discussed. After implantation, composites were resorbed up to 50% after only 4 weeks and up to 65% after 8 weeks. In addition, 14% new bone formation after 4 weeks and 37% after 8 weeks were detected. All these investigations demonstrate the outstanding suitability of the one-pot-process to create, in a customisable and reliable way, biocompatible scaffolds with sufficient mechanical strength for handling and surgical insertion, and for potential use as biodegradable bone substitutes and versatile platform for local drug delivery. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced biocompatibility of PLGA nanofibers with gelatin/nano-hydroxyapatite bone biomimetics incorporation.

PubMed

Li, Daowei; Sun, Haizhu; Jiang, Liming; Zhang, Kai; Liu, Wendong; Zhu, Yang; Fangteng, Jiaozi; Shi, Ce; Zhao, Liang; Sun, Hongchen; Yang, Bai

2014-06-25

The biocompatibility of biomaterials is essentially for its application. The aim of current study was to evaluate the biocompatibility of poly(lactic-co-glycolic acid) (PLGA)/gelatin/nanohydroxyapatite (n-HA) (PGH) nanofibers systemically to provide further rationales for the application of the composite electrospun fibers as a favorable platform for bone tissue engineering. The PGH composite scaffold with diameter ranging from nano- to micrometers was fabricated by using electrospinning technique. Subsequently, we utilized confocal laser scanning microscopy (CLSM) and MTT assay to evaluate its cyto-compatibility in vitro. Besides, real-time quantitative polymerase chain reaction (qPCR) analysis and alizarin red staining (ARS) were performed to assess the osteoinductive activity. To further test in vivo, we implanted either PLGA or PGH composite scaffold in a rat subcutaneous model. The results demonstrated that PGH scaffold could better support osteoblasts adhesion, spreading, and proliferation and show better cyto-compatibility than pure PLGA scaffold. Besides, qPCR analysis and ARS showed that PGH composite scaffold exhibited higher osteoinductive activity owing to higher phenotypic expression of typical osteogenic genes and calcium deposition. The histology evaluation indicated that the incorporation of Gelatin/nanohydroxyapatite (GH) biomimetics could significantly reduce local inflammation. Our data indicated that PGH composite electrospun nanofibers possessed excellent cyto-compatibility, good osteogenic activity, as well as good performance of host tissue response, which could be versatile biocompatible scaffolds for bone tissue engineering.

PEGylated graphene oxide-mediated quercetin-modified collagen hybrid scaffold for enhancement of MSCs differentiation potential and diabetic wound healing.

PubMed

Chu, Jing; Shi, Panpan; Yan, Wenxia; Fu, Jinping; Yang, Zhi; He, Chengmin; Deng, Xiaoyuan; Liu, Hanping

2018-05-24

Nanoscale delivery based on polyethylene glycol (PEG)ylated graphene oxide (GO-PEG) merits attention for biomedical applications owing to its functional surface modification, superior solubility/biocompatibility and controllable drug release capability. However, impaired skin regeneration in applications of these fascinating nanomaterials in diabetes is still limited, and critical issues need to be addressed regarding insufficient collagen hyperplasia and inadequate blood supply. Therefore, a high-performance tissue engineering scaffold with biocompatible and biodegradable properties is essential for diabetic wound healing. Natural and artificial acellular dermal matrix (ADM) scaffolds with spatially organized collagen fibers can provide a suitable architecture and environment for cell attachment and proliferation. Here, a novel collagen-nanomaterial-drug hybrid scaffold was constructed from GO-PEG-mediated quercetin (GO-PEG/Que)-modified ADM (ADM-GO-PEG/Que). The resulting unique and versatile hybrid scaffold exhibited multiple advantages, including the following: a biocompatible, cell-adhesive surface for accelerating mesenchymal stem cell (MSC) attachment and proliferation; superior stability and adjustability of the conduction potential of quercetin for inducing the differentiation of MSCs into adipocytes and osteoblasts; and a biodegradable nanofiber interface for promoting collagen deposition and angiogenesis in diabetic wound repair. This study provides new prospects for the design of innovative GO-PEG-based collagen hybrid scaffolds for application in efficient therapeutic drug delivery, stem cell-based therapies, tissue engineering and regenerative medicine.

Ancient pathogen DNA in archaeological samples detected with a Microbial Detection Array.

PubMed

Devault, Alison M; McLoughlin, Kevin; Jaing, Crystal; Gardner, Shea; Porter, Teresita M; Enk, Jacob M; Thissen, James; Allen, Jonathan; Borucki, Monica; DeWitte, Sharon N; Dhody, Anna N; Poinar, Hendrik N

2014-03-06

Ancient human remains of paleopathological interest typically contain highly degraded DNA in which pathogenic taxa are often minority components, making sequence-based metagenomic characterization costly. Microarrays may hold a potential solution to these challenges, offering a rapid, affordable, and highly informative snapshot of microbial diversity in complex samples without the lengthy analysis and/or high cost associated with high-throughput sequencing. Their versatility is well established for modern clinical specimens, but they have yet to be applied to ancient remains. Here we report bacterial profiles of archaeological and historical human remains using the Lawrence Livermore Microbial Detection Array (LLMDA). The array successfully identified previously-verified bacterial human pathogens, including Vibrio cholerae (cholera) in a 19th century intestinal specimen and Yersinia pestis ("Black Death" plague) in a medieval tooth, which represented only minute fractions (0.03% and 0.08% alignable high-throughput shotgun sequencing reads) of their respective DNA content. This demonstrates that the LLMDA can identify primary and/or co-infecting bacterial pathogens in ancient samples, thereby serving as a rapid and inexpensive paleopathological screening tool to study health across both space and time.

Exploring the transcription activator-like effectors scaffold versatility to expand the toolbox of designer nucleases

PubMed Central

2014-01-01

Background The past decade has seen the emergence of several molecular tools that render possible modification of cellular functions through accurate and easy addition, removal, or exchange of genomic DNA sequences. Among these technologies, transcription activator-like effectors (TALE) has turned out to be one of the most versatile and incredibly robust platform for generating targeted molecular tools as demonstrated by fusion to various domains such as transcription activator, repressor and nucleases. Results In this study, we generated a novel nuclease architecture based on the transcription activator-like effector scaffold. In contrast to the existing Tail to Tail (TtT) and head to Head (HtH) nuclease architectures based on the symmetrical association of two TALE DNA binding domains fused to the C-terminal (TtT) or N-terminal (HtH) end of FokI, this novel architecture consists of the asymmetrical association of two different engineered TALE DNA binding domains fused to the N- and C-terminal ends of FokI (TALE::FokI and FokI::TALE scaffolds respectively). The characterization of this novel Tail to Head (TtH) architecture in yeast enabled us to demonstrate its nuclease activity and define its optimal target configuration. We further showed that this architecture was able to promote substantial level of targeted mutagenesis at three endogenous loci present in two different mammalian cell lines. Conclusion Our results demonstrated that this novel functional TtH architecture which requires binding to only one DNA strand of a given endogenous locus has the potential to extend the targeting possibility of FokI-based TALE nucleases. PMID:24997498

Ball with hair: modular functionalization of highly stable G-quadruplex DNA nano-scaffolds through N2-guanine modification.

PubMed

Lech, Christopher Jacques; Phan, Anh Tuân

2017-06-20

Functionalized nanoparticles have seen valuable applications, particularly in the delivery of therapeutic and diagnostic agents in biological systems. However, the manufacturing of such nano-scale systems with the consistency required for biological application can be challenging, as variation in size and shape have large influences in nanoparticle behavior in vivo. We report on the development of a versatile nano-scaffold based on the modular functionalization of a DNA G-quadruplex. DNA sequences are functionalized in a modular fashion using well-established phosphoramidite chemical synthesis with nucleotides containing modification of the amino (N2) position of the guanine base. In physiological conditions, these sequences fold into well-defined G-quadruplex structures. The resulting DNA nano-scaffolds are thermally stable, consistent in size, and functionalized in a manner that allows for control over the density and relative orientation of functional chemistries on the nano-scaffold surface. Various chemistries including small modifications (N2-methyl-guanine), bulky aromatic modifications (N2-benzyl-guanine), and long chain-like modifications (N2-6-amino-hexyl-guanine) are tested and are found to be generally compatible with G-quadruplex formation. Furthermore, these modifications stabilize the G-quadruplex scaffold by 2.0-13.3 °C per modification in the melting temperature, with concurrent modifications producing extremely stable nano-scaffolds. We demonstrate the potential of this approach by functionalizing nano-scaffolds for use within the biotin-avidin conjugation approach. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Manipulation of in vitro collagen matrix architecture for scaffolds of improved physiological relevance

NASA Astrophysics Data System (ADS)

Hapach, Lauren A.; VanderBurgh, Jacob A.; Miller, Joseph P.; Reinhart-King, Cynthia A.

2015-12-01

Type I collagen is a versatile biomaterial that is widely used in medical applications due to its weak antigenicity, robust biocompatibility, and its ability to be modified for a wide array of applications. As such, collagen has become a major component of many tissue engineering scaffolds, drug delivery platforms, and substrates for in vitro cell culture. In these applications, collagen constructs are fabricated to recapitulate a diverse set of conditions. Collagen fibrils can be aligned during or post-fabrication, cross-linked via numerous techniques, polymerized to create various fibril sizes and densities, and copolymerized into a wide array of composite scaffolds. Here, we review approaches that have been used to tune collagen to better recapitulate physiological environments for use in tissue engineering applications and studies of basic cell behavior. We discuss techniques to control fibril alignment, methods for cross-linking collagen constructs to modulate stiffness, and composite collagen constructs to better mimic physiological extracellular matrix.

Isothermal folding of a light-up bio-orthogonal RNA origami nanoribbon.

PubMed

Torelli, Emanuela; Kozyra, Jerzy Wieslaw; Gu, Jing-Ying; Stimming, Ulrich; Piantanida, Luca; Voïtchovsky, Kislon; Krasnogor, Natalio

2018-05-03

RNA presents intringuing roles in many cellular processes and its versatility underpins many different applications in synthetic biology. Nonetheless, RNA origami as a method for nanofabrication is not yet fully explored and the majority of RNA nanostructures are based on natural pre-folded RNA. Here we describe a biologically inert and uniquely addressable RNA origami scaffold that self-assembles into a nanoribbon by seven staple strands. An algorithm is applied to generate a synthetic De Bruijn scaffold sequence that is characterized by the lack of biologically active sites and repetitions larger than a predetermined design parameter. This RNA scaffold and the complementary staples fold in a physiologically compatible isothermal condition. In order to monitor the folding, we designed a new split Broccoli aptamer system. The aptamer is divided into two nonfunctional sequences each of which is integrated into the 5' or 3' end of two staple strands complementary to the RNA scaffold. Using fluorescence measurements and in-gel imaging, we demonstrate that once RNA origami assembly occurs, the split aptamer sequences are brought into close proximity forming the aptamer and turning on the fluorescence. This light-up 'bio-orthogonal' RNA origami provides a prototype that can have potential for in vivo origami applications.

[3 + 2] Cycloaddition reactions of thioisatin with thiazolidine-2-carboxylic acid: a versatile route to new heterocyclic scaffolds

PubMed Central

2011-01-01

A facile synthesis of azabicycloadducts is described by 1,3-dipolar cycloaddition reactions of thioisatin with thiazolidine-2-carboxylic acid in the presence of various electron rich and electron deficient dipolarophiles. Theoritical calculations have been performed to study the regioselectivity of products. The geometrical and energetic properties have been analyzed for the different reactants, transition states and cycloadducts formed. PMID:22373364

Photoreactive elastin-like proteins for use as versatile bioactive materials and surface coatings

PubMed Central

Raphel, Jordan; Parisi-Amon, Andreina; Heilshorn, Sarah

2012-01-01

Photocrosslinkable, protein-engineered biomaterials combine a rapid, controllable, cytocompatible crosslinking method with a modular design strategy to create a new family of bioactive materials. These materials have a wide range of biomedical applications, including the development of bioactive implant coatings, drug delivery vehicles, and tissue engineering scaffolds. We present the successful functionalization of a bioactive elastin-like protein with photoreactive diazirine moieties. Scalable synthesis is achieved using a standard recombinant protein expression host followed by site-specific modification of lysine residues with a heterobifunctional N-hydroxysuccinimide ester-diazirine crosslinker. The resulting biomaterial is demonstrated to be processable by spin coating, drop casting, soft lithographic patterning, and mold casting to fabricate a variety of two- and three-dimensional photocrosslinked biomaterials with length scales spanning the nanometer to millimeter range. Protein thin films proved to be highly stable over a three-week period. Cell-adhesive functional domains incorporated into the engineered protein materials were shown to remain active post-photo-processing. Human adipose-derived stem cells achieved faster rates of cell adhesion and larger spread areas on thin films of the engineered protein compared to control substrates. The ease and scalability of material production, processing versatility, and modular bioactive functionality make this recombinantly engineered protein an ideal candidate for the development of novel biomaterial coatings, films, and scaffolds. PMID:23015764

Photoreactive elastin-like proteins for use as versatile bioactive materials and surface coatings.

PubMed

Raphel, Jordan; Parisi-Amon, Andreina; Heilshorn, Sarah

2012-10-07

Photocrosslinkable, protein-engineered biomaterials combine a rapid, controllable, cytocompatible crosslinking method with a modular design strategy to create a new family of bioactive materials. These materials have a wide range of biomedical applications, including the development of bioactive implant coatings, drug delivery vehicles, and tissue engineering scaffolds. We present the successful functionalization of a bioactive elastin-like protein with photoreactive diazirine moieties. Scalable synthesis is achieved using a standard recombinant protein expression host followed by site-specific modification of lysine residues with a heterobifunctional N-hydroxysuccinimide ester-diazirine crosslinker. The resulting biomaterial is demonstrated to be processable by spin coating, drop casting, soft lithographic patterning, and mold casting to fabricate a variety of two- and three-dimensional photocrosslinked biomaterials with length scales spanning the nanometer to millimeter range. Protein thin films proved to be highly stable over a three-week period. Cell-adhesive functional domains incorporated into the engineered protein materials were shown to remain active post-photo-processing. Human adipose-derived stem cells achieved faster rates of cell adhesion and larger spread areas on thin films of the engineered protein compared to control substrates. The ease and scalability of material production, processing versatility, and modular bioactive functionality make this recombinantly engineered protein an ideal candidate for the development of novel biomaterial coatings, films, and scaffolds.

Preparation and surface characterization of plasma-treated and biomolecular-micropatterned polymer substrates

NASA Astrophysics Data System (ADS)

Langowski, Bryan Alfred

A micropatterning process creates distinct microscale domains on substrate surfaces that differ from the surfaces' original chemical/physical properties. Numerous micropatterning methods exist, each having relative advantages and disadvantages in terms of cost, ease, reproducibility, and versatility. Polymeric surfaces micropatterned with biomolecules have many applications, but are specifically utilized in tissue engineering as cell scaffolds that attempt to controlled tissue generation in vivo and ex vivo. As the physical and chemical cues presented by micropatterned substrates control resulting cellular behavior, characterization of these cues via surface-sensitive analytical techniques is essential in developing cell scaffolds that mimic complex in vivo physicochemical environments. The initial focus of this thesis is the chemical and physical characterization of plasma-treated, microcontact-printed (muCP) polymeric substrates used to direct nerve cell behavior. Unmodified and oxygen plasma-treated poly(methyl methacrylate) (PMMA) substrates were analyzed by surface sensitive techniques to monitor plasma-induced chemical and physical modifications. Additionally, protein-micropattern homogeneity and size were microscopically evaluated. Lastly, poly(dimethylsiloxane) (PDMS) stamps and contaminated PMMA substrates were characterized by spectroscopic and microscopic methods to identify a contamination source during microcontact printing. The final focus of this thesis is the development of microscale plasma-initiated patterning (muPIP) as a versatile, reproducible micropatterning method. Using muPIP, polymeric substrates were micropatterned with several biologically relevant inks. Polymeric substrates were characterized following muPIP by surface-sensitive techniques to identify the technique's underlying physical and chemical bases. In addition, neural stem cell response to muPIP-generated laminin micropatterns was microscopically and biologically evaluated. Finally, enhanced versatility of muPIP in generating microscale poly-L-lysine gradients was demonstrated.

L. inermis-loaded nanofibrous scaffolds for wound dressing applications.

PubMed

Vakilian, Saeid; Norouzi, Mohammad; Soufi-Zomorrod, Mahsa; Shabani, Iman; Hosseinzadeh, Simzar; Soleimani, Masoud

2018-04-01

Since ancient times, some herbal medicines have been extensively used for burn and wound treatments, showing preference to the common synthetic medications by virtue of having less side effects and faster healing rate. In this study, hybrid nanofibrous scaffolds of poly-l-lactic-acid (PLLA) and gelatin incorporated L. inermis were fabricated via electrospinning technique. Morphology and characteristics of the scaffolds were studied by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR), respectively. The release profile of the L. inermis from the nanofibers was also assessed in vitro. Moreover, the structural stability of the released L. inermis from the nanofibers was evaluated using high-performance liquid chromatography (HPLC). The nanofibers showed a gradual release of L. inermis up to two days while the intact structure was preserved. Furthermore, antibacterial assay demonstrated that L. inermis-loaded nanofibrous scaffolds could effectively kill E. coli and S. aureus within 2 h. Finally, biocompatibility of the nanofibers was proven on 3T3 fibroblasts. Therefore, the L. inermis loaded PLLA-Gelatin nanofibers showed a potential application as a wound dressing in order to control wound infections. Copyright © 2018. Published by Elsevier Ltd.

Evolution of an ancient protein function involved in organized multicellularity in animals

PubMed Central

Anderson, Douglas P; Whitney, Dustin S; Hanson-Smith, Victor; Woznica, Arielle; Campodonico-Burnett, William; Volkman, Brian F; King, Nicole; Thornton, Joseph W; Prehoda, Kenneth E

2016-01-01

To form and maintain organized tissues, multicellular organisms orient their mitotic spindles relative to neighboring cells. A molecular complex scaffolded by the GK protein-interaction domain (GKPID) mediates spindle orientation in diverse animal taxa by linking microtubule motor proteins to a marker protein on the cell cortex localized by external cues. Here we illuminate how this complex evolved and commandeered control of spindle orientation from a more ancient mechanism. The complex was assembled through a series of molecular exploitation events, one of which – the evolution of GKPID’s capacity to bind the cortical marker protein – can be recapitulated by reintroducing a single historical substitution into the reconstructed ancestral GKPID. This change revealed and repurposed an ancient molecular surface that previously had a radically different function. We show how the physical simplicity of this binding interface enabled the evolution of a new protein function now essential to the biological complexity of many animals. DOI: http://dx.doi.org/10.7554/eLife.10147.001 PMID:26740169

3D Printing Polymers with Supramolecular Functionality for Biological Applications.

PubMed

Pekkanen, Allison M; Mondschein, Ryan J; Williams, Christopher B; Long, Timothy E

2017-09-11

Supramolecular chemistry continues to experience widespread growth, as fine-tuned chemical structures lead to well-defined bulk materials. Previous literature described the roles of hydrogen bonding, ionic aggregation, guest/host interactions, and π-π stacking to tune mechanical, viscoelastic, and processing performance. The versatility of reversible interactions enables the more facile manufacturing of molded parts with tailored hierarchical structures such as tissue engineered scaffolds for biological applications. Recently, supramolecular polymers and additive manufacturing processes merged to provide parts with control of the molecular, macromolecular, and feature length scales. Additive manufacturing, or 3D printing, generates customizable constructs desirable for many applications, and the introduction of supramolecular interactions will potentially increase production speed, offer a tunable surface structure for controlling cell/scaffold interactions, and impart desired mechanical properties through reinforcing interlayer adhesion and introducing gradients or self-assembled structures. This review details the synthesis and characterization of supramolecular polymers suitable for additive manufacture and biomedical applications as well as the use of supramolecular polymers in additive manufacturing for drug delivery and complex tissue scaffold formation. The effect of supramolecular assembly and its dynamic behavior offers potential for controlling the anisotropy of the printed objects with exquisite geometrical control. The potential for supramolecular polymers to generate well-defined parts, hierarchical structures, and scaffolds with gradient properties/tuned surfaces provides an avenue for developing next-generation biomedical devices and tissue scaffolds.

Silk constructs for delivery of muskuloskeletal therapeutics

PubMed Central

Meinel, Lorenz; Kaplan, David L.

2012-01-01

Silk fibroin (SF) is a biopolymer with distinguishing features from many other bio- as well as synthetic polymers. From a biomechanical and drug delivery perspective, SF combines remarkable versatility for scaffolding (solid implants, hydrogels, threads, solutions), with advanced mechanical properties and good stabilization and controlled delivery of entrapped protein and small molecule drugs, respectively. It is this combination of mechanical and pharmaceutical features which render SF so exciting for biomedical applications. his pattern along with the versatility of this biopolymer have been translated into progress for musculoskeletal applications. We review the use and potential of silk fibroin for systemic and localized delivery of therapeutics in diseases affecting the musculoskeletal system. We also present future directions for this biopolymer as well as the necessary research and development steps for their achievement. PMID:22522139

Hybrid Tissue Engineering Scaffolds by Combination of Three-Dimensional Printing and Cell Photoencapsulation.

PubMed

Markovic, Marica; Van Hoorick, Jasper; Hölzl, Katja; Tromayer, Maximilian; Gruber, Peter; Nürnberger, Sylvia; Dubruel, Peter; Van Vlierberghe, Sandra; Liska, Robert; Ovsianikov, Aleksandr

2015-05-01

Three-dimensional (3D) printing offers versatile possibilities for adapting the structural parameters of tissue engineering scaffolds. However, it is also essential to develop procedures allowing efficient cell seeding independent of scaffold geometry and pore size. The aim of this study was to establish a method for seeding the scaffolds using photopolymerizable cell-laden hydrogels. The latter facilitates convenient preparation, and handling of cell suspension, while distributing the hydrogel precursor throughout the pores, before it is cross-linked with light. In addition, encapsulation of living cells within hydrogels can produce constructs with high initial cell loading and intimate cell-matrix contact, similar to that of the natural extra-cellular matrix (ECM). Three dimensional scaffolds were produced from poly(lactic) acid (PLA) by means of fused deposition modeling. A solution of methacrylamide-modified gelatin (Gel-MOD) in cell culture medium containing photoinitiator Li-TPO-L was used as a hydrogel precursor. Being an enzymatically degradable derivative of natural collagen, gelatin-based matrices are biomimetic and potentially support the process of cell-induced remodeling. Preosteoblast cells MC3T3-E1 at a density of 10 × 10 6 cells per 1 mL were used for testing the seeding procedure and cell proliferation studies. Obtained results indicate that produced constructs support cell survival and proliferation over extended duration of our experiment. The established two-step approach for scaffold seeding with the cells is simple, rapid, and is shown to be highly reproducible. Furthermore, it enables precise control of the initial cell density, while yielding their uniform distribution throughout the scaffold. Such hybrid tissue engineering constructs merge the advantages of rigid 3D printed constructs with the soft hydrogel matrix, potentially mimicking the process of ECM remodeling.

Electrospun poly-l-lactide scaffold for the controlled and targeted delivery of a synthetically obtained Diclofenac prodrug to treat actinic keratosis.

PubMed

Piccirillo, Germano; Bochicchio, Brigida; Pepe, Antonietta; Schenke-Layland, Katja; Hinderer, Svenja

2017-04-01

Actinic Keratosis' (AKs) are small skin lesions that are related to a prolonged sun-damage, which can develop into invasive squamous cell carcinoma (SCC) when left untreated. Effective, specific and well tolerable therapies to cure AKs are still of great interest. Diclofenac (DCF) is the current gold standard for the local treatment of AKs in terms of costs, effectiveness, side effects and tolerability. In this work, an electrospun polylactic acid (PLA) scaffold loaded with a synthetic DCF prodrug was developed and characterized. Specifically, the prodrug was successfully synthetized by binding DCF to a glycine residue via solid phase peptide synthesis (SPPS) and then incorporated in an electrospun PLA scaffold. The drug encapsulation was verified using multiphoton microscopy (MPM) and its scaffold release was spectrophotometrically monitored and confirmed with MPM. The scaffold was further characterized with scanning electron microscopy (SEM), tensile testing and contact angle measurements. Its biocompatibility was verified by performing a cell proliferation assay and compared to PLA scaffolds containing the same amount of DCF sodium salt (DCFONa). Finally, the effect of the electrospun scaffolds on human dermal fibroblasts (HDFs) morphology and metabolism was investigated by combining MPM with fluorescence lifetime imaging microscopy (FLIM). The obtained results suggest that the obtained scaffold could be suitable for the controlled and targeted delivery of the synthesized prodrug for the treatment of AKs. Electrospun scaffolds are of growing interest as materials for a controlled drug delivery. In this work, an electrospun polylactic acid scaffold containing a synthetically obtained Diclofenac prodrug is proposed as a novel substrate for the topical treatment of actinic keratosis. A controlled drug delivery targeted to the area of interest could enhance the efficacy of the therapy and favor the healing process. The prodrug was synthesized via solid phase, employing a clean and versatile approach to obtain Diclofenac derivatives. Here, we used multiphoton microscopy to image drug encapsulation within the fibrous scaffold and fluorescence lifetime imaging microscopy to investigate Diclofenac effects and potential mechanisms of action. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Chemical and morphological gradient scaffolds to mimic hierarchically complex tissues: From theoretical modeling to their fabrication.

PubMed

Marrella, Alessandra; Aiello, Maurizio; Quarto, Rodolfo; Scaglione, Silvia

2016-10-01

Porous multiphase scaffolds have been proposed in different tissue engineering applications because of their potential to artificially recreate the heterogeneous structure of hierarchically complex tissues. Recently, graded scaffolds have been also realized, offering a continuum at the interface among different phases for an enhanced structural stability of the scaffold. However, their internal architecture is often obtained empirically and the architectural parameters rarely predetermined. The aim of this work is to offer a theoretical model as tool for the design and fabrication of functional and structural complex graded scaffolds with predicted morphological and chemical features, to overcome the time-consuming trial and error experimental method. This developed mathematical model uses laws of motions, Stokes equations, and viscosity laws to describe the dependence between centrifugation speed and fiber/particles sedimentation velocity over time, which finally affects the fiber packing, and thus the total porosity of the 3D scaffolds. The efficacy of the theoretical model was tested by realizing engineered graded grafts for osteochondral tissue engineering applications. The procedure, based on combined centrifugation and freeze-drying technique, was applied on both polycaprolactone (PCL) and collagen-type-I (COL) to test the versatility of the entire process. A functional gradient was combined to the morphological one by adding hydroxyapatite (HA) powders, to mimic the bone mineral phase. Results show that 3D bioactive morphologically and chemically graded grafts can be properly designed and realized in agreement with the theoretical model. Biotechnol. Bioeng. 2016;113: 2286-2297. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Chlorite dismutases, DyPs, and EfeB: 3 microbial heme enzyme families comprise the CDE structural superfamily

PubMed Central

Goblirsch, Brandon; Kurker, Richard C.; Streit, Bennett R.; Wilmot, Carrie M.; DuBois, Jennifer L.

2011-01-01

Heme proteins are extremely diverse, widespread, and versatile biocatalysts, sensors, and molecular transporters. The chlorite dismutase family of hemoproteins received its name due to the ability of the first-isolated members to detoxify anthropogenic ClO2−, a function believed to have evolved only in the last few decades. Family members have since been found in fifteen bacterial and archaeal genera, suggesting ancient roots. A structure- and sequence-based examination of the family is presented, in which key sequence and structural motifs are identified and possible functions for family proteins are proposed. Newly identified structural homologies moreover demonstrate clear connections to two other large, ancient, and functionally mysterious protein families. We propose calling them collectively the CDE superfamily of heme proteins. PMID:21354424

Engineered Aptamers to Probe Molecular Interactions on the Cell Surface

PubMed Central

Batool, Sana; Bhandari, Sanam; George, Shanell; Okeoma, Precious; Van, Nabeela; Zümrüt, Hazan E.; Mallikaratchy, Prabodhika

2017-01-01

Significant progress has been made in understanding the nature of molecular interactions on the cell membrane. To decipher such interactions, molecular scaffolds can be engineered as a tool to modulate these events as they occur on the cell membrane. To guarantee reliability, scaffolds that function as modulators of cell membrane events must be coupled to a targeting moiety with superior chemical versatility. In this regard, nucleic acid aptamers are a suitable class of targeting moieties. Aptamers are inherently chemical in nature, allowing extensive site-specific chemical modification to engineer sensing molecules. Aptamers can be easily selected using a simple laboratory-based in vitro evolution method enabling the design and development of aptamer-based functional molecular scaffolds against wide range of cell surface molecules. This article reviews the application of aptamers as monitors and modulators of molecular interactions on the mammalian cell surface with the aim of increasing our understanding of cell-surface receptor response to external stimuli. The information gained from these types of studies could eventually prove useful in engineering improved medical diagnostics and therapeutics. PMID:28850067

A Scalable Perfusion Culture System with Miniature Peristaltic Pumps for Live-Cell Imaging Assays with Provision for Microfabricated Scaffolds

PubMed Central

Balakrishnan, Sreenath; Suma, M.S.; Raju, Shilpa R.; Bhargav, Santosh D.B.; Arunima, S.; Das, Saumitra

2015-01-01

Abstract We present a perfusion culture system with miniature bioreactors and peristaltic pumps. The bioreactors are designed for perfusion, live-cell imaging studies, easy incorporation of microfabricated scaffolds, and convenience of operation in standard cell culture techniques. By combining with miniature peristaltic pumps—one for each bioreactor to avoid cross-contamination and to maintain desired flow rate in each—we have made a culture system that facilitates perfusion culture inside standard incubators. This scalable system can support multiple parallel perfusion experiments. The major components are fabricated by three-dimensional printing using VeroWhite, which we show to be amenable to ex vivo cell culture. Furthermore, the components of the system can be reused, thus making it economical. We validate the system and illustrate its versatility by culturing primary rat hepatocytes, live imaging the growth of mouse fibroblasts (NIH 3T3) on microfabricated ring-scaffolds inserted into the bioreactor, performing perfusion culture of breast cancer cells (MCF7), and high-magnification imaging of hepatocarcinoma cells (HuH7). PMID:26309810

Polydopamine-mediated surface modification of scaffold materials for human neural stem cell engineering.

PubMed

Yang, Kisuk; Lee, Jung Seung; Kim, Jin; Lee, Yu Bin; Shin, Heungsoo; Um, Soong Ho; Kim, Jeong Beom; Park, Kook In; Lee, Haeshin; Cho, Seung-Woo

2012-10-01

Surface modification of tissue engineering scaffolds and substrates is required for improving the efficacy of stem cell therapy by generating physicochemical stimulation promoting proliferation and differentiation of stem cells. However, typical surface modification methods including chemical conjugation or physical absorption have several limitations such as multistep, complicated procedures, surface denaturation, batch-to-batch inconsistencies, and low surface conjugation efficiency. In this study, we report a mussel-inspired, biomimetic approach to surface modification for efficient and reliable manipulation of human neural stem cell (NSC) differentiation and proliferation. Our study demonstrates that polydopamine coating facilitates highly efficient, simple immobilization of neurotrophic growth factors and adhesion peptides onto polymer substrates. The growth factor or peptide-immobilized substrates greatly enhance differentiation and proliferation of human NSCs (human fetal brain-derived NSCs and human induced pluripotent stem cell-derived NSCs) at a level comparable or greater than currently available animal-derived coating materials (Matrigel) with safety issues. Therefore, polydopamine-mediated surface modification can provide a versatile platform technology for developing chemically defined, safe, functional substrates and scaffolds for therapeutic applications of human NSCs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multifaceted Applications of Chitosan in Cancer Drug Delivery and Therapy.

PubMed

Babu, Anish; Ramesh, Rajagopal

2017-03-27

Chitosan is a versatile polysaccharide of biological origin. Due to the biocompatible and biodegradable nature of chitosan, it is intensively utilized in biomedical applications in scaffold engineering as an absorption enhancer, and for bioactive and controlled drug release. In cancer therapy, chitosan has multifaceted applications, such as assisting in gene delivery and chemotherapeutic delivery, and as an immunoadjuvant for vaccines. The present review highlights the recent applications of chitosan and chitosan derivatives in cancer therapy.

Multifaceted Applications of Chitosan in Cancer Drug Delivery and Therapy

PubMed Central

Babu, Anish; Ramesh, Rajagopal

2017-01-01

Chitosan is a versatile polysaccharide of biological origin. Due to the biocompatible and biodegradable nature of chitosan, it is intensively utilized in biomedical applications in scaffold engineering as an absorption enhancer, and for bioactive and controlled drug release. In cancer therapy, chitosan has multifaceted applications, such as assisting in gene delivery and chemotherapeutic delivery, and as an immunoadjuvant for vaccines. The present review highlights the recent applications of chitosan and chitosan derivatives in cancer therapy. PMID:28346381

Recent advance in the pharmacology of dihydropyrimidinone.

PubMed

Wan, J-P; Pan, Y

2012-04-01

Dihydropyrimidinones (DHPMs) are a series of highly valuable small molecules possessing versatile pharmaceutical properties. Although the first one-pot synthesis of DHPMs had been reported more than 100 years ago, the fascinating achievement in DHPMs-based pharmacology during the past century promoted durative interests to the pharmacological and related studies of the scaffold, which lead to the discovery of many new biological functions of DHPMs. Recent pharmacological development on DHPMs-based molecules have been summarized in this review.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells.

PubMed

Yeh, Chia-Hung; Chen, Yi-Wen; Shie, Ming-You; Fang, Hsin-Yuan

2015-07-14

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs' responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells

PubMed Central

Yeh, Chia-Hung; Chen, Yi-Wen; Shie, Ming-You; Fang, Hsin-Yuan

2015-01-01

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs’ responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs. PMID:28793441

Poly(dopamine) coating of 3D printed poly(lactic acid) scaffolds for bone tissue engineering.

PubMed

Kao, Chia-Tze; Lin, Chi-Chang; Chen, Yi-Wen; Yeh, Chia-Hung; Fang, Hsin-Yuan; Shie, Ming-You

2015-11-01

3D printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating to regulate cell adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared PLA 3D scaffolds coated with polydopamine (PDA). The chemical composition and surface properties of PDA/PLA were characterized by XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation, and cell cycle of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. In addition, the collagen I secreted from cells was increased and promoted cell attachment and cell cycle progression were depended on the PDA content. In osteogenesis assay, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on pure PLA scaffolds. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hADSCs. Copyright © 2015 Elsevier B.V. All rights reserved.

Braided nanofibrous scaffold for tendon and ligament tissue engineering.

PubMed

Barber, John G; Handorf, Andrew M; Allee, Tyler J; Li, Wan-Ju

2013-06-01

Tendon and ligament (T/L) injuries present an important clinical challenge due to their intrinsically poor healing capacity. Natural healing typically leads to the formation of scar-like tissue possessing inferior mechanical properties. Therefore, tissue engineering has gained considerable attention as a promising alternative for T/L repair. In this study, we fabricated braided nanofibrous scaffolds (BNFSs) as a potential construct for T/L tissue engineering. Scaffolds were fabricated by braiding 3, 4, or 5 aligned bundles of electrospun poly(L-lactic acid) nanofibers, thus introducing an additional degree of flexibility to alter the mechanical properties of individual scaffolds. We observed that the Young's modulus, yield stress, and ultimate stress were all increased in the 3-bundle compared to the 4- and 5-bundle BNFSs. Interestingly, acellular BNFSs mimicked the normal tri-phasic mechanical behavior of native tendon and ligament (T/L) during loading. When cultured on the BNFSs, human mesenchymal stem cells (hMSCs) adhered, aligned parallel to the length of the nanofibers, and displayed a concomitant realignment of the actin cytoskeleton. In addition, the BNFSs supported hMSC proliferation and induced an upregulation in the expression of key pluripotency genes. When cultured on BNFSs in the presence of tenogenic growth factors and stimulated with cyclic tensile strain, hMSCs differentiated into the tenogenic lineage, evidenced most notably by the significant upregulation of Scleraxis gene expression. These results demonstrate that BNFSs provide a versatile scaffold capable of supporting both stem cell expansion and differentiation for T/L tissue engineering applications.

Benzomorphan skeleton, a versatile scaffold for different targets: A comprehensive review.

PubMed

Turnaturi, Rita; Montenegro, Lucia; Marrazzo, Agostino; Parenti, Rosalba; Pasquinucci, Lorella; Parenti, Carmela

2018-06-07

Despite the fact that the benzomorphan skeleton has mainly been employed in medicinal chemistry for the development of opioid analgesics, it is a versatile structure. Its stereochemistry, as well as opportune modifications at the phenolic hydroxyl group and at the basic nitrogen, play a pivotal role addressing the benzomorphan-based compounds to a specific target. In this review, we describe the structure activity-relationships (SARs) of benzomorphan-based compounds acting at sigma 1 receptor (σ1R), sigma 2 receptor (σ2R), voltage-dependent sodium channel, N-Methyl-d-Aspartate (NMDA) receptor-channel complex and other targets. Collectively, the SARs data have highlighted that the benzomorphan nucleus could be regarded as a useful template for the synthesis of drug candidates for different targets. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Foamed oligo(poly(ethylene glycol)fumarate) hydrogels as versatile prefabricated scaffolds for tissue engineering.

PubMed

Henke, Matthias; Baumer, Julia; Blunk, Torsten; Tessmar, Joerg

2014-03-01

Radically cross-linked hydrogels are frequently used as cell carriers due to their excellent biocompatibility and their tissue-like mechanical properties. Through frequent investigation, PEG-based polymers such as oligo(poly(ethylene glycol)fumarate [OPF] have proven to be especially suitable as cell carriers by encapsulating cells during hydrogel formation. In some cases, NaCl or biodegradable gelatin microparticles were added prior to cross-linking in order to provide space for the proliferating cells, which would otherwise stay embedded in the hydrogel matrix. However, all of these immediate cross-linking procedures involve time consuming sample preparation and sterilization directly before cell culture and often show notable swelling after their preparation. In this study, ready to use OPF-hydrogel scaffolds were prepared by gas foaming, freeze drying, individual packing into bags and subsequent γ-sterilization. The scaffolds could be stored and used "off-the-shelf" without any need for further processing prior to cell culture. Thus the handling was simplified and the sterility of the cell carrier was assured. Further improvement of the gel system was achieved using a two component injectable system, which may be used for homogenous injection molding in order to create individually shaped three dimensional scaffolds. In order to evaluate the suitability of the scaffolds for tissue engineering, constructs were seeded with juvenile bovine chondrocytes and cultured for 28 days. Cross-sections of the respective constructs showed an intense and homogenous red staining of GAG with safranin O, indicating a homogenous cell distribution within the scaffolds and the production of substantial amounts of GAG-rich matrix. Copyright © 2012 John Wiley & Sons, Ltd.

A versatile fabrication strategy of three-dimensional foams for soft and hard tissue engineering.

PubMed

Xu, Changlu; Bai, Yanjie; Yang, Shaofeng; Yang, Huilin; Stout, David A; Tran, Phong; Yang, Lei

2017-12-15

The fabrication strategies of three-dimensional porous biomaterials have been extensively studied and well established in the past decades, yet the biocompatibility and versatility in preparing porous architecture still lacks. Herewith, we present a novel and green fabrication technique of 3D porous foams for both soft and hard engineering. By utilizing the gelatinization and retrogradation property of starches, stabilized porous constructs made of various building blocks from living cells to ceramic particles were created for the first time. In soft tissue engineering applications, 3D cultured tissue foam (CTF) with controlled release property of cells was developed and the foams constituted by osteoblasts, fibroblasts and vascular endothelial cells all exhibited high mechanical stability and preservation of cell viability or functions. More importantly, the CTF achieved sustained self-release of cells controlled by serum (containing amylase) concentration and the released cells also maintained high viability and functions. In the context of hard tissue engineering applications, ceramic/bioglass (BG) foam scaffolds were developed by the similar starch-assisted foaming strategy where the resultant bone scaffolds of hydroxyapatite (HA)/BG and Si3N4/BG possessed>70% porosity with interconnected macropores (sizes 200~400μm) and fine pores (sizes1~10 μm) and superior mechanical properties despite the high porosity. Additionally, in vitro and in vivo evaluations on the biological properties revealed that porous HA/BG foam exhibited desired biocompatibility and osteogenesis. The in vivo study indicated new bone ingrowth after 1 week and significant increases in new bone volume after 2 weeks. In conclusion, the presented foaming strategy provides opportunities for biofabricating CTF with different cells for different target soft tissues and preparing porous ceramic/BG foams with different material components and high strengths-showing great versatility in soft and hard tissue engineering. © 2017 IOP Publishing Ltd.

Programming Self-Assembly of DNA Origami Honeycomb Two-Dimensional Lattices and Plasmonic Metamaterials.

PubMed

Wang, Pengfei; Gaitanaros, Stavros; Lee, Seungwoo; Bathe, Mark; Shih, William M; Ke, Yonggang

2016-06-22

Scaffolded DNA origami has proven to be a versatile method for generating functional nanostructures with prescribed sub-100 nm shapes. Programming DNA-origami tiles to form large-scale 2D lattices that span hundreds of nanometers to the micrometer scale could provide an enabling platform for diverse applications ranging from metamaterials to surface-based biophysical assays. Toward this end, here we design a family of hexagonal DNA-origami tiles using computer-aided design and demonstrate successful self-assembly of micrometer-scale 2D honeycomb lattices and tubes by controlling their geometric and mechanical properties including their interconnecting strands. Our results offer insight into programmed self-assembly of low-defect supra-molecular DNA-origami 2D lattices and tubes. In addition, we demonstrate that these DNA-origami hexagon tiles and honeycomb lattices are versatile platforms for assembling optical metamaterials via programmable spatial arrangement of gold nanoparticles (AuNPs) into cluster and superlattice geometries.

Privileged scaffolds or promiscuous binders: a glance of pyrrolo[2,1-f][1,2,4]triazines and related bridgehead nitrogen heterocycles in medicinal chemistry.

PubMed

Song, Yu'ning; Zhan, Peng; Zhang, Qingzhu; Liu, Xinyong

2013-01-01

Pyrrolo[2,1-f][1,2,4]triazine template, a unique bridgehead nitrogen heterocycle, certainly deserves the title of "privileged scaffold" in the drug discovery field because of the versatility and potential to yield derivatives with a wide range of biological activities, such as anti-anaplastic lymphoma kinase (ALK), Janus kinase 2 (JAK2), VEGFR-2, EGFR and/or HER2, Met kinase, p38α mitogen-activated protein (MAP) kinase and insulin-like growth factor receptor (IGF-1R) kinase activities, etc. These different biological properties of pyrrolo[2,1-f][1,2,4]triazine derivatives have motivated new studies in searching for novel derivatives with improved activity and also other applications in pharmaceutical field. However, no systematic review is available in the literature on the pyrrolo[2,1- f][1,2,4]triazine derivatives concerning the design of potent drug-like compounds. Owing to the importance of this heterocyclic system, the present paper is an attempt to the pharmacological activities, structural modifications and the structure-activity relationship (SAR) reported for bridgehead nitrogen heterocycles in the current literature, making an effort to highlight the importance and therapeutic potentials of the pyrrolo[2,1-f][1,2,4]triazine scaffold and its bridgehead nitrogen bioisosters as heterocyclic privileged medicinal scaffolds.

Polymorphic design of DNA origami structures through mechanical control of modular components.

PubMed

Lee, Chanseok; Lee, Jae Young; Kim, Do-Nyun

2017-12-12

Scaffolded DNA origami enables the bottom-up fabrication of diverse DNA nanostructures by designing hundreds of staple strands, comprised of complementary sequences to the specific binding locations of a scaffold strand. Despite its exceptionally high design flexibility, poor reusability of staples has been one of the major hurdles to fabricate assorted DNA constructs in an effective way. Here we provide a rational module-based design approach to create distinct bent shapes with controllable geometries and flexibilities from a single, reference set of staples. By revising the staple connectivity within the desired module, we can control the location, stiffness, and included angle of hinges precisely, enabling the construction of dozens of single- or multiple-hinge structures with the replacement of staple strands up to 12.8% only. Our design approach, combined with computational shape prediction and analysis, can provide a versatile and cost-effective procedure in the design of DNA origami shapes with stiffness-tunable units.

Nucleic Acid-Based Nanodevices in Biological Imaging.

PubMed

Chakraborty, Kasturi; Veetil, Aneesh T; Jaffrey, Samie R; Krishnan, Yamuna

2016-06-02

The nanoscale engineering of nucleic acids has led to exciting molecular technologies for high-end biological imaging. The predictable base pairing, high programmability, and superior new chemical and biological methods used to access nucleic acids with diverse lengths and in high purity, coupled with computational tools for their design, have allowed the creation of a stunning diversity of nucleic acid-based nanodevices. Given their biological origin, such synthetic devices have a tremendous capacity to interface with the biological world, and this capacity lies at the heart of several nucleic acid-based technologies that are finding applications in biological systems. We discuss these diverse applications and emphasize the advantage, in terms of physicochemical properties, that the nucleic acid scaffold brings to these contexts. As our ability to engineer this versatile scaffold increases, its applications in structural, cellular, and organismal biology are clearly poised to massively expand.

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

NASA Astrophysics Data System (ADS)

Naseem, Raasti; Zhao, Liguo; Liu, Yang; Silberschmidt, Vadim V.

2017-12-01

Stents are commonly used in medical procedures to alleviate the symptoms of coronary heart disease, a prevalent modern society disease. These structures are employed to maintain vessel patency and restore blood flow. Traditionally stents are made of metals such as stainless steel or cobalt chromium; however, these scaffolds have known disadvantages. An emergence of transient scaffolds is gaining popularity, with the structure engaged for a required period whilst healing of the diseased arterial wall occurs. Polymers dominate a medical device sector, with incorporation in sutures, scaffolds and screws. Thanks to their good mechanical and biological properties and their ability to degrade naturally. Polylactic acid is an extremely versatile polymer, with its properties easily tailored to applications. Its dominance in the stenting field increases continually, with the first polymer scaffold gaining FDA approval in 2016. Still some challenges with PLLA bioresorbable materials remain, especially with regard to understanding their mechanical response, assessment of its changes with degradation and comparison of their performance with that of metallic drug-eluting stent. Currently, there is still a lack of works on evaluating both the pre-degradation properties and degradation performance of these scaffolds. Additionally, there are no established material models incorporating non-linear viscoelastic behaviour of PLLA and its evolution with in-service degradation. Assessing these features through experimental analysis accompanied by analytical and numerical studies will provide powerful tools for design and optimisation of these structures endorsing their broader use in stenting. This overview assesses the recent studies investigating mechanical and computational performance of poly(l-lactic) acid and its use in stenting applications.

An ancient protein-DNA interaction underlying metazoan sex determination.

PubMed

Murphy, Mark W; Lee, John K; Rojo, Sandra; Gearhart, Micah D; Kurahashi, Kayo; Banerjee, Surajit; Loeuille, Guy-André; Bashamboo, Anu; McElreavey, Kenneth; Zarkower, David; Aihara, Hideki; Bardwell, Vivian J

2015-06-01

DMRT transcription factors are deeply conserved regulators of metazoan sexual development. They share the DM DNA-binding domain, a unique intertwined double zinc-binding module followed by a C-terminal recognition helix, which binds a pseudopalindromic target DNA. Here we show that DMRT proteins use a unique binding interaction, inserting two adjacent antiparallel recognition helices into a widened DNA major groove to make base-specific contacts. Versatility in how specific base contacts are made allows human DMRT1 to use multiple DNA binding modes (tetramer, trimer and dimer). Chromatin immunoprecipitation with exonuclease treatment (ChIP-exo) indicates that multiple DNA binding modes also are used in vivo. We show that mutations affecting residues crucial for DNA recognition are associated with an intersex phenotype in flies and with male-to-female sex reversal in humans. Our results illuminate an ancient molecular interaction underlying much of metazoan sexual development.

An ancient protein-DNA interaction underlying metazoan sex determination

DOE PAGES

Murphy, Mark W.; Lee, John K.; Rojo, Sandra; ...

2015-05-25

DMRT transcription factors are deeply conserved regulators of metazoan sexual development. They share the DM DNA-binding domain, a unique intertwined double zinc-binding module followed by a C-terminal recognition helix, which binds a pseudopalindromic target DNA. In this paper, we show that DMRT proteins use a unique binding interaction, inserting two adjacent antiparallel recognition helices into a widened DNA major groove to make base-specific contacts. Versatility in how specific base contacts are made allows human DMRT1 to use multiple DNA binding modes (tetramer, trimer and dimer). Chromatin immunoprecipitation with exonuclease treatment (ChIP-exo) indicates that multiple DNA binding modes also are usedmore » in vivo. We show that mutations affecting residues crucial for DNA recognition are associated with an intersex phenotype in flies and with male-to-female sex reversal in humans. Finally, our results illuminate an ancient molecular interaction underlying much of metazoan sexual development.« less

An ancient protein-DNA interaction underlying metazoan sex determination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, Mark W.; Lee, John K.; Rojo, Sandra

DMRT transcription factors are deeply conserved regulators of metazoan sexual development. They share the DM DNA-binding domain, a unique intertwined double zinc-binding module followed by a C-terminal recognition helix, which binds a pseudopalindromic target DNA. In this paper, we show that DMRT proteins use a unique binding interaction, inserting two adjacent antiparallel recognition helices into a widened DNA major groove to make base-specific contacts. Versatility in how specific base contacts are made allows human DMRT1 to use multiple DNA binding modes (tetramer, trimer and dimer). Chromatin immunoprecipitation with exonuclease treatment (ChIP-exo) indicates that multiple DNA binding modes also are usedmore » in vivo. We show that mutations affecting residues crucial for DNA recognition are associated with an intersex phenotype in flies and with male-to-female sex reversal in humans. Finally, our results illuminate an ancient molecular interaction underlying much of metazoan sexual development.« less

Fabrication of novel high surface area mushroom gilled fibers and their effects on human adipose derived stem cells under pulsatile fluid flow for tissue engineering applications.

PubMed

Tuin, Stephen A; Pourdeyhimi, Behnam; Loboa, Elizabeth G

2016-05-01

The fabrication and characterization of novel high surface area hollow gilled fiber tissue engineering scaffolds via industrially relevant, scalable, repeatable, high speed, and economical nonwoven carding technology is described. Scaffolds were validated as tissue engineering scaffolds using human adipose derived stem cells (hASC) exposed to pulsatile fluid flow (PFF). The effects of fiber morphology on the proliferation and viability of hASC, as well as effects of varied magnitudes of shear stress applied via PFF on the expression of the early osteogenic gene marker runt related transcription factor 2 (RUNX2) were evaluated. Gilled fiber scaffolds led to a significant increase in proliferation of hASC after seven days in static culture, and exhibited fewer dead cells compared to pure PLA round fiber controls. Further, hASC-seeded scaffolds exposed to 3 and 6dyn/cm(2) resulted in significantly increased mRNA expression of RUNX2 after one hour of PFF in the absence of soluble osteogenic induction factors. This is the first study to describe a method for the fabrication of high surface area gilled fibers and scaffolds. The scalable manufacturing process and potential fabrication across multiple nonwoven and woven platforms makes them promising candidates for a variety of applications that require high surface area fibrous materials. We report here for the first time the successful fabrication of novel high surface area gilled fiber scaffolds for tissue engineering applications. Gilled fibers led to a significant increase in proliferation of human adipose derived stem cells after one week in culture, and a greater number of viable cells compared to round fiber controls. Further, in the absence of osteogenic induction factors, gilled fibers led to significantly increased mRNA expression of an early marker for osteogenesis after exposure to pulsatile fluid flow. This is the first study to describe gilled fiber fabrication and their potential for tissue engineering applications. The repeatable, industrially scalable, and versatile fabrication process makes them promising candidates for a variety of scaffold-based tissue engineering applications. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Moldable elastomeric polyester-carbon nanotube scaffolds for cardiac tissue engineering.

PubMed

Ahadian, Samad; Davenport Huyer, Locke; Estili, Mehdi; Yee, Bess; Smith, Nathaniel; Xu, Zhensong; Sun, Yu; Radisic, Milica

2017-04-01

Polymer biomaterials are used to construct scaffolds in tissue engineering applications to assist in mechanical support, organization, and maturation of tissues. Given the flexibility, electrical conductance, and contractility of native cardiac tissues, it is desirable that polymeric scaffolds for cardiac tissue regeneration exhibit elasticity and high electrical conductivity. Herein, we developed a facile approach to introduce carbon nanotubes (CNTs) into poly(octamethylene maleate (anhydride) 1,2,4-butanetricarboxylate) (124 polymer), and developed an elastomeric scaffold for cardiac tissue engineering that provides electrical conductivity and structural integrity to 124 polymer. 124 polymer-CNT materials were developed by first dispersing CNTs in poly(ethylene glycol) dimethyl ether porogen and mixing with 124 prepolymer for molding into shapes and crosslinking under ultraviolet light. 124 polymers with 0.5% and 0.1% CNT content (wt) exhibited improved conductivity against pristine 124 polymer. With increasing the CNT content, surface moduli of hybrid polymers were increased, while their bulk moduli were decreased. Furthermore, increased swelling of hybrid 124 polymer-CNT materials was observed, suggesting their improved structural support in an aqueous environment. Finally, functional characterization of engineered cardiac tissues using the 124 polymer-CNT scaffolds demonstrated improved excitation threshold in materials with 0.5% CNT content (3.6±0.8V/cm) compared to materials with 0% (5.1±0.8V/cm) and 0.1% (5.0±0.7V/cm), suggesting greater tissue maturity. 124 polymer-CNT materials build on the advantages of 124 polymer elastomer to give a versatile biomaterial for cardiac tissue engineering applications. Achieving a high elasticity and a high conductivity in a single cardiac tissue engineering material remains a challenge. We report the use of CNTs in making electrically conductive and mechanically strong polymeric scaffolds in cardiac tissue regeneration. CNTs were incorporated in elastomeric polymers in a facile and reproducible approach. Polymer-CNT materials were able to construct complicated scaffold structures by injecting the prepolymer into a mold and crosslinking the prepolymer under ultraviolet light. CNTs enhanced electrical conductivity and structural support of elastomeric polymers. Hybrid polymeric scaffolds containing 0.5wt% CNTs increased the maturation of cardiac tissues fabricated on them compared to pure polymeric scaffolds. The cardiac tissues on hybrid polymer-CNT scaffolds showed earlier beating than those on pure polymer scaffolds. In the future, fabricated polymer-CNT scaffolds could also be used to fabricate other electro-active tissues, such neural and skeletal muscle tissues. In the future, fabricated polymer-CNT scaffolds could also be used to fabricate other electro-active tissues, such as neural and skeletal muscle tissues. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Brominated Luciferins Are Versatile Bioluminescent Probes

DOE PAGES

Steinhardt, Rachel C.; Rathbun, Colin M.; Krull, Brandon T.; ...

2016-12-08

Here, we report a set of brominated luciferins for bioluminescence imaging. These regioisomeric scaffolds were accessed by using a common synthetic route. All analogues produced light with firefly luciferase, although varying levels of emission were observed. Differences in photon output were analyzed by computation and photophysical measurements. The brightest brominated luciferin was further evaluated in cell and animal models. At low doses, the analogue outperformed the native substrate in cells. The remaining luciferins, although weak emitters with firefly luciferase, were inherently capable of light production and thus potential substrates for orthogonal mutant enzymes.

Extending the Compositional Range of Nanocasting in the Oxozirconium Cluster-Based Metal–Organic Framework NU-1000—A Comparative Structural Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Wenyang; Wang, Zhao; Malonzo, Camille D.

The process of nanocasting in metal-organic frameworks (MOFs) is a versatile approach to modify these porous materials by introducing supporting scaffolds. The nanocast scaffolds can stabilize metal-oxo clusters in MOFs at high temperatures and modulate their chemical environments. Here we demonstrate a range of nanocasting approaches in the MOF NU-1000, which contains hexanuclear oxozirconium clusters (denoted as Zr6 clusters) that are suitable for modification with other metals. We developed methods for introducing SiO2, TiO2, polymeric, and carbon scaffolds into the NU-1000 structure. The responses of NU-1000 towards different scaffold precursors were studied, including the effects on morphology, precursor distribution, andmore » porosity after nanocasting. Upon removal of organic linkers in the MOF by calcination/pyrolysis at 500 °C or above, the Zr6 clusters remained accessible and maintained their Lewis acidity in SiO2 nanocast samples, whereas additional treatment was necessary for Zr6 clusters to become accessible in carbon nanocast samples. Aggregation of Zr6 clusters was largely prevented with SiO2 or carbon scaffolds even after thermal treatment at 500 °C or above. In the case of titania nanocasting, NU- 1000 crystals underwent a pseudomorphic transformation, in which Zr6 clusters reacted with titania to form small oxaggregates of a Zr/Ti mixed oxide with a local structure resembling that of ZrTi2O6. The ability to maintain high densities of discrete Lewis acidic Zr6 clusters on SiO2 or carbon supports at high temperatures provides a starting point for designing new thermally stable catalysts.« less

Immobilization of FLAG-Tagged Recombinant Adeno-Associated Virus 2 onto Tissue Engineering Scaffolds for the Improvement of Transgene Delivery in Cell Transplants.

PubMed

Li, Hua; Zhang, Feng-Lan; Shi, Wen-Jie; Bai, Xue-Jia; Jia, Shu-Qin; Zhang, Chen-Guang; Ding, Wei

2015-01-01

The technology of virus-based genetic modification in tissue engineering has provided the opportunity to produce more flexible and versatile biomaterials for transplantation. Localizing the transgene expression with increased efficiency is critical for tissue engineering as well as a challenge for virus-based gene delivery. In this study, we tagged the VP2 protein of type 2 adeno-associated virus (AAV) with a 3×FLAG plasmid at the N-terminus and packaged a FLAG-tagged recombinant AAV2 chimeric mutant. The mutant AAVs were immobilized onto the tissue engineering scaffolds with crosslinked anti-FLAG antibodies by N-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP). Cultured cells were seeded to scaffolds to form 3D transplants, and then tested for viral transduction both in vitro and in vivo. The results showed that our FLAG-tagged AAV2 exerted similar transduction efficiency compared with the wild type AAV2 when infected cultured cells. Following immobilization onto the scaffolds of PLGA or gelatin sponge with anti-FLAG antibodies, the viral mediated transgene expression was significantly improved and more localized. Our data demonstrated that the mutation of AAV capsid targeted for antibody-based immobilization could be a practical approach for more efficient and precise transgene delivery. It was also suggested that the immobilization of AAV might have attractive potentials in applications of tissue engineering involving the targeted gene manipulation in 3D tissue cultures.

Targeting diverse protein–protein interaction interfaces with α/β-peptides derived from the Z-domain scaffold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Checco, James W.; Kreitler, Dale F.; Thomas, Nicole C.

Peptide-based agents derived from well-defined scaffolds offer an alternative to antibodies for selective and high-affinity recognition of large and topologically complex protein surfaces. In this paper, we describe a strategy for designing oligomers containing both α- and β-amino acid residues (“α/β-peptides”) that mimic several peptides derived from the three-helix bundle “Z-domain” scaffold. We show that α/β-peptides derived from a Z-domain peptide targeting vascular endothelial growth factor (VEGF) can structurally and functionally mimic the binding surface of the parent peptide while exhibiting significantly decreased susceptibility to proteolysis. The tightest VEGF-binding α/β-peptide inhibits the VEGF 165-induced proliferation of human umbilical vein endothelialmore » cells. We demonstrate the versatility of this strategy by showing how principles underlying VEGF signaling inhibitors can be rapidly extended to produce Z-domain–mimetic α/β-peptides that bind to two other protein partners, IgG and tumor necrosis factor-α. Because well-established selection techniques can identify high-affinity Z-domain derivatives from large DNA-encoded libraries, our findings should enable the design of biostable α/β-peptides that bind tightly and specifically to diverse targets of biomedical interest. Finally, such reagents would be useful for diagnostic and therapeutic applications.« less

Additive manufacturing of scaffolds with dexamethasone controlled release for enhanced bone regeneration.

PubMed

Costa, Pedro F; Puga, Ana M; Díaz-Gomez, Luis; Concheiro, Angel; Busch, Dirk H; Alvarez-Lorenzo, Carmen

2015-12-30

The adoption of additive manufacturing in tissue engineering and regenerative medicine (TERM) strategies greatly relies on the development of novel 3D printable materials with advanced properties. In this work we have developed a material for bone TERM applications with tunable bioerosion rate and dexamethasone release profile which can be further employed in fused deposition modelling (the most common and accessible 3D printing technology in the market). The developed material consisted of a blend of poly-ϵ-caprolactone (PCL) and poloxamine (Tetronic®) and was processed into a ready-to-use filament form by means of a simplified melt-based methodology, therefore eliminating the utilization of solvents. 3D scaffolds composed of various blend formulations were additively manufactured and analyzed revealing blend ratio-specific degradation rates and dexamethasone release profiles. Furthermore, in vitro culture studies revealed a similar blend ratio-specific trend concerning the osteoinductive activity of the fabricated scaffolds when these were seeded and cultured with human mesenchymal stem cells. The developed material enables to specifically address different regenerative requirements found in various tissue defects. The versatility of such strategy is further increased by the ability of additive manufacturing to accurately fabricate implants matching any given defect geometry. Copyright © 2015 Elsevier B.V. All rights reserved.

Targeting diverse protein–protein interaction interfaces with α/β-peptides derived from the Z-domain scaffold

DOE PAGES

Checco, James W.; Kreitler, Dale F.; Thomas, Nicole C.; ...

2015-03-30

Peptide-based agents derived from well-defined scaffolds offer an alternative to antibodies for selective and high-affinity recognition of large and topologically complex protein surfaces. In this paper, we describe a strategy for designing oligomers containing both α- and β-amino acid residues (“α/β-peptides”) that mimic several peptides derived from the three-helix bundle “Z-domain” scaffold. We show that α/β-peptides derived from a Z-domain peptide targeting vascular endothelial growth factor (VEGF) can structurally and functionally mimic the binding surface of the parent peptide while exhibiting significantly decreased susceptibility to proteolysis. The tightest VEGF-binding α/β-peptide inhibits the VEGF 165-induced proliferation of human umbilical vein endothelialmore » cells. We demonstrate the versatility of this strategy by showing how principles underlying VEGF signaling inhibitors can be rapidly extended to produce Z-domain–mimetic α/β-peptides that bind to two other protein partners, IgG and tumor necrosis factor-α. Because well-established selection techniques can identify high-affinity Z-domain derivatives from large DNA-encoded libraries, our findings should enable the design of biostable α/β-peptides that bind tightly and specifically to diverse targets of biomedical interest. Finally, such reagents would be useful for diagnostic and therapeutic applications.« less

Selective hydrophilic modification of Parylene C films: a new approach to cell micro-patterning for synthetic biology applications.

PubMed

Trantidou, T; Rao, C; Barrett, H; Camelliti, P; Pinto, K; Yacoub, M H; Athanasiou, T; Toumazou, C; Terracciano, C M; Prodromakis, T

2014-06-01

We demonstrate a simple, accurate and versatile method to manipulate Parylene C, a material widely known for its high biocompatibility, and transform it to a substrate that can effectively control the cellular microenvironment and consequently affect the morphology and function of the cells in vitro. The Parylene C scaffolds are fabricated by selectively increasing the material's surface water affinity through lithography and oxygen plasma treatment, providing free bonds for attachment of hydrophilic biomolecules. The micro-engineered constructs were tested as culture scaffolds for rat ventricular fibroblasts and neonatal myocytes (NRVM), toward modeling the unique anisotropic architecture of native cardiac tissue. The scaffolds induced the patterning of extracellular matrix compounds and therefore of the cells, which demonstrated substantial alignment compared to typical unstructured cultures. Ca(2+) cycling properties of the NRVM measured at rates of stimulation 0.5-2 Hz were significantly modified with a shorter time to peak and time to 90% decay, and a larger fluorescence amplitude (p < 0.001). The proposed technique is compatible with standard cell culturing protocols and exhibits long-term pattern durability. Moreover, it allows the integration of monitoring modalities into the micro-engineered substrates for a comprehensive interrogation of physiological parameters.

Fluorescent microparticles for sensing cell microenvironment oxygen levels within 3D scaffolds.

PubMed

Acosta, Miguel A; Ymele-Leki, Patrick; Kostov, Yordan V; Leach, Jennie B

2009-06-01

We present the development and characterization of fluorescent oxygen-sensing microparticles designed for measuring oxygen concentration in microenvironments existing within standard cell culture and transparent three-dimensional (3D) cell scaffolds. The microparticle synthesis employs poly(dimethylsiloxane) to encapsulate silica gel particles bound with an oxygen-sensitive luminophore as well as a reference or normalization fluorophore that is insensitive to oxygen. We developed a rapid, automated and non-invasive sensor analysis method based on fluorescence microscopy to measure oxygen concentration in a hydrogel scaffold. We demonstrate that the microparticles are non-cytotoxic and that their response is comparable to that of a traditional dissolved oxygen meter. Microparticle size (5-40 microm) was selected for microscale-mapping of oxygen concentration to allow measurements local to individual cells. Two methods of calibration were evaluated and revealed that the sensor system enables characterization of a range of hypoxic to hyperoxic conditions relevant to cell and tissue biology (i.e., pO(2) 10-160 mmHg). The calibration analysis also revealed that the microparticles have a high fraction of quenched luminophore (0.90+/-0.02), indicating that the reported approach provides significant advantages for sensor performance. This study thus reports a versatile oxygen-sensing technology that enables future correlations of local oxygen concentration with individual cell response in cultured engineered tissues.

A simple and versatile design concept for fluorophore derivatives with intramolecular photostabilization

NASA Astrophysics Data System (ADS)

van der Velde, Jasper H. M.; Oelerich, Jens; Huang, Jingyi; Smit, Jochem H.; Aminian Jazi, Atieh; Galiani, Silvia; Kolmakov, Kirill; Guoridis, Giorgos; Eggeling, Christian; Herrmann, Andreas; Roelfes, Gerard; Cordes, Thorben

2016-01-01

Intramolecular photostabilization via triple-state quenching was recently revived as a tool to impart synthetic organic fluorophores with `self-healing' properties. To date, utilization of such fluorophore derivatives is rare due to their elaborate multi-step synthesis. Here we present a general strategy to covalently link a synthetic organic fluorophore simultaneously to a photostabilizer and biomolecular target via unnatural amino acids. The modular approach uses commercially available starting materials and simple chemical transformations. The resulting photostabilizer-dye conjugates are based on rhodamines, carbopyronines and cyanines with excellent photophysical properties, that is, high photostability and minimal signal fluctuations. Their versatile use is demonstrated by single-step labelling of DNA, antibodies and proteins, as well as applications in single-molecule and super-resolution fluorescence microscopy. We are convinced that the presented scaffolding strategy and the improved characteristics of the conjugates in applications will trigger the broader use of intramolecular photostabilization and help to emerge this approach as a new gold standard.

Nanosilver: new ageless and versatile biomedical therapeutic scaffold

PubMed Central

Ullah Khan, Shahid; Khan, Muhammad Hafeez Ullah; Khan, Dilfaraz; Ullah Khan, Wasim; Rahim, Abdur; Kamal, Sajid; Ullah Khan, Farman; Fahad, Shah

2018-01-01

Silver nanotechnology has received tremendous attention in recent years, owing to its wide range of applications in various fields and its intrinsic therapeutic properties. In this review, an attempt is made to critically evaluate the chemical, physical, and biological synthesis of silver nanoparticles (AgNPs) as well as their efficacy in the field of theranostics including microbiology and parasitology. Moreover, an outlook is also provided regarding the performance of AgNPs against different biological systems such as bacteria, fungi, viruses, and parasites (leishmanial and malarial parasites) in curing certain fatal human diseases, with a special focus on cancer. The mechanism of action of AgNPs in different biological systems still remains enigmatic. Here, due to limited available literature, we only focused on AgNPs mechanism in biological systems including human (wound healing and apoptosis), bacteria, and viruses which may open new windows for future research to ensure the versatile application of AgNPs in cosmetics, electronics, and medical fields. PMID:29440898

A simple and versatile design concept for fluorophore derivatives with intramolecular photostabilization

PubMed Central

van der Velde, Jasper H. M.; Oelerich, Jens; Huang, Jingyi; Smit, Jochem H.; Aminian Jazi, Atieh; Galiani, Silvia; Kolmakov, Kirill; Gouridis, Giorgos; Eggeling, Christian; Herrmann, Andreas; Roelfes, Gerard; Cordes, Thorben

2016-01-01

Intramolecular photostabilization via triple-state quenching was recently revived as a tool to impart synthetic organic fluorophores with ‘self-healing’ properties. To date, utilization of such fluorophore derivatives is rare due to their elaborate multi-step synthesis. Here we present a general strategy to covalently link a synthetic organic fluorophore simultaneously to a photostabilizer and biomolecular target via unnatural amino acids. The modular approach uses commercially available starting materials and simple chemical transformations. The resulting photostabilizer–dye conjugates are based on rhodamines, carbopyronines and cyanines with excellent photophysical properties, that is, high photostability and minimal signal fluctuations. Their versatile use is demonstrated by single-step labelling of DNA, antibodies and proteins, as well as applications in single-molecule and super-resolution fluorescence microscopy. We are convinced that the presented scaffolding strategy and the improved characteristics of the conjugates in applications will trigger the broader use of intramolecular photostabilization and help to emerge this approach as a new gold standard. PMID:26751640

Direct Enzymatic Branch-End Extension of Glycocluster-Presented Glycans: An Effective Strategy for Programming Glycan Bioactivity.

PubMed

Bayón, Carlos; He, Ning; Deir-Kaspar, Mario; Blasco, Pilar; André, Sabine; Gabius, Hans-Joachim; Rumbero, Ángel; Jiménez-Barbero, Jesús; Fessner, Wolf-Dieter; Hernáiz, María J

2017-01-31

The sequence of a glycan and its topology of presentation team up to determine the specificity and selectivity of recognition by saccharide receptors (lectins). Structure-activity analysis would be furthered if the glycan part of a glycocluster could be efficiently elaborated in situ while keeping all other parameters constant. By using a bacterial α2,6-sialyltransferase and a small library of bi- to tetravalent glycoclusters, we illustrate the complete conversion of scaffold-presented lactoside units into two different sialylated ligands based on N-acetyl/glycolyl-neuraminic acid incorporation. We assess the ensuing effect on their bioactivity for a plant toxin, and present an analysis of the noncovalent substrate binding contacts that the added sialic acid moiety makes to the lectin. Enzymatic diversification of a scaffold-presented glycan can thus be brought to completion in situ, offering a versatile perspective for rational glycocluster engineering. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Myocardial tissue engineering using electrospun nanofiber composites

PubMed Central

Kim, Pyung-Hwan; Cho, Je-Yoel

2016-01-01

Emerging trends for cardiac tissue engineering are focused on increasing the biocompatibility and tissue regeneration ability of artificial heart tissue by incorporating various cell sources and bioactive molecules. Although primary cardiomyocytes can be successfully implanted, clinical applications are restricted due to their low survival rates and poor proliferation. To develop successful cardiovascular tissue regeneration systems, new technologies must be introduced to improve myocardial regeneration. Electrospinning is a simple, versatile technique for fabricating nanofibers. Here, we discuss various biodegradable polymers (natural, synthetic, and combinatorial polymers) that can be used for fiber fabrication. We also describe a series of fiber modification methods that can increase cell survival, proliferation, and migration and provide supporting mechanical properties by mimicking micro-environment structures, such as the extracellular matrix (ECM). In addition, the applications and types of nanofiber-based scaffolds for myocardial regeneration are described. Finally, fusion research methods combined with stem cells and scaffolds to improve biocompatibility are discussed. [BMB Reports 2016; 49(1): 26-36] PMID:26497579

Interactive and Versatile Navigation of Structural Databases.

PubMed

Korb, Oliver; Kuhn, Bernd; Hert, Jérôme; Taylor, Neil; Cole, Jason; Groom, Colin; Stahl, Martin

2016-05-12

We present CSD-CrossMiner, a novel tool for pharmacophore-based searches in crystal structure databases. Intuitive pharmacophore queries describing, among others, protein-ligand interaction patterns, ligand scaffolds, or protein environments can be built and modified interactively. Matching crystal structures are overlaid onto the query and visualized as soon as they are available, enabling the researcher to quickly modify a hypothesis on the fly. We exemplify the utility of the approach by showing applications relevant to real-world drug discovery projects, including the identification of novel fragments for a specific protein environment or scaffold hopping. The ability to concurrently search protein-ligand binding sites extracted from the Protein Data Bank (PDB) and small organic molecules from the Cambridge Structural Database (CSD) using the same pharmacophore query further emphasizes the flexibility of CSD-CrossMiner. We believe that CSD-CrossMiner closes an important gap in mining structural data and will allow users to extract more value from the growing number of available crystal structures.

Blended Polyurethane and Tropoelastin as a Novel Class of Biologically Interactive Elastomer

PubMed Central

Wise, Steven G.; Liu, Hongjuan; Yeo, Giselle C.; Michael, Praveesuda L.; Chan, Alex H.P.; Ngo, Alan K.Y.; Bilek, Marcela M.M.; Bao, Shisan

2016-01-01

Polyurethanes are versatile elastomers but suffer from biological limitations such as poor control over cell attachment and the associated disadvantages of increased fibrosis. We address this problem by presenting a novel strategy that retains elasticity while modulating biological performance. We describe a new biomaterial that comprises a blend of synthetic and natural elastomers: the biostable polyurethane Elast-Eon and the recombinant human tropoelastin protein. We demonstrate that the hybrid constructs yield a class of coblended elastomers with unique physical properties. Hybrid constructs displayed higher elasticity and linear stress–strain responses over more than threefold strain. The hybrid materials showed increased overall porosity and swelling in comparison to polyurethane alone, facilitating enhanced cellular interactions. In vitro, human dermal fibroblasts showed enhanced proliferation, while in vivo, following subcutaneous implantation in mice, hybrid scaffolds displayed a reduced fibrotic response and tunable degradation rate. To our knowledge, this is the first example of a blend of synthetic and natural elastomers and is a promising approach for generating tailored bioactive scaffolds for tissue repair. PMID:26857114

Programmed coherent coupling in a synthetic DNA-based excitonic circuit

NASA Astrophysics Data System (ADS)

Boulais, Étienne; Sawaya, Nicolas P. D.; Veneziano, Rémi; Andreoni, Alessio; Banal, James L.; Kondo, Toru; Mandal, Sarthak; Lin, Su; Schlau-Cohen, Gabriela S.; Woodbury, Neal W.; Yan, Hao; Aspuru-Guzik, Alán; Bathe, Mark

2018-02-01

Natural light-harvesting systems spatially organize densely packed chromophore aggregates using rigid protein scaffolds to achieve highly efficient, directed energy transfer. Here, we report a synthetic strategy using rigid DNA scaffolds to similarly program the spatial organization of densely packed, discrete clusters of cyanine dye aggregates with tunable absorption spectra and strongly coupled exciton dynamics present in natural light-harvesting systems. We first characterize the range of dye-aggregate sizes that can be templated spatially by A-tracts of B-form DNA while retaining coherent energy transfer. We then use structure-based modelling and quantum dynamics to guide the rational design of higher-order synthetic circuits consisting of multiple discrete dye aggregates within a DX-tile. These programmed circuits exhibit excitonic transport properties with prominent circular dichroism, superradiance, and fast delocalized exciton transfer, consistent with our quantum dynamics predictions. This bottom-up strategy offers a versatile approach to the rational design of strongly coupled excitonic circuits using spatially organized dye aggregates for use in coherent nanoscale energy transport, artificial light-harvesting, and nanophotonics.

Ultrafast triggered transient energy storage by atomic layer deposition into porous silicon for integrated transient electronics

NASA Astrophysics Data System (ADS)

Douglas, Anna; Muralidharan, Nitin; Carter, Rachel; Share, Keith; Pint, Cary L.

2016-03-01

Here we demonstrate the first on-chip silicon-integrated rechargeable transient power source based on atomic layer deposition (ALD) coating of vanadium oxide (VOx) into porous silicon. A stable specific capacitance above 20 F g-1 is achieved until the device is triggered with alkaline solutions. Due to the rational design of the active VOx coating enabled by ALD, transience occurs through a rapid disabling step that occurs within seconds, followed by full dissolution of all active materials within 30 minutes of the initial trigger. This work demonstrates how engineered materials for energy storage can provide a basis for next-generation transient systems and highlights porous silicon as a versatile scaffold to integrate transient energy storage into transient electronics.Here we demonstrate the first on-chip silicon-integrated rechargeable transient power source based on atomic layer deposition (ALD) coating of vanadium oxide (VOx) into porous silicon. A stable specific capacitance above 20 F g-1 is achieved until the device is triggered with alkaline solutions. Due to the rational design of the active VOx coating enabled by ALD, transience occurs through a rapid disabling step that occurs within seconds, followed by full dissolution of all active materials within 30 minutes of the initial trigger. This work demonstrates how engineered materials for energy storage can provide a basis for next-generation transient systems and highlights porous silicon as a versatile scaffold to integrate transient energy storage into transient electronics. Electronic supplementary information (ESI) available: (i) Experimental details for ALD and material fabrication, ellipsometry film thickness, preparation of gel electrolyte and separator, details for electrochemical measurements, HRTEM image of VOx coated porous silicon, Raman spectroscopy for VOx as-deposited as well as annealed in air for 1 hour at 450 °C, SEM and transient behavior dissolution tests of uniformly coated VOx on porous silicon, dissolution tests for 0.1 M and 0.01 M NaOH trigger solutions, EIS analysis for VOx coated devices, and EDS compositional analysis of VOx. (ii) Video showing transient behavior of integrated VOx/porous silicon scaffolds. See DOI: 10.1039/c5nr09095d

RACK1 and the microRNA pathway: is it déjà-vu all over again?

PubMed

Speth, Corinna; Laubinger, Sascha

2014-01-01

MicroRNAs (miRNAs) control many aspects of development and adaption in plants and in animals by post-transcriptional control of mRNA stability and translatability. Over the last years numerous proteins have been identified in the miRNA pathway. The versatile scaffold protein RACK1 has been associated with efficient miRNA production and function in plants and metazoans. Here, we briefly summarize the differences of RACK1 function in the plant and animal miRNA pathways and discuss putative mechanisms and functional roles of RACK1 in miRNA biogenesis and action.

At the dawn of geodesy

NASA Astrophysics Data System (ADS)

Fischer, Irene K.

1981-06-01

The first land surveyors were rope stretchers and rope knotters, remembered in ancient documents and tomb paintings and also in some terminology. The L-shaped carpenter’s square, one of the earliest and most versatile basic tools, represents the observed direction of the plumb line versus the water level and appears as the shadow-casting gnomon and also as the geometrical gnomon in magically-restricted enlargements of altars. The related “Pythagorean” theorem was known in antiquity centuries before Pythagoras, with algebraic proofs in Babylonia and China. The spherical shape of the earth, deduced from the observation of circumpolar stars, was part of a complete equatorial astronomical system in ancient China. But although shadow measurements were generally used to establish north-south distances, only the Greeks derived from them the size of the earth. The striking difference between the abstract, geometric approach of Greece and the concrete, algebraic approach of Babylonia and China represents not a difference in talents but a difference in culture-bound interests.

Clawing through Evolution: Toxin Diversification and Convergence in the Ancient Lineage Chilopoda (Centipedes)

PubMed Central

Undheim, Eivind A.B.; Jones, Alun; Clauser, Karl R.; Holland, John W.; Pineda, Sandy S.; King, Glenn F.; Fry, Bryan G.

2014-01-01

Despite the staggering diversity of venomous animals, there seems to be remarkable convergence in regard to the types of proteins used as toxin scaffolds. However, our understanding of this fascinating area of evolution has been hampered by the narrow taxonomical range studied, with entire groups of venomous animals remaining almost completely unstudied. One such group is centipedes, class Chilopoda, which emerged about 440 Ma and may represent the oldest terrestrial venomous lineage next to scorpions. Here, we provide the first comprehensive insight into the chilopod “venome” and its evolution, which has revealed novel and convergent toxin recruitments as well as entirely new toxin families among both high- and low molecular weight venom components. The ancient evolutionary history of centipedes is also apparent from the differences between the Scolopendromorpha and Scutigeromorpha venoms, which diverged over 430 Ma, and appear to employ substantially different venom strategies. The presence of a wide range of novel proteins and peptides in centipede venoms highlights these animals as a rich source of novel bioactive molecules. Understanding the evolutionary processes behind these ancient venom systems will not only broaden our understanding of which traits make proteins and peptides amenable to neofunctionalization but it may also aid in directing bioprospecting efforts. PMID:24847043

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms.

PubMed

Kornmuller, Anna; Brown, Cody F C; Yu, Claire; Flynn, Lauren E

2017-04-11

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

Polymer-Enriched 3D Graphene Foams for Biomedical Applications.

PubMed

Wang, Jun Kit; Xiong, Gordon Minru; Zhu, Minmin; Özyilmaz, Barbaros; Castro Neto, Antonio Helio; Tan, Nguan Soon; Choong, Cleo

2015-04-22

Graphene foams (GFs) are versatile nanoplatforms for biomedical applications because of their excellent physical, chemical, and mechanical properties. However, the brittleness and inflexibility of pristine GF (pGF) are some of the important factors restricting their widespread application. Here, a chemical-vapor-deposition-assisted method was used to synthesize 3D GFs, which were subsequently spin-coated with polymer to produce polymer-enriched 3D GFs with high conductivity and flexibility. Compared to pGF, both poly(vinylidene fluoride)-enriched GF (PVDF/GF) and polycaprolactone-enriched GF (PCL/GF) scaffolds showed improved flexibility and handleability. Despite the presence of the polymers, the polymer-enriched 3D GF scaffolds retained high levels of electrical conductivity because of the presence of microcracks that allowed for the flow of electrons through the material. In addition, polymer enrichment of GF led to an enhancement in the formation of calcium phosphate (Ca-P) compounds when the scaffolds were exposed to simulated body fluid. Between the two polymers tested, PCL enrichment of GF resulted in a higher in vitro mineralization nucleation rate because the oxygen-containing functional group of PCL had a higher affinity for Ca-P deposition and formation compared to the polar carbon-fluorine (C-F) bond in PVDF. Taken together, our current findings are a stepping stone toward future applications of polymer-enriched 3D GFs in the treatment of bone defects as well as other biomedical applications.

Fluorescent microparticles for sensing cell microenvironment oxygen levels within 3D scaffolds

PubMed Central

Acosta, Miguel A.; Ymele-Leki, Patrick; Kostov, Yordan V.; Leach, Jennie B.

2010-01-01

We present the development and characterization of fluorescent oxygen-sensing microparticles designed for measuring oxygen concentration in microenvironments existing within standard cell culture and transparent three-dimensional (3D) cell scaffolds. The microparticle synthesis employs poly(dimethylsiloxane) to encapsulate silica gel particles bound with an oxygen-sensitive luminophore as well as a reference or normalization fluorophore that is insensitive to oxygen. We developed a rapid, automated and non-invasive sensor analysis method based on fluorescence microscopy to measure oxygen concentration in a hydrogel scaffold. We demonstrate that the microparticles are non-cytotoxic and that their response is comparable to that of a traditional dissolved oxygen meter. Microparticle size (5–40 μm) was selected for microscale-mapping of oxygen concentration to allow measurements local to individual cells. Two methods of calibration were evaluated and revealed that the sensor system enables characterization of a range of hypoxic to hyperoxic conditions relevant to cell and tissue biology (i.e., pO2 10–160 mm Hg). The calibration analysis also revealed that the microparticles have a high fraction of quenched luminophore (0.90 ± 0.02), indicating that the reported approach provides significant advantages for sensor performance. This study thus reports a versatile oxygen-sensing technology that enables future correlations of local oxygen concentration with individual cell response in cultured engineered tissues. PMID:19285719

Optimization of tyrosine-derived polycarbonate terpolymers for bone regeneration scaffolds

NASA Astrophysics Data System (ADS)

Resurreccion-Magno, Maria Hanshella C.

Tyrosine-derived polycarbonates (TyrPC) are a versatile class of polymers highly suitable for bone tissue engineering. Among the tyrosine-derived polycarbonates, poly(DTE carbonate) has an FDA masterfile that documents its biocompatibility and non-toxicity and has shown potential utility in orthopedics due to its osteoconductive properties and strength. DTE stands for desaminotyrosyl-tyrosine ethyl ester and is the most commonly used tyrosine-derived monomer. However, in vitro degradation studies showed that poly(DTE carbonate) did not completely resorb even after four years of incubation in phosphate buffered saline. Thus for bone regeneration, which only requires a temporary implant until the bone heals, poly(DTE carbonate) would not be the best choice. The goal of the present research was to optimize a scaffold composition for bone regeneration that is based on desaminotyrosyl-tyrosine alkyl ester (DTR), desaminotyrosyl-tyrosine (DT) and poly(ethylene glycol) (PEG). Five areas of research were presented: (1) synthesis and characterization of a focused library of TyrPC terpolymers; (2) evaluation of the effects of how small changes on the composition affected the mechanism and kinetics of polymer degradation and erosion; (3) fabrication of bioactive three-dimensional porous scaffold constructs for bone regeneration; (4) assessment of osteogenic properties in vitro using pre-osteoblasts; and (5) evaluation of bone regeneration potential, with or without recombinant human bone morphogenetic protein-2 (rhBMP-2), in vivo using a critical sized defect (CSD) rabbit calvaria (cranium) model. Small changes in the composition, such as changing the R group of DTR from ethyl to methyl, varying the mole percentages of DT and PEG, and using a different PEG block length, affected the overall properties of these polymers. Porous scaffolds were prepared by a combination of solvent casting, porogen leaching and phase separation techniques. Calcium phosphate was coated on the surface post-fabrication. The scaffolds displayed (i) a bimodal pore architecture with micropores (< 20 mum) and macropores (200 -- 400 mum), (ii) a highly interconnected and open pore structure, and (iii) a highly organized microstructure. These scaffolds supported robust cell attachment and promoted osteogenic differentiation of pre-osteoblasts. This is the first report that a synthetic polymeric scaffold either without a biological supplement or with a minimal dose of rhBMP-2 induced comparable bone regeneration to a commercially available bone substitute in a non-rodent CSD animal model.

A macroporous heparin-releasing silk fibroin scaffold improves islet transplantation outcome by promoting islet revascularisation and survival.

PubMed

Mao, Duo; Zhu, Meifeng; Zhang, Xiuyuan; Ma, Rong; Yang, Xiaoqing; Ke, Tingyu; Wang, Lianyong; Li, Zongjin; Kong, Deling; Li, Chen

2017-09-01

Islet transplantation is considered the most promising therapeutic option with the potential to cure diabetes. However, efficacy of current clinical islet transplantation is limited by long-term graft dysfunction and attrition. We have investigated the therapeutic potential of a silk fibroin macroporous (SF) scaffold for syngeneic islet transplantation in diabetic mice. The SF scaffold was prepared via lyophilisation, which enables incorporation of active compounds including cytokines, peptide and growth factors without compromising their biological activity. For the present study, a heparin-releasing SF scaffold (H-SF) in order to evaluate the versatility of the SF scaffold for biological functionalisation. Islets were then co-transplanted with H-SF or SF scaffolds in the epididymal fat pad of diabetic mice. Mice from both H-SF and SF groups achieved 100% euglycaemia, which was maintained for 1year. More importantly, the H-SF-islets co-transplantation led to more rapid reversal of hyperglycaemia, complete normalisation of glucose responsiveness and lower long-term blood glucose levels. This superior transplantation outcome is attributable to H-SF-facilitated islet revascularisation and cell proliferation since significant increase of islet endocrine and endothelial cells proliferation was shown in grafts retrieved from H-SF-islets co-transplanted mice. Better intra-islet vascular reformation was also evident, accompanied by VEGF upregulation. In addition, when H-SF was co-transplanted with islets extracted from vegfr2-luc transgenic mice in vivo, sustained elevation of bioluminescent signal that corresponds to vegfr2 expression was collected, implicating a role of heparin-dependent activation of endogenous VEGF/VEGFR2 pathway in promoting islet revascularisation and proliferation. In summary, the SF scaffolds provide an open platform as scaffold development for islet transplantation. Furthermore, given the pro-angiogenic, pro-survival and minimal post-transplantation inflammatory reactions of H-SF, our data also support the feasibility of clinical implementation of H-SF to improve islet transplantation outcome. 1) The silk fibroin scaffold presented in the present study provides an open platform for scaffold development in islet transplantation, with heparinisation as an example. 2) Both heparin and silk fibroin have been used clinically. The excellent in vivo therapeutic outcome reported here may therefore be clinically relevant and provide valuable insights for bench to bed translation. 3) Compared to conventional clinical islet transplantation, during which islets are injected via the hepatic portal vein, the physical/mechanical properties of silk fibroin scaffolds create a more accessible transplantation site (i.e., within fat pad), which significantly reduces discomfort. 4) Islet implantation into the fat pad also avoids an instant blood mediated inflammatory response, which occurs upon contact of islet with recipient's blood during intraportal injection, and prolongs survival and function of implanted islets. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Selective and Orthogonal Post-Polymerization Modification using Sulfur(VI) Fluoride Exchange (SuFEx) and Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC) Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oakdale, James S.; Kwisnek, Luke; Fokin, Valery V.

2016-06-10

Functional polystyrenes and polyacrylamides, containing combinations of fluorosulfate, aromatic silyl ether, and azide side chains, were used as scaffolds to demonstrate the postpolymerization modification capabilities of sulfur(VI) fluoride exchange (SuFEx) and CuAAC chemistries. Fluorescent dyes bearing appropriate functional groups were sequentially attached to the backbone of the copolymers, quantitatively and selectively addressing their reactive partners. Furthermore, this combined SuFEx and CuAAC approach proved to be robust and versatile, allowing for a rare accomplishment: triple orthogonal functionalization of a copolymer under essentially ambient conditions without protecting groups.

Regenerative biomaterials that "click": simple, aqueous-based protocols for hydrogel synthesis, surface immobilization, and 3D patterning.

PubMed

Nimmo, Chelsea M; Shoichet, Molly S

2011-11-16

The click chemistry era has generated a library of versatile "spring-loaded" reactions that offer high yields, regio- and stereospecificity, and outstanding functional group tolerance. These powerful transformations are particularly advantageous for the design of sophisticated biomaterials that require high levels of precision and control, namely, materials that promote tissue regeneration such as hydrogels, 2D functionalized substrates, and 3D biomimetic scaffolds. In this review, the synthesis and application of regenerative biomaterials via click chemistry are summarized. Particular emphasis is placed on the copper(I)-catalyzed alkyne-azide cycloaddition, Diels-Alder cycloadditions, and thiol-click coupling.

On-Demand Drug Delivery System Using Micro-organogels with Gold Nanorods

PubMed Central

2016-01-01

In this study, we designed a biocompatible drug carrier: micro-organogels prepared by emulsification using vegetable oils and self-assembled gelator fibers. Flurbiprofen was chosen as a hydrophobic model drug and is classified as a nonsteroidal anti-inflammatory drug. In the absence of NIR light, flurbiprofen encapsulated in micro-organogels with gold nanorods (GNRs) was released slowly, while release was accelerated in the presence of NIR light due to the increase in the temperature surrounding the GNRs that transforms the gels into liquid. These results suggest that our system can be efficiently used as a versatile scaffold for on-demand drug delivery systems. PMID:27994743

Schiff bases in medicinal chemistry: a patent review (2010-2015).

PubMed

Hameed, Abdul; Al-Rashida, Mariya; Uroos, Maliha; Abid Ali, Syed; Khan, Khalid Mohammed

2017-01-01

Schiff bases are synthetically accessible and structurally diverse compounds, typically obtained by facile condensation between an aldehyde, or a ketone with primary amines. Schiff bases contain an azomethine (-C = N-) linkage that stitches together two or more biologically active aromatic/heterocyclic scaffolds to form various molecular hybrids with interesting biological properties. Schiff bases are versatile metal complexing agents and have been known to coordinate all metals to form stable metal complexes with vast therapeutic applications. Areas covered: This review aims to provide a comprehensive overview of the various patented therapeutic applications of Schiff bases and their metal complexes from 2010 to 2015. Expert opinion: Schiff bases are a popular class of compounds with interesting biological properties. Schiff bases are also versatile metal complexing ligands and have been used to coordinate almost all d-block metals as well as lanthanides. Therapeutically, Schiff bases and their metal complexes have been reported to exhibit a wide range of biological activities such as antibacterial including antimycobacterial, antifungal, antiviral, antimalarial, antiinflammatory, antioxidant, pesticidal, cytotoxic, enzyme inhibitory, and anticancer including DNA damage.

NHS-Esters As Versatile Reactivity-Based Probes for Mapping Proteome-Wide Ligandable Hotspots.

PubMed

Ward, Carl C; Kleinman, Jordan I; Nomura, Daniel K

2017-06-16

Most of the proteome is considered undruggable, oftentimes hindering translational efforts for drug discovery. Identifying previously unknown druggable hotspots in proteins would enable strategies for pharmacologically interrogating these sites with small molecules. Activity-based protein profiling (ABPP) has arisen as a powerful chemoproteomic strategy that uses reactivity-based chemical probes to map reactive, functional, and ligandable hotspots in complex proteomes, which has enabled inhibitor discovery against various therapeutic protein targets. Here, we report an alkyne-functionalized N-hydroxysuccinimide-ester (NHS-ester) as a versatile reactivity-based probe for mapping the reactivity of a wide range of nucleophilic ligandable hotspots, including lysines, serines, threonines, and tyrosines, encompassing active sites, allosteric sites, post-translational modification sites, protein interaction sites, and previously uncharacterized potential binding sites. Surprisingly, we also show that fragment-based NHS-ester ligands can be made to confer selectivity for specific lysine hotspots on specific targets including Dpyd, Aldh2, and Gstt1. We thus put forth NHS-esters as promising reactivity-based probes and chemical scaffolds for covalent ligand discovery.

Chemically Treated 3D Printed Polymer Scaffolds for Biomineral Formation.

PubMed

Jackson, Richard J; Patrick, P Stephen; Page, Kristopher; Powell, Michael J; Lythgoe, Mark F; Miodownik, Mark A; Parkin, Ivan P; Carmalt, Claire J; Kalber, Tammy L; Bear, Joseph C

2018-04-30

We present the synthesis of nylon-12 scaffolds by 3D printing and demonstrate their versatility as matrices for cell growth, differentiation, and biomineral formation. We demonstrate that the porous nature of the printed parts makes them ideal for the direct incorporation of preformed nanomaterials or material precursors, leading to nanocomposites with very different properties and environments for cell growth. Additives such as those derived from sources such as tetraethyl orthosilicate applied at a low temperature promote successful cell growth, due partly to the high surface area of the porous matrix. The incorporation of presynthesized iron oxide nanoparticles led to a material that showed rapid heating in response to an applied ac magnetic field, an excellent property for use in gene expression and, with further improvement, chemical-free sterilization. These methods also avoid changing polymer feedstocks and contaminating or even damaging commonly used selective laser sintering printers. The chemically treated 3D printed matrices presented herein have great potential for use in addressing current issues surrounding bone grafting, implants, and skeletal repair, and a wide variety of possible incorporated material combinations could impact many other areas.

Printability of calcium phosphate powders for three-dimensional printing of tissue engineering scaffolds.

PubMed

Butscher, Andre; Bohner, Marc; Roth, Christian; Ernstberger, Annika; Heuberger, Roman; Doebelin, Nicola; von Rohr, Philipp Rudolf; Müller, Ralph

2012-01-01

Three-dimensional printing (3DP) is a versatile method to produce scaffolds for tissue engineering. In 3DP the solid is created by the reaction of a liquid selectively sprayed onto a powder bed. Despite the importance of the powder properties, there has to date been a relatively poor understanding of the relation between the powder properties and the printing outcome. This article aims at improving this understanding by looking at the link between key powder parameters (particle size, flowability, roughness, wettability) and printing accuracy. These powder parameters are determined as key factors with a predictive value for the final 3DP outcome. Promising results can be expected for mean particle size in the range of 20-35 μm, compaction rate in the range of 1.3-1.4, flowability in the range of 5-7 and powder bed surface roughness of 10-25 μm. Finally, possible steps and strategies in pushing the physical limits concerning improved quality in 3DP are addressed and discussed. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Chemically Treated 3D Printed Polymer Scaffolds for Biomineral Formation

PubMed Central

2018-01-01

We present the synthesis of nylon-12 scaffolds by 3D printing and demonstrate their versatility as matrices for cell growth, differentiation, and biomineral formation. We demonstrate that the porous nature of the printed parts makes them ideal for the direct incorporation of preformed nanomaterials or material precursors, leading to nanocomposites with very different properties and environments for cell growth. Additives such as those derived from sources such as tetraethyl orthosilicate applied at a low temperature promote successful cell growth, due partly to the high surface area of the porous matrix. The incorporation of presynthesized iron oxide nanoparticles led to a material that showed rapid heating in response to an applied ac magnetic field, an excellent property for use in gene expression and, with further improvement, chemical-free sterilization. These methods also avoid changing polymer feedstocks and contaminating or even damaging commonly used selective laser sintering printers. The chemically treated 3D printed matrices presented herein have great potential for use in addressing current issues surrounding bone grafting, implants, and skeletal repair, and a wide variety of possible incorporated material combinations could impact many other areas. PMID:29732454

Digital Alchemy for Materials Design: Colloids and Beyond

NASA Astrophysics Data System (ADS)

van Anders, Greg; Klotsa, Daphne; Karas, Andrew; Dodd, Paul; Glotzer, Sharon

Starting with the early alchemists, a holy grail of science has been to make desired materials by manipulating basic building blocks. Building blocks that show promise for assembling new complex materials can be synthesized at the nanoscale with attributes that would astonish the ancient alchemists in their versatility. However, this versatility means that connecting building-block attributes to bulk structure is both necessary for rationally engineering materials and difficult because building block attributes can be altered in many ways. We show how to exploit the malleability of colloidal nanoparticle ``elements'' to quantitatively link building-block attributes to bulk structure through a statistical thermodynamic framework we term ``digital alchemy''. We use this framework to optimize building blocks for a given target structure and to determine which building-block attributes are most important to control for self-assembly, through a set of novel thermodynamic response functions. We thereby establish direct links between the attributes of colloidal building blocks and the bulk structures they form. Moreover, our results give concrete solutions to the more general conceptual challenge of optimizing emergent behaviors in nature and can be applied to other types of matter.

W.R. Grove and the fuel cell

NASA Astrophysics Data System (ADS)

Meurig Thomas, John

2012-11-01

Though known these days largely because he invented the fuel cell, Grove also had many other distinguished achievements to his credit. His monumental book On the Correlation of Physical Forces contained all the arguments that led to the enunciation of the first law of thermodynamics. He was also an extremely versatile natural philosopher who was, in addition, well versed in classical literature, particularly the works of the eminent scholars of ancient Greece and Rome. This article touches upon these qualities, but is predominantly concerned with the emergence and modern aspects of the H2/O2 fuel cell and its potential for the clean generation of energy.

The triple helix of collagens - an ancient protein structure that enabled animal multicellularity and tissue evolution.

PubMed

Fidler, Aaron L; Boudko, Sergei P; Rokas, Antonis; Hudson, Billy G

2018-04-09

The cellular microenvironment, characterized by an extracellular matrix (ECM), played an essential role in the transition from unicellularity to multicellularity in animals (metazoans), and in the subsequent evolution of diverse animal tissues and organs. A major ECM component are members of the collagen superfamily -comprising 28 types in vertebrates - that exist in diverse supramolecular assemblies ranging from networks to fibrils. Each assembly is characterized by a hallmark feature, a protein structure called a triple helix. A current gap in knowledge is understanding the mechanisms of how the triple helix encodes and utilizes information in building scaffolds on the outside of cells. Type IV collagen, recently revealed as the evolutionarily most ancient member of the collagen superfamily, serves as an archetype for a fresh view of fundamental structural features of a triple helix that underlie the diversity of biological activities of collagens. In this Opinion, we argue that the triple helix is a protein structure of fundamental importance in building the extracellular matrix, which enabled animal multicellularity and tissue evolution. © 2018. Published by The Company of Biologists Ltd.

Ancient deuterostome origins of vertebrate brain signalling centres.

PubMed

Pani, Ariel M; Mullarkey, Erin E; Aronowicz, Jochanan; Assimacopoulos, Stavroula; Grove, Elizabeth A; Lowe, Christopher J

2012-03-14

Neuroectodermal signalling centres induce and pattern many novel vertebrate brain structures but are absent, or divergent, in invertebrate chordates. This has led to the idea that signalling-centre genetic programs were first assembled in stem vertebrates and potentially drove morphological innovations of the brain. However, this scenario presumes that extant cephalochordates accurately represent ancestral chordate characters, which has not been tested using close chordate outgroups. Here we report that genetic programs homologous to three vertebrate signalling centres-the anterior neural ridge, zona limitans intrathalamica and isthmic organizer-are present in the hemichordate Saccoglossus kowalevskii. Fgf8/17/18 (a single gene homologous to vertebrate Fgf8, Fgf17 and Fgf18), sfrp1/5, hh and wnt1 are expressed in vertebrate-like arrangements in hemichordate ectoderm, and homologous genetic mechanisms regulate ectodermal patterning in both animals. We propose that these genetic programs were components of an unexpectedly complex, ancient genetic regulatory scaffold for deuterostome body patterning that degenerated in amphioxus and ascidians, but was retained to pattern divergent structures in hemichordates and vertebrates. © 2012 Macmillan Publishers Limited. All rights reserved

β-Propeller Blades as Ancestral Peptides in Protein Evolution

PubMed Central

Kopec, Klaus O.; Lupas, Andrei N.

2013-01-01

Proteins of the β-propeller fold are ubiquitous in nature and widely used as structural scaffolds for ligand binding and enzymatic activity. This fold comprises between four and twelve four-stranded β-meanders, the so called blades that are arranged circularly around a central funnel-shaped pore. Despite the large size range of β-propellers, their blades frequently show sequence similarity indicative of a common ancestry and it has been proposed that the majority of β-propellers arose divergently by amplification and diversification of an ancestral blade. Given the structural versatility of β-propellers and the hypothesis that the first folded proteins evolved from a simpler set of peptides, we investigated whether this blade may have given rise to other folds as well. Using sequence comparisons, we identified proteins of four other folds as potential homologs of β-propellers: the luminal domain of inositol-requiring enzyme 1 (IRE1-LD), type II β-prisms, β-pinwheels, and WW domains. Because, with increasing evolutionary distance and decreasing sequence length, the statistical significance of sequence comparisons becomes progressively harder to distinguish from the background of convergent similarities, we complemented our analyses with a new method that evaluates possible homology based on the correlation between sequence and structure similarity. Our results indicate a homologous relationship of IRE1-LD and type II β-prisms with β-propellers, and an analogous one for β-pinwheels and WW domains. Whereas IRE1-LD most likely originated by fold-changing mutations from a fully formed PQQ motif β-propeller, type II β-prisms originated by amplification and differentiation of a single blade, possibly also of the PQQ type. We conclude that both β-propellers and type II β-prisms arose by independent amplification of a blade-sized fragment, which represents a remnant of an ancient peptide world. PMID:24143202

Recent advances in the use of gelatin in biomedical research.

PubMed

Su, Kai; Wang, Chunming

2015-11-01

The biomacromolecule, gelatin, has increasingly been used in biomedicine-beyond its traditional use in food and cosmetics. The appealing advantages of gelatin, such as its cell-adhesive structure, low cost, off-the-shelf availability, high biocompatibility, biodegradability and low immunogenicity, among others, have made it a desirable candidate for the development of biomaterials for tissue engineering and drug delivery. Gelatin can be formulated in the form of nanoparticles, employed as size-controllable porogen, adopted as surface coating agent and mixed with synthetic or natural biopolymers forming composite scaffolds. In this article, we review recent advances in the versatile applications of gelatin within biomedical context and attempt to draw upon its advantages and potential challenges.

Poly (lactic acid)-based biomaterials for orthopaedic regenerative engineering.

PubMed

Narayanan, Ganesh; Vernekar, Varadraj N; Kuyinu, Emmanuel L; Laurencin, Cato T

2016-12-15

Regenerative engineering converges tissue engineering, advanced materials science, stem cell science, and developmental biology to regenerate complex tissues such as whole limbs. Regenerative engineering scaffolds provide mechanical support and nanoscale control over architecture, topography, and biochemical cues to influence cellular outcome. In this regard, poly (lactic acid) (PLA)-based biomaterials may be considered as a gold standard for many orthopaedic regenerative engineering applications because of their versatility in fabrication, biodegradability, and compatibility with biomolecules and cells. Here we discuss recent developments in PLA-based biomaterials with respect to processability and current applications in the clinical and research settings for bone, ligament, meniscus, and cartilage regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

Catalytic Enantioselective and Diastereoselective Allylic Alkylation with Fluoroenolates: Efficient Access to C3-Fluorinated and All-Carbon Quaternary Oxindoles

PubMed Central

Balaraman, Kaluvu; Wolf, Christian

2017-01-01

Synthetically versatile 3,3-disubstituted fluorooxindoles exhibiting vicinal chirality centers were obtained in high yields and with excellent enantio-, diastereo- and regioselectivity by catalytic asymmetric fluoroenolate alkylation with allylic acetates. The reaction proceeds under mild conditions and can be upscaled without compromising the asymmetric induction. The unique synthetic usefulness of the products is highlighted with the incorporation of additional functionalities and the formation of 3-fluorinated oxindoles exhibiting an array of four adjacent chirality centers. A new C-F bond functionalization path that provides unprecedented means for stereoselective generation of a chiral quaternary carbon center in the alkaloid scaffold is introduced. PMID:28026079

A New, Simple and Versatile Strategy for the Synthesis of Short Segments of Zigzag-Type Carbon Nanotubes.

PubMed

André, Etienne; Boutonnet, Baptiste; Charles, Pauline; Martini, Cyril; Aguiar-Hualde, Juan-Manuel; Latil, Sylvain; Guérineau, Vincent; Hammad, Karim; Ray, Priyanka; Guillot, Régis; Huc, Vincent

2016-02-24

Short segments of zigzag single-walled carbon nanotubes (SWCNTs) were obtained from a calixarene scaffold by using a completely new, simple and expedited strategy that allowed fine-tuning of their diameters. This new approach also allows for functionalised short segments of zigzag SWCNTs to be obtained; a prerequisite towards their lengthening. These new SWCNT short segments/calixarene composites show interesting behaviour in solution. DFT analysis of these new compounds also suggests interesting photophysical behaviour. Along with the synthesis of various SWCNTs segments, this approach also constitutes a powerful tool for the construction of new, radially oriented π systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and Absolute Configuration of Jurassic Polyketide-Derived Spiroborate Pigments Obtained from Microgram Quantities.

PubMed

Wolkenstein, Klaus; Sun, Han; Falk, Heinz; Griesinger, Christian

2015-10-28

Complete structural elucidation of natural products is often challenging due to structural complexity and limited availability. This is true for present-day secondary metabolites, but even more for exceptionally preserved secondary metabolites of ancient organisms that potentially provide insights into the evolutionary history of natural products. Here, we report the full structure and absolute configuration of the borolithochromes, enigmatic boron-containing pigments from a Jurassic putative red alga, from samples of less than 50 μg using microcryoprobe NMR, circular dichroism spectroscopy, and density functional theory calculations and reveal their polyketide origin. The pigments are identified as spiroborates with two pentacyclic sec-butyl-trihydroxy-methyl-benzo[gh]tetraphen-one ligands and less-substituted derivatives. The configuration of the sec-butyl group is found to be (S). Because the exceptional benzo[gh]tetraphene scaffold is otherwise only observed in the recently discovered polyketide clostrubin from a present-day Clostridium bacterium, the Jurassic borolithochromes now can be unambiguously linked to the modern polyketide, providing evidence that the fossil pigments are almost originally preserved secondary metabolites and suggesting that the pigments in fact may have been produced by an ancient bacterium. The borolithochromes differ fundamentally from previously described boronated polyketides and represent the first boronated aromatic polyketides found so far. Our results demonstrate the potential of microcryoprobe NMR in the analysis of previously little-explored secondary metabolites from ancient organisms and reveal the evolutionary significance of clostrubin-type polyketides.

Self-assembling triblock proteins for biofunctional surface modification

NASA Astrophysics Data System (ADS)

Fischer, Stephen E.

Despite the tremendous promise of cell/tissue engineering, significant challenges remain in engineering functional scaffolds to precisely regulate the complex processes of tissue growth and development. As the point of contact between the cells and the scaffold, the scaffold surface plays a major role in mediating cellular behaviors. In this dissertation, the development and utility of self-assembling, artificial protein hydrogels as biofunctional surface modifiers is described. The design of these recombinant proteins is based on a telechelic triblock motif, in which a disordered polyelectrolyte central domain containing embedded bioactive ligands is flanked by two leucine zipper domains. Under moderate conditions of temperature and pH, the leucine zipper end domains form amphiphilic alpha-helices that reversibly associate into homo-trimeric aggregates, driving hydrogel formation. Moreover, the amphiphilic nature of these helical domains enables surface adsorption to a variety of scaffold materials to form biofunctional protein coatings. The nature and stability of these coatings in various solution conditions, and their interaction with mammalian cells is the primary focus of this dissertation. In particular, triblock protein coatings functionalized with cell recognition sequences are shown to produce well-defined surfaces with precise control over ligand density. The impact of this is demonstrated in multiple cell types through ligand density-dependent cell-substrate interactions. To improve the stability of these physically self-assembled coatings, two covalent crosslinking strategies are described---one in which a zero-length chemical crosslinker (EDC) is utilized and a second in which disulfide bonds are engineered into the recombinant proteins. These targeted crosslinking approaches are shown to increase the stability of surface adsorbed protein layers with minimal effect on the presentation of many bioactive ligands. Finally, to demonstrate the versatility of the triblock protein hydrogels, and the ease of introducing multiple functionalities to a substrate surface, a surface coating is tailored for neural stem cell culture in order to improve proliferation on the scaffold, while maintaining the stem cell phenotype. These studies demonstrate the unique advantages of genetic engineering over traditional techniques for surface modification. In addition to their unmatched sequence fidelity, recombinant proteins can easily be modified with bioactive ligands and their organization into coherent, supramolecular structures mimics natural self-assembly processes.

The comet assay in human biomonitoring.

PubMed

Anderson, Diana; Dhawan, Alok; Laubenthal, Julian

2013-01-01

Human biomonitoring studies aim to identify potential exposures to environmental, occupational, or lifestyle toxicants in human populations and are commonly used by public health decision makers to predict disease risk. The Comet assay measures changes in genomic stability and is one of the most reliable biomarkers to indicate early biological effects, and therefore accepted by various governmental regulatory agencies. The appeal of the Comet assay lies in its relative simplicity, rapidity, sensitivity, and economic efficiency. Furthermore, the assay is known for its broad versatility, as it can be applied to virtually any human cell and easily adapted in order to detect particular biomarkers of interest, such as DNA repair capacity or single- and double-strand breaks. In a standard experiment, isolated single cells are first embedded in agarose, and then lysed in high-salt solutions in order to remove all cellular contents except the DNA attached to a nuclear scaffold. Subsequent electrophoresis results in accumulation of undamaged DNA sequences at the proximity of the nuclear scaffold, while damaged sequences migrate towards the anode. When visualized with fluorochromes, these migrated DNA fragments resemble a comet tail and can be quantified for their intensity and shape according to internationally drafted guidelines.

Knitting for heart valve tissue engineering

PubMed Central

Ayad, Nadia; Wojciechowska, Dorota; Zielińska, Dorota; Struszczyk, Marcin H.; Latif, Najma; Yacoub, Magdi

Knitting is a versatile technology which offers a large portfolio of products and solutions of interest in heart valve (HV) tissue engineering (TE). One of the main advantages of knitting is its ability to construct complex shapes and structures by precisely assembling the yarns in the desired position. With this in mind, knitting could be employed to construct a HV scaffold that closely resembles the authentic valve. This has the potential to reproduce the anisotropic structure that is characteristic of the heart valve with the yarns, in particular the 3-layered architecture of the leaflets. These yarns can provide oriented growth of cells lengthwise and consequently enable the deposition of extracellular matrix (ECM) proteins in an oriented manner. This technique, therefore, has a potential to provide a functional knitted scaffold, but to achieve that textile engineers need to gain a basic understanding of structural and mechanical aspects of the heart valve and in addition, tissue engineers must acquire the knowledge of tools and capacities that are essential in knitting technology. The aim of this review is to provide a platform to consolidate these two fields as well as to enable an efficient communication and cooperation among these two research areas. PMID:29043276

First example of a modular porphyrinoid assembly capable of stabilizing different metal ions in a single molecular scaffold.

PubMed

Murugavel, Muthuchamy; Reddy, R V Ramana; Dey, Dhananjay; Sankar, Jeyaraman

2015-10-05

We report the synthesis and characterization of porphyrin-corrole-porphyrin (Por-Cor-Por) hybrids directly linked at the meso-meso positions for the first time. The stability and solubility of the trimer are carefully balanced by adding electron-withdrawing substituents to the corrole ring and sterically bulky groups on the porphyrins. The new hybrids are capable of stabilizing more than one metal ion in a single molecular scaffold. The versatility of the triad has been demonstrated by successfully stabilizing homo- (Ni) and heterotrinuclear (Ni-Cu-Ni) coordination motifs. The solid-state structure of the NiPor-CuCor-PorNi hybrid was revealed by single-crystal X-ray diffraction studies. The Ni(II) porphyrins are significantly ruffled and tilted by 83° from the plane of corrole. The robustness of the synthesized hybrids was reflected in the electrochemical investigations and the redox behaviour of the hybrids show that the oxidation processes are mostly corrole-centred. In particular it is worth noting that the Por-Cor-Por hybrid can further be manipulated due to the presence of substituent-free meso-positions on both the terminals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Developing Ligands for Palladium(II)-Catalyzed C–H Functionalization: Intimate Dialogue between Ligand and Substrate

PubMed Central

Engle, Keary M.; Yu, Jin-Quan

2013-01-01

Homogeneous transition metal–catalyzed reactions are indispensable to all facets of modern chemical synthesis. It is thus difficult to imagine that for much of the early 20th century, the reactivity and selectivity of all known homogeneous metal catalysts paled in comparison to their heterogeneous and biological counterparts. In the intervening decades, advances in ligand design bridged this divide, such that today some of the most demanding bond-forming events are mediated by ligand-supported homogeneous metal species. While ligand design has propelled many areas of homogeneous catalysis, in the field of Pd(II)-catalyzed C–H functionalization, suitable ligand scaffolds are lacking, which has hampered the development of broadly practical transformations based on C–H functionalization logic. In this review, we offer an account of our research employing three ligand scaffolds, mono-N-protected amino acids, 2,6-disubstituted pyridines, and 2,2′-bipyridines, to address challenges posed by several synthetically versatile substrate classes. Drawing on this work, we discuss principles of ligand design, such as the need to match a ligand to a particular substrate class, and how ligand traits such as tunability and modularity can be advantageous in reaction discovery. PMID:23565982

Alginate: A Versatile Biomaterial to Encapsulate Isolated Ovarian Follicles.

PubMed

Vanacker, Julie; Amorim, Christiani A

2017-07-01

In vitro culture of ovarian follicles isolated or enclosed in ovarian tissue fragments and grafting of isolated ovarian follicles represent a potential alternative to restore fertility in cancer patients who cannot undergo cryopreservation of embryos or oocytes or transplantation of frozen-thawed ovarian tissue. In this regard, respecting the three-dimensional (3D) architecture of isolated follicles is crucial to maintaining their proper follicular physiology. To this end, alginate hydrogel has been widely investigated using follicles from numerous animal species, yielding promising results. The goal of this review is therefore to provide an overview of alginate applications utilizing the biomaterial as a scaffold for 3D encapsulation of isolated ovarian follicles. Different methods of isolated follicle encapsulation in alginate are discussed in this review, as its use of 3D alginate culture systems as a tool for in vitro follicle analysis. Possible improvements of this matrix, namely modification with arginine-glycine-aspartic acid peptide or combination with fibrin, are also summarized. Encouraging results have been obtained in different animal models, and particularly with isolated follicles encapsulated in alginate matrices and grafted to mice. This summary is designed to guide the reader towards development of next-generation alginate scaffolds, with enhanced properties for follicle encapsulation.

Next generation phage display by use of pVII and pIX as display scaffolds.

PubMed

Løset, Geir Åge; Sandlie, Inger

2012-09-01

Phage display technology has evolved to become an extremely versatile and powerful platform for protein engineering. The robustness of the phage particle, its ease of handling and its ability to tolerate a range of different capsid fusions are key features that explain the dominance of phage display in combinatorial engineering. Implementation of new technology is likely to ensure the continuation of its success, but has also revealed important short comings inherent to current phage display systems. This is in particular related to the biology of the two most popular display capsids, namely pIII and pVIII. Recent findings using two alternative capsids, pVII and pIX, located to the phage tip opposite that of pIII, suggest how they may be exploited to alleviate or circumvent many of these short comings. This review addresses important aspects of the current phage display standard and then discusses the use of pVII and pIX. These may both complement current systems and be used as alternative scaffolds for display and selection to further improve phage display as the ultimate combinatorial engineering platform. Copyright © 2012 Elsevier Inc. All rights reserved.

The Two-pore channel (TPC) interactome unmasks isoform-specific roles for TPCs in endolysosomal morphology and cell pigmentation

PubMed Central

Lin-Moshier, Yaping; Keebler, Michael V.; Hooper, Robert; Boulware, Michael J.; Liu, Xiaolong; Churamani, Dev; Abood, Mary E.; Walseth, Timothy F.; Brailoiu, Eugen; Patel, Sandip; Marchant, Jonathan S.

2014-01-01

The two-pore channels (TPC1 and TPC2) belong to an ancient family of intracellular ion channels expressed in the endolysosomal system. Little is known about how regulatory inputs converge to modulate TPC activity, and proposed activation mechanisms are controversial. Here, we compiled a proteomic characterization of the human TPC interactome, which revealed that TPCs complex with many proteins involved in Ca2+ homeostasis, trafficking, and membrane organization. Among these interactors, TPCs were resolved to scaffold Rab GTPases and regulate endomembrane dynamics in an isoform-specific manner. TPC2, but not TPC1, caused a proliferation of endolysosomal structures, dysregulating intracellular trafficking, and cellular pigmentation. These outcomes required both TPC2 and Rab activity, as well as their interactivity, because TPC2 mutants that were inactive, or rerouted away from their endogenous expression locale, or deficient in Rab binding, failed to replicate these outcomes. Nicotinic acid adenine dinucleotide phosphate (NAADP)-evoked Ca2+ release was also impaired using either a Rab binding-defective TPC2 mutant or a Rab inhibitor. These data suggest a fundamental role for the ancient TPC complex in trafficking that holds relevance for lysosomal proliferative scenarios observed in disease. PMID:25157141

The Two-pore channel (TPC) interactome unmasks isoform-specific roles for TPCs in endolysosomal morphology and cell pigmentation.

PubMed

Lin-Moshier, Yaping; Keebler, Michael V; Hooper, Robert; Boulware, Michael J; Liu, Xiaolong; Churamani, Dev; Abood, Mary E; Walseth, Timothy F; Brailoiu, Eugen; Patel, Sandip; Marchant, Jonathan S

2014-09-09

The two-pore channels (TPC1 and TPC2) belong to an ancient family of intracellular ion channels expressed in the endolysosomal system. Little is known about how regulatory inputs converge to modulate TPC activity, and proposed activation mechanisms are controversial. Here, we compiled a proteomic characterization of the human TPC interactome, which revealed that TPCs complex with many proteins involved in Ca(2+) homeostasis, trafficking, and membrane organization. Among these interactors, TPCs were resolved to scaffold Rab GTPases and regulate endomembrane dynamics in an isoform-specific manner. TPC2, but not TPC1, caused a proliferation of endolysosomal structures, dysregulating intracellular trafficking, and cellular pigmentation. These outcomes required both TPC2 and Rab activity, as well as their interactivity, because TPC2 mutants that were inactive, or rerouted away from their endogenous expression locale, or deficient in Rab binding, failed to replicate these outcomes. Nicotinic acid adenine dinucleotide phosphate (NAADP)-evoked Ca(2+) release was also impaired using either a Rab binding-defective TPC2 mutant or a Rab inhibitor. These data suggest a fundamental role for the ancient TPC complex in trafficking that holds relevance for lysosomal proliferative scenarios observed in disease.

Antimicrobial Peptides in Reptiles

PubMed Central

van Hoek, Monique L.

2014-01-01

Reptiles are among the oldest known amniotes and are highly diverse in their morphology and ecological niches. These animals have an evolutionarily ancient innate-immune system that is of great interest to scientists trying to identify new and useful antimicrobial peptides. Significant work in the last decade in the fields of biochemistry, proteomics and genomics has begun to reveal the complexity of reptilian antimicrobial peptides. Here, the current knowledge about antimicrobial peptides in reptiles is reviewed, with specific examples in each of the four orders: Testudines (turtles and tortosises), Sphenodontia (tuataras), Squamata (snakes and lizards), and Crocodilia (crocodilans). Examples are presented of the major classes of antimicrobial peptides expressed by reptiles including defensins, cathelicidins, liver-expressed peptides (hepcidin and LEAP-2), lysozyme, crotamine, and others. Some of these peptides have been identified and tested for their antibacterial or antiviral activity; others are only predicted as possible genes from genomic sequencing. Bioinformatic analysis of the reptile genomes is presented, revealing many predicted candidate antimicrobial peptides genes across this diverse class. The study of how these ancient creatures use antimicrobial peptides within their innate immune systems may reveal new understandings of our mammalian innate immune system and may also provide new and powerful antimicrobial peptides as scaffolds for potential therapeutic development. PMID:24918867

Modulating the Behaviors of Mesenchymal Stem Cells Via the Combination of High-Frequency Vibratory Stimulations and Fibrous Scaffolds

PubMed Central

Tong, Zhixiang; Duncan, Randall L.

2013-01-01

We are interested in the in vitro engineering of artificial vocal fold tissues via the strategic combination of multipotent mesenchymal stem cells (MSCs), physiologically relevant mechanical stimulations, and biomimetic artificial matrices. We have constructed a vocal fold bioreactor that is capable of imposing vibratory stimulations on the cultured cells at human phonation frequencies. Separately, fibrous poly (ɛ-caprolactone) (PCL) scaffolds emulating the ligamentous structure of the vocal fold were prepared by electrospinning, were incorporated in the vocal fold bioreactor, and were driven into a wave-like motion in an axisymmetrical fashion by the oscillating air. MSC-laden PCL scaffolds were subjected to vibrations at 200 Hz with a normal center displacement of ∼40 μm for a total of 7 days. A continuous (CT) or a 1 h-on-1 h-off (OF) regime with a total dynamic culture time of 12 h per day was applied. The dynamic loading did not cause any physiological trauma to the cells. Immunohistotochemical staining revealed the reinforcement of the actin filament and the enhancement of α5β1 integrin expression under selected dynamic culture conditions. Cellular expression of essential vocal fold extracellular matrix components, such as elastin, hyaluronic acid, and matrix metalloproteinase-1, was significantly elevated as compared with the static controls, and the OF regime is more conducive to matrix production than the CT vibration mode. Analyses of genes of typical fibroblast hallmarks (tenascin-C, collagen III, and procollagen I) as well as markers for MSC differentiation into nonfibroblastic lineages confirmed MSCs' adaptation of fibroblastic behaviors. Overall, the high-frequency vibratory stimulation, when combined with a synthetic fibrous scaffold, serves as a potent modulator of MSC functions. The novel bioreactor system presented here, as a versatile, yet well-controlled model, offers an in vitro platform for understanding vibration-induced mechanotransduction and for engineering of functional vocal fold tissues. PMID:23516973

Self-assembled nanoscale DNA-porphyrin complex for artificial light harvesting.

PubMed

Woller, Jakob G; Hannestad, Jonas K; Albinsson, Bo

2013-02-20

Mimicking green plants' and bacteria's extraordinary ability to absorb a vast number of photons and harness their energy is a longstanding goal in artificial photosynthesis. Resonance energy transfer among donor dyes has been shown to play a crucial role on the overall transfer of energy in the natural systems. Here, we present artificial, self-assembled, light-harvesting complexes consisting of DNA scaffolds, intercalated YO-PRO-1 (YO) donor dyes and a porphyrin acceptor anchored to a lipid bilayer, conceptually mimicking the natural light-harvesting systems. A model system consisting of 39-mer duplex DNA in a linear wire configuration with the porphyrin attached in the middle of the wire is primarily investigated. Utilizing intercalated donor fluorophores to sensitize the excitation of the porphyrin acceptor, we obtain an effective absorption coefficient 12 times larger than for direct excitation of the porphyrin. On the basis of steady-state and time-resolved emission measurements and Markov chain simulations, we show that YO-to-YO resonance energy transfer substantially contributes to the overall flow of energy to the porphyrin. This increase is explained through energy migration along the wire allowing the excited state energy to transfer to positions closer to the porphyrin. The versatility of DNA as a structural material is demonstrated through the construction of a more complex, hexagonal, light-harvesting scaffold yielding further increase in the effective absorption coefficient. Our results show that, by using DNA as a scaffold, we are able to arrange chromophores on a nanometer scale and in this way facilitate the assembly of efficient light-harvesting systems.

SAM/SAH Analogs as Versatile Tools for SAM-Dependent Methyltransferases.

PubMed

Zhang, Jing; Zheng, Yujun George

2016-03-18

S-Adenosyl-L-methionine (SAM) is a sulfonium molecule with a structural hybrid of methionine and adenosine. As the second largest cofactor in the human body, its major function is to serve as methyl donor for SAM-dependent methyltransferases (MTases). The resultant transmethylation of biomolecules constitutes a significant biochemical mechanism in epigenetic regulation, cellular signaling, and metabolite degradation. Recently, numerous SAM analogs have been developed as synthetic cofactors to transfer the activated groups on MTase substrates for downstream ligation and identification. Meanwhile, new compounds built upon or derived from the SAM scaffold have been designed and tested as selective inhibitors for important MTase targets. Here, we summarized the recent development and application of SAM analogs as chemical biology tools for MTases.

Phosphorylation of RACK1 in plants

DOE PAGES

Chen, Jay -Gui

2015-08-31

Receptor for Activated C Kinase 1 (RACK1) is a versatile scaffold protein that interacts with a large, diverse group of proteins to regulate various signaling cascades. RACK1 has been shown to regulate hormonal signaling, stress responses and multiple processes of growth and development in plants. However, little is known about the molecular mechanism underlying these regulations. Recently, it has been demonstrated that Arabidopsis RACK1 is phosphorylated by an atypical serine/threonine protein kinase, WITH NO LYSINE 8 (WNK8). Furthermore, RACK1 phosphorylation by WNK8 negatively regulates RACK1 function by influencing its protein stability. In conclusion, these findings promote a new regulatory systemmore » in which the action of RACK1 is controlled by phosphorylation and subsequent protein degradation.« less

Reaction of Donor-Acceptor Cyclobutanes with Indoles: A General Protocol for the Formal Total Synthesis of (±)-Strychnine and the Total Synthesis of (±)-Akuammicine.

PubMed

Feng, Liang-Wen; Ren, Hai; Xiong, Hu; Wang, Pan; Wang, Lijia; Tang, Yong

2017-03-06

A ligand-promoted catalytic [4+2] annulation reaction using indole derivatives and donor-acceptor (D-A) cyclobutanes is reported, thus providing an efficient and atom-economical access to versatile cyclohexa-fused indolines with excellent levels of diastereoselectivity and a broad substrate scope. In the presence of a chiral SaBOX ligand, excellent enantioselectivity was realized with up to 94 % ee. This novel synthetic method is applied as a general protocol for the total synthesis of (±)-akuammicine and the formal total synthesis of (±)-strychnine from the same common-core scaffold. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physicochemical Properties and Applications of Poly(lactic-co-glycolic acid) for Use in Bone Regeneration

PubMed Central

Félix Lanao, Rosa P.; Jonker, Anika M.; Wolke, Joop G.C.; Jansen, John A.; van Hest, Jan C.M.

2013-01-01

Poly(lactic-co-glycolic acid) (PLGA) is the most often used synthetic polymer within the field of bone regeneration owing to its biocompatibility and biodegradability. As a consequence, a large number of medical devices comprising PLGA have been approved for clinical use in humans by the American Food and Drug Administration. As compared with the homopolymers of lactic acid poly(lactic acid) and poly(glycolic acid), the co-polymer PLGA is much more versatile with regard to the control over degradation rate. As a material for bone regeneration, the use of PLGA has been extensively studied for application and is included as either scaffolds, coatings, fibers, or micro- and nanospheres to meet various clinical requirements. PMID:23350707

Evolution stings: the origin and diversification of scorpion toxin peptide scaffolds.

PubMed

Sunagar, Kartik; Undheim, Eivind A B; Chan, Angelo H C; Koludarov, Ivan; Muñoz-Gómez, Sergio A; Antunes, Agostinho; Fry, Bryan G

2013-12-13

The episodic nature of natural selection and the accumulation of extreme sequence divergence in venom-encoding genes over long periods of evolutionary time can obscure the signature of positive Darwinian selection. Recognition of the true biocomplexity is further hampered by the limited taxon selection, with easy to obtain or medically important species typically being the subject of intense venom research, relative to the actual taxonomical diversity in nature. This holds true for scorpions, which are one of the most ancient terrestrial venomous animal lineages. The family Buthidae that includes all the medically significant species has been intensely investigated around the globe, while almost completely ignoring the remaining non-buthid families. Australian scorpion lineages, for instance, have been completely neglected, with only a single scorpion species (Urodacus yaschenkoi) having its venom transcriptome sequenced. Hence, the lack of venom composition and toxin sequence information from an entire continent's worth of scorpions has impeded our understanding of the molecular evolution of scorpion venom. The molecular origin, phylogenetic relationships and evolutionary histories of most scorpion toxin scaffolds remain enigmatic. In this study, we have sequenced venom gland transcriptomes of a wide taxonomical diversity of scorpions from Australia, including buthid and non-buthid representatives. Using state-of-art molecular evolutionary analyses, we show that a majority of CSα/β toxin scaffolds have experienced episodic influence of positive selection, while most non-CSα/β linear toxins evolve under the extreme influence of negative selection. For the first time, we have unraveled the molecular origin of the major scorpion toxin scaffolds, such as scorpion venom single von Willebrand factor C-domain peptides (SV-SVC), inhibitor cystine knot (ICK), disulphide-directed beta-hairpin (DDH), bradykinin potentiating peptides (BPP), linear non-disulphide bridged peptides and antimicrobial peptides (AMP). We have thus demonstrated that even neglected lineages of scorpions are a rich pool of novel biochemical components, which have evolved over millions of years to target specific ion channels in prey animals, and as a result, possess tremendous implications in therapeutics.

Turning Saccharomyces cerevisiae into a Frataxin-Independent Organism

PubMed Central

Yoon, Heeyong; Knight, Simon A. B.; Pandey, Alok; Pain, Jayashree; Turkarslan, Serdar; Pain, Debkumar; Dancis, Andrew

2015-01-01

Frataxin (Yfh1 in yeast) is a conserved protein and deficiency leads to the neurodegenerative disease Friedreich’s ataxia. Frataxin is a critical protein for Fe-S cluster assembly in mitochondria, interacting with other components of the Fe-S cluster machinery, including cysteine desulfurase Nfs1, Isd11 and the Isu1 scaffold protein. Yeast Isu1 with the methionine to isoleucine substitution (M141I), in which the E. coli amino acid is inserted at this position, corrected most of the phenotypes that result from lack of Yfh1 in yeast. This suppressor Isu1 behaved as a genetic dominant. Furthermore frataxin-bypass activity required a completely functional Nfs1 and correlated with the presence of efficient scaffold function. A screen of random Isu1 mutations for frataxin-bypass activity identified only M141 substitutions, including Ile, Cys, Leu, or Val. In each case, mitochondrial Nfs1 persulfide formation was enhanced, and mitochondrial Fe-S cluster assembly was improved in the absence of frataxin. Direct targeting of the entire E. coli IscU to ∆yfh1 mitochondria also ameliorated the mutant phenotypes. In contrast, expression of IscU with the reverse substitution i.e. IscU with Ile to Met change led to worsening of the ∆yfh1 phenotypes, including severely compromised growth, increased sensitivity to oxygen, deficiency in Fe-S clusters and heme, and impaired iron homeostasis. A bioinformatic survey of eukaryotic Isu1/prokaryotic IscU database entries sorted on the amino acid utilized at the M141 position identified unique groupings, with virtually all of the eukaryotic scaffolds using Met, and the preponderance of prokaryotic scaffolds using other amino acids. The frataxin-bypassing amino acids Cys, Ile, Leu, or Val, were found predominantly in prokaryotes. This amino acid position 141 is unique in Isu1, and the frataxin-bypass effect likely mimics a conserved and ancient feature of the prokaryotic Fe-S cluster assembly machinery. PMID:25996596

The phylogenomic roots of modern biochemistry: origins of proteins, cofactors and protein biosynthesis.

PubMed

Caetano-Anollés, Gustavo; Kim, Kyung Mo; Caetano-Anollés, Derek

2012-02-01

The complexity of modern biochemistry developed gradually on early Earth as new molecules and structures populated the emerging cellular systems. Here, we generate a historical account of the gradual discovery of primordial proteins, cofactors, and molecular functions using phylogenomic information in the sequence of 420 genomes. We focus on structural and functional annotations of the 54 most ancient protein domains. We show how primordial functions are linked to folded structures and how their interaction with cofactors expanded the functional repertoire. We also reveal protocell membranes played a crucial role in early protein evolution and show translation started with RNA and thioester cofactor-mediated aminoacylation. Our findings allow elaboration of an evolutionary model of early biochemistry that is firmly grounded in phylogenomic information and biochemical, biophysical, and structural knowledge. The model describes how primordial α-helical bundles stabilized membranes, how these were decorated by layered arrangements of β-sheets and α-helices, and how these arrangements became globular. Ancient forms of aminoacyl-tRNA synthetase (aaRS) catalytic domains and ancient non-ribosomal protein synthetase (NRPS) modules gave rise to primordial protein synthesis and the ability to generate a code for specificity in their active sites. These structures diversified producing cofactor-binding molecular switches and barrel structures. Accretion of domains and molecules gave rise to modern aaRSs, NRPS, and ribosomal ensembles, first organized around novel emerging cofactors (tRNA and carrier proteins) and then more complex cofactor structures (rRNA). The model explains how the generation of protein structures acted as scaffold for nucleic acids and resulted in crystallization of modern translation.

Benzoxaborole compounds for therapeutic uses: a patent review (2010- 2018).

PubMed

Nocentini, Alessio; Supuran, Claudiu T; Winum, Jean-Yves

2018-06-01

Benzoxaborole is a versatile boron-heterocyclic scaffold which has found in the last 10 years a broad spectrum of applications in medicinal chemistry, due to its physicochemical and drug-like properties. Use of benzoxaborole moiety in the design of compounds led to the discovery of new classes of anti-bacterial, anti-fungal, anti-protozoal, anti-viral as well as anti-inflammatory agents with interesting drug development perspectives. Areas covered: This article reviews the patent literature as well as chemistry literature during the period 2010-2018 where in several benzoxaborole derivatives with therapeutic options were reported. Expert opinion: Two benzoxaborole derivatives are already clinically used for the treatment of onychomycosis (tavaborole) and atopic dermatitis (crisaborole), with several others in various phases of clinical trials. By inhibiting enzymes essential in the life cycle of fungal, protozoan, bacterial and viral pathogens, it is probable that other compounds may soon enter the armamentarium of anti-infective agents. On the other hand, phosphodiesterase 4 seems to be the human target responsible of the anti-inflammatory action of some benzoxaboroles. The chemical versatility, peculiar mechanism of action related to the electron deficient nature of the boron atom, and ease of preparation make benzoxaboroles a highly interesting field for the pharmaceutical industry.

Low-Voltage Continuous Electrospinning Patterning.

PubMed

Li, Xia; Li, Zhaoying; Wang, Liyun; Ma, Guokun; Meng, Fanlong; Pritchard, Robyn H; Gill, Elisabeth L; Liu, Ye; Huang, Yan Yan Shery

2016-11-30

Electrospinning is a versatile technique for the construction of microfibrous and nanofibrous structures with considerable potential in applications ranging from textile manufacturing to tissue engineering scaffolds. In the simplest form, electrospinning uses a high voltage of tens of thousands volts to draw out ultrafine polymer fibers over a large distance. However, the high voltage limits the flexible combination of material selection, deposition substrate, and control of patterns. Prior studies show that by performing electrospinning with a well-defined "near-field" condition, the operation voltage can be decreased to the kilovolt range, and further enable more precise patterning of fibril structures on a planar surface. In this work, by using solution dependent "initiators", we demonstrate a further lowering of voltage with an ultralow voltage continuous electrospinning patterning (LEP) technique, which reduces the applied voltage threshold to as low as 50 V, simultaneously permitting direct fiber patterning. The versatility of LEP is shown using a wide range of combination of polymer and solvent systems for thermoplastics and biopolymers. Novel functionalities are also incorporated when a low voltage mode is used in place of a high voltage mode, such as direct printing of living bacteria; the construction of suspended single fibers and membrane networks. The LEP technique reported here should open up new avenues in the patterning of bioelements and free-form nano- to microscale fibrous structures.

Gene Therapy Vectors with Enhanced Transfection Based on Hydrogels Modified with Affinity Peptides

PubMed Central

Shepard, Jaclyn A.; Wesson, Paul J.; Wang, Christine E.; Stevans, Alyson C.; Holland, Samantha J.; Shikanov, Ariella; Grzybowski, Bartosz A.; Shea, Lonnie D.

2011-01-01

Regenerative strategies for damaged tissue aim to present biochemical cues that recruit and direct progenitor cell migration and differentiation. Hydrogels capable of localized gene delivery are being developed to provide a support for tissue growth, and as a versatile method to induce the expression of inductive proteins; however, the duration, level, and localization of expression isoften insufficient for regeneration. We thus investigated the modification of hydrogels with affinity peptides to enhance vector retention and increase transfection within the matrix. PEG hydrogels were modified with lysine-based repeats (K4, K8), which retained approximately 25% more vector than control peptides. Transfection increased 5- to 15-fold with K8 and K4 respectively, over the RDG control peptide. K8- and K4-modified hydrogels bound similar quantities of vector, yet the vector dissociation rate was reduced for K8, suggesting excessive binding that limited transfection. These hydrogels were subsequently applied to an in vitro co-culture model to induce NGF expression and promote neurite outgrowth. K4-modified hydrogels promoted maximal neurite outgrowth, likely due to retention of both the vector and the NGF. Thus, hydrogels modified with affinity peptides enhanced vector retention and increased gene delivery, and these hydrogels may provide a versatile scaffold for numerous regenerative medicine applications. PMID:21514659

CRISPR-Cas9 for medical genetic screens: applications and future perspectives.

PubMed

Xue, Hui-Ying; Ji, Li-Juan; Gao, Ai-Mei; Liu, Ping; He, Jing-Dong; Lu, Xiao-Jie

2016-02-01

CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR associated nuclease 9) systems have emerged as versatile and convenient (epi)genome editing tools and have become an important player in medical genetic research. CRISPR-Cas9 and its variants such as catalytically inactivated Cas9 (dead Cas9, dCas9) and scaffold-incorporating single guide sgRNA (scRNA) have been applied in various genomic screen studies. CRISPR screens enable high-throughput interrogation of gene functions in health and diseases. Compared with conventional RNAi screens, CRISPR screens incur less off-target effects and are more versatile in that they can be used in multiple formats such as knockout, knockdown and activation screens, and can target coding and non-coding regions throughout the genome. This powerful screen platform holds the potential of revolutionising functional genomic studies in the near future. Herein, we introduce the mechanisms of (epi)genome editing mediated by CRISPR-Cas9 and its variants, introduce the procedures and applications of CRISPR screen in functional genomics, compare it with conventional screen tools and at last discuss current challenges and opportunities and propose future directions. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Tissue Regeneration: A Silk Road.

PubMed

Jao, Dave; Mou, Xiaoyang; Hu, Xiao

2016-08-05

Silk proteins are natural biopolymers that have extensive structural possibilities for chemical and mechanical modifications to facilitate novel properties, functions, and applications in the biomedical field. The versatile processability of silk fibroins (SF) into different forms such as gels, films, foams, membranes, scaffolds, and nanofibers makes it appealing in a variety of applications that require mechanically superior, biocompatible, biodegradable, and functionalizable biomaterials. There is no doubt that nature is the world's best biological engineer, with simple, exquisite but powerful designs that have inspired novel technologies. By understanding the surface interaction of silk materials with living cells, unique characteristics can be implemented through structural modifications, such as controllable wettability, high-strength adhesiveness, and reflectivity properties, suggesting its potential suitability for surgical, optical, and other biomedical applications. All of the interesting features of SF, such as tunable biodegradation, anti-bacterial properties, and mechanical properties combined with potential self-healing modifications, make it ideal for future tissue engineering applications. In this review, we first demonstrate the current understanding of the structures and mechanical properties of SF and the various functionalizations of SF matrices through chemical and physical manipulations. Then the diverse applications of SF architectures and scaffolds for different regenerative medicine will be discussed in detail, including their current applications in bone, eye, nerve, skin, tendon, ligament, and cartilage regeneration.

αRep A3: A Versatile Artificial Scaffold for Metalloenzyme Design.

PubMed

Di Meo, Thibault; Ghattas, Wadih; Herrero, Christian; Velours, Christophe; Minard, Philippe; Mahy, Jean-Pierre; Ricoux, Rémy; Urvoas, Agathe

2017-07-26

αRep refers to a new family of artificial proteins based on a thermostable α-helical repeated motif. One of its members, αRep A3, forms a stable homo-dimer with a wide cleft that is able to accommodate metal complexes and thus appears to be suitable for generating new artificial biocatalysts. Based on the crystal structure of αRep A3, two positions (F119 and Y26) were chosen, and independently changed into cysteine residues. A phenanthroline ligand was covalently attached to the unique cysteine residue of each protein variant, and the corresponding biohybrids were purified and characterized. Once mutated and coupled to phenanthroline, the protein remained folded and dimeric. Copper(II) was specifically bound by the two biohybrids with two different binding modes. Furthermore, the holo-biohybrid A3F119NPH was found to be capable of enantioselectively catalyzing Diels-Alder (D-A) cycloadditions with up to 62 % ee. This study validates the choice of the αRep A3 dimer as a protein scaffold and provides a promising new route for the design and production of new enantioselective biohybrids based on entirely artificial proteins obtained from a highly diverse library. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalable synthesis and post-modification of a mesoporous metal-organic framework called NU-1000

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Timothy C.; Vermeulen, Nicolaas A.; Kim, In Soo

The synthesis of NU-1000, a highly robust mesoporous (containing pores >2 nm) metal-organic framework (MOF), can be conducted efficiently on a multigram scale from inexpensive starting materials. Tetrabromopyrene and (4-(ethoxycarbonyl)phenyl)boronic acid can easily be coupled to prepare the requisite organic strut with four metal-binding sites in the form of four carboxylic acids, while zirconyl chloride octahydrate is used as a precursor for the well-defined metal oxide clusters. NU-1000 has been reported as an excellent candidate for the separation of gases, and it is a versatile scaffold for heterogeneous catalysis. In particular, it is ideal for the catalytic deactivation of nervemore » agents, and it shows great promise as a new generic platform for a wide range of applications. Multiple post-synthetic modification protocols have been developed using NU-1000 as the parent material, making it a potentially useful scaffold for several catalytic applications. The procedure for the preparation of NU-1000 can be scaled up reliably, and it is suitable for the production of 50 g of the tetracarboxylic acid containing organic linker and 200 mg–2.5 g of NU-1000. The entire synthesis is performed without purification by column chromatography and can be completed within 10 d.« less

Dispensing of very low volumes of ultra high viscosity alginate gels: a new tool for encapsulation of adherent cells and rapid prototyping of scaffolds and implants.

PubMed

Gepp, Michael M; Ehrhart, Friederike; Shirley, Stephen G; Howitz, Steffen; Zimmermann, Heiko

2009-01-01

We present a tool for dispensing very low volumes (20 nL or more) of ultra high viscosity (UHV) medical-grade alginate hydrogels. It uses a modified piezo-driven micrometering valve, integrated into a versatile system that allows fast prototyping of encapsulation procedures and scaffold production. Valves show excellent dispensing properties for UHV alginate in concentrations of 0.4% and 0.7% and also for aqueous liquids. An optimized process flow provides excellent handling of biological samples under sterile conditions. This technique allows the encapsulation of adherent cells and structuring of substrates for biotechnology and regenerative medicine. A variety of cell lines showed at least 70% viability after encapsulation (including cell lines that are relevant in regenerative medicine like Hep G2), and time-lapse analysis revealed cells proliferating and showing limited motility under alginate spots. Cells show metabolic activity, gene product expression, and physiological function. Encapsulated cells have contact with the substrate and can exchange metabolites while being isolated from macromolecules in the environment. Contactless dispensing allows structuring of substrates with alginate, isolation and transfer of cell-alginate complexes, and the dispensing of biological active hydrogels like extracellular matrix-derived gels.

Potential of Electrospun Nanofibers for Biomedical and Dental Applications

PubMed Central

Zafar, Muhammad; Najeeb, Shariq; Khurshid, Zohaib; Vazirzadeh, Masoud; Zohaib, Sana; Najeeb, Bilal; Sefat, Farshid

2016-01-01

Electrospinning is a versatile technique that has gained popularity for various biomedical applications in recent years. Electrospinning is being used for fabricating nanofibers for various biomedical and dental applications such as tooth regeneration, wound healing and prevention of dental caries. Electrospun materials have the benefits of unique properties for instance, high surface area to volume ratio, enhanced cellular interactions, protein absorption to facilitate binding sites for cell receptors. Extensive research has been conducted to explore the potential of electrospun nanofibers for repair and regeneration of various dental and oral tissues including dental pulp, dentin, periodontal tissues, oral mucosa and skeletal tissues. However, there are a few limitations of electrospinning hindering the progress of these materials to practical or clinical applications. In terms of biomaterials aspects, the better understanding of controlled fabrication, properties and functioning of electrospun materials is required to overcome the limitations. More in vivo studies are definitely required to evaluate the biocompatibility of electrospun scaffolds. Furthermore, mechanical properties of such scaffolds should be enhanced so that they resist mechanical stresses during tissue regeneration applications. The objective of this article is to review the current progress of electrospun nanofibers for biomedical and dental applications. In addition, various aspects of electrospun materials in relation to potential dental applications have been discussed. PMID:28787871

Scalable synthesis and post-modification of a mesoporous metal-organic framework called NU-1000.

PubMed

Wang, Timothy C; Vermeulen, Nicolaas A; Kim, In Soo; Martinson, Alex B F; Stoddart, J Fraser; Hupp, Joseph T; Farha, Omar K

2016-01-01

The synthesis of NU-1000, a highly robust mesoporous (containing pores >2 nm) metal-organic framework (MOF), can be conducted efficiently on a multigram scale from inexpensive starting materials. Tetrabromopyrene and (4-(ethoxycarbonyl)phenyl)boronic acid can easily be coupled to prepare the requisite organic strut with four metal-binding sites in the form of four carboxylic acids, while zirconyl chloride octahydrate is used as a precursor for the well-defined metal oxide clusters. NU-1000 has been reported as an excellent candidate for the separation of gases, and it is a versatile scaffold for heterogeneous catalysis. In particular, it is ideal for the catalytic deactivation of nerve agents, and it shows great promise as a new generic platform for a wide range of applications. Multiple post-synthetic modification protocols have been developed using NU-1000 as the parent material, making it a potentially useful scaffold for several catalytic applications. The procedure for the preparation of NU-1000 can be scaled up reliably, and it is suitable for the production of 50 g of the tetracarboxylic acid containing organic linker and 200 mg-2.5 g of NU-1000. The entire synthesis is performed without purification by column chromatography and can be completed within 10 d.

Versatility of Chitosan-Based Biomaterials and Their Use as Scaffolds for Tissue Regeneration

PubMed Central

Vieira, Rodrigo Silveira; Melo, Iracema Matos; Araújo, Vilana Maria Adriano

2017-01-01

Chitosan is a naturally occurring polysaccharide obtained from chitin, present in abundance in the exoskeletons of crustaceans and insects. It has aroused great interest as a biomaterial for tissue engineering on account of its biocompatibility and biodegradation and its affinity for biomolecules. A significant number of research groups have investigated the application of chitosan as scaffolds for tissue regeneration. However, there is a wide variability in terms of physicochemical characteristics of chitosan used in some studies and its combinations with other biomaterials, making it difficult to compare results and standardize its properties. The current systematic review of literature on the use of chitosan for tissue regeneration consisted of a study of 478 articles in the PubMed database, which resulted, after applying inclusion criteria, in the selection of 61 catalogued, critically analysed works. The results demonstrated the effectiveness of chitosan-based biomaterials in 93.4% of the studies reviewed, whether or not combined with cells and growth factors, in the regeneration of various types of tissues in animals. However, the absence of clinical studies in humans, the inadequate experimental designs, and the lack of information concerning chitosan's characteristics limit the reproducibility and relevance of studies and the clinical applicability of chitosan. PMID:28567441

The Presence of Multiple Cellular Defects Associated with a Novel G50E Iron-Sulfur Cluster Scaffold Protein (ISCU) Mutation Leads to Development of Mitochondrial Myopathy*

PubMed Central

Saha, Prasenjit Prasad; Kumar, S. K. Praveen; Srivastava, Shubhi; Sinha, Devanjan; Pareek, Gautam; D'Silva, Patrick

2014-01-01

Iron-sulfur (Fe-S) clusters are versatile cofactors involved in regulating multiple physiological activities, including energy generation through cellular respiration. Initially, the Fe-S clusters are assembled on a conserved scaffold protein, iron-sulfur cluster scaffold protein (ISCU), in coordination with iron and sulfur donor proteins in human mitochondria. Loss of ISCU function leads to myopathy, characterized by muscle wasting and cardiac hypertrophy. In addition to the homozygous ISCU mutation (g.7044G→C), compound heterozygous patients with severe myopathy have been identified to carry the c.149G→A missense mutation converting the glycine 50 residue to glutamate. However, the physiological defects and molecular mechanism associated with G50E mutation have not been elucidated. In this report, we uncover mechanistic insights concerning how the G50E ISCU mutation in humans leads to the development of severe ISCU myopathy, using a human cell line and yeast as the model systems. The biochemical results highlight that the G50E mutation results in compromised interaction with the sulfur donor NFS1 and the J-protein HSCB, thus impairing the rate of Fe-S cluster synthesis. As a result, electron transport chain complexes show significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, the G50E mutant mitochondria display enhancement in iron level and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. Thus, our findings provide compelling evidence that the respiration defect due to impaired biogenesis of Fe-S clusters in myopathy patients leads to manifestation of complex clinical symptoms. PMID:24573684

Developing Targeted Hybrid Imaging Probes by Chelator Scaffolding

PubMed Central

2017-01-01

Positron emission tomography (PET) as well as optical imaging (OI) with peptide receptor targeting probes have proven their value for oncological applications but also show restrictions depending on the clinical field of interest. Therefore, the combination of both methods, particularly in a single molecule, could improve versatility in clinical routine. This proof of principle study aims to show that a chelator, Fusarinine C (FSC), can be utilized as scaffold for novel dimeric dual-modality imaging agents. Two targeting vectors (a minigastrin analogue (MG11) targeting cholecystokinin-2 receptor overexpression (CCK2R) or integrin αVβ3 targeting cyclic pentapeptides (RGD)) and a near-infrared fluorophore (Sulfo-Cyanine7) were conjugated to FSC. The probes were efficiently labeled with gallium-68 and in vitro experiments including determination of logD, stability, protein binding, cell binding, internalization, and biodistribution studies as well as in vivo micro-PET/CT and optical imaging in U-87MG αVβ3- and A431-CCK2R expressing tumor xenografted mice were carried out. Novel bioconjugates showed high receptor affinity and highly specific targeting properties at both receptors. Ex vivo biodistribution and micro-PET/CT imaging studies revealed specific tumor uptake accompanied by slow blood clearance and retention in nontargeted tissues (spleen, liver, and kidneys) leading to visualization of tumors at early (30 to 120 min p.i.). Excellent contrast in corresponding optical imaging studies was achieved especially at delayed time points (24 to 72 h p.i.). Our findings show the proof of principle of chelator scaffolding for hybrid imaging agents and demonstrate FSC being a suitable bifunctional chelator for this approach. Improvements to fine-tune pharmacokinetics are needed to translate this into a clinical setting. PMID:28462989

Stem cell culture and differentiation in microfluidic devices toward organ-on-a-chip.

PubMed

Zhang, Jie; Wei, Xiaofeng; Zeng, Rui; Xu, Feng; Li, XiuJun

2017-06-01

Microfluidic lab-on-a-chip provides a new platform with unique advantages to mimic complex physiological microenvironments in vivo and has been increasingly exploited to stem cell research. In this review, we highlight recent advances of microfluidic devices for stem cell culture and differentiation toward the development of organ-on-a-chip, especially with an emphasis on vital innovations within the last 2 years. Various aspects for improving on-chip stem-cell culture and differentiation, particularly toward organ-on-a-chip, are discussed, along with microenvironment control, surface modification, extracellular scaffolds, high throughput and stimuli. The combination of microfluidic technologies and stem cells hold great potential toward versatile systems of 'organ-on-a-chip' as desired. Adapted with permission from [1-8].

One-shot preparation of an inherently chiral trifunctional calix[4]arene from an easily available cone-triformylcalix[4]arene.

PubMed

Ciaccia, Maria; Tosi, Irene; Cacciapaglia, Roberta; Casnati, Alessandro; Baldini, Laura; Di Stefano, Stefano

2013-06-14

Via selective 1,3-distal intramolecular Cannizzaro disproportionation of an easily available cone-triformylcalix[4]arene, an inherently chiral trifunctional cone-calix[4]arene derivative has been prepared. The presence of three different functional groups (-CH2OH, -CHO and -COOH) at the upper rim of the calixarene scaffold makes this compound a versatile intermediate for the development of multifunctional devices. Interesting chiral discrimination of serine derivatives has been observed, presumably thanks to a multipoint-interaction involving the reversible imine bond formation and the hydrogen bonding of the hydroxyl group of the amino acid side-chain with the upper rim functional groups. Consistently, chiral discrimination was not observed with alanine and valine derivatives, lacking hydrogen bonding groups on the side-chain.

Beyond DNA origami: A look on the bright future of nucleic acid nanotechnology

PubMed Central

Michelotti, Nicole; Johnson-Buck, Alexander; Manzo, Anthony J.

2012-01-01

Nucleic acid nanotechnology exploits the programmable molecular recognition properties of natural and synthetic nucleic acids to assemble structures with nanometer-scale precision. In 2006, DNA origami transformed the field by providing a versatile platform for self-assembly of arbitrary shapes from one long DNA strand held in place by hundreds of short, site-specific (spatially addressable) DNA ”staples”. This revolutionary approach has led to the creation of a multitude of 2D and 3D scaffolds that form the basis for functional nanodevices. Not limited to nucleic acids, these nanodevices can incorporate other structural and functional materials, such as proteins and nanoparticles, making them broadly useful for current and future applications in emerging fields such as nanomedicine, nanoelectronics, and alternative energy. PMID:22131292

TMV Disk Scaffolds for Making sub-30 nm Silver Nanorings.

PubMed

Bayram, Serene; Zahr, Omar; Del Re, Julia; Blum, Amy Szuchmacher

2018-01-01

Nanosized bioscaffolds can be utilized to tackle the challenge of size reduction of metallic rings owing to their miniature features as well as their well-known biomineralization capacity. The tobacco mosaic virus coat protein is used as a command surface to grow and assemble silver nanoparticles into sub-30 nm rings. The versatility of TMV allows the formation of both solid silver rings and rings consisting of discrete silver nanoparticles. The pH-dependent coulombic surface map along with the annular geometry of the protein aggregate allow the generation of rings with or without a central nanoparticle. Our silver rings are believed to be the smallest to date, and they can offer a test material for existing theories on metallic nanorings of this heretofore unreached size scale.

Novel biocompatible polymeric blends for bone regeneration: Material and matrix design and development

NASA Astrophysics Data System (ADS)

Deng, Meng

The first part of the work presented in this dissertation is focused on the design and development of novel miscible and biocompatible polyphosphazene-polyester blends as candidate materials for scaffold-based bone tissue engineering applications. Biodegradable polyesters such as poly(lactide-co-glycolide) (PLAGA) are among the most widely used polymeric materials for bone tissue engineering. However, acidic degradation products resulting from the bulk degradation mechanism often lead to catastrophic failure of the structure integrity, and adversely affect biocompatibility both in vitro and in vivo. One promising approach to circumvent these limitations is to blend PLAGA with other macromolecules that can buffer the acidic degradation products with a controlled degradation rate. Biodegradable polyphosphazenes (PPHOS), a new class of biomedical materials, have proved to be superior candidate materials to achieve this objective due to their unique buffering degradation products. A highly practical blending approach was adopted to develop novel biocompatible, miscible blends of these two polymers. In order to achieve this miscibility, a series of amino acid ester, alkoxy, aryloxy, and dipeptide substituted PPHOS were synthesized to promote hydrogen bonding interactions with PLAGA. Five mixed-substituent PPHOS compositions were designed and blended with PLAGA at different weight ratios producing candidate blends via a mutual solvent method. Preliminary characterization identified two specific side groups namely glycylglycine dipeptide and phenylphenoxy that resulted in improved blend miscibility and enhanced in vitro osteocompatibility. These findings led to the synthesis of a mixed-substituent polyphosphazene poly[(glycine ethyl glycinato)1(phenylphenoxy)1phosphazene] (PNGEGPhPh) for blending with PLAGA. Two dipeptide-based blends having weight ratios of PNGEGPhPh to PLAGA namely 25:75 (Matrix1) and 50:50 (Matrix2) were fabricated. Both of the blends were characterized for miscibility, mechanical properties, degradation kinetics, and in vitro osteocompatibility. Primary rat osteoblasts (PRO) isolated from rat calvaria were used to evaluate their in vitro osteocompatibility. The blends were also characterized for in vivo biodegradability and biocompatibility using a rat subcutaneous implantation model. Successful in vivo scaffold-based tissue regeneration greatly depends on the scaffold material biocompatibility, mechanical stability, and scaffold architecture to promote tissue in-growth. The other part of the work in the dissertation is focused on the development of mechanically competent bioresorbable nano-structured three-dimensional (3D) hiomimetic scaffolds for bone tissue engineering applications. Scaffold material selection was based on achieving improved mechanical stability, in vitro osteoblast performance, and in vivo biocompatibility. A miscible PNGEGPhPh-PLAGA blend system developed and characterized in the first part of the thesis work was chosen to fabricate a nanofiber-based mechanically competent biomimetic scaffold via electrospinning. Due to its versatility, controllability and reproducibility, the technique of electrospinning was adopted to produce blend nanofibers. The polymer solution concentration and electrospinning parameters were optimized to produce blend fibers in the range of 50-500 nm to mimic dimensions of collagen fibrils present in the natural extracellular matrix of native bone. These blend nanofiber matrices supported PRO adhesion, proliferation and showed an elevated phenotype expression compared to PLAGA nanofibers. Orienting electrospun nanofibers in a concentric manner with an open central cavity created a mechanically competent 3D scaffold mimicking the bone marrow cavity, as well as, the lamellar structure of bone. The 3D biomimetic scaffold exhibited a similar characteristic mechanical behavior to that of native bone. Compressive modulus of the scaffold was found to be within the range of human trabecular bone. To our knowledge this is the first mechanically competent 3D electrospun nanofiber scaffold with mechanical properties in the middle range of human trabecular bone. The potential of this scaffold for bone repair was further investigated by monitoring the cellular activity and mechanical performance over time using in vitro culture. This biomimetic scaffold supported the robust PRO growth throughout the scaffold architecture and maintained osteoblast phenotype expression in vitro, which resulted in a similar cell-matrix organization to that of native bone and maintenance of structure integrity. (Abstract shortened by UMI.)

Efficient Moment-Based Inference of Admixture Parameters and Sources of Gene Flow

PubMed Central

Levin, Alex; Reich, David; Patterson, Nick; Berger, Bonnie

2013-01-01

The recent explosion in available genetic data has led to significant advances in understanding the demographic histories of and relationships among human populations. It is still a challenge, however, to infer reliable parameter values for complicated models involving many populations. Here, we present MixMapper, an efficient, interactive method for constructing phylogenetic trees including admixture events using single nucleotide polymorphism (SNP) genotype data. MixMapper implements a novel two-phase approach to admixture inference using moment statistics, first building an unadmixed scaffold tree and then adding admixed populations by solving systems of equations that express allele frequency divergences in terms of mixture parameters. Importantly, all features of the model, including topology, sources of gene flow, branch lengths, and mixture proportions, are optimized automatically from the data and include estimates of statistical uncertainty. MixMapper also uses a new method to express branch lengths in easily interpretable drift units. We apply MixMapper to recently published data for Human Genome Diversity Cell Line Panel individuals genotyped on a SNP array designed especially for use in population genetics studies, obtaining confident results for 30 populations, 20 of them admixed. Notably, we confirm a signal of ancient admixture in European populations—including previously undetected admixture in Sardinians and Basques—involving a proportion of 20–40% ancient northern Eurasian ancestry. PMID:23709261

Single-molecule sequencing and Hi-C-based proximity-guided assembly of amaranth (Amaranthus hypochondriacus) chromosomes provide insights into genome evolution.

PubMed

Lightfoot, D J; Jarvis, D E; Ramaraj, T; Lee, R; Jellen, E N; Maughan, P J

2017-08-31

Amaranth (Amaranthus hypochondriacus) was a food staple among the ancient civilizations of Central and South America that has recently received increased attention due to the high nutritional value of the seeds, with the potential to help alleviate malnutrition and food security concerns, particularly in arid and semiarid regions of the developing world. Here, we present a reference-quality assembly of the amaranth genome which will assist the agronomic development of the species. Utilizing single-molecule, real-time sequencing (Pacific Biosciences) and chromatin interaction mapping (Hi-C) to close assembly gaps and scaffold contigs, respectively, we improved our previously reported Illumina-based assembly to produce a chromosome-scale assembly with a scaffold N50 of 24.4 Mb. The 16 largest scaffolds contain 98% of the assembly and likely represent the haploid chromosomes (n = 16). To demonstrate the accuracy and utility of this approach, we produced physical and genetic maps and identified candidate genes for the betalain pigmentation pathway. The chromosome-scale assembly facilitated a genome-wide syntenic comparison of amaranth with other Amaranthaceae species, revealing chromosome loss and fusion events in amaranth that explain the reduction from the ancestral haploid chromosome number (n = 18) for a tetraploid member of the Amaranthaceae. The assembly method reported here minimizes cost by relying primarily on short-read technology and is one of the first reported uses of in vivo Hi-C for assembly of a plant genome. Our analyses implicate chromosome loss and fusion as major evolutionary events in the 2n = 32 amaranths and clearly establish the homoeologous relationship among most of the subgenome chromosomes, which will facilitate future investigations of intragenomic changes that occurred post polyploidization.

Bulky Trichomonad Genomes: Encoding a Swiss Army Knife.

PubMed

Barratt, Joel; Gough, Rory; Stark, Damien; Ellis, John

2016-10-01

The trichomonads are a remarkably successful lineage of ancient, predominantly parasitic protozoa. Recent molecular analyses have revealed extensive duplication of certain genetic loci in trichomonads. Consequently, their genomes are exceptionally large compared to other parasitic protozoa. Retention of these large gene expansions across different trichomonad families raises the question: do these duplications afford an advantage? Many duplicated genes are linked to the parasitic lifestyle and some are regulated differently to their paralogues, suggesting they have acquired new functions. It is proposed that these large genomes encode a Swiss army knife of sorts, packed with a multitude of tools for use in many different circumstances. This may have bestowed trichomonads with the extraordinary versatility that has undoubtedly contributed to their success. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aminoacyl-tRNA synthetases: versatile players in the changing theater of translation.

PubMed Central

Francklyn, Christopher; Perona, John J; Puetz, Joern; Hou, Ya-Ming

2002-01-01

Aminoacyl-tRNA synthetases attach amino acids to the 3' termini of cognate tRNAs to establish the specificity of protein synthesis. A recent Asilomar conference (California, January 13-18, 2002) discussed new research into the structure-function relationship of these crucial enzymes, as well as a multitude of novel functions, including participation in amino acid biosynthesis, cell cycle control, RNA splicing, and export of tRNAs from nucleus to cytoplasm in eukaryotic cells. Together with the discovery of their role in the cellular synthesis of proteins to incorporate selenocysteine and pyrrolysine, these diverse functions of aminoacyl-tRNA synthetases underscore the flexibility and adaptability of these ancient enzymes and stimulate the development of new concepts and methods for expanding the genetic code. PMID:12458790

Designing a Bio-responsive Robot from DNA Origami

PubMed Central

Ben-Ishay, Eldad; Abu-Horowitz, Almogit; Bachelet, Ido

2013-01-01

Nucleic acids are astonishingly versatile. In addition to their natural role as storage medium for biological information1, they can be utilized in parallel computing2,3 , recognize and bind molecular or cellular targets4,5 , catalyze chemical reactions6,7 , and generate calculated responses in a biological system8,9. Importantly, nucleic acids can be programmed to self-assemble into 2D and 3D structures10-12, enabling the integration of all these remarkable features in a single robot linking the sensing of biological cues to a preset response in order to exert a desired effect. Creating shapes from nucleic acids was first proposed by Seeman13, and several variations on this theme have since been realized using various techniques11,12,14,15 . However, the most significant is perhaps the one proposed by Rothemund, termed scaffolded DNA origami16. In this technique, the folding of a long (>7,000 bases) single-stranded DNA 'scaffold' is directed to a desired shape by hundreds of short complementary strands termed 'staples'. Folding is carried out by temperature annealing ramp. This technique was successfully demonstrated in the creation of a diverse array of 2D shapes with remarkable precision and robustness. DNA origami was later extended to 3D as well17,18 . The current paper will focus on the caDNAno 2.0 software19 developed by Douglas and colleagues. caDNAno is a robust, user-friendly CAD tool enabling the design of 2D and 3D DNA origami shapes with versatile features. The design process relies on a systematic and accurate abstraction scheme for DNA structures, making it relatively straightforward and efficient. In this paper we demonstrate the design of a DNA origami nanorobot that has been recently described20. This robot is 'robotic' in the sense that it links sensing to actuation, in order to perform a task. We explain how various sensing schemes can be integrated into the structure, and how this can be relayed to a desired effect. Finally we use Cando21 to simulate the mechanical properties of the designed shape. The concept we discuss can be adapted to multiple tasks and settings. PMID:23893007

Evolution Stings: The Origin and Diversification of Scorpion Toxin Peptide Scaffolds

PubMed Central

Sunagar, Kartik; Undheim, Eivind A. B.; Chan, Angelo H. C.; Koludarov, Ivan; Muñoz-Gómez, Sergio A.; Antunes, Agostinho; Fry, Bryan G.

2013-01-01

The episodic nature of natural selection and the accumulation of extreme sequence divergence in venom-encoding genes over long periods of evolutionary time can obscure the signature of positive Darwinian selection. Recognition of the true biocomplexity is further hampered by the limited taxon selection, with easy to obtain or medically important species typically being the subject of intense venom research, relative to the actual taxonomical diversity in nature. This holds true for scorpions, which are one of the most ancient terrestrial venomous animal lineages. The family Buthidae that includes all the medically significant species has been intensely investigated around the globe, while almost completely ignoring the remaining non-buthid families. Australian scorpion lineages, for instance, have been completely neglected, with only a single scorpion species (Urodacus yaschenkoi) having its venom transcriptome sequenced. Hence, the lack of venom composition and toxin sequence information from an entire continent’s worth of scorpions has impeded our understanding of the molecular evolution of scorpion venom. The molecular origin, phylogenetic relationships and evolutionary histories of most scorpion toxin scaffolds remain enigmatic. In this study, we have sequenced venom gland transcriptomes of a wide taxonomical diversity of scorpions from Australia, including buthid and non-buthid representatives. Using state-of-art molecular evolutionary analyses, we show that a majority of CSα/β toxin scaffolds have experienced episodic influence of positive selection, while most non-CSα/β linear toxins evolve under the extreme influence of negative selection. For the first time, we have unraveled the molecular origin of the major scorpion toxin scaffolds, such as scorpion venom single von Willebrand factor C-domain peptides (SV-SVC), inhibitor cystine knot (ICK), disulphide-directed beta-hairpin (DDH), bradykinin potentiating peptides (BPP), linear non-disulphide bridged peptides and antimicrobial peptides (AMP). We have thus demonstrated that even neglected lineages of scorpions are a rich pool of novel biochemical components, which have evolved over millions of years to target specific ion channels in prey animals, and as a result, possess tremendous implications in therapeutics. PMID:24351712

Benzomorphan scaffold for opioid analgesics and pharmacological tools development: A comprehensive review.

PubMed

Turnaturi, Rita; Marrazzo, Agostino; Parenti, Carmela; Pasquinucci, Lorella

2018-03-25

Benzomorphan, derived by morphine skeleton simplification, has been the subject of exploration in medicinal chemistry for the development of new drugs and pharmacological tools to explore opioid pharmacology in vitro and in vivo. Building upon these evidences, the design and synthesis of benzomorphan-based compounds, appropriately modified at the basic nitrogen and/or the phenolic hydroxyl (8-OH) group, represent a valid and versatile strategy to obtain analgesics. In this review, to improve the body of information in this field, we report structure activity-relationships (SARs) of benzomorphan-based compounds analysing data literature of last 25 years. Collectively, SARs data highlighted that the benzomorphan nucleus represents a template in the achievement of a specific functional profile, by modifying N-substituent or 8-OH group. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Micromotors for "Chemistry-on-the-Fly".

PubMed

Karshalev, Emil; Esteban-Fernández de Ávila, Berta; Wang, Joseph

2018-03-21

This perspective reviews mobile micro/nanomotor scaffolds for performing "chemistry-on-the-fly". Synthetic nano/micromotors offer great versatility and distinct advantages in diverse chemical applications owing to their efficient propulsion and facile surface functionalization that allow these mobile platforms to move and disperse reactive materials across the solution. Such dynamic microreactors have led to accelerated chemical processes, including organic pollutant degradation, metal chelation, biorecognition, redox chemistry, chemical "writing", and a variety of other chemical transformations. Representative examples of such micromotor-enhanced chemical reactions are discussed, focusing on the specific chemical role of these mobile microreactors. The advantages, gaps and limitations of using micromotors as mobile chemical platforms are discussed, concluding with the future prospects of this emerging field. We envision that artificial nano/micromotors will become attractive dynamic tools for speeding up and enhancing "on-the-fly" chemical reactions.

Endoradiotherapy in cancer treatment--basic concepts and future trends.

PubMed

Zoller, Frederic; Eisenhut, Michael; Haberkorn, Uwe; Mier, Walter

2009-12-25

Endoradiotherapy represents an alternative therapeutic method in cancer treatment with advantageous features compared to chemotherapy and radiation therapy. Intelligent dose delivery concepts using small drugs, peptides or antibodies as radionuclide carriers enable the verification of a selective accumulation in the tumour lesion and to reduce radiation toxicity for the peripheral organs. The development of endoradiotherapeutic agents, especially chelator-conjugated biomolecules, for example ibritumomab tiuxetan or DOTATOC, gains importance due to the stable complexation of versatile radiometals, such as (90)Y or (177)Lu. The rational design of novel target binding sides and their grafting into a drug scaffold is a highly promising strategy, which may promote further implication in endoradiotherapy. This review highlights the basic concepts of endoradiotherapy and discusses the potential of targeted therapy and the properties of energy-rich particles emitted by radionuclides for tumour therapy.

Designing Dendrimer and Miktoarm Polymer Based Multi-Tasking Nanocarriers for Efficient Medical Therapy.

PubMed

Sharma, Anjali; Kakkar, Ashok

2015-09-17

To address current complex health problems, there has been an increasing demand for smart nanocarriers that could perform multiple complimentary biological tasks with high efficacy. This has provoked the design of tailor made nanocarriers, and the scientific community has made tremendous effort in meeting daunting challenges associated with synthetically articulating multiple functions into a single scaffold. Branched and hyper-branched macromolecular architectures have offered opportunities in enabling carriers with capabilities including location, delivery, imaging etc. Development of simple and versatile synthetic methodologies for these nanomaterials has been the key in diversifying macromolecule based medical therapy and treatment. This review highlights the advancement from conventional "only one function" to multifunctional nanomedicine. It is achieved by synthetic elaboration of multivalent platforms in miktoarm polymers and dendrimers by physical encapsulation, covalent linking and combinations thereof.

Synthesis of Benzannulated Medium-ring Lactams via a Tandem Oxidative Dearomatization-Ring Expansion Reaction.

PubMed

Guney, Tezcan; Wenderski, Todd A; Boudreau, Matthew W; Tan, Derek S

2018-06-23

Medium-ring natural products exhibit diverse biological activities but such scaffolds are underrepresented in probe and drug discovery efforts due to the limitations of classical macrocyclization reactions. We report herein a tandem oxidative dearomatization-ring-expanding rearoma¬tization (ODRE) reaction that generates benzannulated medium-ring lactams directly from simple bicyclic substrates. The reaction accommodates diverse aryl substrates (haloarenes, aryl ethers, aryl amides, heterocycles) and strategic incorporation of a bridgehead alcohol generates a versatile ketone moiety in the products amenable to downstream modifications. Cheminformatic analysis indicates that these medium rings access regions of chemical space that overlap with related natural products and are distinct from synthetic drugs, setting the stage for their use in discovery screening against novel biological targets. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ru(II) dyads derived from 2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline: versatile photosensitizers for photodynamic applications.

PubMed

Stephenson, Mat; Reichardt, Christian; Pinto, Mitch; Wächtler, Maria; Sainuddin, Tariq; Shi, Ge; Yin, Huimin; Monro, Susan; Sampson, Eric; Dietzek, Benjamin; McFarland, Sherri A

2014-11-13

Combining the best attributes of organic photosensitizers with those of coordination complexes is an elegant way to achieve prolonged excited state lifetimes in Ru(II) dyads. Not only do their reduced radiative and nonradiative rates provide ample time for photosensitization of reactive oxygen species at low oxygen tension but they also harness the unique properties of (3)IL states that can act as discrete units or in concert with (3)MLCT states. The imidazo[4,5-f][1,10]phenanthroline framework provides a convenient tether for linking π-expansive ligands such as pyrene to a Ru(II) scaffold, and the stabilizing coligands can fine-tune the chemical and biological properties of these bichromophoric systems. The resulting dyads described in this study exhibited nanomolar light cytotoxicities against cancer cells with photocytotoxicity indices exceeding 400 for some coligands employed. This potency extended to bacteria, where concentrations as low as 10 nM destroyed 75% of a bacterial population. Notably, these dyads remained extremely active against biofilm with light photocytotoxicities against these more resistant bacterial populations in the 10-100 nM regime. The results from this study demonstrate the versatility of these highly potent photosensitizers in destroying both cancer and bacterial cells and expand the scope of compounds that utilize low-lying (3)IL states for photobiological applications.

Achieving biopolymer synergy in systems chemistry.

PubMed

Bai, Yushi; Chotera, Agata; Taran, Olga; Liang, Chen; Ashkenasy, Gonen; Lynn, David G

2018-05-31

Synthetic and materials chemistry initiatives have enabled the translation of the macromolecular functions of biology into synthetic frameworks. These explorations into alternative chemistries of life attempt to capture the versatile functionality and adaptability of biopolymers in new orthogonal scaffolds. Information storage and transfer, however, so beautifully represented in the central dogma of biology, require multiple components functioning synergistically. Over a single decade, the emerging field of systems chemistry has begun to catalyze the construction of mutualistic biopolymer networks, and this review begins with the foundational small-molecule-based dynamic chemical networks and peptide amyloid-based dynamic physical networks on which this effort builds. The approach both contextualizes the versatile approaches that have been developed to enrich chemical information in synthetic networks and highlights the properties of amyloids as potential alternative genetic elements. The successful integration of both chemical and physical networks through β-sheet assisted replication processes further informs the synergistic potential of these networks. Inspired by the cooperative synergies of nucleic acids and proteins in biology, synthetic nucleic-acid-peptide chimeras are now being explored to extend their informational content. With our growing range of synthetic capabilities, structural analyses, and simulation technologies, this foundation is radically extending the structural space that might cross the Darwinian threshold for the origins of life as well as creating an array of alternative systems capable of achieving the progressive growth of novel informational materials.

Methodology of citrate-based biomaterial development and application

NASA Astrophysics Data System (ADS)

Tran, M. Richard

Biomaterials play central roles in modern strategies of regenerative medicine and tissue engineering. Attempts to find tissue-engineered solutions to cure various injuries or diseases have led to an enormous increase in the number of polymeric biomaterials over the past decade. The breadth of new materials arises from the multiplicity of anatomical locations, cell types, and mode of application, which all place application-specific requirements on the biomaterial. Unfortunately, many of the currently available biodegradable polymers are limited in their versatility to meet the wide range of requirements for tissue engineering. Therefore, a methodology of biomaterial development, which is able to address a broad spectrum of requirements, would be beneficial to the biomaterial field. This work presents a methodology of citrate-based biomaterial design and application to meet the multifaceted needs of tissue engineering. We hypothesize that (1) citric acid, a non-toxic metabolic product of the body (Krebs Cycle), can be exploited as a universal multifunctional monomer and reacted with various diols to produce a new class of soft biodegradable elastomers with the flexibility to tune the material properties of the resulting material to meet a wide range of requirements; (2) the newly developed citrate-based polymers can be used as platform biomaterials for the design of novel tissue engineering scaffolding; and (3) microengineering approaches in the form thin scaffold sheets, microchannels, and a new porogen design can be used to generate complex cell-cell and cell-microenvironment interactions to mimic tissue complexity and architecture. To test these hypotheses, we first developed a methodology of citrate-based biomaterial development through the synthesis and characterization of a family of in situ crosslinkable and urethane-doped elastomers, which are synthesized using simple, cost-effective strategies and offer a variety methods to tailor the material properties to meet the needs of a particular application. Next, we introduced a new porogen generation technique, and showed the potential application of the newly developed materials through the fabrication and characterization of scaffold sheets, multiphasic small diameter vascular grafts, and multichanneled nerve guides. Finally, the in vivo applications of citrate-based materials are exemplified through the evaluation of peripheral nerve regeneration using multichanneled guides and the ability to assist in injection-based endoscopic mucosal resection therapy. The results presented in this work show that citric acid can be utilized as a cornerstone in the development of novel biodegradable materials, and combined with microengineering approaches to produce the next generation of tissue engineering scaffolding. These enabling new biomaterials and scaffolding strategies should address many of the existing challenges in tissue engineering and advance the field as a whole.

The performance of silk scaffolds in a rat model of augmentation cystoplasty.

PubMed

Seth, Abhishek; Chung, Yeun Goo; Gil, Eun Seok; Tu, Duong; Franck, Debra; Di Vizio, Dolores; Adam, Rosalyn M; Kaplan, David L; Estrada, Carlos R; Mauney, Joshua R

2013-07-01

The diverse processing plasticity of silk-based biomaterials offers a versatile platform for understanding the impact of structural and mechanical matrix properties on bladder regenerative processes. Three distinct groups of 3-D matrices were fabricated from aqueous solutions of Bombyx mori silk fibroin either by a gel spinning technique (GS1 and GS2 groups) or a solvent-casting/salt-leaching method in combination with silk film casting (FF group). SEM analyses revealed that GS1 matrices consisted of smooth, compact multi-laminates of parallel-oriented silk fibers while GS2 scaffolds were composed of porous (pore size range, 5-50 μm) lamellar-like sheets buttressed by a dense outer layer. Bi-layer FF scaffolds were comprised of porous foams (pore size, ~400 μm) fused on their external face with a homogenous, nonporous silk film. Silk groups and small intestinal submucosa (SIS) matrices were evaluated in a rat model of augmentation cystoplasty for 10 weeks of implantation and compared to cystotomy controls. Gross tissue evaluations revealed the presence of intra-luminal stones in all experimental groups. The incidence and size of urinary calculi was the highest in animals implanted with gel spun silk matrices and SIS with frequencies ≥57% and stone diameters of 3-4 mm. In contrast, rats augmented with FF scaffolds displayed substantially lower rates (20%) and stone size (2 mm), similar to the levels observed in controls (13%, 2 mm). Histological (hematoxylin and eosin, Masson's trichrome) and immunohistochemical (IHC) analyses showed comparable extents of smooth muscle regeneration and contractile protein (α-smooth muscle actin and SM22α) expression within defect sites supported by all matrix groups similar to controls. Parallel evaluations demonstrated the formation of a transitional, multi-layered urothelium with prominent uroplakin and p63 protein expression in all experimental groups. De novo innervation and vascularization processes were evident in all regenerated tissues indicated by Fox3-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. In comparison to other biomaterial groups, cystometric analyses at 10 weeks post-op revealed that animals implanted with the FF matrix configuration displayed superior urodynamic characteristics including compliance, functional capacity, as well as spontaneous non voiding contractions consistent with control levels. Our data demonstrate that variations in scaffold processing techniques can influence the in vivo functional performance of silk matrices in bladder reconstructive procedures. Copyright © 2013 Elsevier Ltd. All rights reserved.

Activated GTPase movement on an RNA scaffold drives cotranslational protein targeting

PubMed Central

Shen, Kuang; Arslan, Sinan; Akopian, David; Ha, Taekjip; Shan, Shu-ou

2012-01-01

Roughly one third of the proteome is initially destined for the eukaryotic endoplasmic reticulum or the bacterial plasma membrane1. The proper localization of these proteins is mediated by a universally conserved protein targeting machinery, the signal recognition particle (SRP), which recognizes ribosomes carrying signal sequences2–4 and, via interactions with the SRP receptor5,6, delivers them to the protein translocation machinery on the target membrane7. The SRP is an ancient ribonucleoprotein particle containing an essential, elongated SRP RNA whose precise functions have remained elusive. Here, we used single molecule fluorescence microscopy to demonstrate that the SRP-receptor GTPase complex, after initial assembly at the tetraloop end of SRP RNA, travels over 100 Å to the distal end of this RNA where rapid GTP hydrolysis occurs. This movement is negatively regulated by the translating ribosome and, at a later stage, positively regulated by the SecYEG translocon, providing an attractive mechanism to ensure the productive exchange of the targeting and translocation machineries at the ribosome exit site with exquisite spatial and temporal accuracy. Our results show that large RNAs can act as molecular scaffolds that enable the facile exchange of distinct factors and precise timing of molecular events in a complex cellular process; this concept may be extended to similar phenomena in other ribonucleoprotein complexes. PMID:23235881

Bioconjugated Quantum Dots for In Vivo Molecular and Cellular Imaging

PubMed Central

Smith, Andrew M.; Duan, Hongwei; Mohs, Aaron M.; Nie, Shuming

2008-01-01

Semiconductor quantum dots (QDs) are tiny light-emitting particles on the nanometer scale, and are emerging as a new class of fluorescent labels for biology and medicine. In comparison with organic dyes and fluorescent proteins, they have unique optical and electronic properties, with size-tunable light emission, superior signal brightness, resistance to photobleaching, and broad absorption spectra for simultaneous excitation of multiple fluorescence colors. QDs also provide a versatile nanoscale scaffold for designing multifunctional nanoparticles with both imaging and therapeutic functions. When linked with targeting ligands such as antibodies, peptides or small molecules, QDs can be used to target tumor biomarkers as well as tumor vasculatures with high affinity and specificity. Here we discuss the synthesis and development of state-of-the-art QD probes and their use for molecular and cellular imaging. We also examine key issues for in vivo imaging and therapy, such as nanoparticle biodistribution, pharmacokinetics, and toxicology. PMID:18495291

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

PubMed Central

Shirazi, Seyed Farid Seyed; Gharehkhani, Samira; Mehrali, Mehdi; Yarmand, Hooman; Metselaar, Hendrik Simon Cornelis; Adib Kadri, Nahrizul; Osman, Noor Azuan Abu

2015-01-01

Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article. PMID:27877783

The eukaryotic RNA exosome: same scaffold but variable catalytic subunits.

PubMed

Lykke-Andersen, Søren; Tomecki, Rafal; Jensen, Torben Heick; Dziembowski, Andrzej

2011-01-01

The RNA exosome is a versatile ribonucleolytic protein complex that participates in a multitude of cellular RNA processing and degradation events. It consists of an invariable nine-subunit core that associates with a variety of enzymatically active subunits and co-factors. These contribute to or even provide the catalytic activity and substrate specificity of the complex. The S. cerevisiae exosome has been intensively studied since its discovery in 1997 and thus serves as the archetype of eukaryotic exosomes. Notably, its catalytic potential, derived exclusively from associated subunits, differs between the nuclear and cytoplasmic versions of the complex. The same holds true for other eukaryotes, however, recent discoveries from various laboratories including our own have revealed that there are variations on this theme. Here, we review the latest findings concerning catalytic subunits of eukaryotic exosomes, and we discuss the apparent need for differential composition and subcellular distribution of exosome variants.

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing.

PubMed

Shirazi, Seyed Farid Seyed; Gharehkhani, Samira; Mehrali, Mehdi; Yarmand, Hooman; Metselaar, Hendrik Simon Cornelis; Adib Kadri, Nahrizul; Osman, Noor Azuan Abu

2015-06-01

Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.

GPU-enabled molecular dynamics simulations of ankyrin kinase complex

NASA Astrophysics Data System (ADS)

Gautam, Vertika; Chong, Wei Lim; Wisitponchai, Tanchanok; Nimmanpipug, Piyarat; Zain, Sharifuddin M.; Rahman, Noorsaadah Abd.; Tayapiwatana, Chatchai; Lee, Vannajan Sanghiran

2014-10-01

The ankyrin repeat (AR) protein can be used as a versatile scaffold for protein-protein interactions. It has been found that the heterotrimeric complex between integrin-linked kinase (ILK), PINCH, and parvin is an essential signaling platform, serving as a convergence point for integrin and growth-factor signaling and regulating cell adhesion, spreading, and migration. Using ILK-AR with high affinity for the PINCH1 as our model system, we explored a structure-based computational protocol to probe and characterize binding affinity hot spots at protein-protein interfaces. In this study, the long time scale dynamics simulations with GPU accelerated molecular dynamics (MD) simulations in AMBER12 have been performed to locate the hot spots of protein-protein interaction by the analysis of the Molecular Mechanics-Poisson-Boltzmann Surface Area/Generalized Born Solvent Area (MM-PBSA/GBSA) of the MD trajectories. Our calculations suggest good binding affinity of the complex and also the residues critical in the binding.

Electrospinning as a powerful technique for biomedical applications: a critically selected survey.

PubMed

Villarreal-Gómez, Luis Jesús; Cornejo-Bravo, José Manuel; Vera-Graziano, Ricardo; Grande, Daniel

2016-01-01

Nowadays, electrospinning has become one of the most versatile, easy, and cost-effective techniques to engineer advanced materials used for many applications, especially in the biomedical and environmental areas. Like the numerous patents around the world, the increasing number of papers witnesses the huge potential of this simple process, and many companies have been emerged during the last years to exploit its innumerable applications. This article presents a critically selected overview of polymers that can be used to produce nanofibers, along with the biomedical applications of the resulting electrospun scaffolds. We have focused on about seven natural and synthetic polymers, but many more can be found in the literature, either as their pristine state or as composites with ceramics, metals, and other polymers. The description of some strategies for nanofiber production, and the characterization used to evaluate their optimization, has been discussed. Finally, several polymers have been recognized as highlights for future work.

Macroscopic ordering of helical pores for arraying guest molecules noncentrosymmetrically

PubMed Central

Li, Chunji; Cho, Joonil; Yamada, Kuniyo; Hashizume, Daisuke; Araoka, Fumito; Takezoe, Hideo; Aida, Takuzo; Ishida, Yasuhiro

2015-01-01

Helical nanostructures have attracted continuous attention, not only as media for chiral recognition and synthesis, but also as motifs for studying intriguing physical phenomena that never occur in centrosymmetric systems. To improve the quality of signals from these phenomena, which is a key issue for their further exploration, the most straightforward is the macroscopic orientation of helices. Here as a versatile scaffold to rationally construct this hardly accessible structure, we report a polymer framework with helical pores that unidirectionally orient over a large area (∼10 cm2). The framework, prepared by crosslinking a supramolecular liquid crystal preorganized in a magnetic field, is chemically robust, functionalized with carboxyl groups and capable of incorporating various basic or cationic guest molecules. When a nonlinear optical chromophore is incorporated in the framework, the resultant complex displays a markedly efficient nonlinear optical output, owing to the coherence of signals ensured by the macroscopically oriented helical structure. PMID:26416086

Novel solution-phase structures of gallium-containing pyrogallol[4]arene scaffolds**

PubMed Central

Kumari, Harshita; Kline, Steven R.; Wycoff, Wei G.; Paul, Rick L.; Mossine, Andrew V.; Deakyne, Carol A.; Atwood, Jerry L.

2012-01-01

The variations in architecture of gallium-seamed (PgC4Ga) and gallium-zinc-seamed (PgC4GaZn) C-butylpyrogallol[4]arene nanoassemblies in solution (SANS/NMR) versus the solid state (XRD) have been investigated. Rearrangement from the solid-state spheroidal to the solution-phase toroidal shape differentiates the gallium-containing pyrogallol[4]arene nanoassemblies from all other PgCnM nanocapsules studied thus far. Different structural arrangements of the metals and arenes of PgC4Ga versus PgC4GaZn have been deduced from the different toroidal dimensions, C–H proton environments and guest encapsulation of the two toroids. PGAA of mixed-metal hexamers reveals a decrease in gallium-to-metal ratio as the second metal varies from cobalt to zinc. Overall, the combined study demonstrates the versatility of gallium in directing the self-assembly of pyrogallol[4]arenes into novel nanoarchitectures. PMID:22511521

A virus-based biocatalyst

NASA Astrophysics Data System (ADS)

Carette, Noëlle; Engelkamp, Hans; Akpa, Eric; Pierre, Sebastien J.; Cameron, Neil R.; Christianen, Peter C. M.; Maan, Jan C.; Thies, Jens C.; Weberskirch, Ralf; Rowan, Alan E.; Nolte, Roeland J. M.; Michon, Thierry; van Hest, Jan C. M.

2007-04-01

Virus particles are probably the most precisely defined nanometre-sized objects that can be formed by protein self-assembly. Although their natural function is the storage and transport of genetic material, they have more recently been applied as scaffolds for mineralization and as containers for the encapsulation of inorganic compounds. The reproductive power of viruses has been used to develop versatile analytical methods, such as phage display, for the selection and identification of (bio)active compounds. To date, the combined use of self-assembly and reproduction has not been used for the construction of catalytic systems. Here we describe a self-assembled system based on a plant virus that has its coat protein genetically modified to provide it with a lipase enzyme. Using single-object and bulk catalytic studies, we prove that the virus-anchored lipase molecules are catalytically active. This anchored biocatalyst, unlike man-made supported catalysts, has the capability to reproduce itself in vivo, generating many independent catalytically active copies.

Lipid-bilayer-assisted two-dimensional self-assembly of DNA origami nanostructures

NASA Astrophysics Data System (ADS)

Suzuki, Yuki; Endo, Masayuki; Sugiyama, Hiroshi

2015-08-01

Self-assembly is a ubiquitous approach to the design and fabrication of novel supermolecular architectures. Here we report a strategy termed `lipid-bilayer-assisted self-assembly' that is used to assemble DNA origami nanostructures into two-dimensional lattices. DNA origami structures are electrostatically adsorbed onto a mica-supported zwitterionic lipid bilayer in the presence of divalent cations. We demonstrate that the bilayer-adsorbed origami units are mobile on the surface and self-assembled into large micrometre-sized lattices in their lateral dimensions. Using high-speed atomic force microscopy imaging, a variety of dynamic processes involved in the formation of the lattice, such as fusion, reorganization and defect filling, are successfully visualized. The surface modifiability of the assembled lattice is also demonstrated by in situ decoration with streptavidin molecules. Our approach provides a new strategy for preparing versatile scaffolds for nanofabrication and paves the way for organizing functional nanodevices in a micrometer space.

Dynamic Covalent Chemistry within Biphenyl Scaffolds: Reversible Covalent Bonding, Control of Selectivity, and Chirality Sensing with a Single System.

PubMed

Ni, Cailing; Zha, Daijun; Ye, Hebo; Hai, Yu; Zhou, Yuntao; Anslyn, Eric V; You, Lei

2018-01-26

Axial chirality is a prevalent and important phenomenon in chemistry. Herein we report a combination of dynamic covalent chemistry and axial chirality for the development of a versatile platform for the binding and chirality sensing of multiple classes of mononucleophiles. An equilibrium between an open aldehyde and its cyclic hemiaminal within biphenyl derivatives enabled the dynamic incorporation of a broad range of alcohols, thiols, primary amines, and secondary amines with high efficiency. Selectivity toward different classes of nucleophiles was also achieved by regulating the distinct reactivity of the system with external stimuli. Through induced helicity as a result of central-to-axial chirality transfer, the handedness and ee values of chiral monoalcohol and monoamine analytes were reported by circular dichroism. The strategies introduced herein should find application in many contexts, including assembly, sensing, and labeling. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Review: Tauopathy in the retina and optic nerve: does it shadow pathological changes in the brain?

PubMed Central

Ho, Wing-Lau; Leung, Yen; Tsang, Andrea Wing-Ting; So, Kwok-Fai; Chiu, Kin

2012-01-01

Tau protein’s versatility lies in its functions within the central nervous system, including protein scaffolding and intracellular signaling. Tauopathy has been one of the most extensively studied neuropathologies among the neurodegenerative diseases. Because the retina and optic nerve are parts of the central nervous system, we hypothesize that tauopathy also plays a role in various eye diseases. However, little is known about tauopathy in the retina and optic nerve. Here, we summarize the findings from histopathological studies on animal models and human specimens with distinct neurodegenerative diseases. Similar pathological changes of tau protein can be found in Alzheimer’s disease, frontotemporal lobe dementia, and glaucoma. In view of the important roles of tauopathy in the brain, it is hoped that this review can stimulate research on eye diseases of the retina and optic nerve. PMID:23170062

Lipid-bilayer-assisted two-dimensional self-assembly of DNA origami nanostructures

PubMed Central

Endo, Masayuki; Sugiyama, Hiroshi

2015-01-01

Self-assembly is a ubiquitous approach to the design and fabrication of novel supermolecular architectures. Here we report a strategy termed ‘lipid-bilayer-assisted self-assembly' that is used to assemble DNA origami nanostructures into two-dimensional lattices. DNA origami structures are electrostatically adsorbed onto a mica-supported zwitterionic lipid bilayer in the presence of divalent cations. We demonstrate that the bilayer-adsorbed origami units are mobile on the surface and self-assembled into large micrometre-sized lattices in their lateral dimensions. Using high-speed atomic force microscopy imaging, a variety of dynamic processes involved in the formation of the lattice, such as fusion, reorganization and defect filling, are successfully visualized. The surface modifiability of the assembled lattice is also demonstrated by in situ decoration with streptavidin molecules. Our approach provides a new strategy for preparing versatile scaffolds for nanofabrication and paves the way for organizing functional nanodevices in a micrometer space. PMID:26310995

New Method for Producing Significant Amounts of RNA Labeled at Specific Sites | Center for Cancer Research

Cancer.gov

Among biomacromolecules, RNA is the most versatile, and it plays indispensable roles in almost all aspects of biology. For example, in addition to serving as mRNAs coding for proteins, RNAs regulate gene expression, such as controlling where, when, and how efficiently a gene gets expressed, participate in RNA processing, encode the genetic information of some viruses, serve as scaffolds, and even possess enzymatic activity. To study these RNAs and their biological functions and to make use of those RNA activities for biomedical applications, researchers first need to make various types of RNA. For structural biologists incorporating modified or labeled nucleotides at specific sites in RNA molecules of interest is critical to gain structural insight into RNA functions. However, placing labeled or modified residue(s) in desired positions in a large RNA has not been possible until now.

Clinical applications of decellularized extracellular matrices for tissue engineering and regenerative medicine.

PubMed

Parmaksiz, Mahmut; Dogan, Arin; Odabas, Sedat; Elçin, A Eser; Elçin, Y Murat

2016-03-17

Decellularization is the process of removing the cellular components from tissues or organs. It is a promising technology for obtaining a biomaterial with a highly preserved extracellular matrix (ECM), which may also act as a biological scaffold for tissue engineering and regenerative therapies. Decellularized products are gaining clinical importance and market space due to their ease of standardized production, constant availability for grafting and mechanical or biochemical superiority against competing clinical options, yielding clinical results ahead of the ones with autografts in some applications. Current drawbacks and limitations of traditional treatments and clinical applications can be overcome by using decellularized or acellular matrices. Several companies are leading the market with versatile acellular products designed for diverse use in the reconstruction of tissues and organs. This review describes ECM-based decellularized and acellular products that are currently in use for different branches of clinic.

A Multidimensional Diversity‐Oriented Synthesis Strategy for Structurally Diverse and Complex Macrocycles

PubMed Central

Nie, Feilin; Kunciw, Dominique L.; Wilcke, David; Stokes, Jamie E.; Galloway, Warren R. J. D.; Bartlett, Sean; Sore, Hannah F.

2016-01-01

Abstract Synthetic macrocycles are an attractive area in drug discovery. However, their use has been hindered by a lack of versatile platforms for the generation of structurally (and thus shape) diverse macrocycle libraries. Herein, we describe a new concept in library synthesis, termed multidimensional diversity‐oriented synthesis, and its application towards macrocycles. This enabled the step‐efficient generation of a library of 45 novel, structurally diverse, and highly‐functionalized macrocycles based around a broad range of scaffolds and incorporating a wide variety of biologically relevant structural motifs. The synthesis strategy exploited the diverse reactivity of aza‐ylides and imines, and featured eight different macrocyclization methods, two of which were novel. Computational analyses reveal a broad coverage of molecular shape space by the library and provides insight into how the various diversity‐generating steps of the synthesis strategy impact on molecular shape. PMID:27484830

A DNA-scaffold platform enhances a multi-enzymatic cycling reaction.

PubMed

Mashimo, Yasumasa; Mie, Masayasu; Kobatake, Eiry

2018-04-01

We explored the co-localization of multiple enzymes on a DNA backbone via a DNA-binding protein, Gene-A* (A*-tag) to increase the efficiency of cascade enzymatic reactions. Firefly luciferase (FLuc) and pyruvate orthophosphate dikinase (PPDK) were genetically fused with A*-tag and modified with single-stranded (ss) DNA via A*-tag. The components were assembled on ssDNA by hybridization, thereby enhancing the efficiency of the cascading bioluminescent reaction producing light emission from pyrophosphate. The activity of A*-tag in each enzyme was investigated with dye-labeled DNA. Co-localization of the enzymes via hybridization was examined using a gel shift assay. The multi-enzyme complex showed significant improvement in the overall efficiency of the cascading reaction in comparison to a mixture of free enzymes. A*-tag is highly convenient for ssDNA modification of versatile enzymes, and it can be used for construction of functional DNA-enzyme complexes.

Laser-based three-dimensional multiscale micropatterning of biocompatible hydrogels for customized tissue engineering scaffolds

PubMed Central

Applegate, Matthew B.; Coburn, Jeannine; Partlow, Benjamin P.; Moreau, Jodie E.; Mondia, Jessica P.; Marelli, Benedetto; Kaplan, David L.; Omenetto, Fiorenzo G.

2015-01-01

Light-induced material phase transitions enable the formation of shapes and patterns from the nano- to the macroscale. From lithographic techniques that enable high-density silicon circuit integration, to laser cutting and welding, light–matter interactions are pervasive in everyday materials fabrication and transformation. These noncontact patterning techniques are ideally suited to reshape soft materials of biological relevance. We present here the use of relatively low-energy (< 2 nJ) ultrafast laser pulses to generate 2D and 3D multiscale patterns in soft silk protein hydrogels without exogenous or chemical cross-linkers. We find that high-resolution features can be generated within bulk hydrogels through nearly 1 cm of material, which is 1.5 orders of magnitude deeper than other biocompatible materials. Examples illustrating the materials, results, and the performance of the machined geometries in vitro and in vivo are presented to demonstrate the versatility of the approach. PMID:26374842

An ancient genome duplication contributed to the abundance of metabolic genes in the moss Physcomitrella patens

PubMed Central

Rensing, Stefan A; Ick, Julia; Fawcett, Jeffrey A; Lang, Daniel; Zimmer, Andreas; Van de Peer, Yves; Reski, Ralf

2007-01-01

Background: Analyses of complete genomes and large collections of gene transcripts have shown that most, if not all seed plants have undergone one or more genome duplications in their evolutionary past. Results: In this study, based on a large collection of EST sequences, we provide evidence that the haploid moss Physcomitrella patens is a paleopolyploid as well. Based on the construction of linearized phylogenetic trees we infer the genome duplication to have occurred between 30 and 60 million years ago. Gene Ontology and pathway association of the duplicated genes in P. patens reveal different biases of gene retention compared with seed plants. Conclusion: Metabolic genes seem to have been retained in excess following the genome duplication in P. patens. This might, at least partly, explain the versatility of metabolism, as described for P. patens and other mosses, in comparison to other land plants. PMID:17683536

Emergence and Evolution

PubMed Central

Bullwinkle, Tammy J.

2013-01-01

The aminoacyl-tRNA synthetases (aaRSs) are essential components of the protein synthesis machinery responsible for defining the genetic code by pairing the correct amino acids to their cognate tRNAs. The aaRSs are an ancient enzyme family believed to have origins that may predate the last common ancestor and as such they provide insights into the evolution and development of the extant genetic code. Although the aaRSs have long been viewed as a highly conserved group of enzymes, findings within the last couple of decades have started to demonstrate how diverse and versatile these enzymes really are. Beyond their central role in translation, aaRSs and their numerous homologs have evolved a wide array of alternative functions both inside and outside translation. Current understanding of the emergence of the aaRSs, and their subsequent evolution into a functionally diverse enzyme family, are discussed in this chapter. PMID:23478877

Multivalent Bifunctional Chelator Scaffolds for Gallium-68 Based Positron Emission Tomography Imaging Probe Design: Signal Amplification via Multivalency

PubMed Central

Singh, Ajay N.; Liu, Wei; Hao, Guiyang; Kumar, Amit; Gupta, Anjali; Öz, Orhan K.; Hsieh, Jer-Tsong; Sun, Xiankai

2011-01-01

The role of the multivalent effect has been well recognized in the design of molecular imaging probes towards the desired imaging signal amplification. Recently we reported a bifunctional chelator (BFC) scaffold design, which provides a simple and versatile approach to impart multivalency to radiometal based nuclear imaging probes. In this work, we report a series of BFC scaffolds (tBu3-1-COOH, tBu3-2-(COOH)2 and tBu3-3-(COOH)3) constructed on the framework of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) for 68Ga-based PET probe design and signal amplification via multivalent effect. For proof of principle, a known integrin αvβ3 specific ligand (c(RGDyK)) was used to build the corresponding NOTA conjugates (H31, H32, and H33), which present 1 – 3 copies of c(RGDyK) peptide, respectively, in a systematic manner. Using the integrin αvβ3 binding affinities (IC50 values), the enhanced specific binding was observed for multivalent conjugates (H32: 43.9 ± 16.1 nM; H33: 14.7 ± 5.0 nM) as compared to their monovalent counterpart (H31: 171 ± 60 nM) and the intact c(RGDyK) peptide (204 ± 76 nM). The obtained conjugates were efficiently labeled with 68Ga3+ within 30 min at room temperature in high radiochemical yields (> 95%). The in vivo evaluation of the labeled conjugates, 68Ga-1, 68Ga-2 and 68Ga-3, was performed using male severe combined immunodeficiency (SCID) mice bearing integrin αvβ3 positive PC-3 tumor xenografts (n = 3). All 68Ga -labeled conjugates showed high in vivo stability with no detectable metabolites found by radio-HPLC within 2 h post-injection (p.i.). The PET signal amplification in PC-3 tumor by multivalent effect was clearly displayed by the tumor uptake of the 68Ga-labeled conjugates (68Ga-3: 2.55 ± 0.50%ID/g; 68Ga-2: 1.90 ± 0.10 %ID/g; 68Ga-1: 1.66 ± 0.15 %ID/g) at 2 h p.i. In summary, we have designed and synthesized a series of NOTA-based BFC scaffolds with signal amplification properties, which may find potential applications in diagnostic gallium radiopharmaceuticals. PMID:21740059

The role of biology in planetary evolution: cyanobacterial primary production in low‐oxygen Proterozoic oceans

PubMed Central

Bryant, Donald A.; Macalady, Jennifer L.

2016-01-01

Summary Understanding the role of biology in planetary evolution remains an outstanding challenge to geobiologists. Progress towards unravelling this puzzle for Earth is hindered by the scarcity of well‐preserved rocks from the Archean (4.0 to 2.5 Gyr ago) and Proterozoic (2.5 to 0.5 Gyr ago) Eons. In addition, the microscopic life that dominated Earth's biota for most of its history left a poor fossil record, consisting primarily of lithified microbial mats, rare microbial body fossils and membrane‐derived hydrocarbon molecules that are still challenging to interpret. However, it is clear from the sulfur isotope record and other geochemical proxies that the production of oxygen or oxidizing power radically changed Earth's surface and atmosphere during the Proterozoic Eon, pushing it away from the more reducing conditions prevalent during the Archean. In addition to ancient rocks, our reconstruction of Earth's redox evolution is informed by our knowledge of biogeochemical cycles catalysed by extant biota. The emergence of oxygenic photosynthesis in ancient cyanobacteria represents one of the most impressive microbial innovations in Earth's history, and oxygenic photosynthesis is the largest source of O 2 in the atmosphere today. Thus the study of microbial metabolisms and evolution provides an important link between extant biota and the clues from the geologic record. Here, we consider the physiology of cyanobacteria (the only microorganisms capable of oxygenic photosynthesis), their co‐occurrence with anoxygenic phototrophs in a variety of environments and their persistence in low‐oxygen environments, including in water columns as well as mats, throughout much of Earth's history. We examine insights gained from both the rock record and cyanobacteria presently living in early Earth analogue ecosystems and synthesize current knowledge of these ancient microbial mediators in planetary redox evolution. Our analysis supports the hypothesis that anoxygenic photosynthesis, including the activity of metabolically versatile cyanobacteria, played an important role in delaying the oxygenation of Earth's surface ocean during the Proterozoic Eon. PMID:26549614

Biomedical and Catalytic Opportunities of Virus-Like Particles in Nanotechnology

PubMed Central

Schwarz, B.; Uchida, M.; Douglas, T.

2016-01-01

Within biology, molecules are arranged in hierarchical structures that coordinate and control the many processes that allow for complex organisms to exist. Proteins and other functional macromolecules are often studied outside their natural nanostructural context because it remains difficult to create controlled arrangements of proteins at this size scale. Viruses are elegantly simple nanosystems that exist at the interface of living organisms and nonliving biological machines. Studied and viewed primarily as pathogens to be combatted, viruses have emerged as models of structural efficiency at the nanoscale and have spurred the development of biomimetic nanoparticle systems. Virus-like particles (VLPs) are noninfectious protein cages derived from viruses or other cage-forming systems. VLPs provide incredibly regular scaffolds for building at the nanoscale. Composed of self-assembling protein subunits, VLPs provide both a model for studying materials’ assembly at the nanoscale and useful building blocks for materials design. The robustness and degree of understanding of many VLP structures allow for the ready use of these systems as versatile nanoparticle platforms for the conjugation of active molecules or as scaffolds for the structural organization of chemical processes. Lastly the prevalence of viruses in all domains of life has led to unique activities of VLPs in biological systems most notably the immune system. Here we discuss recent efforts to apply VLPs in a wide variety of applications with the aim of highlighting how the common structural elements of VLPs have led to their emergence as paradigms for the understanding and design of biological nanomaterials. PMID:28057256

Proteus: Mythology to modern times.

PubMed

Sellaturay, Senthy V; Nair, Raj; Dickinson, Ian K; Sriprasad, Seshadri

2012-10-01

It is common knowledge that proteus bacteria are associated with urinary tract infections and urinary stones. Far more interesting however, is the derivation of the word proteus. This study examines the origin of the word proteus, its mythological, historical and literary connections and evolution to present-day usage. A detailed search for primary and secondary sources was undertaken using the library and internet. Greek mythology describes Proteus as an early sea-god, noted for being versatile and capable of assuming many different forms. In the 8(th) century BC, the ancient Greek poet, Homer, famous for his epic poems the Iliad and Odyssey, describes Proteus as a prophetic old sea-god, and herdsman of the seals of Poseidon, God of the Sea. Shakespeare re-introduced Proteus into English literature, in the 15(th) century AD, in the comedy The Two Gentleman of Verona, as one of his main characters who is inconstant with his affections. The 'elephant man' was afflicted by a severely disfiguring disease, described as 'Proteus syndrome'. It is particularly difficult to distinguish from neurofibromatosis, due to its various forms in different individuals. The Oxford English Dictionary defines the word 'protean' as to mean changeable, variable, and existing in multiple forms. Proteus bacteria directly derive their name from the Sea God, due to their rapid swarming growth and motility on agar plates. They demonstrate versatility by secreting enzymes, which allow them to evade the host's defense systems. Thus proteus, true to its name, has had a myriad of connotations over the centuries.

Recent Sex Chromosome Divergence despite Ancient Dioecy in the Willow Salix viminalis

PubMed Central

Pucholt, Pascal; Wright, Alison E.; Conze, Lei Liu; Mank, Judith E.; Berlin, Sofia

2017-01-01

Abstract Sex chromosomes can evolve when recombination is halted between a pair of chromosomes, and this can lead to degeneration of the sex-limited chromosome. In the early stages of differentiation sex chromosomes are homomorphic, and even though homomorphic sex chromosomes are very common throughout animals and plants, we know little about the evolutionary forces shaping these types of sex chromosomes. We used DNA- and RNA-Seq data from females and males to explore the sex chromosomes in the female heterogametic willow, Salix viminalis, a species with ancient dioecy but with homomorphic sex chromosomes. We detected no major sex differences in read coverage in the sex determination (SD) region, indicating that the W region has not significantly degenerated. However, single nucleotide polymorphism densities in the SD region are higher in females compared with males, indicating very recent recombination suppression, followed by the accumulation of sex-specific single nucleotide polymorphisms. Interestingly, we identified two female-specific scaffolds that likely represent W-chromosome-specific sequence. We show that genes located in the SD region display a mild excess of male-biased expression in sex-specific tissue, and we use allele-specific gene expression analysis to show that this is the result of masculinization of expression on the Z chromosome rather than degeneration of female-expression on the W chromosome. Together, our results demonstrate that insertion of small DNA fragments and accumulation of sex-biased gene expression can occur before the detectable decay of the sex-limited chromosome. PMID:28453634

Catalytic activation of carbon-carbon bonds in cyclopentanones.

PubMed

Xia, Ying; Lu, Gang; Liu, Peng; Dong, Guangbin

2016-11-24

In the chemical industry, molecules of interest are based primarily on carbon skeletons. When synthesizing such molecules, the activation of carbon-carbon single bonds (C-C bonds) in simple substrates is strategically important: it offers a way of disconnecting such inert bonds, forming more active linkages (for example, between carbon and a transition metal) and eventually producing more versatile scaffolds. The challenge in achieving such activation is the kinetic inertness of C-C bonds and the relative weakness of newly formed carbon-metal bonds. The most common tactic starts with a three- or four-membered carbon-ring system, in which strain release provides a crucial thermodynamic driving force. However, broadly useful methods that are based on catalytic activation of unstrained C-C bonds have proven elusive, because the cleavage process is much less energetically favourable. Here we report a general approach to the catalytic activation of C-C bonds in simple cyclopentanones and some cyclohexanones. The key to our success is the combination of a rhodium pre-catalyst, an N-heterocyclic carbene ligand and an amino-pyridine co-catalyst. When an aryl group is present in the C3 position of cyclopentanone, the less strained C-C bond can be activated; this is followed by activation of a carbon-hydrogen bond in the aryl group, leading to efficient synthesis of functionalized α-tetralones-a common structural motif and versatile building block in organic synthesis. Furthermore, this method can substantially enhance the efficiency of the enantioselective synthesis of some natural products of terpenoids. Density functional theory calculations reveal a mechanism involving an intriguing rhodium-bridged bicyclic intermediate.

Polydopamine Inter-Fiber Networks: New Strategy for Producing Rigid, Sticky, 3D Fluffy Electrospun Fibrous Polycaprolactone Sponges.

PubMed

Choi, Wuyong; Lee, Slgirim; Kim, Seung-Hyun; Jang, Jae-Hyung

2016-06-01

Designing versatile 3D interfaces that can precisely represent a biological environment is a prerequisite for the creation of artificial tissue structures. To this end, electrospun fibrous sponges, precisely mimicking an extracellular matrix and providing highly porous interfaces, have capabilities that can function as versatile physical cues to regenerate various tissues. However, their intrinsic features, such as sheet-like, thin, and weak structures, limit the design of a number of uses in tissue engineering applications. Herein, a highly facile methodology capable of fabricating rigid, sticky, spatially expanded fluffy electrospun fibrous sponges is proposed. A bio-inspired adhesive material, poly(dopamine) (pDA), is employed as a key mediator to provide rigidity and stickiness to the 3D poly(ε-caprolactone) (PCL) fibrous sponges, which are fabricated using a coaxial electrospinning with polystyrene followed by a selective leaching process. The iron ion induced oxidation of dopamine into pDA networks interwoven with PCL fibers results in significant increases in the rigidity of 3D fibrous sponges. Furthermore, the exposure of catecholamine groups on the fiber surfaces promotes the stable attachment of the sponges on wet organ surfaces and triggers the robust immobilization of biomolecules (e.g., proteins and gene vectors), demonstrating their potential for 3D scaffolds as well as drug delivery vehicles. Because fibrous structures are ubiquitous in the human body, these rigid, sticky, 3D fibrous sponges are good candidates for powerful biomaterial systems that functionally mimic a variety of tissue structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A versatile 3D tissue matrix scaffold system for tumor modeling and drug screening

PubMed Central

Rijal, Girdhari; Li, Weimin

2017-01-01

Most of the anticancer drug candidates entering preclinical trials fail to be approved for clinical applications. The following are among the main causes of these failures: studying molecular mechanisms of cancer development, identifying therapeutic targets, and testing drug candidates using inappropriate tissue culture models, which do not recapitulate the native microenvironment where the cancer cells originate. It has become clear that three-dimensional (3D) cell cultures are more biologically and clinically relevant than 2D models. The spatial and mechanical conditions of 3D cultures enable the cancer cells to display heterogeneous growth, assume diverse phenotypes, express distinct gene and protein products, and attain metastatic potential and resistance to drugs that are reminiscent of tumors in humans. However, the current 3D culture systems using synthetic polymers or selected components of the extracellular matrix (ECM) are defective (particularly the biophysical and biochemical properties of the native ECM) and remain distant to optimally support the signaling cue–oriented cell survival and growth. We introduce a reconstitutable tissue matrix scaffold (TMS) system fabricated using native tissue ECM, with tissue-like architecture and resilience. The structural and compositional properties of TMS favor robust cell survival, proliferation, migration, and invasion in culture and vascularized tumor formation in animals. The combination of porous and hydrogel TMS allows compartmental culture of cancerous and stromal cells, which are distinguishable by biomarkers. The response of the cancer cells grown on TMS to drugs well reflects animal and clinical observations. TMS enables more biologically relevant studies and is suitable for preclinical drug screening. PMID:28924608

Multiple-Step Injection Molding for Fibrin-Based Tissue-Engineered Heart Valves

PubMed Central

Weber, Miriam; Gonzalez de Torre, Israel; Moreira, Ricardo; Frese, Julia; Oedekoven, Caroline; Alonso, Matilde; Rodriguez Cabello, Carlos J.

2015-01-01

Heart valves are elaborate and highly heterogeneous structures of the circulatory system. Despite the well accepted relationship between the structural and mechanical anisotropy and the optimal function of the valves, most approaches to create tissue-engineered heart valves (TEHVs) do not try to mimic this complexity and rely on one homogenous combination of cells and materials for the whole construct. The aim of this study was to establish an easy and versatile method to introduce spatial diversity into a heart valve fibrin scaffold. We developed a multiple-step injection molding process that enables the fabrication of TEHVs with heterogeneous composition (cell/scaffold material) of wall and leaflets without the need of gluing or suturing components together, with the leaflets firmly connected to the wall. The integrity of the valves and their functionality was proved by either opening/closing cycles in a bioreactor (proof of principle without cells) or with continuous stimulation over 2 weeks. We demonstrated the potential of the method by the two-step molding of the wall and the leaflets containing different cell lines. Immunohistology after stimulation confirmed tissue formation and demonstrated the localization of the different cell types. Furthermore, we showed the proof of principle fabrication of valves using different materials for wall (fibrin) and leaflets (hybrid gel of fibrin/elastin-like recombinamer) and with layered leaflets. The method is easy to implement, does not require special facilities, and can be reproduced in any tissue-engineering lab. While it has been demonstrated here with fibrin, it can easily be extended to other hydrogels. PMID:25654448

Multiple-Step Injection Molding for Fibrin-Based Tissue-Engineered Heart Valves.

PubMed

Weber, Miriam; Gonzalez de Torre, Israel; Moreira, Ricardo; Frese, Julia; Oedekoven, Caroline; Alonso, Matilde; Rodriguez Cabello, Carlos J; Jockenhoevel, Stefan; Mela, Petra

2015-08-01

Heart valves are elaborate and highly heterogeneous structures of the circulatory system. Despite the well accepted relationship between the structural and mechanical anisotropy and the optimal function of the valves, most approaches to create tissue-engineered heart valves (TEHVs) do not try to mimic this complexity and rely on one homogenous combination of cells and materials for the whole construct. The aim of this study was to establish an easy and versatile method to introduce spatial diversity into a heart valve fibrin scaffold. We developed a multiple-step injection molding process that enables the fabrication of TEHVs with heterogeneous composition (cell/scaffold material) of wall and leaflets without the need of gluing or suturing components together, with the leaflets firmly connected to the wall. The integrity of the valves and their functionality was proved by either opening/closing cycles in a bioreactor (proof of principle without cells) or with continuous stimulation over 2 weeks. We demonstrated the potential of the method by the two-step molding of the wall and the leaflets containing different cell lines. Immunohistology after stimulation confirmed tissue formation and demonstrated the localization of the different cell types. Furthermore, we showed the proof of principle fabrication of valves using different materials for wall (fibrin) and leaflets (hybrid gel of fibrin/elastin-like recombinamer) and with layered leaflets. The method is easy to implement, does not require special facilities, and can be reproduced in any tissue-engineering lab. While it has been demonstrated here with fibrin, it can easily be extended to other hydrogels.

Tailoring nanostructure and bioactivity of 3D printable hydrogels with self-assemble Peptides Amphiphile (PA) for promoting bile duct formation.

PubMed

Yan, Ming; Lewis, Phillip L; Shah, Ramille N

2018-05-31

3D-printing has expanded our ability to produce reproducible and more complex scaffold architectures for tissue engineering applications. In order to enhance the biological response within these 3D printed scaffolds incorporating nanostructural features and/or specific biological signaling may be an effective means to optimize tissue regeneration. Peptides Amphiphiles (PAs) are a versatile supramolecular biomaterial with tailorable nanostructural and biochemical features. PAs are widely used in tissue engineering applications such as angiogenesis, neurogenesis, and bone regeneration. Thus, the addition of PAs is a potential solution that can greatly expand the utility of 3D bio-printing hydrogels in the field of regenerative medicine. In this paper, we firstly developed a 3D printable thiolated-gelatin bioink supplemented with PAs to tailor the bioactivity and nanostructure which allows for the incorporation of cells. The bioink can be printed at 4 °C and stabilized to last a long time (>1 month) in culture at 37 °C by via a dual secondary cross-linking strategy using calcium ions and homobifunctional maleiminde-poly (ethylene glycol). Rheological properties of inks were characterized and were suitable for printing multi-layered structures. We additionally demonstrated enhanced functionality of ink formulations by utilizing a laminin-mimetic IKVAV-based PA system within a 3D-printable ink containing cholangiocytes. Viability and functional staining showed that the IKVAV PA nanofibers stimulated cholangioctyes to form functional tubular structures, which was not observed in other ink formulations. . © 2018 IOP Publishing Ltd.

A versatile microfluidic platform for the study of cellular interactions between endothelial cells and neutrophils.

PubMed

Wu, Xiaojie; Newbold, Molly A; Gao, Zhe; Haynes, Christy L

2017-05-01

Endothelial migration is a critical physiological process during vascular angiogenesis, growth and development, as well as in various disease conditions, such as cancer and cardiovascular diseases. Neutrophil migration, known as the important characteristic of immune responses, is also recognized as a contributor to the diseases involving endothelial migration. Herein, the mutually dependent relationship between neutrophil recruitment and endothelial migration was studied on a microfluidic platform for the first time. An in vivo-like microenvironment is created inside microfluidic devices by embedding a gel scaffold into the micro-chambers. This approach, with controllable stable chemical gradients and the ability to quantitate interaction characteristics, overcomes the limitations of the current in vivo and in vitro assays for cell migration studies. The number of neutrophils migrating through the endothelial cell layer is heavily influenced by the concentration of vascular endothelial growth factor (VEGF) that induces endothelial cell migration in the gel scaffold, and is not as correlated to the concentration of chemokine solution used for initiating neutrophil migration. More importantly, neutrophil migration diminishes the effects of the drug that inhibits endothelial migration and this process is regulated by the concentration of chemokine molecules instead of VEGF concentration. The results presented herein demonstrate the complicated cellular interactions between endothelial cells and neutrophils: endothelial migration delicately regulates neutrophil migration while the presence of neutrophils stabilizes the structures of endothelial migration. This study provides deeper understanding of the dynamic cellular interactions between neutrophils and endothelial cells as well as the pathogenesis of relevant diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

Biomedical and Catalytic Opportunities of Virus-Like Particles in Nanotechnology.

PubMed

Schwarz, B; Uchida, M; Douglas, T

2017-01-01

Within biology, molecules are arranged in hierarchical structures that coordinate and control the many processes that allow for complex organisms to exist. Proteins and other functional macromolecules are often studied outside their natural nanostructural context because it remains difficult to create controlled arrangements of proteins at this size scale. Viruses are elegantly simple nanosystems that exist at the interface of living organisms and nonliving biological machines. Studied and viewed primarily as pathogens to be combatted, viruses have emerged as models of structural efficiency at the nanoscale and have spurred the development of biomimetic nanoparticle systems. Virus-like particles (VLPs) are noninfectious protein cages derived from viruses or other cage-forming systems. VLPs provide incredibly regular scaffolds for building at the nanoscale. Composed of self-assembling protein subunits, VLPs provide both a model for studying materials' assembly at the nanoscale and useful building blocks for materials design. The robustness and degree of understanding of many VLP structures allow for the ready use of these systems as versatile nanoparticle platforms for the conjugation of active molecules or as scaffolds for the structural organization of chemical processes. Lastly the prevalence of viruses in all domains of life has led to unique activities of VLPs in biological systems most notably the immune system. Here we discuss recent efforts to apply VLPs in a wide variety of applications with the aim of highlighting how the common structural elements of VLPs have led to their emergence as paradigms for the understanding and design of biological nanomaterials. © 2017 Elsevier Inc. All rights reserved.

DNA nanostructure-directed assembly of metal nanoparticle superlattices

NASA Astrophysics Data System (ADS)

Julin, Sofia; Nummelin, Sami; Kostiainen, Mauri A.; Linko, Veikko

2018-05-01

Structural DNA nanotechnology provides unique, well-controlled, versatile, and highly addressable motifs and templates for assembling materials at the nanoscale. These methods to build from the bottom-up using DNA as a construction material are based on programmable and fully predictable Watson-Crick base pairing. Researchers have adopted these techniques to an increasing extent for creating numerous DNA nanostructures for a variety of uses ranging from nanoelectronics to drug-delivery applications. Recently, an increasing effort has been put into attaching nanoparticles (the size range of 1-20 nm) to the accurate DNA motifs and into creating metallic nanostructures (typically 20-100 nm) using designer DNA nanoshapes as molds or stencils. By combining nanoparticles with the superior addressability of DNA-based scaffolds, it is possible to form well-ordered materials with intriguing and completely new optical, plasmonic, electronic, and magnetic properties. This focused review discusses the DNA structure-directed nanoparticle assemblies covering the wide range of different one-, two-, and three-dimensional systems.

Design of virus-based nanomaterials for medicine, biotechnology, and energy

PubMed Central

Wen, Amy M.; Steinmetz, Nicole F.

2016-01-01

Virus-based nanomaterials are versatile materials that naturally self-assemble and have relevance for a broad range of applications including medicine, biotechnology, and energy. This review provides an overview of recent developments in “chemical virology.” Viruses, as materials, provide unique nanoscale scaffolds that have relevance in chemical biology and nanotechnology, with diverse areas of applications. Some fundamental advantages of viruses, compared to synthetically programmed materials, include the highly precise spatial arrangement of their subunits into a diverse array of shapes and sizes and many available avenues for easy and reproducible modification. Here, we will first survey the broad distribution of viruses and various methods for producing virus-based nanoparticles, as well as engineering principles used to impart new functionalities. We will then examine the broad range of applications and implications of virus-based materials, focusing on the medical, biotechnology, and energy sectors. We anticipate that this field will continue to evolve and grow, with exciting new possibilities stemming from advancements in the rational design of virus-based nanomaterials. PMID:27152673

Multivalency at Interfaces: Supramolecular Carbohydrate-Functionalized Graphene Derivatives for Bacterial Capture, Release, and Disinfection.

PubMed

Qi, Zhenhui; Bharate, Priya; Lai, Chian-Hui; Ziem, Benjamin; Böttcher, Christoph; Schulz, Andrea; Beckert, Fabian; Hatting, Benjamin; Mülhaupt, Rolf; Seeberger, Peter H; Haag, Rainer

2015-09-09

A supramolecular carbohydrate-functionalized two-dimensional (2D) surface was designed and synthesized by decorating thermally reduced graphene sheets with multivalent sugar ligands. The formation of host-guest inclusions on the carbon surface provides a versatile strategy, not only to increase the intrinsic water solubility of graphene-based materials, but more importantly to let the desired biofunctional binding groups bind to the surface. Combining the vital recognition role of carbohydrates and the unique 2D large flexible surface area of the graphene sheets, the addition of multivalent sugar ligands makes the resulting carbon material an excellent platform for selectively wrapping and agglutinating Escherichia coli (E. coli). By taking advantage of the responsive property of supramolecular interactions, the captured bacteria can then be partially released by adding a competitive guest. Compared to previously reported scaffolds, the unique thermal IR-absorption properties of graphene derivatives provide a facile method to kill the captured bacteria by IR-laser irradiation of the captured graphene-sugar-E. coli complex.

Asymmetric intramolecular α-cyclopropanation of aldehydes using a donor/acceptor carbene mimetic

PubMed Central

Luo, Chaosheng; Wang, Zhen; Huang, Yong

2015-01-01

Enantioselective α-alkylation of carbonyl is considered as one of the most important processes for asymmetric synthesis. Common alkylation agents, that is, alkyl halides, are notorious substrates for both Lewis acids and organocatalysts. Recently, olefins emerged as a benign alkylating species via photo/radical mechanisms. However, examples of enantioselective alkylation of aldehydes/ketones are scarce and direct asymmetric dialkylation remains elusive. Here we report an intramolecular α-cyclopropanation reaction of olefinic aldehydes to form chiral cyclopropane aldehydes. We demonstrate that an α-iodo aldehyde can function as a donor/acceptor carbene equivalent, which engages in a formal [2+1] annulation with a tethered double bond. Privileged bicyclo[3.1.0]hexane-type scaffolds are prepared in good optical purity using a chiral amine. The synthetic utility of the products is demonstrated by versatile transformations of the bridgehead formyl functionality. We expect the concept of using α-iodo iminium as a donor/acceptor carbene surrogate will find wide applications in chemical reaction development. PMID:26644194

Increased NIH 3T3 fibroblast functions on cell culture dishes which mimic the nanometer fibers of natural tissues.

PubMed

Bhardwaj, Garima; Webster, Thomas J

2015-01-01

Traditional flat tissue cell culture dishes have consisted of polystyrene treated with plasma gases for growing, subculturing, and studying cell behavior in vitro. However, increasingly it has been observed that mimicking natural tissue properties (such as chemistry, three-dimensional structure, mechanical properties, etc) in vitro can lead to a better correlation of in vitro to in vivo cellular functions. The following studies compared traditional NIH 3T3 fibroblasts' functions on XanoMatrix scaffolds to standard tissue culture polystyrene. Results found significantly greater fibroblast adhesion and proliferation on XanoMatrix cell culture dishes which mimic the nanoscale geometry of natural tissue fibers with true, tortuous fiber beds creating a robust, consistent, and versatile growth platform. In this manner, this study supports that cell culture dishes which mimic features of natural tissues should be continually studied for a wide range of applications in which mimicking natural cellular functions are important.

Affimer proteins are versatile and renewable affinity reagents

PubMed Central

Tiede, Christian; Bedford, Robert; Heseltine, Sophie J; Smith, Gina; Wijetunga, Imeshi; Ross, Rebecca; AlQallaf, Danah; Roberts, Ashley PE; Balls, Alexander; Curd, Alistair; Hughes, Ruth E; Martin, Heather; Needham, Sarah R; Zanetti-Domingues, Laura C; Sadigh, Yashar; Peacock, Thomas P; Tang, Anna A; Gibson, Naomi; Kyle, Hannah; Platt, Geoffrey W; Ingram, Nicola; Taylor, Thomas; Coletta, Louise P; Manfield, Iain; Knowles, Margaret; Bell, Sandra; Esteves, Filomena; Maqbool, Azhar; Prasad, Raj K; Drinkhill, Mark; Bon, Robin S; Patel, Vikesh; Goodchild, Sarah A; Martin-Fernandez, Marisa; Owens, Ray J; Nettleship, Joanne E; Webb, Michael E; Harrison, Michael; Lippiat, Jonathan D; Ponnambalam, Sreenivasan; Peckham, Michelle; Smith, Alastair; Ferrigno, Paul Ko; Johnson, Matt; McPherson, Michael J; Tomlinson, Darren Charles

2017-01-01

Molecular recognition reagents are key tools for understanding biological processes and are used universally by scientists to study protein expression, localisation and interactions. Antibodies remain the most widely used of such reagents and many show excellent performance, although some are poorly characterised or have stability or batch variability issues, supporting the use of alternative binding proteins as complementary reagents for many applications. Here we report on the use of Affimer proteins as research reagents. We selected 12 diverse molecular targets for Affimer selection to exemplify their use in common molecular and cellular applications including the (a) selection against various target molecules; (b) modulation of protein function in vitro and in vivo; (c) labelling of tumour antigens in mouse models; and (d) use in affinity fluorescence and super-resolution microscopy. This work shows that Affimer proteins, as is the case for other alternative binding scaffolds, represent complementary affinity reagents to antibodies for various molecular and cell biology applications. DOI: http://dx.doi.org/10.7554/eLife.24903.001 PMID:28654419

Peptide-based, two-fluorophore, ratiometric probe for quantifying mobile zinc in biological solutions.

PubMed

Zhang, Daniel Y; Azrad, Maria; Demark-Wahnefried, Wendy; Frederickson, Christopher J; Lippard, Stephen J; Radford, Robert J

2015-02-20

Small-molecule fluorescent sensors are versatile agents for detecting mobile zinc in biology. Capitalizing on the abundance of validated mobile zinc probes, we devised a strategy for repurposing existing intensity-based sensors for quantitative applications. Using solid-phase peptide synthesis, we conjugated a zinc-sensitive Zinpyr-1 derivative and a zinc-insensitive 7-hydroxycoumarin derivative onto opposite ends of a rigid P9K peptide scaffold to create HcZ9, a ratiometric fluorescent probe for mobile zinc. A plate reader-based assay using HcZ9 was developed, the accuracy of which is comparable to that of atomic absorption spectroscopy. We investigated zinc accumulation in prostatic cells and zinc levels in human seminal fluid. When normal and tumorigenic cells are bathed in zinc-enriched media, cellular mobile zinc is buffered and changes slightly, but total zinc levels increase significantly. Quantification of mobile and total zinc levels in human seminal plasma revealed that the two are positively correlated with a Pearson's coefficient of 0.73.

3D hydrogel scaffold doped with 2D graphene materials for biosensors and bioelectronics.

PubMed

Song, Hyun Seok; Kwon, Oh Seok; Kim, Jae-Hong; Conde, João; Artzi, Natalie

2017-03-15

Hydrogels consisting of three-dimensional (3D) polymeric networks have found a wide range of applications in biotechnology due to their large water capacity, high biocompatibility, and facile functional versatility. The hydrogels with stimulus-responsive swelling properties have been particularly instrumental to realizing signal transduction in biosensors and bioelectronics. Graphenes are two-dimensional (2D) nanomaterials with unprecedented physical, optical, and electronic properties and have also found many applications in biosensors and bioelectronics. These two classes of materials present complementary strengths and limitations which, when effectively coupled, can result in significant synergism in their electrical, mechanical, and biocompatible properties. This report reviews recent advances made with hydrogel and graphene materials for the development of high-performance bioelectronics devices. The report focuses on the interesting intersection of these materials wherein 2D graphenes are hybridized with 3D hydrogels to develop the next generation biosensors and bioelectronics. Copyright © 2016 Elsevier B.V. All rights reserved.

9,10-Azaboraphenanthrene-containing small molecules and conjugated polymers: synthesis and their application in chemodosimeters for the ratiometric detection of fluoride ions.

PubMed

Zhang, Weidong; Li, Guoping; Xu, Letian; Zhuo, Yue; Wan, Wenming; Yan, Ni; He, Gang

2018-05-21

The introduction of main group elements into conjugated scaffolds is emerging as a key route to novel optoelectronic materials. Herein, an efficient and versatile way to synthesize polymerizable 9,10-azaboraphenanthrene ( BNP )-containing monomers by aromaticity-driven ring expansion reactions between highly antiaromatic borafluorene and azides is reported, and the corresponding conjugated small molecules and polymers are developed as well. The BNP -containing small molecules and conjugated polymers showed good air/moisture stability and notable fluorescence properties. Addition of fluoride ions to the BNP -based small molecules and polymers induced a rapid change in the emission color from blue to green/yellow, respectively, accompanied by strong intensity changes. The conjugated polymers showed better ratiometric sensing performance than small molecules due to the exciton migration along the conjugated chains. Further experiments showed that the sensing process is fully reversible. The films prepared by solution-deposition of BNP -based compounds in the presence of polycaprolactone also showed good ratiometric sensing for fluoride ions.

3D Bioprinting for Tissue and Organ Fabrication

PubMed Central

Zhang, Yu Shrike; Yang, Jingzhou; Jia, Weitao; Dell’Erba, Valeria; Assawes, Pribpandao; Shin, Su Ryon; Dokmeci, Mehmet Remzi; Oklu, Rahmi; Khademhosseini, Ali

2016-01-01

The field of regenerative medicine has progressed tremendously over the past few decades in its ability to fabricate functional tissue substitutes. Conventional approaches based on scaffolding and microengineering are limited in their capacity of producing tissue constructs with precise biomimetic properties. Three-dimensional (3D) bioprinting technology, on the other hand, promises to bridge the divergence between artificially engineered tissue constructs and native tissues. In a sense, 3D bioprinting offers unprecedented versatility to co-deliver cells and biomaterials with precise control over their compositions, spatial distributions, and architectural accuracy, therefore achieving detailed or even personalized recapitulation of the fine shape, structure, and architecture of target tissues and organs. Here we briefly describe recent progresses of 3D bioprinting technology and associated bioinks suitable for the printing process. We then focus on the applications of this technology in fabrication of biomimetic constructs of several representative tissues and organs, including blood vessel, heart, liver, and cartilage. We finally conclude with future challenges in 3D bioprinting as well as potential solutions for further development. PMID:27126775

3D Bioprinting for Tissue and Organ Fabrication.

PubMed

Zhang, Yu Shrike; Yue, Kan; Aleman, Julio; Moghaddam, Kamyar Mollazadeh; Bakht, Syeda Mahwish; Yang, Jingzhou; Jia, Weitao; Dell'Erba, Valeria; Assawes, Pribpandao; Shin, Su Ryon; Dokmeci, Mehmet Remzi; Oklu, Rahmi; Khademhosseini, Ali

2017-01-01

The field of regenerative medicine has progressed tremendously over the past few decades in its ability to fabricate functional tissue substitutes. Conventional approaches based on scaffolding and microengineering are limited in their capacity of producing tissue constructs with precise biomimetic properties. Three-dimensional (3D) bioprinting technology, on the other hand, promises to bridge the divergence between artificially engineered tissue constructs and native tissues. In a sense, 3D bioprinting offers unprecedented versatility to co-deliver cells and biomaterials with precise control over their compositions, spatial distributions, and architectural accuracy, therefore achieving detailed or even personalized recapitulation of the fine shape, structure, and architecture of target tissues and organs. Here we briefly describe recent progresses of 3D bioprinting technology and associated bioinks suitable for the printing process. We then focus on the applications of this technology in fabrication of biomimetic constructs of several representative tissues and organs, including blood vessel, heart, liver, and cartilage. We finally conclude with future challenges in 3D bioprinting as well as potential solutions for further development.

Design, selection, and characterization of a split chorismate mutase

PubMed Central

Müller, Manuel M; Kries, Hajo; Csuhai, Eva; Kast, Peter; Hilvert, Donald

2010-01-01

Split proteins are versatile tools for detecting protein–protein interactions and studying protein folding. Here, we report a new, particularly small split enzyme, engineered from a thermostable chorismate mutase (CM). Upon dissecting the helical-bundle CM from Methanococcus jannaschii into a short N-terminal helix and a 3-helix segment and attaching an antiparallel leucine zipper dimerization domain to the individual fragments, we obtained a weakly active heterodimeric mutase. Using combinatorial mutagenesis and in vivo selection, we optimized the short linker sequences connecting the leucine zipper to the enzyme domain. One of the selected CMs was characterized in detail. It spontaneously assembles from the separately inactive fragments and exhibits wild-type like CM activity. Owing to the availability of a well characterized selection system, the simple 4-helix bundle topology, and the small size of the N-terminal helix, the heterodimeric CM could be a valuable scaffold for enzyme engineering efforts and as a split sensor for specifically oriented protein–protein interactions. PMID:20306491

Thermally Stable Cellulose Nanocrystals toward High-Performance 2D and 3D Nanostructures.

PubMed

Jia, Chao; Bian, Huiyang; Gao, Tingting; Jiang, Feng; Kierzewski, Iain Michael; Wang, Yilin; Yao, Yonggang; Chen, Liheng; Shao, Ziqiang; Zhu, J Y; Hu, Liangbing

2017-08-30

Cellulose nanomaterials have attracted much attention in a broad range of fields such as flexible electronics, tissue engineering, and 3D printing for their excellent mechanical strength and intriguing optical properties. Economic, sustainable, and eco-friendly production of cellulose nanomaterials with high thermal stability, however, remains a tremendous challenge. Here versatile cellulose nanocrystals (DM-OA-CNCs) are prepared through fully recyclable oxalic acid (OA) hydrolysis along with disk-milling (DM) pretreatment of bleached kraft eucalyptus pulp. Compared with the commonly used cellulose nanocrystals from sulfuric acid hydrolysis, DM-OA-CNCs show several advantages including large aspect ratio, carboxylated surface, and excellent thermal stability along with high yield. We also successfully demonstrate the fabrication of high-performance films and 3D-printed patterns using DM-OA-CNCs. The high-performance films with high transparency, ultralow haze, and excellent thermal stability have the great potential for applications in flexible electronic devices. The 3D-printed patterns with porous structures can be potentially applied in the field of tissue engineering as scaffolds.

Clinical application of a tissue-cultured skin autograft: an alternative for the treatment of non-healing or slowly healing wounds?

PubMed

Zöller, Nadja; Valesky, Eva; Butting, Manuel; Hofmann, Matthias; Kippenberger, Stefan; Bereiter-Hahn, Jürgen; Bernd, August; Kaufmann, Roland

2014-01-01

The treatment regime of non-healing or slowly healing wounds is constantly improving. One aspect is surgical defect coverage whereby mesh grafts and keratinocyte suspension are applied. Tissue-cultured skin autografts may be an alternative for the treatment of full-thickness wounds and wounds that cover large areas of the body surface. Autologous epidermal and dermal cells were isolated, expanded in vitro and seeded on collagen-elastin scaffolds. The developed autograft was immunohistochemically characterized and subsequently transplanted onto a facial chronic ulceration of a 71-year-old patient with vulnerable atrophic skin. Characterization of the skin equivalent revealed comparability to healthy human skin due to the epidermal strata, differentiation and proliferation markers. Within 138 days, the skin structure at the transplantation site closely correlated with the adjacent undisturbed skin. The present study demonstrates the comparability of the developed organotypic skin equivalent to healthy human skin and the versatility for clinical applications.

Nanoparticles of adaptive supramolecular networks self-assembled from nucleotides and lanthanide ions.

PubMed

Nishiyabu, Ryuhei; Hashimoto, Nozomi; Cho, Ten; Watanabe, Kazuto; Yasunaga, Takefumi; Endo, Ayataka; Kaneko, Kenji; Niidome, Takuro; Murata, Masaharu; Adachi, Chihaya; Katayama, Yoshiki; Hashizume, Makoto; Kimizuka, Nobuo

2009-02-18

Amorphous nanoparticles of supramolecular coordination polymer networks are spontaneously self-assembled from nucleotides and lanthanide ions in water. They show intrinsic functions such as energy transfer from nucleobase to lanthanide ions and excellent performance as contrast enhancing agents for magnetic resonance imaging (MRI). Furthermore, adaptive inclusion properties are observed in the self-assembly process: functional materials such as fluorescent dyes, metal nanoparticles, and proteins are facilely encapsulated. Dyes in these nanoparticles fluoresce in high quantum yields with a single exponential decay, indicating that guest molecules are monomerically wrapped in the network. Gold nanoparticles and ferritin were also wrapped by the supramolecular shells. In addition, these nucleotide/lanthanide nanoparticles also serve as scaffolds for immobilizing enzymes. The adaptive nature of present supramolecular nanoparticles provides a versatile platform that can be utilized in a variety of applications ranging from material to biomedical sciences. As examples, biocompatibility and liver-directing characteristics in in vivo tissue localization experiments are demonstrated.

DNA Three-Way Junction for Differentiation of Single-Nucleotide Polymorphisms with Fluorescent Copper Nanoparticles.

PubMed

Sun, Feifei; You, Ying; Liu, Jie; Song, Quanwei; Shen, Xiaotong; Na, Na; Ouyang, Jin

2017-05-23

A label- and enzyme-free fluorescent sensor for the detection of single-nucleotide polymorphisms (SNPs) at room temperature is proposed, using new copper nanoparticles (CuNPs) as fluorescent reporters. The CuNPs were constructed by using a DNA three-way junction (3WJ) template. In this assay, two complementary adenine/thymine-rich probes can hybridize with the wild-type target simultaneously to construct a 3WJ structure, serving as an efficient scaffold for the generation of CuNPs. However, the CuNPs produce weak fluorescence when the probes bind with a mutant-type target. SNPs can be identified by the difference in fluorescence intensity of the CuNPs. This SNPs detection strategy is straightforward, cost-effective, and avoids the complicated procedures of labeling or enzymatic reactions. The fluorescent sensor is versatile and can be applied to all types of mutation because the probes are programmable. Moreover, the sensor exhibits good detection performance in biological samples. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Composite Biomaterials Based on Sol-Gel Mesoporous Silicate Glasses: A Review

PubMed Central

Baino, Francesco; Fiorilli, Sonia; Vitale-Brovarone, Chiara

2017-01-01

Bioactive glasses are able to bond to bone and stimulate the growth of new tissue while dissolving over time, which makes them ideal materials for regenerative medicine. The advent of mesoporous glasses, which are typically synthesized via sol-gel routes, allowed researchers to develop a broad and versatile class of novel biomaterials that combine superior bone regenerative potential (compared to traditional melt-derived glasses) with the ability of incorporating drugs and various biomolecules for targeted therapy in situ. Mesoporous glass particles can be directly embedded as a bioactive phase within a non-porous (e.g., microspheres), porous (3D scaffolds) or injectable matrix, or be processed to manufacture a surface coating on inorganic or organic (macro)porous substrates, thereby obtaining hierarchical structures with multiscale porosity. This review provides a picture of composite systems and coatings based on mesoporous glasses and highlights the challenges for the future, including the great potential of inorganic–organic hybrid sol-gel biomaterials. PMID:28952496

Proteus: Mythology to modern times

PubMed Central

Sellaturay, Senthy V.; Nair, Raj; Dickinson, Ian K.; Sriprasad, Seshadri

2012-01-01

Aims: It is common knowledge that proteus bacteria are associated with urinary tract infections and urinary stones. Far more interesting however, is the derivation of the word proteus. This study examines the origin of the word proteus, its mythological, historical and literary connections and evolution to present-day usage. Materials and Methods: A detailed search for primary and secondary sources was undertaken using the library and internet. Results: Greek mythology describes Proteus as an early sea-god, noted for being versatile and capable of assuming many different forms. In the 8th century BC, the ancient Greek poet, Homer, famous for his epic poems the Iliad and Odyssey, describes Proteus as a prophetic old sea-god, and herdsman of the seals of Poseidon, God of the Sea. Shakespeare re-introduced Proteus into English literature, in the 15th century AD, in the comedy The Two Gentleman of Verona, as one of his main characters who is inconstant with his affections. The ‘elephant man’ was afflicted by a severely disfiguring disease, described as ‘Proteus syndrome’. It is particularly difficult to distinguish from neurofibromatosis, due to its various forms in different individuals. The Oxford English Dictionary defines the word ‘protean’ as to mean changeable, variable, and existing in multiple forms. Proteus bacteria directly derive their name from the Sea God, due to their rapid swarming growth and motility on agar plates. They demonstrate versatility by secreting enzymes, which allow them to evade the host's defense systems. Conclusions: Thus proteus, true to its name, has had a myriad of connotations over the centuries. PMID:23450503

Biodegradable and adjustable sol-gel glass based hybrid scaffolds from multi-armed oligomeric building blocks.

PubMed

Kascholke, Christian; Hendrikx, Stephan; Flath, Tobias; Kuzmenka, Dzmitry; Dörfler, Hans-Martin; Schumann, Dirk; Gressenbuch, Mathias; Schulze, F Peter; Schulz-Siegmund, Michaela; Hacker, Michael C

2017-11-01

Biodegradability is a crucial characteristic to improve the clinical potential of sol-gel-derived glass materials. To this end, a set of degradable organic/inorganic class II hybrids from a tetraethoxysilane(TEOS)-derived silica sol and oligovalent cross-linker oligomers containing oligo(d,l-lactide) domains was developed and characterized. A series of 18 oligomers (Mn: 1100-3200Da) with different degrees of ethoxylation and varying length of oligoester units was established and chemical composition was determined. Applicability of an established indirect rapid prototyping method enabled fabrication of a total of 85 different hybrid scaffold formulations from 3-isocyanatopropyltriethoxysilane-functionalized macromers. In vitro degradation was analyzed over 12months and a continuous linear weight loss (0.2-0.5wt%/d) combined with only moderate material swelling was detected which was controlled by oligo(lactide) content and matrix hydrophilicity. Compressive strength (2-30MPa) and compressive modulus (44-716MPa) were determined and total content, oligo(ethylene oxide) content, oligo(lactide) content and molecular weight of the oligomeric cross-linkers as well as material porosity were identified as the main factors determining hybrid mechanics. Cytocompatibility was assessed by cell culture experiments with human adipose tissue-derived stem cells (hASC). Cell migration into the entire scaffold pore network was indicated and continuous proliferation over 14days was found. ALP activity linearly increased over 2weeks indicating osteogenic differentiation. The presented glass-based hybrid concept with precisely adjustable material properties holds promise for regenerative purposes. Adaption of degradation kinetics toward physiological relevance is still an unmet challenge of (bio-)glass engineering. We therefore present a glass-derived hybrid material with adjustable degradation. A flexible design concept based on degradable multi-armed oligomers was combined with an established indirect rapid prototyping method to produce a systematic set of porous sol-gel-derived class II hybrid scaffolds. Mechanical properties in the range of cancellous bone were narrowly controlled by hybrid composition. The oligoester introduction resulted in significantly increased compressive moduli. Cytocompatible hybrids degraded in physiologically relevant time frames and a promising linear and controllable weight loss profile was found. To our knowledge, our degradation study represents the most extensive long-term investigation of sol-gel-derived class II hybrids. Due to the broad adjustability of material properties, our concept offers potential for engineering of biodegradable hybrid materials for versatile applications. Copyright © 2017. Published by Elsevier Ltd.

Electrospraying of microfluidic encapsulated cells for the fabrication of cell-laden electrospun hybrid tissue constructs.

PubMed

Weidenbacher, L; Abrishamkar, A; Rottmar, M; Guex, A G; Maniura-Weber, K; deMello, A J; Ferguson, S J; Rossi, R M; Fortunato, G

2017-12-01

The fabrication of functional 3D tissues is a major goal in tissue engineering. While electrospinning is a promising technique to manufacture a structure mimicking the extracellular matrix, cell infiltration into electrospun scaffolds remains challenging. The robust and in situ delivery of cells into such biomimetic scaffolds would potentially enable the design of tissue engineered constructs with spatial control over cellular distribution but often solvents employed in the spinning process are problematic due to their high cytotoxicity. Herein, microfluidic cell encapsulation is used to establish a temporary protection vehicle for the in situ delivery of cells for the development of a fibrous, cell-laden hybrid biograft. Therefore a layer-by-layer process is used by alternating fiber electrospinning and cell spraying procedures. Both encapsulation and subsequent electrospraying of capsules has no negative effect on the viability and myogenic differentiation of murine myoblast cells. Propidium iodide positive stained cells were analyzed to quantify the amount of dead cells and the presence of myosin heavy chain positive cells after the processes was shown. Furthermore, encapsulation successfully protects cells from cytotoxic solvents (such as dimethylformamide) during in situ delivery of the cells into electrospun poly(vinylidene fluoride-co-hexafluoropropylene) scaffolds. The resulting cell-populated biografts demonstrate the clear potential of this approach in the creation of viable tissue engineering constructs. Infiltration of cells and their controlled spatial distribution within fibrous electrospun membranes is a challenging task but allows for the development of functional highly organized 3D hybrid tissues. Combining polymer electrospinning and cell electrospraying in a layer-by-layer approach is expected to overcome current limitations of reduced cell infiltration after traditional static seeding. However, organic solvents, used during the electrospinning process, impede often major issues due to their high cytotoxicity. Utilizing microfluidic encapsulation as a mean to embed cells within a protective polymer casing enables the controlled deposition of viable cells without interfering with the cellular phenotype. The presented techniques allow for novel cell manipulation approaches being significant for enhanced 3D tissue engineering based on its versatility in terms of material and cell selection. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Calcium phosphate deposition rate, structure and osteoconductivity on electrospun poly(l-lactic acid) matrix using electrodeposition or simulated body fluid incubation

PubMed Central

He, Chuanglong; Jin, Xiaobing; Ma, Peter X.

2013-01-01

Mineralized nanofibrous scaffolds have been proposed as promising scaffolds for bone regeneration due to their ability to mimic both nanoscale architecture and chemical composition of natural bone extracellular matrix (ECM). In this study, a novel electrodeposition method was compared with an extensively explored simulated body fluid (SBF) incubation method in terms of the deposition rate, chemical composition, and morphology of calcium phosphate formed on electrospun fibrous thin matrices with a fiber diameter in the range from about 200 nm to about 1400 nm prepared using 6, 8, 10 and 12 wt% poly(l-lactic acid) (PLLA) solutions in a mixture of dichloromethane and acetone (2:1 in volume). The effects of the surface modification using the two mineralization techniques on osteoblastic cell (MC3T3-E1) proliferation and differentiation were also examined. It was found that electrodeposition was two to three orders of magnitude faster than the SBF method in mineralizing the fibrous matrices, reducing the mineralization time from about two weeks to an hour to achieve the same amounts of mineralization. The mineralization rate also varied with the fiber diameter but in opposite directions between the two mineralization methods. As a general trend, the increase of fiber diameter resulted in a faster mineralization rate for the electrodeposition method but a slower mineralization rate for the SBF incubation method. Using the electrodeposition method, one can control the chemical composition and morphology of the calcium phosphate by varying the electric deposition potential and electrolyte temperature to tune the mixture of dicalcium phosphate dihydrate (DCPD) and hydroxy apatite (HAp). Using the SBF method, one can only obtain a low crystallinity HAp. The mineralized electrospun PLLA fibrous matrices from either method similarly facilitate the proliferation and osteogenic differentiation of preosteoblastic MC3T3-E1 cells as compared to neat PLLA matrices. Therefore, the electrodeposition method can be utilized as a fast and versatile technique to fabricate mineralized nanofibrous scaffolds for bone tissue engineering. PMID:24012605

New Techniques for Ancient Proteins: Direct Coupling Analysis Applied on Proteins Involved in Iron Sulfur Cluster Biogenesis

PubMed Central

Fantini, Marco; Malinverni, Duccio; De Los Rios, Paolo; Pastore, Annalisa

2017-01-01

Direct coupling analysis (DCA) is a powerful statistical inference tool used to study protein evolution. It was introduced to predict protein folds and protein-protein interactions, and has also been applied to the prediction of entire interactomes. Here, we have used it to analyze three proteins of the iron-sulfur biogenesis machine, an essential metabolic pathway conserved in all organisms. We show that DCA can correctly reproduce structural features of the CyaY/frataxin family (a protein involved in the human disease Friedreich's ataxia) despite being based on the relatively small number of sequences allowed by its genomic distribution. This result gives us confidence in the method. Its application to the iron-sulfur cluster scaffold protein IscU, which has been suggested to function both as an ordered and a disordered form, allows us to distinguish evolutionary traces of the structured species, suggesting that, if present in the cell, the disordered form has not left evolutionary imprinting. We observe instead, for the first time, direct indications of how the protein can dimerize head-to-head and bind 4Fe4S clusters. Analysis of the alternative scaffold protein IscA provides strong support to a coordination of the cluster by a dimeric form rather than a tetramer, as previously suggested. Our analysis also suggests the presence in solution of a mixture of monomeric and dimeric species, and guides us to the prevalent one. Finally, we used DCA to analyze interactions between some of these proteins, and discuss the potentials and limitations of the method. PMID:28664160

The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences

PubMed Central

Touchon, Marie; Cury, Jean; Yoon, Eun-Jeong; Krizova, Lenka; Cerqueira, Gustavo C.; Murphy, Cheryl; Feldgarden, Michael; Wortman, Jennifer; Clermont, Dominique; Lambert, Thierry; Grillot-Courvalin, Catherine; Nemec, Alexandr; Courvalin, Patrice; Rocha, Eduardo P.C.

2014-01-01

Bacterial genomics has greatly expanded our understanding of microdiversification patterns within a species, but analyses at higher taxonomical levels are necessary to understand and predict the independent rise of pathogens in a genus. We have sampled, sequenced, and assessed the diversity of genomes of validly named and tentative species of the Acinetobacter genus, a clade including major nosocomial pathogens and biotechnologically important species. We inferred a robust global phylogeny and delimited several new putative species. The genus is very ancient and extremely diverse: Genomes of highly divergent species share more orthologs than certain strains within a species. We systematically characterized elements and mechanisms driving genome diversification, such as conjugative elements, insertion sequences, and natural transformation. We found many error-prone polymerases that may play a role in resistance to toxins, antibiotics, and in the generation of genetic variation. Surprisingly, temperate phages, poorly studied in Acinetobacter, were found to account for a significant fraction of most genomes. Accordingly, many genomes encode clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems with some of the largest CRISPR-arrays found so far in bacteria. Integrons are strongly overrepresented in Acinetobacter baumannii, which correlates with its frequent resistance to antibiotics. Our data suggest that A. baumannii arose from an ancient population bottleneck followed by population expansion under strong purifying selection. The outstanding diversification of the species occurred largely by horizontal transfer, including some allelic recombination, at specific hotspots preferentially located close to the replication terminus. Our work sets a quantitative basis to understand the diversification of Acinetobacter into emerging resistant and versatile pathogens. PMID:25313016

Dual origin of tribosphenic mammals.

PubMed

Luo, Z X; Cifelli, R L; Kielan-Jaworowska, Z

2001-01-04

Marsupials, placentals and their close therian relatives possess complex (tribosphenic) molars that are capable of versatile occlusal functions. This functional complex is widely thought to be a key to the early diversification and evolutionary success of extant therians and their close relatives (tribosphenidans). Long thought to have arisen on northern continents, tribosphenic mammals have recently been reported from southern landmasses. The great age and advanced morphology of these new mammals has led to the alternative suggestion of a Gondwanan origin for the group. Implicit in both biogeographic hypotheses is the assumption that tribosphenic molars evolved only once in mammalian evolutionary history. Phylogenetic and morphometric analyses including these newly discovered taxa suggest a different interpretation: that mammals with tribosphenic molars are not monophyletic. Tribosphenic molars evolved independently in two ancient (holotherian) mammalian groups with different geographic distributions during the Jurassic/Early Cretaceous: an australosphenidan clade endemic to Gondwanan landmasses, survived by extant monotremes; and a boreosphenidan clade of Laurasian continents, including extant marsupials, placentals and their relatives.

(Per)chlorate in Biology on Earth and Beyond.

PubMed

Youngblut, Matthew D; Wang, Ouwei; Barnum, Tyler P; Coates, John D

2016-09-08

Respiration of perchlorate and chlorate [collectively, (per)chlorate] was only recognized in the last 20 years, yet substantial advances have been made in our understanding of the underlying metabolisms. Although it was once considered solely anthropogenic, pervasive natural sources, both terrestrial and extraterrestrial, indicate an ancient (per)chlorate presence across our solar system. These discoveries stimulated interest in (per)chlorate microbiology, and the application of advanced approaches highlights exciting new facets. Forward and reverse genetics revealed new information regarding underlying molecular biology and associated regulatory mechanisms. Structural and functional analysis characterized core enzymes and identified novel reaction sequences. Comparative genomics elucidated evolutionary aspects, and stress analysis identified novel response mechanisms to reactive chlorine species. Finally, systems biology identified unique metabolic versatility and novel mechanisms of (per)chlorate respiration, including symbiosis and a hybrid enzymatic-abiotic metabolism. While many published studies focus on (per)chlorate and their basic metabolism, this review highlights seminal advances made over the last decade and identifies new directions and potential novel applications.

Recent Sex Chromosome Divergence despite Ancient Dioecy in the Willow Salix viminalis.

PubMed

Pucholt, Pascal; Wright, Alison E; Conze, Lei Liu; Mank, Judith E; Berlin, Sofia

2017-08-01

Sex chromosomes can evolve when recombination is halted between a pair of chromosomes, and this can lead to degeneration of the sex-limited chromosome. In the early stages of differentiation sex chromosomes are homomorphic, and even though homomorphic sex chromosomes are very common throughout animals and plants, we know little about the evolutionary forces shaping these types of sex chromosomes. We used DNA- and RNA-Seq data from females and males to explore the sex chromosomes in the female heterogametic willow, Salix viminalis, a species with ancient dioecy but with homomorphic sex chromosomes. We detected no major sex differences in read coverage in the sex determination (SD) region, indicating that the W region has not significantly degenerated. However, single nucleotide polymorphism densities in the SD region are higher in females compared with males, indicating very recent recombination suppression, followed by the accumulation of sex-specific single nucleotide polymorphisms. Interestingly, we identified two female-specific scaffolds that likely represent W-chromosome-specific sequence. We show that genes located in the SD region display a mild excess of male-biased expression in sex-specific tissue, and we use allele-specific gene expression analysis to show that this is the result of masculinization of expression on the Z chromosome rather than degeneration of female-expression on the W chromosome. Together, our results demonstrate that insertion of small DNA fragments and accumulation of sex-biased gene expression can occur before the detectable decay of the sex-limited chromosome. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Small homologous blocks in phytophthora genomes do not point to an ancient whole-genome duplication.

PubMed

van Hooff, Jolien J E; Snel, Berend; Seidl, Michael F

2014-05-01

Genomes of the plant-pathogenic genus Phytophthora are characterized by small duplicated blocks consisting of two consecutive genes (2HOM blocks) and by an elevated abundance of similarly aged gene duplicates. Both properties, in particular the presence of 2HOM blocks, have been attributed to a whole-genome duplication (WGD) at the last common ancestor of Phytophthora. However, large intraspecies synteny-compelling evidence for a WGD-has not been detected. Here, we revisited the WGD hypothesis by deducing the age of 2HOM blocks. Two independent timing methods reveal that the majority of 2HOM blocks arose after divergence of the Phytophthora lineages. In addition, a large proportion of the 2HOM block copies colocalize on the same scaffold. Therefore, the presence of 2HOM blocks does not support a WGD at the last common ancestor of Phytophthora. Thus, genome evolution of Phytophthora is likely driven by alternative mechanisms, such as bursts of transposon activity.

Structural basis of the 9-fold symmetry of centrioles.

PubMed

Kitagawa, Daiju; Vakonakis, Ioannis; Olieric, Natacha; Hilbert, Manuel; Keller, Debora; Olieric, Vincent; Bortfeld, Miriam; Erat, Michèle C; Flückiger, Isabelle; Gönczy, Pierre; Steinmetz, Michel O

2011-02-04

The centriole, and the related basal body, is an ancient organelle characterized by a universal 9-fold radial symmetry and is critical for generating cilia, flagella, and centrosomes. The mechanisms directing centriole formation are incompletely understood and represent a fundamental open question in biology. Here, we demonstrate that the centriolar protein SAS-6 forms rod-shaped homodimers that interact through their N-terminal domains to form oligomers. We establish that such oligomerization is essential for centriole formation in C. elegans and human cells. We further generate a structural model of the related protein Bld12p from C. reinhardtii, in which nine homodimers assemble into a ring from which nine coiled-coil rods radiate outward. Moreover, we demonstrate that recombinant Bld12p self-assembles into structures akin to the central hub of the cartwheel, which serves as a scaffold for centriole formation. Overall, our findings establish a structural basis for the universal 9-fold symmetry of centrioles. Copyright © 2011 Elsevier Inc. All rights reserved.

Genomic insights into the Ixodes scapularis tick vector of Lyme disease

PubMed Central

Gulia-Nuss, Monika; Nuss, Andrew B.; Meyer, Jason M.; Sonenshine, Daniel E.; Roe, R. Michael; Waterhouse, Robert M.; Sattelle, David B.; de la Fuente, José; Ribeiro, Jose M.; Megy, Karine; Thimmapuram, Jyothi; Miller, Jason R.; Walenz, Brian P.; Koren, Sergey; Hostetler, Jessica B.; Thiagarajan, Mathangi; Joardar, Vinita S.; Hannick, Linda I.; Bidwell, Shelby; Hammond, Martin P.; Young, Sarah; Zeng, Qiandong; Abrudan, Jenica L.; Almeida, Francisca C.; Ayllón, Nieves; Bhide, Ketaki; Bissinger, Brooke W.; Bonzon-Kulichenko, Elena; Buckingham, Steven D.; Caffrey, Daniel R.; Caimano, Melissa J.; Croset, Vincent; Driscoll, Timothy; Gilbert, Don; Gillespie, Joseph J.; Giraldo-Calderón, Gloria I.; Grabowski, Jeffrey M.; Jiang, David; Khalil, Sayed M. S.; Kim, Donghun; Kocan, Katherine M.; Koči, Juraj; Kuhn, Richard J.; Kurtti, Timothy J.; Lees, Kristin; Lang, Emma G.; Kennedy, Ryan C.; Kwon, Hyeogsun; Perera, Rushika; Qi, Yumin; Radolf, Justin D.; Sakamoto, Joyce M.; Sánchez-Gracia, Alejandro; Severo, Maiara S.; Silverman, Neal; Šimo, Ladislav; Tojo, Marta; Tornador, Cristian; Van Zee, Janice P.; Vázquez, Jesús; Vieira, Filipe G.; Villar, Margarita; Wespiser, Adam R.; Yang, Yunlong; Zhu, Jiwei; Arensburger, Peter; Pietrantonio, Patricia V.; Barker, Stephen C.; Shao, Renfu; Zdobnov, Evgeny M.; Hauser, Frank; Grimmelikhuijzen, Cornelis J. P.; Park, Yoonseong; Rozas, Julio; Benton, Richard; Pedra, Joao H. F.; Nelson, David R.; Unger, Maria F.; Tubio, Jose M. C.; Tu, Zhijian; Robertson, Hugh M.; Shumway, Martin; Sutton, Granger; Wortman, Jennifer R.; Lawson, Daniel; Wikel, Stephen K.; Nene, Vishvanath M.; Fraser, Claire M.; Collins, Frank H.; Birren, Bruce; Nelson, Karen E.; Caler, Elisabet; Hill, Catherine A.

2016-01-01

Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing ∼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick–host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host ‘questing', prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent. PMID:26856261

Genomic insights into the Ixodes scapularis tick vector of Lyme disease.

PubMed

Gulia-Nuss, Monika; Nuss, Andrew B; Meyer, Jason M; Sonenshine, Daniel E; Roe, R Michael; Waterhouse, Robert M; Sattelle, David B; de la Fuente, José; Ribeiro, Jose M; Megy, Karine; Thimmapuram, Jyothi; Miller, Jason R; Walenz, Brian P; Koren, Sergey; Hostetler, Jessica B; Thiagarajan, Mathangi; Joardar, Vinita S; Hannick, Linda I; Bidwell, Shelby; Hammond, Martin P; Young, Sarah; Zeng, Qiandong; Abrudan, Jenica L; Almeida, Francisca C; Ayllón, Nieves; Bhide, Ketaki; Bissinger, Brooke W; Bonzon-Kulichenko, Elena; Buckingham, Steven D; Caffrey, Daniel R; Caimano, Melissa J; Croset, Vincent; Driscoll, Timothy; Gilbert, Don; Gillespie, Joseph J; Giraldo-Calderón, Gloria I; Grabowski, Jeffrey M; Jiang, David; Khalil, Sayed M S; Kim, Donghun; Kocan, Katherine M; Koči, Juraj; Kuhn, Richard J; Kurtti, Timothy J; Lees, Kristin; Lang, Emma G; Kennedy, Ryan C; Kwon, Hyeogsun; Perera, Rushika; Qi, Yumin; Radolf, Justin D; Sakamoto, Joyce M; Sánchez-Gracia, Alejandro; Severo, Maiara S; Silverman, Neal; Šimo, Ladislav; Tojo, Marta; Tornador, Cristian; Van Zee, Janice P; Vázquez, Jesús; Vieira, Filipe G; Villar, Margarita; Wespiser, Adam R; Yang, Yunlong; Zhu, Jiwei; Arensburger, Peter; Pietrantonio, Patricia V; Barker, Stephen C; Shao, Renfu; Zdobnov, Evgeny M; Hauser, Frank; Grimmelikhuijzen, Cornelis J P; Park, Yoonseong; Rozas, Julio; Benton, Richard; Pedra, Joao H F; Nelson, David R; Unger, Maria F; Tubio, Jose M C; Tu, Zhijian; Robertson, Hugh M; Shumway, Martin; Sutton, Granger; Wortman, Jennifer R; Lawson, Daniel; Wikel, Stephen K; Nene, Vishvanath M; Fraser, Claire M; Collins, Frank H; Birren, Bruce; Nelson, Karen E; Caler, Elisabet; Hill, Catherine A

2016-02-09

Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing ∼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick-host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host 'questing', prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent.

The role of biology in planetary evolution: cyanobacterial primary production in low-oxygen Proterozoic oceans.

PubMed

Hamilton, Trinity L; Bryant, Donald A; Macalady, Jennifer L

2016-02-01

Understanding the role of biology in planetary evolution remains an outstanding challenge to geobiologists. Progress towards unravelling this puzzle for Earth is hindered by the scarcity of well-preserved rocks from the Archean (4.0 to 2.5 Gyr ago) and Proterozoic (2.5 to 0.5 Gyr ago) Eons. In addition, the microscopic life that dominated Earth's biota for most of its history left a poor fossil record, consisting primarily of lithified microbial mats, rare microbial body fossils and membrane-derived hydrocarbon molecules that are still challenging to interpret. However, it is clear from the sulfur isotope record and other geochemical proxies that the production of oxygen or oxidizing power radically changed Earth's surface and atmosphere during the Proterozoic Eon, pushing it away from the more reducing conditions prevalent during the Archean. In addition to ancient rocks, our reconstruction of Earth's redox evolution is informed by our knowledge of biogeochemical cycles catalysed by extant biota. The emergence of oxygenic photosynthesis in ancient cyanobacteria represents one of the most impressive microbial innovations in Earth's history, and oxygenic photosynthesis is the largest source of O2 in the atmosphere today. Thus the study of microbial metabolisms and evolution provides an important link between extant biota and the clues from the geologic record. Here, we consider the physiology of cyanobacteria (the only microorganisms capable of oxygenic photosynthesis), their co-occurrence with anoxygenic phototrophs in a variety of environments and their persistence in low-oxygen environments, including in water columns as well as mats, throughout much of Earth's history. We examine insights gained from both the rock record and cyanobacteria presently living in early Earth analogue ecosystems and synthesize current knowledge of these ancient microbial mediators in planetary redox evolution. Our analysis supports the hypothesis that anoxygenic photosynthesis, including the activity of metabolically versatile cyanobacteria, played an important role in delaying the oxygenation of Earth's surface ocean during the Proterozoic Eon. © 2015 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Mechanically enhanced nested-network hydrogels as a coating material for biomedical devices.

PubMed

Wang, Zhengmu; Zhang, Hongbin; Chu, Axel J; Jackson, John; Lin, Karen; Lim, Chinten James; Lange, Dirk; Chiao, Mu

2018-04-01

Well-organized composite formations such as hierarchical nested-network (NN) structure in bone tissue and reticular connective tissue present remarkable mechanical strength and play a crucial role in achieving physical and biological functions for living organisms. Inspired by these delicate microstructures in nature, an analogous scaffold of double network hydrogel was fabricated by creating a poly(2-hydroxyethyl methacrylate) (pHEMA) network in the porous structure of alginate hydrogels. The resulting hydrogel possessed hierarchical NN structure and showed significantly improved mechanical strength but still maintained high elasticity comparable to soft tissues due to a mutual strengthening effect between the two networks. The tough hydrogel is also self-lubricated, exhibiting a surface friction coefficient comparable with polydimethylsiloxane (PDMS) substrates lubricated by a commercial aqueous lubricant (K-Y Jelly) and other low surface friction hydrogels. Additional properties of this hydrogel include high hydrophilicity, good biocompatibility, tunable cell adhesion and bacterial resistance after incorporation of silver nanoparticles. Firm bonding of the hydrogel on silicone substrates could be achieved through facile chemical modification, thus enabling the use of this hydrogel as a versatile coating material for biomedical applications. In this study, we developed a tough hydrogel by crosslinking HEMA monomers in alginate hydrogels and forming a well-organized structure of hierarchical nested network (NN). Different from most reported stretchable alginate-based hydrogels, the NN hydrogel shows higher compressive strength but retains comparable softness to alginate counterparts. This work further demonstrated the good integration of the tough hydrogel with silicone substrates through chemical modification and micropillar structures. Other properties including surface friction, biocompatibility and bacterial resistance were investigated and the hydrogel shows a great promise as a versatile coating material for biomedical applications. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

PubMed

Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

2017-12-13

Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

The Toluene o-Xylene Monooxygenase Enzymatic Activity for the Biosynthesis of Aromatic Antioxidants

PubMed Central

Pizzo, Elio; Notomista, Eugenio; Pezzella, Alessandro; Di Cristo, Carlo; De Lise, Federica; Di Donato, Alberto; Izzo, Viviana

2015-01-01

Monocyclic phenols and catechols are important antioxidant compounds for the food and pharmaceutic industries; their production through biotransformation of low-added value starting compounds is of major biotechnological interest. The toluene o-xylene monooxygenase (ToMO) from Pseudomonas sp. OX1 is a bacterial multicomponent monooxygenase (BMM) that is able to hydroxylate a wide array of aromatic compounds and has already proven to be a versatile biochemical tool to produce mono- and dihydroxylated derivatives of aromatic compounds. The molecular determinants of its regioselectivity and substrate specificity have been thoroughly investigated, and a computational strategy has been developed which allows designing mutants able to hydroxylate non-natural substrates of this enzyme to obtain high-added value compounds of commercial interest. In this work, we have investigated the use of recombinant ToMO, expressed in cells of Escherichia coli strain JM109, for the biotransformation of non-natural substrates of this enzyme such as 2-phenoxyethanol, phthalan and 2-indanol to produce six hydroxylated derivatives. The hydroxylated products obtained were identified, isolated and their antioxidant potential was assessed both in vitro, using the DPPH assay, and on the rat cardiomyoblast cell line H9c2. Incubation of H9c2 cells with the hydroxylated compounds obtained from ToMO-catalyzed biotransformation induced a differential protective effect towards a mild oxidative stress induced by the presence of sodium arsenite. The results obtained confirm once again the versatility of the ToMO system for oxyfunctionalization reactions of biotechnological importance. Moreover, the hydroxylated derivatives obtained possess an interesting antioxidant potential that encourages the use of the enzyme for further functionalization reactions and their possible use as scaffolds to design novel bioactive molecules. PMID:25915063

Catalytic activation of carbon–carbon bonds in cyclopentanones

PubMed Central

Xia, Ying; Lu, Gang; Liu, Peng; Dong, Guangbin

2017-01-01

In the chemical industry, molecules of interest are based primarily on carbon skeletons. When synthesizing such molecules, the activation of carbon–carbon single bonds (C–C bonds) in simple substrates is strategically important: it offers a way of disconnecting such inert bonds, forming more active linkages (for example, between carbon and a transition metal) and eventually producing more versatile scaffolds1–13. The challenge in achieving such activation is the kinetic inertness of C–C bonds and the relative weakness of newly formed carbon–metal bonds6,14. The most common tactic starts with a three- or four-membered carbon-ring system9–13, in which strain release provides a crucial thermodynamic driving force. However, broadly useful methods that are based on catalytic activation of unstrained C–C bonds have proven elusive, because the cleavage process is much less energetically favourable. Here we report a general approach to the catalytic activation of C–C bonds in simple cyclopentanones and some cyclohexanones. The key to our success is the combination of a rhodium pre-catalyst, an N-heterocyclic carbene ligand and an amino-pyridine co-catalyst. When an aryl group is present in the C3 position of cyclopentanone, the less strained C–C bond can be activated; this is followed by activation of a carbon–hydrogen bond in the aryl group, leading to efficient synthesis of functionalized α-tetralones—a common structural motif and versatile building block in organic synthesis. Furthermore, this method can substantially enhance the efficiency of the enantioselective synthesis of some natural products of terpenoids. Density functional theory calculations reveal a mechanism involving an intriguing rhodium-bridged bicyclic intermediate. PMID:27806379

CRISPR-Cas9 systems: versatile cancer modelling platforms and promising therapeutic strategies.

PubMed

Wen, Wan-Shun; Yuan, Zhi-Min; Ma, Shi-Jie; Xu, Jiang; Yuan, Dong-Tang

2016-03-15

The RNA-guided nuclease CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR associated nuclease 9) and its variants such as nickase Cas9, dead Cas9, guide RNA scaffolds and RNA-targeting Cas9 are convenient and versatile platforms for site-specific genome editing and epigenome modulation. They are easy-to-use, simple-to-design and capable of targeting multiple loci simultaneously. Given that cancer develops from cumulative genetic and epigenetic alterations, CRISPR-Cas9 and its variants (hereafter referred to as CRISPR-Cas9 systems) hold extensive application potentials in cancer modeling and therapy. To date, they have already been applied to model oncogenic mutations in cell lines (e.g., Choi and Meyerson, Nat Commun 2014;5:3728) and in adult animals (e.g., Xue et al., Nature 2014;514:380-4), as well as to combat cancer by disabling oncogenic viruses (e.g., Hu et al., Biomed Res Int 2014;2014:612823) or by manipulating cancer genome (e.g., Liu et al., Nat Commun 2014;5:5393). Given the importance of epigenome and transcriptome in tumourigenesis, manipulation of cancer epigenome and transcriptome for cancer modeling and therapy is a promising area in the future. Whereas (epi)genetic modifications of cancer microenvironment with CRISPR-Cas9 systems for therapeutic purposes represent another promising area in cancer research. Herein, we introduce the functions and mechanisms of CRISPR-Cas9 systems in genome editing and epigenome modulation, retrospect their applications in cancer modelling and therapy, discuss limitations and possible solutions and propose future directions, in hope of providing concise and enlightening information for readers interested in this area. © 2015 UICC.

Novel Cu(I)-selective chelators based on a bis(phosphorothioyl)amide scaffold.

PubMed

Amir, Aviran; Ezra, Alon; Shimon, Linda J W; Fischer, Bilha

2014-08-04

Bis(dialkyl/aryl-phosphorothioyl)amide (BPA) derivatives are versatile ligands known by their high metal-ion affinity and selectivity. Here, we synthesized related chelators based on bis(1,3,2-dithia/dioxaphospholane-2-sulfide)amide (BTPA/BOPA) scaffolds targeting the chelation of soft metal ions. Crystal structures of BTPA compounds 6 (N(-)R3NH(+)) and 8 (NEt) revealed a gauche geometry, while BOPA compound 7 (N(-)R3NH(+)) exhibited an anti-geometry. Solid-state (31)P magic-angle spinning NMR spectra of BTPA 6-Hg(II) and 6-Zn(II) complexes imply a square planar or tetrahedral geometry of the former and a distorted tetrahedral geometry of the latter, while both BTPA 6-Ni(II) and BOPA 7-Ni(II) complexes possibly form a polymeric structure. In Cu(I)-H2O2 system (Fenton reaction conditions) BTPA compounds 6, 8, and 10 (NCH2Ph) were identified as most potent antioxidants (IC50 32, 56, and 29 μM, respectively), whereas BOPA analogues 7, 9 (NEt), and 11 (NCH2Ph) were found to be poor antioxidants. In Fe(II)-H2O2 system, IC50 values for both BTPA and BOPA compounds exceeded 500 μM indicating high selectivity to Cu(I) versus the borderline Fe(II)-ion. Neither BTPA nor BOPA derivatives showed radical scavenging properties in H2O2 photolysis, implying that inhibition of the Cu(I)-induced Fenton reaction by both BTPA and BOPA analogues occurred predominantly through Cu(I)-chelation. In addition, NMR-monitored Cu(I)- and Zn(II)-titration of BTPA compounds 8 and 10 showed their high selectivity to a soft metal ion, Cu(I), as compared to a borderline metal ion, Zn(II). In summary, lipophilic BTPA analogues are promising highly selective Cu(I) ion chelators.

Noncanonical Gβ Gib2 is a scaffolding protein promoting cAMP signaling through functions of Ras1 and Cac1 proteins in Cryptococcus neoformans.

PubMed

Wang, Yanli; Shen, Gui; Gong, Jinjun; Shen, Danyu; Whittington, Amy; Qing, Jiang; Treloar, Joshua; Boisvert, Scott; Zhang, Zhengguang; Yang, Cai; Wang, Ping

2014-05-02

Gβ-like/RACK1 functions as a key mediator of various pathways and contributes to numerous cellular functions in eukaryotic organisms. In the pathogenic fungus Cryptococcus neoformans, noncanonical Gβ Gib2 promotes cAMP signaling in cells lacking normal Gpa1 function while displaying versatility in interactions with Gα Gpa1, protein kinase Pkc1, and endocytic intersectin Cin1. To elucidate the Gib2 functional mechanism(s), we demonstrate that Gib2 is required for normal growth and virulence. We show that Gib2 directly binds to Gpa1 and Gγ Gpg1/Gpg2 and that it interacts with phosphodiesterase Pde2 and monomeric GTPase Ras1. Pde2 remains functionally dispensable, but Ras1 is found to associate with adenylyl cyclase Cac1 through the conserved Ras association domain. In addition, the ras1 mutant exhibits normal capsule formation, whereas the ras1 gpa1 mutant displays enhanced capsule formation, and the ras1 gpa1 cac1 mutant is acapsular. Collectively, these findings suggest that Gib2 promotes cAMP levels by relieving an inhibitory function of Ras1 on Cac1 in the absence of Gpa1. In addition, using GST affinity purification combined with mass spectrometry, we identified 47 additional proteins that interact with Gib2. These proteins have putative functions ranging from signal transduction, energy generation, metabolism, and stress response to ribosomal function. After establishing and validating a protein-protein interactive network, we believe Gib2 to be a key adaptor/scaffolding protein that drives the formation of various protein complexes required for growth and virulence. Our study reveals Gib2 as an essential component in deciphering the complexity of regulatory networks that control growth and virulence in C. neoformans.

In Situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering

PubMed Central

Deng, Meng; Nair, Lakshmi S.; Nukavarapu, Syam P.; Kumbar, Sangamesh G.; Jiang, Tao; Weikel, Arlin L.; Krogman, Nicholas R.; Allcock, Harry R.; Laurencin, Cato T.

2011-01-01

Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here we demonstrated for the first time a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure. This polymer system was developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generated a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permitted the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures revealed macropores (10-100 μm) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern was confirmed in vivo using a rat subcutaneous implantation model. 12 weeks of implantation resulted in an interconnected porous structure with 82-87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirmed the formation of an in situ 3D interconnected porous structure. It was determined that the in situ porous structure resulted from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. PMID:21789036

Biomaterial design for specific cellular interactions: Role of surface functionalization and geometric features

NASA Astrophysics Data System (ADS)

Kolhar, Poornima

The areas of drug delivery and tissue engineering have experienced extraordinary growth in recent years with the application of engineering principles and their potential to support and improve the field of medicine. The tremendous progress in nanotechnology and biotechnology has lead to this explosion of research and development in biomedical applications. Biomaterials can now be engineered at a nanoscale and their specific interactions with the biological tissues can be modulated. Various design parameters are being established and researched for design of drug-delivery carriers and scaffolds to be implanted into humans. Nanoparticles made from versatile biomaterial can deliver both small-molecule drugs and various classes of bio-macromolecules, such as proteins and oligonucleotides. Similarly in the field of tissue engineering, current approaches emphasize nanoscale control of cell behavior by mimicking the natural extracellular matrix (ECM) unlike, traditional scaffolds. Drug delivery and tissue engineering are closely connected fields and both of these applications require materials with exceptional physical, chemical, biological, and biomechanical properties to provide superior therapy. In the current study the surface functionalization and the geometric features of the biomaterials has been explored. In particular, a synthetic surface for culture of human embryonic stem cells has been developed, demonstrating the importance of surface functionalization in maintaining the pluripotency of hESCs. In the second study, the geometric features of the drug delivery carriers are investigated and the polymeric nanoneedles mediated cellular permeabilization and direct cytoplasmic delivery is reported. In the third study, the combined effect of surface functionalization and geometric modification of carriers for vascular targeting is enunciated. These studies illustrate how the biomaterials can be designed to achieve various cellular behaviors and control the interactions with cells in vivo .

Chemically-defined camelid antibody bioconjugate for the magnetic resonance imaging of Alzheimer's disease.

PubMed

Vandesquille, Matthias; Li, Tengfei; Po, Chrystelle; Ganneau, Christelle; Lenormand, Pascal; Dudeffant, Clémence; Czech, Christian; Grueninger, Fiona; Duyckaerts, Charles; Delatour, Benoît; Dhenain, Marc; Lafaye, Pierre; Bay, Sylvie

Today, molecular imaging of neurodegenerative diseases is mainly based on small molecule probes. Alternatively, antibodies are versatile tools that may be developed as new imaging agents. Indeed, they can be readily obtained to specifically target any antigen of interest and their scaffold can be functionalized. One of the critical issues involved in translating antibody-based probes to the clinic is the design and synthesis of perfectly-defined conjugates. Camelid single-domain antibody-fragments (VHHs) are very small and stable antibodies that are able to diffuse in tissues and potentially cross the blood brain barrier (BBB). Here, we selected a VHH (R3VQ) specifically targeting one of the main lesions of Alzheimer's disease (AD), namely the amyloid-beta (Aß) deposits. It was used as a scaffold for the design of imaging probes for magnetic resonance imaging (MRI) and labeled with the contrastophore gadolinium using either a random or site-specific approach. In contrast to the random strategy, the site-specific conjugation to a single reduced cysteine in the C-terminal part of the R3VQ generates a well-defined bioconjugate in a high yield process. This new imaging probe is able to cross the BBB and label Aß deposits after intravenous injection. Also, it displays improved r1 and r2 relaxivities, up to 30 times higher than a widely used clinical contrast agent, and it allows MRI detection of amyloid deposits in post mortem brain tissue of a mouse model of AD. The ability to produce chemically-defined VHH conjugates that cross the BBB opens the way for future development of tailored imaging probes targeting intracerebral antigens.

Bottom-up fabrication of artery-mimicking tubular co-cultures in collagen-based microchannel scaffolds.

PubMed

Tan, A; Fujisawa, K; Yukawa, Y; Matsunaga, Y T

2016-10-20

We developed a robust bottom-up approach to construct open-ended, tubular co-culture constructs that simulate the human vascular morphology and microenvironment. By design, these three-dimensional artificial vessels mimic the basic architecture of an artery: a collagen-rich extracellular matrix (as the tunica externa), smooth muscle cells (SMCs) (as the tunica media), and an endothelial cell (EC) lining (as the tunica interna). A versatile needle-based fabrication technique was employed to achieve controllable arterial layouts within a PDMS-hosted collagen microchannel scaffold (330 ± 10 μm in diameter): (direct co-culture) a SMC/EC bilayer to follow the structure of an arteriole-like segment; and (encapsulated co-culture) a lateral SMC multilayer covered by an EC monolayer lining to simulate the architecture of a larger artery. Optical and fluorescence microscopy images clearly evidenced the progressive cell elongation and sprouting behavior of SMCs and ECs along the collagen gel contour and within the gel matrix under static co-culture conditions. The progressive cell growth patterns effectively led to the formation of a tubular co-culture with an internal endothelial lining expressing prominent CD31 (cluster of differentiation 31) intercellular junction markers. During a 4-day static maturation period, the artery constructs showed modest alteration in the luminal diameters (i.e. less than 10% changes from the initial measurements). This argues in favor of stable and predictable arterial architecture achieved via the proposed fabrication protocols. Both co-culture models showed a high glucose metabolic rate during the initial proliferation phase, followed by a temporary quiescent (and thus, mature) stage. These proof-of-concept models with a controllable architecture create an important foundation for advanced vessel manipulations such as the integration of relevant physiological functionality or remodeling into a vascular disease-mimicking tissue.

Substrate growth dynamics and biomineralization of an Ediacaran encrusting poriferan.

PubMed

Wood, Rachel; Penny, Amelia

2018-01-10

The ability to encrust in order to secure and maintain growth on a substrate is a key competitive innovation in benthic metazoans. Here we describe the substrate growth dynamics, mode of biomineralization and possible affinity of Namapoikia rietoogensis , a large (up to 1 m), robustly skeletal, and modular Ediacaran metazoan which encrusted the walls of synsedimentary fissures within microbial-metazoan reefs. Namapoikia formed laminar or domal morphologies with an internal structure of open tubules and transverse elements, and had a very plastic, non-deterministic growth form which could encrust both fully lithified surfaces as well as living microbial substrates, the latter via modified skeletal holdfasts. Namapoikia shows complex growth interactions and substrate competition with contemporary living microbialites and thrombolites, including the production of plate-like dissepiments in response to microbial overgrowth which served to elevate soft tissue above the microbial surface. Namapoikia could also recover from partial mortality due to microbial fouling. We infer initial skeletal growth to have propagated via the rapid formation of an organic scaffold via a basal pinacoderm prior to calcification. This is likely an ancient mode of biomineralization with similarities to the living calcified demosponge Vaceletia. Namapoikia also shows inferred skeletal growth banding which, combined with its large size, implies notable individual longevity. In sum, Namapoikia was a large, relatively long-lived Ediacaran clonal skeletal metazoan that propagated via an organic scaffold prior to calcification, enabling rapid, effective and dynamic substrate occupation and competition in cryptic reef settings. The open tubular internal structure, highly flexible, non-deterministic skeletal organization, and inferred style of biomineralization of Namapoikia places probable affinity within total-group poriferans. © 2018 The Author(s).

The genome of flax (Linum usitatissimum) assembled de novo from short shotgun sequence reads.

PubMed

Wang, Zhiwen; Hobson, Neil; Galindo, Leonardo; Zhu, Shilin; Shi, Daihu; McDill, Joshua; Yang, Linfeng; Hawkins, Simon; Neutelings, Godfrey; Datla, Raju; Lambert, Georgina; Galbraith, David W; Grassa, Christopher J; Geraldes, Armando; Cronk, Quentin C; Cullis, Christopher; Dash, Prasanta K; Kumar, Polumetla A; Cloutier, Sylvie; Sharpe, Andrew G; Wong, Gane K-S; Wang, Jun; Deyholos, Michael K

2012-11-01

Flax (Linum usitatissimum) is an ancient crop that is widely cultivated as a source of fiber, oil and medicinally relevant compounds. To accelerate crop improvement, we performed whole-genome shotgun sequencing of the nuclear genome of flax. Seven paired-end libraries ranging in size from 300 bp to 10 kb were sequenced using an Illumina genome analyzer. A de novo assembly, comprised exclusively of deep-coverage (approximately 94× raw, approximately 69× filtered) short-sequence reads (44-100 bp), produced a set of scaffolds with N(50) =694 kb, including contigs with N(50)=20.1 kb. The contig assembly contained 302 Mb of non-redundant sequence representing an estimated 81% genome coverage. Up to 96% of published flax ESTs aligned to the whole-genome shotgun scaffolds. However, comparisons with independently sequenced BACs and fosmids showed some mis-assembly of regions at the genome scale. A total of 43384 protein-coding genes were predicted in the whole-genome shotgun assembly, and up to 93% of published flax ESTs, and 86% of A. thaliana genes aligned to these predicted genes, indicating excellent coverage and accuracy at the gene level. Analysis of the synonymous substitution rates (K(s) ) observed within duplicate gene pairs was consistent with a recent (5-9 MYA) whole-genome duplication in flax. Within the predicted proteome, we observed enrichment of many conserved domains (Pfam-A) that may contribute to the unique properties of this crop, including agglutinin proteins. Together these results show that de novo assembly, based solely on whole-genome shotgun short-sequence reads, is an efficient means of obtaining nearly complete genome sequence information for some plant species. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

The genomic diversification of the whole Acinetobacter genus: origins, mechanisms, and consequences.

PubMed

Touchon, Marie; Cury, Jean; Yoon, Eun-Jeong; Krizova, Lenka; Cerqueira, Gustavo C; Murphy, Cheryl; Feldgarden, Michael; Wortman, Jennifer; Clermont, Dominique; Lambert, Thierry; Grillot-Courvalin, Catherine; Nemec, Alexandr; Courvalin, Patrice; Rocha, Eduardo P C

2014-10-13

Bacterial genomics has greatly expanded our understanding of microdiversification patterns within a species, but analyses at higher taxonomical levels are necessary to understand and predict the independent rise of pathogens in a genus. We have sampled, sequenced, and assessed the diversity of genomes of validly named and tentative species of the Acinetobacter genus, a clade including major nosocomial pathogens and biotechnologically important species. We inferred a robust global phylogeny and delimited several new putative species. The genus is very ancient and extremely diverse: Genomes of highly divergent species share more orthologs than certain strains within a species. We systematically characterized elements and mechanisms driving genome diversification, such as conjugative elements, insertion sequences, and natural transformation. We found many error-prone polymerases that may play a role in resistance to toxins, antibiotics, and in the generation of genetic variation. Surprisingly, temperate phages, poorly studied in Acinetobacter, were found to account for a significant fraction of most genomes. Accordingly, many genomes encode clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems with some of the largest CRISPR-arrays found so far in bacteria. Integrons are strongly overrepresented in Acinetobacter baumannii, which correlates with its frequent resistance to antibiotics. Our data suggest that A. baumannii arose from an ancient population bottleneck followed by population expansion under strong purifying selection. The outstanding diversification of the species occurred largely by horizontal transfer, including some allelic recombination, at specific hotspots preferentially located close to the replication terminus. Our work sets a quantitative basis to understand the diversification of Acinetobacter into emerging resistant and versatile pathogens. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Genes, Genomes, and Assemblages of Modern Anoxygenic Photosynthetic Cyanobacteria as Proxies for Ancient Cyanobacteria

NASA Astrophysics Data System (ADS)

Grim, S. L.; Dick, G.

2015-12-01

Oxygenic photosynthetic (OP) cyanobacteria were responsible for the production of O2 during the Proterozoic. However, the extent and degree of oxygenation of the atmosphere and oceans varied for over 2 Ga after OP cyanobacteria first appeared in the geologic record. Cyanobacteria capable of anoxygenic photosynthesis (AP) may have altered the trajectory of oxygenation, yet the scope of their role in the Proterozoic is not well known. Modern cyanobacterial populations from Middle Island Sinkhole (MIS), Michigan and a handful of cultured cyanobacterial strains, are capable of OP and AP. With their metabolic versatility, these microbes may approximate ancient cyanobacterial assemblages that mediated Earth's oxygenation. To better characterize the taxonomic and genetic signatures of these modern AP/OP cyanobacteria, we sequenced 16S rRNA genes and conducted 'omics analyses on cultured strains, lab mesocosms, and MIS cyanobacterial mat samples collected over multiple years from May to September. Diversity in the MIS cyanobacterial mat is low, with one member of Oscillatoriales dominating at all times. However, Planktothrix members are more abundant in the cyanobacterial community in late summer and fall. The shift in cyanobacterial community composition may be linked to seasonally changing light intensity. In lab mesocosms of MIS microbial mat, we observed a shift in dominant cyanobacterial groups as well as the emergence of Chlorobium, bacteria that specialize in AP. These shifts in microbial community composition and metabolism are likely in response to changing environmental parameters such as the availability of light and sulfide. Further research is needed to understand the impacts of the changing photosynthetic community on oxygen production and the entire microbial consortium. Our study connects genes and genomes of AP cyanobacteria to their environment, and improves understanding of cyanobacterial metabolic strategies that may have shaped Earth's redox evolution.

Preparation and characterization of collagen/PLA, chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds for cartilage tissue engineering.

PubMed

Haaparanta, Anne-Marie; Järvinen, Elina; Cengiz, Ibrahim Fatih; Ellä, Ville; Kokkonen, Harri T; Kiviranta, Ilkka; Kellomäki, Minna

2014-04-01

In this study, three-dimensional (3D) porous scaffolds were developed for the repair of articular cartilage defects. Novel collagen/polylactide (PLA), chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds were fabricated by combining freeze-dried natural components and synthetic PLA mesh, where the 3D PLA mesh gives mechanical strength, and the natural polymers, collagen and/or chitosan, mimic the natural cartilage tissue environment of chondrocytes. In total, eight scaffold types were studied: four hybrid structures containing collagen and/or chitosan with PLA, and four parallel plain scaffolds with only collagen and/or chitosan. The potential of these types of scaffolds for cartilage tissue engineering applications were determined by the analysis of the microstructure, water uptake, mechanical strength, and the viability and attachment of adult bovine chondrocytes to the scaffolds. The manufacturing method used was found to be applicable for the manufacturing of hybrid scaffolds with highly porous 3D structures. All the hybrid scaffolds showed a highly porous structure with open pores throughout the scaffold. Collagen was found to bind water inside the structure in all collagen-containing scaffolds better than the chitosan-containing scaffolds, and the plain collagen scaffolds had the highest water absorption. The stiffness of the scaffold was improved by the hybrid structure compared to plain scaffolds. The cell viability and attachment was good in all scaffolds, however, the collagen hybrid scaffolds showed the best penetration of cells into the scaffold. Our results show that from the studied scaffolds the collagen/PLA hybrids are the most promising scaffolds from this group for cartilage tissue engineering.

Comparison of the properties of collagen-chitosan scaffolds after γ-ray irradiation and carbodiimide cross-linking.

PubMed

Chen, Zihao; Du, Tianming; Tang, Xiangyu; Liu, Changjun; Li, Ruixin; Xu, Cheng; Tian, Feng; Du, Zhenjie; Wu, Jimin

2016-07-01

The property of collagen-chitosan porous scaffold varies according to cross-linking density and scaffold composition. This study was designed to compare the properties of collagen-chitosan porous scaffolds cross-linked with γ-irradiation and carbodiimide (CAR) for the first time. Eleven sets of collagen-chitosan scaffolds containing different concentrations of chitosan at a 5% increasing gradient were fabricated. Fourier transform infrared spectroscopy was performed to confirm the success of cross-linking in the scaffolds. The scaffold morphology was evaluated under scanning electron microscope (SEM). SEM revealed that chitosan was an indispensable material for the fabrication of γ-ray irradiation scaffold. The microstructure of γ-ray irradiation scaffold was less stable than those of alternative scaffolds. Based upon swelling ratio, porosity factor, and collagenase degradation, γ-ray irradiation scaffold was less stable than CAR and 25% proportion of chitosan scaffolds. Mechanical property determines the orientation in γ-irradiation and CAR scaffold. In vitro degradation test indicated that γ-irradiation and CAR cross-linking can elevate the scaffold biocompatibility. Compared with γ-ray irradiation, CAR cross-linked scaffold containing 25% chitosan can more significantly enhance the bio-stability and biocompatibility of collagen-chitosan scaffolds. CAR cross-linked scaffold may be the best choice for future tissue engineering.

SHOP: scaffold HOPping by GRID-based similarity searches.

PubMed

Bergmann, Rikke; Linusson, Anna; Zamora, Ismael

2007-05-31

A new GRID-based method for scaffold hopping (SHOP) is presented. In a fully automatic manner, scaffolds were identified in a database based on three types of 3D-descriptors. SHOP's ability to recover scaffolds was assessed and validated by searching a database spiked with fragments of known ligands of three different protein targets relevant for drug discovery using a rational approach based on statistical experimental design. Five out of eight and seven out of eight thrombin scaffolds and all seven HIV protease scaffolds were recovered within the top 10 and 31 out of 31 neuraminidase scaffolds were in the 31 top-ranked scaffolds. SHOP also identified new scaffolds with substantially different chemotypes from the queries. Docking analysis indicated that the new scaffolds would have similar binding modes to those of the respective query scaffolds observed in X-ray structures. The databases contained scaffolds from published combinatorial libraries to ensure that identified scaffolds could be feasibly synthesized.

Use of the interior cavity of the P22 capsid for site-specific initiation of atom-transfer radical polymerization with high-density cargo loading

NASA Astrophysics Data System (ADS)

Lucon, Janice; Qazi, Shefah; Uchida, Masaki; Bedwell, Gregory J.; Lafrance, Ben; Prevelige, Peter E.; Douglas, Trevor

2012-10-01

Virus-like particles (VLPs) have emerged as important and versatile architectures for chemical manipulation in the development of functional hybrid nanostructures. Here we demonstrate a successful site-selective initiation of atom-transfer radical polymerization reactions to form an addressable polymer constrained within the interior cavity of a VLP. Potentially, this protein-polymer hybrid of P22 and cross-linked poly(2-aminoethyl methacrylate) could be useful as a new high-density delivery vehicle for the encapsulation and delivery of small-molecule cargos. In particular, the encapsulated polymer can act as a scaffold for the attachment of small functional molecules, such as fluorescein dye or the magnetic resonance imaging (MRI) contrast agent Gd-diethylenetriaminepentacetate, through reactions with its pendant primary amine groups. Using this approach, a significant increase in the labelling density of the VLP, compared to that of previous modifications of VLPs, can be achieved. These results highlight the use of multimeric protein-polymer conjugates for their potential utility in the development of VLP-based MRI contrast agents with the possibility of loading other cargos.

Metabolism of nitrodiphenyl ether herbicides by dioxin-degrading bacterium Sphingomonas wittichii RW1.

PubMed

Keum, Young Soo; Lee, Young Ju; Kim, Jeong-Han

2008-10-08

Nitrodiphenyl ether herbicides, including chlomethoxyfen, nitrofen, and oxyfluorfen are potent herbicides. Some metabolites and parent compounds are considered as possible mutagens and endocrine disruptors. Both properties pose serious hygienic and environmental risks. Sphingomonas wittichii RW1 is a well-known degrader of polychlorinated dibenzo- p-dioxins, dibenzofurans, and diphenyl ethers. However, no detailed research of its metabolic activity has been performed against pesticides with a diphenyl ether scaffold. In this study, we report S. wittichii RW1 as a very potent diphenyl ether herbicide-metabolizing bacterium with broad substrate specificity. The structures of metabolites were determined by instrumental analysis and synthetic standards. Most pesticides were rapidly removed from the culture medium in the order of nitrofen > oxyfluorfen > chlomethoxyfen. In general, herbicides were degraded through the initial reduction and N-acetylation of nitro groups, followed by ether bond cleavage. Relatively low concentrations of phenolic and catecholic metabolites throughout the study suggested that these metabolites were rapidly metabolized and incorporated into primary metabolism. These results indicate that strain RW1 has very versatile metabolic activities over a wide range of environmental contaminants.

Caffeine-catalyzed gels.

PubMed

DiCiccio, Angela M; Lee, Young-Ah Lucy; Glettig, Dean L; Walton, Elizabeth S E; de la Serna, Eva L; Montgomery, Veronica A; Grant, Tyler M; Langer, Robert; Traverso, Giovanni

2018-07-01

Covalently cross-linked gels are utilized in a broad range of biomedical applications though their synthesis often compromises easy implementation. Cross-linking reactions commonly utilize catalysts or conditions that can damage biologics and sensitive compounds, producing materials that require extensive post processing to achieve acceptable biocompatibility. As an alternative, we report a batch synthesis platform to produce covalently cross-linked materials appropriate for direct biomedical application enabled by green chemistry and commonly available food grade ingredients. Using caffeine, a mild base, to catalyze anhydrous carboxylate ring-opening of diglycidyl-ether functionalized monomers with citric acid as a tri-functional crosslinking agent we introduce a novel poly(ester-ether) gel synthesis platform. We demonstrate that biocompatible Caffeine Catalyzed Gels (CCGs) exhibit dynamic physical, chemical, and mechanical properties, which can be tailored in shape, surface texture, solvent response, cargo release, shear and tensile strength, among other potential attributes. The demonstrated versatility, low cost and facile synthesis of these CCGs renders them appropriate for a broad range of customized engineering applications including drug delivery constructs, tissue engineering scaffolds, and medical devices. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

An updated patent review: xanthine oxidase inhibitors for the treatment of hyperuricemia and gout (2011-2015).

PubMed

Ojha, Ritu; Singh, Jagjeet; Ojha, Anu; Singh, Harbinder; Sharma, Sahil; Nepali, Kunal

2017-03-01

Xanthine oxidase (XO) is a versatile molybdoflavoprotein, widely distributed, occurring in milk, kidney, lung, heart, and vascular endothelium. Catalysis by XO to produce uric acid and reactive oxygen species leads to many diseases. Anti hyperuricemic therapy by xanthine oxidase inhibitors has been mainly employed for the treatment of gout. Area covered: This review covers the patent literature (2011-2015) and also presents the interesting strategies/rational approaches employed for the design of xanthine oxidase inhibitors reported recently. Expert opinion: Recent literature indicates that various non purine scaffolds have been extensively investigated for xanthine oxidase inhibition. The significant potential endowed by heteroaryl based compounds, in particularly fused heterocycles clearly highlights their clinical promise and the need for detailed investigation. Studies by various research groups have also revealed that the flavone framework is open for isosteric replacements and structural modifications for yielding potent non purine xanthine oxidase inhibitors. In addition, various plant extracts recently reported to possess significant xanthine oxidase inhibitory potential presents enough promise to initiate a screening program for the identification of other plant extracts and phytoconstituents possessing inhibitory potential towards the enzyme.

Light-emitting self-assembled peptide nucleic acids exhibit both stacking interactions and Watson-Crick base pairing.

PubMed

Berger, Or; Adler-Abramovich, Lihi; Levy-Sakin, Michal; Grunwald, Assaf; Liebes-Peer, Yael; Bachar, Mor; Buzhansky, Ludmila; Mossou, Estelle; Forsyth, V Trevor; Schwartz, Tal; Ebenstein, Yuval; Frolow, Felix; Shimon, Linda J W; Patolsky, Fernando; Gazit, Ehud

2015-04-01

The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs-CG, GC and GG-could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.

Bioactive factor delivery strategies from engineered polymer hydrogels for therapeutic medicine

PubMed Central

Nguyen, Minh Khanh; Alsberg, Eben

2014-01-01

Polymer hydrogels have been widely explored as therapeutic delivery matrices because of their ability to present sustained, localized and controlled release of bioactive factors. Bioactive factor delivery from injectable biopolymer hydrogels provides a versatile approach to treat a wide variety of diseases, to direct cell function and to enhance tissue regeneration. The innovative development and modification of both natural-(e.g., alginate (ALG), chitosan, hyaluronic acid (HA), gelatin, heparin (HEP), etc.) and synthetic-(e.g., polyesters, polyethyleneimine (PEI), etc.) based polymers has resulted in a variety of approaches to design drug delivery hydrogel systems from which loaded therapeutics are released. This review presents the state-of-the-art in a wide range of hydrogels that are formed though self-assembly of polymers and peptides, chemical crosslinking, ionic crosslinking and biomolecule recognition. Hydrogel design for bioactive factor delivery is the focus of the first section. The second section then thoroughly discusses release strategies of payloads from hydrogels for therapeutic medicine, such as physical incorporation, covalent tethering, affinity interactions, on demand release and/or use of hybrid polymer scaffolds, with an emphasis on the last 5 years. PMID:25242831

Nanocomposite capsules with directional, pulsed nanoparticle release.

PubMed

Udoh, Christiana E; Cabral, João T; Garbin, Valeria

2017-12-01

The precise spatiotemporal delivery of nanoparticles from polymeric capsules is required for applications ranging from medicine to materials science. These capsules derive key performance aspects from their overall shape and dimensions, porosity, and internal microstructure. To this effect, microfluidics provide an exceptional platform for emulsification and subsequent capsule formation. However, facile and robust approaches for nanocomposite capsule fabrication, exhibiting triggered nanoparticle release, remain elusive because of the complex coupling of polymer-nanoparticle phase behavior, diffusion, phase inversion, and directional solidification. We investigate a model system of polyelectrolyte sodium poly(styrene sulfonate) and 22-nm colloidal silica and demonstrate a robust capsule morphology diagram, achieving a range of internal morphologies, including nucleated and bicontinuous microstructures, as well as isotropic and non-isotropic external shapes. Upon dissolution in water, we find that capsules formed with either neat polymers or neat nanoparticles dissolve rapidly and isotropically, whereas bicontinuous, hierarchical, composite capsules dissolve via directional pulses of nanoparticle clusters without disrupting the scaffold, with time scales tunable from seconds to hours. The versatility, facile assembly, and response of these nanocomposite capsules thus show great promise in precision delivery.

Organic Nanoflowers from a Wide Variety of Molecules Templated by a Hierarchical Supramolecular Scaffold.

PubMed

Negrón, Luis M; Díaz, Tanya L; Ortiz-Quiles, Edwin O; Dieppa-Matos, Diómedes; Madera-Soto, Bismark; Rivera, José M

2016-03-15

Nanoflowers (NFs) are flowered-shaped particles with overall sizes or features in the nanoscale. Beyond their pleasing aesthetics, NFs have found a number of applications ranging from catalysis, to sensing, to drug delivery. Compared to inorganic based NFs, their organic and hybrid counterparts are relatively underdeveloped mostly because of the lack of a reliable and versatile method for their construction. We report here a method for constructing NFs from a wide variety of biologically relevant molecules (guests), ranging from small molecules, like doxorubicin, to biomacromolecules, like various proteins and plasmid DNA. The method relies on the encapsulation of the guests within a hierarchically structured particle made from supramolecular G-quadruplexes. The size and overall flexibility of the guests dictate the broad morphological features of the resulting NFs, specifically, small and rigid guests favor the formation of NFs with spiky petals, while large and/or flexible guests promote NFs with wide petals. The results from experiments using confocal fluorescence microscopy, and scanning electron microscopy provides the basis for the proposed mechanism for the NF formation.

DNA origami nanorobot fiber optic genosensor to TMV.

PubMed

Torelli, Emanuela; Manzano, Marisa; Srivastava, Sachin K; Marks, Robert S

2018-01-15

In the quest of greater sensitivity and specificity of diagnostic systems, one continually searches for alternative DNA hybridization methods, enabling greater versatility and where possible field-enabled detection of target analytes. We present, herein, a hybrid molecular self-assembled scaffolded DNA origami entity, intimately immobilized via capture probes linked to aminopropyltriethoxysilane, onto a glass optical fiber end-face transducer, thus producing a novel biosensor. Immobilized DNA nanorobots with a switchable flap can then be actuated by a specific target DNA present in a sample, by exposing a hemin/G-quadruplex DNAzyme, which then catalyzes the generation of chemiluminescence, once the specific fiber probes are immersed in a luminol-based solution. Integrating organic nanorobots to inorganic fiber optics creates a hybrid system that we demonstrate as a proof-of-principle can be utilized in specific DNA sequence detection. This system has potential applications in a wide range of fields, including point-of-care diagnostics or cellular in vivo biosensing when using ultrathin fiber optic probes for research purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

Metal-Organic Polyhedral Core as a Versatile Scaffold for Divergent and Convergent Star Polymer Synthesis.

PubMed

Hosono, Nobuhiko; Gochomori, Mika; Matsuda, Ryotaro; Sato, Hiroshi; Kitagawa, Susumu

2016-05-25

We herein report the divergent and convergent synthesis of coordination star polymers (CSP) by using metal-organic polyhedrons (MOPs) as a multifunctional core. For the divergent route, copper-based great rhombicuboctahedral MOPs decorated with dithiobenzoate or trithioester chain transfer groups at the periphery were designed. Subsequent reversible addition-fragmentation chain transfer (RAFT) polymerization of monomers mediated by the MOPs gave star polymers, in which 24 polymeric arms were grafted from the MOP core. On the other hand, the convergent route provided identical CSP architectures by simple mixing of a macroligand and copper ions. Isophthalic acid-terminated polymers (so-called macroligands) immediately formed the corresponding CSPs through a coordination reaction with copper(II) ions. This convergent route enabled us to obtain miktoarm CSPs with tunable chain compositions through ligand mixing alone. This powerful method allows instant access to a wide variety of multicomponent star polymers that conventionally have required highly skilled and multistep syntheses. MOP-core CSPs are a new class of star polymer that can offer a design strategy for highly processable porous soft materials by using coordination nanocages as a building component.

Enantioselective Brønsted Acid Catalysis as a Tool for the Synthesis of Natural Products and Pharmaceuticals.

PubMed

Merad, Jérémy; Lalli, Claudia; Bernadat, Guillaume; Maury, Julien; Masson, Géraldine

2018-03-15

Synthesis of biologically active molecules (whether at laboratory or industrial scale) remains a highly appealing area of modern organic chemistry. Nowadays, the need to access original bioactive scaffolds goes together with the desire to improve synthetic efficiency, while reducing the environmental footprint of chemical activities. Long neglected in the field of total synthesis, enantioselective organocatalysis has recently emerged as an environmentally friendly and indispensable tool for the construction of relevant bioactive molecules. Notably, enantioselective Brønsted acid catalysis has offered new opportunities in terms of both retrosynthetic disconnections and controlling stereoselectivity. The present report attempts to provide an overview of enantioselective total or formal syntheses designed around Brønsted acid-catalyzed transformations. To demonstrate the versatility of the reactions promoted and the diversity of the accessible motifs, this Minireview draws a systematic parallel between methods and retrosynthetic analysis. The manuscript is organized according to the main reaction types and the nature of newly-formed bonds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Applications of CRISPR/Cas9 in the Mammalian Central Nervous System



PubMed Central

Savell, Katherine E.; Day, Jeremy J.

2017-01-01

Within the central nervous system, gene regulatory mechanisms are crucial regulators of cellular development and function, and dysregulation of these systems is commonly observed in major neuropsychiatric and neurological disorders. However, due to a lack of tools to specifically modulate the genome and epigenome in the central nervous system, many molecular and genetic mechanisms underlying cognitive function and behavior are still unknown. Although genome editing tools have been around for decades, the recent emergence of inexpensive, straightforward, and widely accessible CRISPR/Cas9 systems has led to a revolution in gene editing. The development of the catalytically dead Cas9 (dCas9) expanded this flexibility even further by acting as an anchoring system for fused effector proteins, structural scaffolds, and RNAs. Together, these advances have enabled robust, modular approaches for specific targeting and modification of the local chromatin environment at a single gene. This review highlights these advancements and how the combination of powerful modulatory tools paired with the versatility of CRISPR-Cas9-based systems offer great potential for understanding the underlying genetic and epigenetic contributions of neuronal function, behavior, and neurobiological diseases. PMID:29259522

ST7612AA1, a thioacetate-ω(γ-lactam carboxamide) derivative selected from a novel generation of oral HDAC inhibitors.

PubMed

Giannini, Giuseppe; Vesci, Loredana; Battistuzzi, Gianfranco; Vignola, Davide; Milazzo, Ferdinando M; Guglielmi, Mario Berardino; Barbarino, Marcella; Santaniello, Mosè; Fantò, Nicola; Mor, Marco; Rivara, Silvia; Pala, Daniele; Taddei, Maurizio; Pisano, Claudio; Cabri, Walter

2014-10-23

A systematic study of medicinal chemistry aimed at identifying a new generation of HDAC inhibitors, through the introduction of a thiol zinc-binding group (ZBG) and of an amide-lactam in the ω-position of the polyethylene chain of the vorinostat scaffold, allowed the selection of a new class of potent pan-HDAC inhibitors (pan-HDACis). Simple, highly versatile, and efficient synthetic approaches were used to synthesize a library of these new derivatives, which were then submitted to a screening for HDAC inhibition as well as to a preliminary in vitro assessment of their antiproliferative activity. Molecular docking into HDAC crystal structures suggested a binding mode for these thiol derivatives consistent with the stereoselectivity observed upon insertion of amide-lactam substituents in the ω-position. ST7612AA1 (117), selected as a drug candidate for further development, showed an in vitro activity in the nanomolar range associated with a remarkable in vivo antitumor activity, highly competitive with the most potent HDAC inhibitors, currently under clinical trials. A preliminary study of PK and metabolism is also illustrated.

Biomimicry at the nanoscale: current research and perspectives of two-photon polymerization.

PubMed

Marino, Attilio; Filippeschi, Carlo; Mattoli, Virgilio; Mazzolai, Barbara; Ciofani, Gianni

2015-02-21

Living systems such as cells and tissues are extremely sensitive to their surrounding physico-chemical microenvironment. In the field of regenerative medicine and tissue engineering, the maintenance of culture conditions suitable for the formation of proliferation niches, for the self-renewal maintenance of stem cells, or for the promotion of a particular differentiation fate is an important issue that has been addressed using different strategies. A number of investigations suggests that a particular cell behavior can be in vitro resembled by mimicking the corresponding in vivo conditions. In this context, several biomimetic environments have been designed in order to control cell phenotypes and functions. In this review, we will analyze the most recent examples of the control of the in vitro physical micro/nano-environment by exploiting an innovative technique of high resolution 3D photolithography, the two-photon polymerization (2pp). The biomedical applications of this versatile and disruptive computer assisted design/manufacturing technology are very wide, and range from the fabrication of biomimetic and nanostructured scaffolds for tissue engineering and regenerative medicine, to the microfabrication of biomedical devices, like ossicular replacement prosthesis and microneedles.

Biomimicry at the nanoscale: current research and perspectives of two-photon polymerization

NASA Astrophysics Data System (ADS)

Marino, Attilio; Filippeschi, Carlo; Mattoli, Virgilio; Mazzolai, Barbara; Ciofani, Gianni

2015-02-01

Living systems such as cells and tissues are extremely sensitive to their surrounding physico-chemical microenvironment. In the field of regenerative medicine and tissue engineering, the maintenance of culture conditions suitable for the formation of proliferation niches, for the self-renewal maintenance of stem cells, or for the promotion of a particular differentiation fate is an important issue that has been addressed using different strategies. A number of investigations suggests that a particular cell behavior can be in vitro resembled by mimicking the corresponding in vivo conditions. In this context, several biomimetic environments have been designed in order to control cell phenotypes and functions. In this review, we will analyze the most recent examples of the control of the in vitro physical micro/nano-environment by exploiting an innovative technique of high resolution 3D photolithography, the two-photon polymerization (2pp). The biomedical applications of this versatile and disruptive computer assisted design/manufacturing technology are very wide, and range from the fabrication of biomimetic and nanostructured scaffolds for tissue engineering and regenerative medicine, to the microfabrication of biomedical devices, like ossicular replacement prosthesis and microneedles.

Nanoring formation via in situ photoreduction of silver on a virus scaffold

NASA Astrophysics Data System (ADS)

Bayram, Serene S.; Zahr, Omar K.; Del Re, Julia; Szuchmacher Blum, Amy

2016-12-01

The fabrication of plasmonic nanorings remains of substantial interest by virtue of their enhanced electric and magnetic response to light fields which can be subsequently exploited in diverse applications. Scaling down the size of nanorings holds promise in creating artificial magnetism at wavelengths matching the solar spectrum. Nanosized bioscaffolds can be utilized to tackle the challenge of size reduction of metallic rings owing to their miniature features as well as their well-known biomineralization capacity. Herein, we use the tobacco mosaic virus coat protein as a command surface to grow and assemble silver nanoparticles into sub-30 nm rings. The versatility of TMV allows the formation of both solid rings and rings consisting of discrete nanoparticles that are characterized by UV-vis and TEM. The pH-dependent coulombic surface map along with the annular geometry of the protein aggregate allow the generation of rings with or without a central nanoparticle. Our silver rings are believed to be the smallest to date, and they can offer a test material for existing theories on metallic nanorings of this heretofore unreached size scale.

Nanoring formation via in situ photoreduction of silver on a virus scaffold.

PubMed

Bayram, Serene S; Zahr, Omar K; Del Re, Julia; Blum, Amy Szuchmacher

2016-12-02

The fabrication of plasmonic nanorings remains of substantial interest by virtue of their enhanced electric and magnetic response to light fields which can be subsequently exploited in diverse applications. Scaling down the size of nanorings holds promise in creating artificial magnetism at wavelengths matching the solar spectrum. Nanosized bioscaffolds can be utilized to tackle the challenge of size reduction of metallic rings owing to their miniature features as well as their well-known biomineralization capacity. Herein, we use the tobacco mosaic virus coat protein as a command surface to grow and assemble silver nanoparticles into sub-30 nm rings. The versatility of TMV allows the formation of both solid rings and rings consisting of discrete nanoparticles that are characterized by UV-vis and TEM. The pH-dependent coulombic surface map along with the annular geometry of the protein aggregate allow the generation of rings with or without a central nanoparticle. Our silver rings are believed to be the smallest to date, and they can offer a test material for existing theories on metallic nanorings of this heretofore unreached size scale.

[Three-dimensional parallel collagen scaffold promotes tendon extracellular matrix formation].

PubMed

Zheng, Zefeng; Shen, Weiliang; Le, Huihui; Dai, Xuesong; Ouyang, Hongwei; Chen, Weishan

2016-03-01

To investigate the effects of three-dimensional parallel collagen scaffold on the cell shape, arrangement and extracellular matrix formation of tendon stem cells. Parallel collagen scaffold was fabricated by unidirectional freezing technique, while random collagen scaffold was fabricated by freeze-drying technique. The effects of two scaffolds on cell shape and extracellular matrix formation were investigated in vitro by seeding tendon stem/progenitor cells and in vivo by ectopic implantation. Parallel and random collagen scaffolds were produced successfully. Parallel collagen scaffold was more akin to tendon than random collagen scaffold. Tendon stem/progenitor cells were spindle-shaped and unified orientated in parallel collagen scaffold, while cells on random collagen scaffold had disorder orientation. Two weeks after ectopic implantation, cells had nearly the same orientation with the collagen substance. In parallel collagen scaffold, cells had parallel arrangement, and more spindly cells were observed. By contrast, cells in random collagen scaffold were disorder. Parallel collagen scaffold can induce cells to be in spindly and parallel arrangement, and promote parallel extracellular matrix formation; while random collagen scaffold can induce cells in random arrangement. The results indicate that parallel collagen scaffold is an ideal structure to promote tendon repairing.

A switchable positive and negative air pressure device for efficient and gentle handling of nanofiber scaffolds

NASA Astrophysics Data System (ADS)

Hotaling, Nathan A.; Khristov, Vladimir; Maminishkis, Arvydas; Bharti, Kapil; Simon, Carl G.

2017-10-01

A scaffold handling device (SHD) has been designed that can switch from gentle suction to positive pressure to lift and place nanofiber scaffolds. In tissue engineering laboratories, delicate fibrous scaffolds, such as electrospun nanofiber scaffolds, are often used as substrates for cell culture. Typical scaffold handling procedures include lifting the scaffolds, moving them from one container to another, sterilization, and loading scaffolds into cell culture plates. Using tweezers to handle the scaffolds can be slow, can damage the scaffolds, and can cause them to wrinkle or fold. Scaffolds may also acquire a static charge which makes them difficult to put down as they cling to tweezers. An SHD has been designed that enables more efficient, gentle lifting, and placement of delicate scaffolds. Most of the parts to make the SHD can be purchased, except for the tip which can be 3D-printed. The SHD enables more reliable handling of nanofiber scaffolds that may improve the consistency of biomanufacturing processes.

Spiral-structured, nanofibrous, 3D scaffolds for bone tissue engineering.

PubMed

Wang, Junping; Valmikinathan, Chandra M; Liu, Wei; Laurencin, Cato T; Yu, Xiaojun

2010-05-01

Polymeric nanofiber matrices have already been widely used in tissue engineering. However, the fabrication of nanofibers into complex three-dimensional (3D) structures is restricted due to current manufacturing techniques. To overcome this limitation, we have incorporated nanofibers onto spiral-structured 3D scaffolds made of poly (epsilon-caprolactone) (PCL). The spiral structure with open geometries, large surface areas, and porosity will be helpful for improving nutrient transport and cell penetration into the scaffolds, which are otherwise limited in conventional tissue-engineered scaffolds for large bone defects repair. To investigate the effect of structure and fiber coating on the performance of the scaffolds, three groups of scaffolds including cylindrical PCL scaffolds, spiral PCL scaffolds (without fiber coating), and spiral-structured fibrous PCL scaffolds (with fiber coating) have been prepared. The morphology, porosity, and mechanical properties of the scaffolds have been characterized. Furthermore, human osteoblast cells are seeded on these scaffolds, and the cell attachment, proliferation, differentiation, and mineralized matrix deposition on the scaffolds are evaluated. The results indicated that the spiral scaffolds possess porosities within the range of human trabecular bone and an appropriate pore structure for cell growth, and significantly lower compressive modulus and strength than cylindrical scaffolds. When compared with the cylindrical scaffolds, the spiral-structured scaffolds demonstrated enhanced cell proliferation, differentiation, and mineralization and allowed better cellular growth and penetration. The incorporation of nanofibers onto spiral scaffolds further enhanced cell attachment, proliferation, and differentiation. These studies suggest that spiral-structured nanofibrous scaffolds may serve as promising alternatives for bone tissue engineering applications. Copyright 2009 Wiley Periodicals, Inc.

Systematic assessment of scaffold hopping versus activity cliff formation across bioactive compound classes following a molecular hierarchy.

PubMed

Stumpfe, Dagmar; Dimova, Dilyana; Bajorath, Jürgen

2015-07-01

Scaffold hopping and activity cliff formation define opposite ends of the activity landscape feature spectrum. To rationalize these events at the level of scaffolds, active compounds involved in scaffold hopping were required to contain topologically distinct scaffolds but have only limited differences in potency, whereas compounds involved in activity cliffs were required to share the same scaffold but have large differences in potency. A systematic search was carried out for compounds involved in scaffold hopping and/or activity cliff formation. Results obtained for compound data sets covering more than 300 human targets revealed clear trends. If scaffolds represented multiple but fewer than 10 active compounds, nearly 90% of all scaffolds were exclusively involved in hopping events. With increasing compound coverage, the fraction of scaffolds involved in both scaffold hopping and activity cliff formation significantly increased to more than 50%. However, ∼40% of the scaffolds representing large numbers of active compounds continued to be exclusively involved in scaffold hopping. More than 200 scaffolds with broad target coverage were identified that consistently represented potent compounds and yielded an abundance of scaffold hops in the low-nanomolar range. These and other subsets of scaffolds we characterized are of prime interest for structure-activity relationship (SAR) exploration and compound design. Therefore, the complete scaffold classification generated in the course of our analysis is made freely available. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fluorescent Nanocrystals Reveal Regulated Portals of Entry into and Between the Cells of Hydra

PubMed Central

Tortiglione, Claudia; Quarta, Alessandra; Malvindi, Maria Ada; Tino, Angela; Pellegrino, Teresa

2009-01-01

Initially viewed as innovative carriers for biomedical applications, with unique photophysical properties and great versatility to be decorated at their surface with suitable molecules, nanoparticles can also play active roles in mediating biological effects, suggesting the need to deeply investigate the mechanisms underlying cell-nanoparticle interaction and to identify the molecular players. Here we show that the cell uptake of fluorescent CdSe/CdS quantum rods (QRs) by Hydra vulgaris, a simple model organism at the base of metazoan evolution, can be tuned by modifying nanoparticle surface charge. At acidic pH, amino-PEG coated QRs, showing positive surface charge, are actively internalized by tentacle and body ectodermal cells, while negatively charged nanoparticles are not uptaken. In order to identify the molecular factors underlying QR uptake at acidic pH, we provide functional evidence of annexins involvement and explain the QR uptake as the combined result of QR positive charge and annexin membrane insertion. Moreover, tracking QR labelled cells during development and regeneration allowed us to uncover novel intercellular trafficking and cell dynamics underlying the remarkable plasticity of this ancient organism. PMID:19888325

IBN SINA AND THE ROOTS OF THE SEVEN DOCTRINES OF PRESERVATION OF HEALTH.

PubMed

Khan, Murad Ahmad; Raza, Fauzia; Khan, Iqbal Akhtar

2015-01-01

Ibn Sina, the most eminent Muslim physician, illuminative philosopher, great thinker and a versatile genius is regarded as the "Father of Early Modern Medicine" and as the "Father of Clinical Pharmacology". The "Kitab al-Qanun fi-al-Tibb", commonly known as the "Canon Medicinae" is the most important of his medical works and, at the same time, the most carefully preserved treasury both in original Arabic and in the initial Latin version. It is the final codification of all Greco-Arabic medical thoughts up to his time, enriched and modified with his own scientific experimentations and independent observations. It is considered "The First Textbook of Medicine on the Earth". The "Canon" surpassed the books of Hippocrates and Galen and remained supreme for more than six centuries, in the West. Ibn Sina described "Seven Doctrines" for Preservation of Health, based on the Mudawa Salookia, in his magnum opus. The roots of these principles can be traced, to a significant extent, to Egyptian Medicine, Hebrew Medicine, Greek Medicine, Roman Medicine, Traditional Chinese Medicine, Ancient Persian Medicine, Ayurvedic Medicine (Hindu Medicine) and Islamic Medicine.

Microbes: Agents of Isotopic Change

NASA Astrophysics Data System (ADS)

Fogel, M. L.

2012-12-01

Microbes drive many of the important oxidation and reduction reactions on Earth; digest almost all forms of organic matter; and can serve as both primary and secondary producers. Because of their versatile biochemistry and physiology, they impart unique isotopic signatures to organic and inorganic materials, which have proven to be key measurements for understanding elemental cycling now and throughout Earth's history. Understanding microbial isotope fractionations in laboratory experiments has been important for interpreting isotopic patterns measured in natural settings. In fact, the pairing of simple experiment with natural observation has been the pathway for interpreting the fingerprint of microbial processes in ancient sediments and rocks. Examples of how key experiments have explained stable isotope fractionations by microbes and advanced the field of microbial ecology will be presented. Learning the isotopic signatures of Earth's microbes is a valuable exercise for predicting what isotopic signatures could be displayed by possible extant or extinct extraterrestrial life. Given the potential for discovery on Mars, Enceladus, and other solar system bodies, new methods and techniques for pinpointing what is unique about microbial isotope signatures is particularly relevant.

Development of hybrid scaffolds using ceramic and hydrogel for articular cartilage tissue regeneration.

PubMed

Seol, Young-Joon; Park, Ju Young; Jeong, Wonju; Kim, Tae-Ho; Kim, Shin-Yoon; Cho, Dong-Woo

2015-04-01

The regeneration of articular cartilage consisting of hyaline cartilage and hydrogel scaffolds has been generally used in tissue engineering. However, success in in vivo studies has been rarely reported. The hydrogel scaffolds implanted into articular cartilage defects are mechanically unstable and it is difficult for them to integrate with the surrounding native cartilage tissue. Therefore, it is needed to regenerate cartilage and bone tissue simultaneously. We developed hybrid scaffolds with hydrogel scaffolds for cartilage tissue and with ceramic scaffolds for bone tissue. For in vivo study, hybrid scaffolds were press-fitted into osteochondral tissue defects in a rabbit knee joints and the cartilage tissue regeneration in blank, hydrogel scaffolds, and hybrid scaffolds was compared. In 12th week after implantation, the histological and immunohistochemical analyses were conducted to evaluate the cartilage tissue regeneration. In the blank and hydrogel scaffold groups, the defects were filled with fibrous tissues and the implanted hydrogel scaffolds could not maintain their initial position; in the hybrid scaffold group, newly generated cartilage tissues were morphologically similar to native cartilage tissues and were smoothly connected to the surrounding native tissues. This study demonstrates hybrid scaffolds containing hydrogel and ceramic scaffolds can provide mechanical stability to hydrogel scaffolds and enhance cartilage tissue regeneration at the defect site. © 2014 Wiley Periodicals, Inc.

Characterization and evaluation of graphene oxide scaffold for periodontal wound healing of class II furcation defects in dog.

PubMed

Kawamoto, Kohei; Miyaji, Hirofumi; Nishida, Erika; Miyata, Saori; Kato, Akihito; Tateyama, Akito; Furihata, Tomokazu; Shitomi, Kanako; Iwanaga, Toshihiko; Sugaya, Tsutomu

2018-01-01

The 3-dimensional scaffold plays a key role in volume and quality of repair tissue in periodontal tissue engineering therapy. We fabricated a novel 3D collagen scaffold containing carbon-based 2-dimensional layered material, named graphene oxide (GO). The aim of this study was to characterize and assess GO scaffold for periodontal tissue healing of class II furcation defects in dog. GO scaffolds were prepared by coating the surface of a 3D collagen sponge scaffold with GO dispersion. Scaffolds were characterized using cytotoxicity and tissue reactivity tests. In addition, GO scaffold was implanted into dog class II furcation defects and periodontal healing was investigated at 4 weeks postsurgery. GO scaffold exhibited low cytotoxicity and enhanced cellular ingrowth behavior and rat bone forming ability. In addition, GO scaffold stimulated healing of dog class II furcation defects. Periodontal attachment formation, including alveolar bone, periodontal ligament-like tissue, and cementum-like tissue, was significantly increased by GO scaffold implantation, compared with untreated scaffold. The results suggest that GO scaffold is biocompatible and possesses excellent bone and periodontal tissue formation ability. Therefore, GO scaffold would be beneficial for periodontal tissue engineering therapy.

MoonProt: a database for proteins that are known to moonlight

PubMed Central

Mani, Mathew; Chen, Chang; Amblee, Vaishak; Liu, Haipeng; Mathur, Tanu; Zwicke, Grant; Zabad, Shadi; Patel, Bansi; Thakkar, Jagravi; Jeffery, Constance J.

2015-01-01

Moonlighting proteins comprise a class of multifunctional proteins in which a single polypeptide chain performs multiple biochemical functions that are not due to gene fusions, multiple RNA splice variants or pleiotropic effects. The known moonlighting proteins perform a variety of diverse functions in many different cell types and species, and information about their structures and functions is scattered in many publications. We have constructed the manually curated, searchable, internet-based MoonProt Database (http://www.moonlightingproteins.org) with information about the over 200 proteins that have been experimentally verified to be moonlighting proteins. The availability of this organized information provides a more complete picture of what is currently known about moonlighting proteins. The database will also aid researchers in other fields, including determining the functions of genes identified in genome sequencing projects, interpreting data from proteomics projects and annotating protein sequence and structural databases. In addition, information about the structures and functions of moonlighting proteins can be helpful in understanding how novel protein functional sites evolved on an ancient protein scaffold, which can also help in the design of proteins with novel functions. PMID:25324305

Defining scaffold geometries for interacting with proteins: geometrical classification of secondary structure linking regions.

PubMed

Tran, Tran T; Kulis, Christina; Long, Steven M; Bryant, Darryn; Adams, Peter; Smythe, Mark L

2010-11-01

Medicinal chemists synthesize arrays of molecules by attaching functional groups to scaffolds. There is evidence suggesting that some scaffolds yield biologically active molecules more than others, these are termed privileged substructures. One role of the scaffold is to present its side-chains for molecular recognition, and biologically relevant scaffolds may present side-chains in biologically relevant geometries or shapes. Since drug discovery is primarily focused on the discovery of compounds that bind to proteinaceous targets, we have been deciphering the scaffold shapes that are used for binding proteins as they reflect biologically relevant shapes. To decipher the scaffold architecture that is important for binding protein surfaces, we have analyzed the scaffold architecture of protein loops, which are defined in this context as continuous four residue segments of a protein chain that are not part of an α-helix or β-strand secondary structure. Loops are an important molecular recognition motif of proteins. We have found that 39 clusters reflect the scaffold architecture of 89% of the 23,331 loops in the dataset, with average intra-cluster and inter-cluster RMSD of 0.47 and 1.91, respectively. These protein loop scaffolds all have distinct shapes. We have used these 39 clusters that reflect the scaffold architecture of protein loops as biological descriptors. This involved generation of a small dataset of scaffold-based peptidomimetics. We found that peptidomimetic scaffolds with reported biological activities matched loop scaffold geometries and those peptidomimetic scaffolds with no reported biologically activities did not. This preliminary evidence suggests that organic scaffolds with tight matches to the preferred loop scaffolds of proteins, implies the likelihood of the scaffold to be biologically relevant.

Defining scaffold geometries for interacting with proteins: geometrical classification of secondary structure linking regions

NASA Astrophysics Data System (ADS)

Tran, Tran T.; Kulis, Christina; Long, Steven M.; Bryant, Darryn; Adams, Peter; Smythe, Mark L.

2010-11-01

Medicinal chemists synthesize arrays of molecules by attaching functional groups to scaffolds. There is evidence suggesting that some scaffolds yield biologically active molecules more than others, these are termed privileged substructures. One role of the scaffold is to present its side-chains for molecular recognition, and biologically relevant scaffolds may present side-chains in biologically relevant geometries or shapes. Since drug discovery is primarily focused on the discovery of compounds that bind to proteinaceous targets, we have been deciphering the scaffold shapes that are used for binding proteins as they reflect biologically relevant shapes. To decipher the scaffold architecture that is important for binding protein surfaces, we have analyzed the scaffold architecture of protein loops, which are defined in this context as continuous four residue segments of a protein chain that are not part of an α-helix or β-strand secondary structure. Loops are an important molecular recognition motif of proteins. We have found that 39 clusters reflect the scaffold architecture of 89% of the 23,331 loops in the dataset, with average intra-cluster and inter-cluster RMSD of 0.47 and 1.91, respectively. These protein loop scaffolds all have distinct shapes. We have used these 39 clusters that reflect the scaffold architecture of protein loops as biological descriptors. This involved generation of a small dataset of scaffold-based peptidomimetics. We found that peptidomimetic scaffolds with reported biological activities matched loop scaffold geometries and those peptidomimetic scaffolds with no reported biologically activities did not. This preliminary evidence suggests that organic scaffolds with tight matches to the preferred loop scaffolds of proteins, implies the likelihood of the scaffold to be biologically relevant.

Drug-likeness analysis of traditional Chinese medicines: 2. Characterization of scaffold architectures for drug-like compounds, non-drug-like compounds, and natural compounds from traditional Chinese medicines.

PubMed

Tian, Sheng; Li, Youyong; Wang, Junmei; Xu, Xiaojie; Xu, Lei; Wang, Xiaohong; Chen, Lei; Hou, Tingjun

2013-01-21

In order to better understand the structural features of natural compounds from traditional Chinese medicines, the scaffold architectures of drug-like compounds in MACCS-II Drug Data Report (MDDR), non-drug-like compounds in Available Chemical Directory (ACD), and natural compounds in Traditional Chinese Medicine Compound Database (TCMCD) were explored and compared. First, the different scaffolds were extracted from ACD, MDDR and TCMCD by using three scaffold representations, including Murcko frameworks, Scaffold Tree, and ring systems with different complexity and side chains. Then, by examining the accumulative frequency of the scaffolds in each dataset, we observed that the Level 1 scaffolds of the Scaffold Tree offer advantages over the other scaffold architectures to represent the scaffold diversity of the compound libraries. By comparing the similarity of the scaffold architectures presented in MDDR, ACD and TCMCD, structural overlaps were observed not only between MDDR and TCMCD but also between MDDR and ACD. Finally, Tree Maps were used to cluster the Level 1 scaffolds of the Scaffold Tree and visualize the scaffold space of the three datasets. The analysis of the scaffold architectures of MDDR, ACD and TCMCD shows that, on average, drug-like molecules in MDDR have the highest diversity while natural compounds in TCMCD have the highest complexity. According to the Tree Maps, it can be observed that the Level 1 scaffolds present in MDDR have higher diversity than those presented in TCMCD and ACD. However, some representative scaffolds in MDDR with high frequency show structural similarities to those in TCMCD and ACD, suggesting that some scaffolds in TCMCD and ACD may be potentially drug-like fragments for fragment-based and de novo drug design.

Drug-likeness analysis of traditional Chinese medicines: 2. Characterization of scaffold architectures for drug-like compounds, non-drug-like compounds, and natural compounds from traditional Chinese medicines

PubMed Central

2013-01-01

Background In order to better understand the structural features of natural compounds from traditional Chinese medicines, the scaffold architectures of drug-like compounds in MACCS-II Drug Data Report (MDDR), non-drug-like compounds in Available Chemical Directory (ACD), and natural compounds in Traditional Chinese Medicine Compound Database (TCMCD) were explored and compared. Results First, the different scaffolds were extracted from ACD, MDDR and TCMCD by using three scaffold representations, including Murcko frameworks, Scaffold Tree, and ring systems with different complexity and side chains. Then, by examining the accumulative frequency of the scaffolds in each dataset, we observed that the Level 1 scaffolds of the Scaffold Tree offer advantages over the other scaffold architectures to represent the scaffold diversity of the compound libraries. By comparing the similarity of the scaffold architectures presented in MDDR, ACD and TCMCD, structural overlaps were observed not only between MDDR and TCMCD but also between MDDR and ACD. Finally, Tree Maps were used to cluster the Level 1 scaffolds of the Scaffold Tree and visualize the scaffold space of the three datasets. Conclusion The analysis of the scaffold architectures of MDDR, ACD and TCMCD shows that, on average, drug-like molecules in MDDR have the highest diversity while natural compounds in TCMCD have the highest complexity. According to the Tree Maps, it can be observed that the Level 1 scaffolds present in MDDR have higher diversity than those presented in TCMCD and ACD. However, some representative scaffolds in MDDR with high frequency show structural similarities to those in TCMCD and ACD, suggesting that some scaffolds in TCMCD and ACD may be potentially drug-like fragments for fragment-based and de novo drug design. PMID:23336706

Scaffolds in Tendon Tissue Engineering

PubMed Central

Longo, Umile Giuseppe; Lamberti, Alfredo; Petrillo, Stefano; Maffulli, Nicola; Denaro, Vincenzo

2012-01-01

Tissue engineering techniques using novel scaffold materials offer potential alternatives for managing tendon disorders. Tissue engineering strategies to improve tendon repair healing include the use of scaffolds, growth factors, cell seeding, or a combination of these approaches. Scaffolds have been the most common strategy investigated to date. Available scaffolds for tendon repair include both biological scaffolds, obtained from mammalian tissues, and synthetic scaffolds, manufactured from chemical compounds. Preliminary studies support the idea that scaffolds can provide an alternative for tendon augmentation with an enormous therapeutic potential. However, available data are lacking to allow definitive conclusion on the use of scaffolds for tendon augmentation. We review the current basic science and clinical understanding in the field of scaffolds and tissue engineering for tendon repair. PMID:22190961

'Breath figure' PLGA films as implant coatings for controlled drug release

NASA Astrophysics Data System (ADS)

Ponnusamy, Thiruselvam

The breath figure method is a versatile and facile approach of generating ordered micro and nanoporous structures in polymeric materials. When a polymer solution (dissolved in a high vapor pressure organic solvent) is evaporated out in the presence of a moist air stream, the evaporative cooling effect causes the condensation and nucleation of water droplets onto the polymer solution surface. This leads to the formation of an imprinted porous structure upon removal of the residual solvent and water. The facile removal of the water droplet template leaving its structural imprint is a specifically appealing aspect of the breath figure film technology. The first part of the dissertation work involves the fabrication of drug loaded breath figure thin films and its utilization as a controlled drug release carrier and biomaterial scaffold. In a single fabrication step, single layer/multilayer porous thin films were designed and developed by combining the breath figure process and a modified spin or dip coating technique. Using biodegradable polymers such as poly (lactic-co-glycolic acid) (PLGA) and poly (ethylene glycol) (PEG), drug loaded films were fabricated onto FDA approved medical devices (the Glaucoma drainage device and the Surgical hernia mesh). The porosity of the films is in the range of 2-4 microm as characterized by scanning electron microscope. The drug coated medical implants were characterized for their surface and bulk morphology, the degradation rate of the film, drug release rate and cell cytotoxicity. The results suggest that the use of breath figure morphologies in biodegradable polymer films adds an additional level of control to drug release. In comparison to non-porous films, the breath figure films showed an increased degradation and enhanced drug release. Furthermore, the porous nature of the film was investigated as a biomaterial scaffold to construct three dimensional in vitro tissue model systems. The breath figure film with interconnected pores facilitates cell infiltration and tissue remodelling in vitro, suggesting its high potential in regenerative medicine and tissue engineering applications. In the second part of the dissertation, the versatility of breath figure polymers was explored as a reverse template to create micropatterned soft materials. Unlike traditional lithographic masters, the breath figure assembly is a simple and cost-effective approach to create micro/nano sized "bead" like uniform patterns on the surface of hydrogels and biopolymers. By incorporating iron nanoparticles into the pores, this technique was extended to form hydrogels decorated with nanoparticles specifically in the pattern. The morphology features and the functional characteristics were demonstrated through scanning electron microscopy. The potential applications of these micro-fabricated materials in biosensors and cell culture substrates are outlined.

Systematic Prediction of Scaffold Proteins Reveals New Design Principles in Scaffold-Mediated Signal Transduction

PubMed Central

Hu, Jianfei; Neiswinger, Johnathan; Zhang, Jin; Zhu, Heng; Qian, Jiang

2015-01-01

Scaffold proteins play a crucial role in facilitating signal transduction in eukaryotes by bringing together multiple signaling components. In this study, we performed a systematic analysis of scaffold proteins in signal transduction by integrating protein-protein interaction and kinase-substrate relationship networks. We predicted 212 scaffold proteins that are involved in 605 distinct signaling pathways. The computational prediction was validated using a protein microarray-based approach. The predicted scaffold proteins showed several interesting characteristics, as we expected from the functionality of scaffold proteins. We found that the scaffold proteins are likely to interact with each other, which is consistent with previous finding that scaffold proteins tend to form homodimers and heterodimers. Interestingly, a single scaffold protein can be involved in multiple signaling pathways by interacting with other scaffold protein partners. Furthermore, we propose two possible regulatory mechanisms by which the activity of scaffold proteins is coordinated with their associated pathways through phosphorylation process. PMID:26393507

Scaffolding Student Participation in Mathematical Practices

ERIC Educational Resources Information Center

Moschkovich, Judit N.

2015-01-01

The concept of scaffolding can be used to describe various types of adult guidance, in multiple settings, across different time scales. This article clarifies what we mean by scaffolding, considering several questions specifically for scaffolding in mathematics: What theoretical assumptions are framing scaffolding? What is being scaffolded? At…

Is scaffold hopping a reliable indicator for the ability of computational methods to identify structurally diverse active compounds?

NASA Astrophysics Data System (ADS)

Dimova, Dilyana; Bajorath, Jürgen

2017-07-01

Computational scaffold hopping aims to identify core structure replacements in active compounds. To evaluate scaffold hopping potential from a principal point of view, regardless of the computational methods that are applied, a global analysis of conventional scaffolds in analog series from compound activity classes was carried out. The majority of analog series was found to contain multiple scaffolds, thus enabling the detection of intra-series scaffold hops among closely related compounds. More than 1000 activity classes were found to contain increasing proportions of multi-scaffold analog series. Thus, using such activity classes for scaffold hopping analysis is likely to overestimate the scaffold hopping (core structure replacement) potential of computational methods, due to an abundance of artificial scaffold hops that are possible within analog series.

Characterization and evaluation of graphene oxide scaffold for periodontal wound healing of class II furcation defects in dog

PubMed Central

Kawamoto, Kohei; Miyaji, Hirofumi; Nishida, Erika; Miyata, Saori; Kato, Akihito; Tateyama, Akito; Furihata, Tomokazu; Shitomi, Kanako; Iwanaga, Toshihiko; Sugaya, Tsutomu

2018-01-01

Introduction The 3-dimensional scaffold plays a key role in volume and quality of repair tissue in periodontal tissue engineering therapy. We fabricated a novel 3D collagen scaffold containing carbon-based 2-dimensional layered material, named graphene oxide (GO). The aim of this study was to characterize and assess GO scaffold for periodontal tissue healing of class II furcation defects in dog. Materials and methods GO scaffolds were prepared by coating the surface of a 3D collagen sponge scaffold with GO dispersion. Scaffolds were characterized using cytotoxicity and tissue reactivity tests. In addition, GO scaffold was implanted into dog class II furcation defects and periodontal healing was investigated at 4 weeks postsurgery. Results GO scaffold exhibited low cytotoxicity and enhanced cellular ingrowth behavior and rat bone forming ability. In addition, GO scaffold stimulated healing of dog class II furcation defects. Periodontal attachment formation, including alveolar bone, periodontal ligament-like tissue, and cementum-like tissue, was significantly increased by GO scaffold implantation, compared with untreated scaffold. Conclusion The results suggest that GO scaffold is biocompatible and possesses excellent bone and periodontal tissue formation ability. Therefore, GO scaffold would be beneficial for periodontal tissue engineering therapy. PMID:29713167

Reinforced nanohydroxyapatite/polyamide66 scaffolds by chitosan coating for bone tissue engineering.

PubMed

Huang, Di; Zuo, Yi; Zou, Qin; Wang, Yanying; Gao, Shibo; Wang, Xiaoyan; Liu, Haohuai; Li, Yubao

2012-01-01

High porosity of scaffold is always accompanied by poor mechanical property; the aim of this study was to enhance the strength and modulus of the highly porous scaffold of nanohydroxyapatite/polyamide66 (n-HA/PA66) by coating chitosan (CS) and to investigate the effect of CS content on the scaffold physical properties and cytological properties. The results show that CS coating can reinforce the scaffold effectively. The compress modulus and strength of the CS coated n-HA/PA66 scaffolds are improved to 32.71 and 2.38 MPa, respectively, being about six times and five times of those of the uncoated scaffolds. Meanwhile, the scaffolds still exhibit a highly interconnected porous structure and the porosity is approximate about 78%, slightly lower than the value (84%) of uncoated scaffold. The cytological properties of scaffolds were also studied in vitro by cocultured with osteoblast-like MG63 cells. The cytological experiments demonstrate that the reinforced scaffolds display favorable cytocompatibility and have no significant difference with the uncoated n-HA/PA66 scaffolds. The CS reinforced n-HA/PA66 scaffolds can meet the basic mechanical requirement of bone tissue engineering scaffold, presenting a potential for biomedical application in bone reconstruction and repair. Copyright © 2011 Wiley Periodicals, Inc.

Elastase-Sensitive Elastomeric Scaffolds with Variable Anisotropy for Soft Tissue Engineering

PubMed Central

Guan, Jianjun; Fujimoto, Kazuro L.; Wagner, William R.

2010-01-01

Purpose To develop elastase-sensitive polyurethane scaffolds that would be applicable to the engineering of mechanically active soft tissues. Methods A polyurethane containing an elastase-sensitive peptide sequence was processed into scaffolds by thermally induced phase separation. Processing conditions were manipulated to alter scaffold properties and anisotropy. The scaffold’s mechanical properties, degradation, and cytocompatibility using muscle-derived stem cells were characterized. Scaffold in vivo degradation was evaluated by subcutaneous implantation. Results When heat transfer was multidirectional, scaffolds had randomly oriented pores. Imposition of a heat transfer gradient resulted in oriented pores. Both scaffolds were flexible and relatively strong with mechanical properties dependent upon fabrication conditions such as solvent type, polymer concentration and quenching temperature. Oriented scaffolds exhibited anisotropic mechanical properties with greater tensile strength in the orientation direction. These scaffolds also supported muscle-derived stem cell growth more effectively than random scaffolds. The scaffolds expressed over 40% weight loss after 56 days in elastase containing buffer. Elastase-sensitive scaffolds were complete degraded after 8 weeks subcutaneous implantation in rats, markedly faster than similar polyurethanes that did not contain the peptide sequence. Conclusion The elastase-sensitive polyurethane scaffolds showed promise for application in soft tissue engineering where controlling scaffold mechanical properties and pore architecture are desirable. PMID:18509596

ASDB: a resource for probing protein functions with small molecules.

PubMed

Liu, Zhihong; Ding, Peng; Yan, Xin; Zheng, Minghao; Zhou, Huihao; Xu, Yuehua; Du, Yunfei; Gu, Qiong; Xu, Jun

2016-06-01

: Identifying chemical probes or seeking scaffolds for a specific biological target is important for protein function studies. Therefore, we create the Annotated Scaffold Database (ASDB), a computer-readable and systematic target-annotated scaffold database, to serve such needs. The scaffolds in ASDB were derived from public databases including ChEMBL, DrugBank and TCMSP, with a scaffold-based classification approach. Each scaffold was assigned with an InChIKey as its unique identifier, energy-minimized 3D conformations, and other calculated properties. A scaffold is also associated with drugs, natural products, drug targets and medical indications. The database can be retrieved through text or structure query tools. ASDB collects 333 601 scaffolds, which are associated with 4368 targets. The scaffolds consist of 3032 scaffolds derived from drugs and 5163 scaffolds derived from natural products. For given scaffolds, scaffold-target networks can be generated from the database to demonstrate the relations of scaffolds and targets. ASDB is freely available at http://www.rcdd.org.cn/asdb/with the major web browsers. junxu@biochemomes.com or xujun9@mail.sysu.edu.cn Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Relationship between micro-porosity, water permeability and mechanical behavior in scaffolds for cartilage engineering.

PubMed

Vikingsson, L; Claessens, B; Gómez-Tejedor, J A; Gallego Ferrer, G; Gómez Ribelles, J L

2015-08-01

In tissue engineering the design and optimization of biodegradable polymeric scaffolds with a 3D-structure is an important field. The porous scaffold provide the cells with an adequate biomechanical environment that allows mechanotransduction signals for cell differentiation and the scaffolds also protect the cells from initial compressive loading. The scaffold have interconnected macro-pores that host the cells and newly formed tissue, while the pore walls should be micro-porous to transport nutrients and waste products. Polycaprolactone (PCL) scaffolds with a double micro- and macro-pore architecture have been proposed for cartilage regeneration. This work explores the influence of the micro-porosity of the pore walls on water permeability and scaffold compliance. A Poly(Vinyl Alcohol) with tailored mechanical properties has been used to simulate the growing cartilage tissue inside the scaffold pores. Unconfined and confined compression tests were performed to characterize both the water permeability and the mechanical response of scaffolds with varying size of micro-porosity while volume fraction of the macro-pores remains constant. The stress relaxation tests show that the stress response of the scaffold/hydrogel construct is a synergic effect determined by the performance of the both components. This is interesting since it suggests that the in vivo outcome of the scaffold is not only dependent upon the material architecture but also the growing tissue inside the scaffold׳s pores. On the other hand, confined compression results show that compliance of the scaffold is mainly controlled by the micro-porosity of the scaffold and less by hydrogel density in the scaffold pores. These conclusions bring together valuable information for customizing the optimal scaffold and to predict the in vivo mechanical behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of Mechanical Properties of Tissue Scaffolds by Phase Contrast Imaging and Finite Element Modeling.

PubMed

Bawolin, Nahshon K; Dolovich, Allan T; Chen, Daniel X B; Zhang, Chris W J

2015-08-01

In tissue engineering, the cell and scaffold approach has shown promise as a treatment to regenerate diseased and/or damaged tissue. In this treatment, an artificial construct (scaffold) is seeded with cells, which organize and proliferate into new tissue. The scaffold itself biodegrades with time, leaving behind only newly formed tissue. The degradation qualities of the scaffold are critical during the treatment period, since the change in the mechanical properties of the scaffold with time can influence cell behavior. To observe in time the scaffold's mechanical properties, a straightforward method is to deform the scaffold and then characterize scaffold deflection accordingly. However, experimentally observing the scaffold deflection is challenging. This paper presents a novel study on characterization of mechanical properties of scaffolds by phase contrast imaging and finite element modeling, which specifically includes scaffold fabrication, scaffold imaging, image analysis, and finite elements (FEs) modeling of the scaffold mechanical properties. The innovation of the work rests on the use of in-line phase contrast X-ray imaging at 20 KeV to characterize tissue scaffold deformation caused by ultrasound radiation forces and the use of the Fourier transform to identify movement. Once deformation has been determined experimentally, it is then compared with the predictions given by the forward solution of a finite element model. A consideration of the number of separate loading conditions necessary to uniquely identify the material properties of transversely isotropic and fully orthotropic scaffolds is also presented, along with the use of an FE as a form of regularization.

Fabrication of chitosan/gallic acid 3D microporous scaffold for tissue engineering applications.

PubMed

Thangavel, Ponrasu; Ramachandran, Balaji; Muthuvijayan, Vignesh

2016-05-01

This study explores the potential of gallic acid incorporated chitosan (CS/GA) 3D scaffolds for tissue engineering applications. Scaffolds were prepared by freezing and lyophilization technique and characterized. FTIR spectra confirmed the presence of GA in chitosan (CS) gel. DSC and TGA analysis revealed that the structure of chitosan was not altered due to the incorporation of GA, but thermal stability was significantly increased compared to the CS scaffold. SEM micrographs showed smooth, homogeneous, and microporous architecture of the scaffolds with good interconnectivity. CS/GA scaffolds exhibited approximately 90% porosity on average, increased swelling (600-900%) and controlled biodegradation (15-40%) in PBS (pH 7.4 at 37°C) with 1 mg/mL of lysozyme. CS/GA scaffolds showed 2-4 fold decrease in CFUs (p < 0.05) for both gram positive and gram negative bacteria compared to the CS scaffold. Cytotoxicity of these scaffolds was evaluated using NIH 3T3 L1 fibroblast cells. CS/GA 0.25% scaffold showed similar viability with CS scaffold at 24 and 48 h. CS/GA scaffolds (0.5-1.0%) showed 60-75% viability at 24 h and 90% at 48 h. SEM images showed that an increased cell attachment was observed for CS/GA scaffolds compared to CS scaffolds. These findings authenticate that CS/GA scaffolds were cytocompatible and would be useful for tissue engineering applications. © 2015 Wiley Periodicals, Inc.

Design, construction and mechanical testing of digital 3D anatomical data-based PCL-HA bone tissue engineering scaffold.

PubMed

Yao, Qingqiang; Wei, Bo; Guo, Yang; Jin, Chengzhe; Du, Xiaotao; Yan, Chao; Yan, Junwei; Hu, Wenhao; Xu, Yan; Zhou, Zhi; Wang, Yijin; Wang, Liming

2015-01-01

The study aims to investigate the techniques of design and construction of CT 3D reconstructional data-based polycaprolactone (PCL)-hydroxyapatite (HA) scaffold. Femoral and lumbar spinal specimens of eight male New Zealand white rabbits were performed CT and laser scanning data-based 3D printing scaffold processing using PCL-HA powder. Each group was performed eight scaffolds. The CAD-based 3D printed porous cylindrical stents were 16 piece × 3 groups, including the orthogonal scaffold, the Pozi-hole scaffold and the triangular hole scaffold. The gross forms, fiber scaffold diameters and porosities of the scaffolds were measured, and the mechanical testing was performed towards eight pieces of the three kinds of cylindrical scaffolds, respectively. The loading force, deformation, maximum-affordable pressure and deformation value were recorded. The pore-connection rate of each scaffold was 100 % within each group, there was no significant difference in the gross parameters and micro-structural parameters of each scaffold when compared with the design values (P > 0.05). There was no significant difference in the loading force, deformation and deformation value under the maximum-affordable pressure of the three different cylinder scaffolds when the load was above 320 N. The combination of CT and CAD reverse technology could accomplish the design and manufacturing of complex bone tissue engineering scaffolds, with no significant difference in the impacts of the microstructures towards the physical properties of different porous scaffolds under large load.

Preparation of porous collagen/hyaluronic acid hybrid scaffolds for biomimetic functionalization through biochemical binding affinity.

PubMed

Lee, Su Jin; Kim, So Yeon; Lee, Young Moo

2007-08-01

This study demonstrated the feasibility of introducing an avidin-biotin system to three-dimensional and highly porous scaffolds for the purpose of designing scaffolds that have binding affinity with bioactive molecules for various biomimetic modifications. Porous hybrid scaffolds composed of collagen and hyaluronic acid (HA) were prepared by a novel overrun process. The overrun-processed scaffolds showed a uniform dual-pore structure because of the injection of gas bubbles and ice recrystallization during the fabrication process and had a higher porosity than scaffolds prepared by a conventional freeze-drying method. The mechanical strength and biodegradation kinetics were controlled by the method of preparation and the composition of collagen/HA. Collagen/HA scaffolds did not show any significant adverse effects on cell viability even after 10 days of incubation. The fibroblasts cultured in the overrun-processed scaffolds were widely distributed and had proliferated on the surfaces of the macropores in the scaffolds, whereas the cells that were seeded in the freeze-dried scaffolds had attached mainly on the dense surface of the scaffolds. As the collagen content in the scaffolds increased, the cellular ingrowth into the inner pores of the scaffolds decreased because of the high affinity between the collagen and the cells. Measurements obtained via confocal microscopy revealed that the porous collagen/HA scaffolds could be functionalized with the biotin by incorporating avidin. Therefore, the present biotinylation approach may allow the incorporation of various bioactive molecules (DNA, growth factors, drug, peptide, etc) into the three-dimensional porous scaffolds.

Periodontal tissue engineering by nano beta-tricalcium phosphate scaffold and fibroblast growth factor-2 in one-wall infrabony defects of dogs.

PubMed

Ogawa, K; Miyaji, H; Kato, A; Kosen, Y; Momose, T; Yoshida, T; Nishida, E; Miyata, S; Murakami, S; Takita, H; Fugetsu, B; Sugaya, T; Kawanami, M

2016-12-01

Nanoparticle bioceramics are being investigated for biomedical applications. We fabricated a regenerative scaffold comprising type I collagen and beta-tricalcium phosphate (β-TCP) nanoparticles. Fibroblast growth factor-2 (FGF-2) is a bioeffective signaling molecule that stimulates cell proliferation and wound healing. This study examined the effects, on bioactivity, of a nano-β-TCP/collagen scaffold loaded with FGF-2, particularly on periodontal tissue wound healing. Beta-tricalcium phosphate was pulverized into nanosize particles (84 nm) and was then dispersed. A nano-β-TCP scaffold was prepared by coating the surface of a collagen scaffold with a nanosize β-TCP dispersion. Scaffolds were characterized using scanning electron microscopy, compressive testing, cell seeding and rat subcutaneous implant testing. Then, nano-β-TCP scaffold, nano-β-TCP scaffold loaded with FGF-2 and noncoated collagen scaffold were implanted into a dog one-wall infrabony defect model. Histological observations were made at 10 d and 4 wk postsurgery. Scanning electron microscopy images show that TCP nanoparticles were attached to collagen fibers. The nano-β-TCP scaffold showed higher compressive strength and cytocompatibility compared with the noncoated collagen scaffold. Rat subcutaneous implant tests showed that the DNA contents of infiltrating cells in the nano-β-TCP scaffold and the FGF-2-loaded scaffold were approximately 2.8-fold and 3.7-fold greater, respectively, than in the collagen scaffold. Histological samples from the periodontal defect model showed about five-fold greater periodontal tissue repair following implantation of the nano-β-TCP scaffold loaded with FGF-2 compared with the collagen scaffold. The β-TCP nanoparticle coating strongly improved the collagen scaffold bioactivity. Nano-β-TCP scaffolds containing FGF-2 are anticipated for use in periodontal tissue engineering. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Nano-ceramic composite scaffolds for bioreactor-based bone engineering.

PubMed

Lv, Qing; Deng, Meng; Ulery, Bret D; Nair, Lakshmi S; Laurencin, Cato T

2013-08-01

Composites of biodegradable polymers and bioactive ceramics are candidates for tissue-engineered scaffolds that closely match the properties of bone. We previously developed a porous, three-dimensional poly (D,L-lactide-co-glycolide) (PLAGA)/nanohydroxyapatite (n-HA) scaffold as a potential bone tissue engineering matrix suitable for high-aspect ratio vessel (HARV) bioreactor applications. However, the physical and cellular properties of this scaffold are unknown. The present study aims to evaluate the effect of n-HA in modulating PLAGA scaffold properties and human mesenchymal stem cell (HMSC) responses in a HARV bioreactor. By comparing PLAGA/n-HA and PLAGA scaffolds, we asked whether incorporation of n-HA (1) accelerates scaffold degradation and compromises mechanical integrity; (2) promotes HMSC proliferation and differentiation; and (3) enhances HMSC mineralization when cultured in HARV bioreactors. PLAGA/n-HA scaffolds (total number = 48) were loaded into HARV bioreactors for 6 weeks and monitored for mass, molecular weight, mechanical, and morphological changes. HMSCs were seeded on PLAGA/n-HA scaffolds (total number = 38) and cultured in HARV bioreactors for 28 days. Cell migration, proliferation, osteogenic differentiation, and mineralization were characterized at four selected time points. The same amount of PLAGA scaffolds were used as controls. The incorporation of n-HA did not alter the scaffold degradation pattern. PLAGA/n-HA scaffolds maintained their mechanical integrity throughout the 6 weeks in the dynamic culture environment. HMSCs seeded on PLAGA/n-HA scaffolds showed elevated proliferation, expression of osteogenic phenotypic markers, and mineral deposition as compared with cells seeded on PLAGA scaffolds. HMSCs migrated into the scaffold center with nearly uniform cell and extracellular matrix distribution in the scaffold interior. The combination of PLAGA/n-HA scaffolds with HMSCs in HARV bioreactors may allow for the generation of engineered bone tissue. In cases of large bone voids (such as bone cancer), tissue-engineered constructs may provide alternatives to traditional bone grafts by culturing patients' own MSCs with PLAGA/n-HA scaffolds in a HARV culture system.

Cell infiltration and growth in a low density, uncompressed three-dimensional electrospun nanofibrous scaffold.

PubMed

Blakeney, Bryan A; Tambralli, Ajay; Anderson, Joel M; Andukuri, Adinarayana; Lim, Dong-Jin; Dean, Derrick R; Jun, Ho-Wook

2011-02-01

A limiting factor of traditional electrospinning is that the electrospun scaffolds consist entirely of tightly packed nanofiber layers that only provide a superficial porous structure due to the sheet-like assembly process. This unavoidable characteristic hinders cell infiltration and growth throughout the nanofibrous scaffolds. Numerous strategies have been tried to overcome this challenge, including the incorporation of nanoparticles, using larger microfibers, or removing embedded salt or water-soluble fibers to increase porosity. However, these methods still produce sheet-like nanofibrous scaffolds, failing to create a porous three-dimensional scaffold with good structural integrity. Thus, we have developed a three-dimensional cotton ball-like electrospun scaffold that consists of an accumulation of nanofibers in a low density and uncompressed manner. Instead of a traditional flat-plate collector, a grounded spherical dish and an array of needle-like probes were used to create a Focused, Low density, Uncompressed nanoFiber (FLUF) mesh scaffold. Scanning electron microscopy showed that the cotton ball-like scaffold consisted of electrospun nanofibers with a similar diameter but larger pores and less-dense structure compared to the traditional electrospun scaffolds. In addition, laser confocal microscopy demonstrated an open porosity and loosely packed structure throughout the depth of the cotton ball-like scaffold, contrasting the superficially porous and tightly packed structure of the traditional electrospun scaffold. Cells seeded on the cotton ball-like scaffold infiltrated into the scaffold after 7 days of growth, compared to no penetrating growth for the traditional electrospun scaffold. Quantitative analysis showed approximately a 40% higher growth rate for cells on the cotton ball-like scaffold over a 7 day period, possibly due to the increased space for in-growth within the three-dimensional scaffolds. Overall, this method assembles a nanofibrous scaffold that is more advantageous for highly porous interconnectivity and demonstrates great potential for tackling current challenges of electrospun scaffolds. 2010 Elsevier Ltd. All rights reserved.

Graphene oxide scaffold accelerates cellular proliferative response and alveolar bone healing of tooth extraction socket.

PubMed

Nishida, Erika; Miyaji, Hirofumi; Kato, Akihito; Takita, Hiroko; Iwanaga, Toshihiko; Momose, Takehito; Ogawa, Kosuke; Murakami, Shusuke; Sugaya, Tsutomu; Kawanami, Masamitsu

2016-01-01

Graphene oxide (GO) consisting of a carbon monolayer has been widely investigated for tissue engineering platforms because of its unique properties. For this study, we fabricated a GO-applied scaffold and assessed the cellular and tissue behaviors in the scaffold. A preclinical test was conducted to ascertain whether the GO scaffold promoted bone induction in dog tooth extraction sockets. For this study, GO scaffolds were prepared by coating the surface of a collagen sponge scaffold with 0.1 and 1 µg/mL GO dispersion. Scaffolds were characterized using scanning electron microscopy (SEM), physical testing, cell seeding, and rat subcutaneous implant testing. Then a GO scaffold was implanted into a dog tooth extraction socket. Histological observations were made at 2 weeks postsurgery. SEM observations show that GO attached to the surface of collagen scaffold struts. The GO scaffold exhibited an interconnected structure resembling that of control subjects. GO application improved the physical strength, enzyme resistance, and adsorption of calcium and proteins. Cytocompatibility tests showed that GO application significantly increased osteoblastic MC3T3-E1 cell proliferation. In addition, an assessment of rat subcutaneous tissue response revealed that implantation of 1 µg/mL GO scaffold stimulated cellular ingrowth behavior, suggesting that the GO scaffold exhibited good biocompatibility. The tissue ingrowth area and DNA contents of 1 µg/mL GO scaffold were, respectively, approximately 2.5-fold and 1.4-fold greater than those of the control. Particularly, the infiltration of ED2-positive (M2) macrophages and blood vessels were prominent in the GO scaffold. Dog bone-formation tests showed that 1 µg/mL GO scaffold implantation enhanced bone formation. New bone formation following GO scaffold implantation was enhanced fivefold compared to that in control subjects. These results suggest that GO was biocompatible and had high bone-formation capability for the scaffold. The GO scaffold is expected to be beneficial for bone tissue engineering therapy.

Pericellular plasma clot negates the influence of scaffold stiffness on chondrogenic differentiation.

PubMed

Arora, Aditya; Kothari, Anjaney; Katti, Dhirendra S

2016-12-01

Matrix stiffness is known to play a pivotal role in cellular differentiation. Studies have shown that soft scaffolds (<2-3kPa) promote cellular aggregation and chondrogenesis, whereas, stiffer ones (>10kPa) show poor chondrogenesis in vitro. In this work we investigated if fibrin matrix from clotted blood can act as a soft surrogate which nullifies the influence of the underlying stiff scaffold, thus promoting chondrogenesis irrespective of bulk scale scaffold stiffness. For this we performed in vitro chondrogenesis on soft (∼1.5kPa) and stiff (∼40kPa) gelatin scaffolds in the presence and absence of pericellular plasma clot. Our results demonstrated that in absence of pericellular plasma clot, chondrocytes showed efficient condensation and cartilaginous matrix secretion only on soft scaffolds, whereas, in presence of pericellular plasma clot, cell rounding and cartilaginous matrix secretion was observed in both soft and stiff scaffolds. More specifically, significantly higher collagen II, chondroitin sulfate and aggrecan deposition was observed in soft scaffolds, and soft and stiff scaffolds with pericellular plasma clot as compared to stiff scaffolds without pericellular plasma clot. Moreover, collagen type I, a fibrocartilage/bone marker was significantly higher only in stiff scaffolds without plasma clot. Therefore, it can be concluded that chondrocytes surrounded by a soft fibrin network were unable to sense the stiffness of the underlying scaffold/substrate and hence facilitate chondrogenesis even on stiff scaffolds. This understanding can have significant implications in the design of scaffolds for cartilage tissue engineering. Cell fate is influenced by the mechanical properties of cell culture substrates. Outside the body, cartilage progenitor cells express significant amounts of cartilage-specific markers on soft scaffolds but not on stiff scaffolds. However, when implanted in joints, stiff scaffolds show equivalent expression of markers as seen in soft scaffolds. This disparity in existing literature prompted our study. Our results suggest that encapsulation of cells in a soft plasma clot, present in any surgical intervention, prevents their perception of stiffness of the underlying scaffold, and hence the ability to distinguish between soft and stiff scaffolds vanishes. This finding would aid the design of new scaffolds that elicit cartilage-like biochemical properties while simultaneously being mechanically comparable to cartilage tissue. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Oxygen Plasma Treatment on 3D-Printed Chitosan/Gelatin/Hydroxyapatite Scaffolds for Bone Tissue Engineering.

PubMed

Lee, Chang-Min; Yang, Seong-Won; Jung, Sang-Chul; Kim, Byung-Hoon

2017-04-01

The 3D hydroxyapatite/gelatin/chitosan composite scaffolds were fabricated by 3D printing technique. The scaffolds were treated by oxygen plasma to improve the bioactivity and its surface characterization and in vitro cell culture were investigated. The scaffolds exhibited the good porosity and interconnectivity of pores. After oxygen plasma etching, roughness and wettability on the scaffolds surface are increased. Plasma treated scaffolds showed higher proliferation than that of untreated scaffolds. Oxygen plasma treatment could be used as potential tool to enhance the biocompatibility on the 3D composite scaffolds.

Modeling and Reconstruction of Micro-structured 3D Chitosan/Gelatin Porous Scaffolds Using Micro-CT

NASA Astrophysics Data System (ADS)

Gong, Haibo; Li, Dichen; He, Jiankang; Liu, Yaxiong; Lian, Qin; Zhao, Jinna

2008-09-01

Three dimensional (3D) channel networks are the key to promise the uniform distribution of nutrients inside 3D hepatic tissue engineering scaffolds and prompt elimination of metabolic products out of the scaffolds. 3D chitosan/gelatin porous scaffolds with predefined internal channels were fabricated and a combination of light microscope, laser confocal microscopy and micro-CT were employed to characterize the structure of porous scaffolds. In order to evaluate the flow field distribution inside the micro-structured 3D scaffolds, a computer reconstructing method based on Micro-CT was proposed. According to this evaluating method, a contrast between 3D porous scaffolds with and without predefined internal channels was also performed to assess scaffolds' fluid characters. Results showed that the internal channel of the 3D scaffolds formed the 3D fluid channel network; the uniformity of flow field distribution of the scaffolds fabricated in this paper was better than the simple porous scaffold without micro-fluid channels.

Comparison between PCL/hydroxyapatite (HA) and PCL/halloysite nanotube (HNT) composite scaffolds prepared by co-extrusion and gas foaming.

PubMed

Jing, Xin; Mi, Hao-Yang; Turng, Lih-Sheng

2017-03-01

In this work, three-dimensional poly(caprolactone) (PCL) tissue engineering scaffolds were prepared by co-extrusion and gas foaming. Biocompatible hydroxyapatite (HA) and halloysite nanotubes (HNT) were added to the polymer matrix to enhance the mechanical properties and bioactivity of the composite scaffolds. The effects of HA and HNT on the rheological behavior, microstructure, and mechanical properties of the composite scaffolds were systematically compared. It was found that the HNT improved viscosity more significantly than HA, and reduced the pore size of scaffolds, while the mechanical performance of PCL/HNT scaffolds was higher than PCL/HA scaffolds with the same filler content. Human mesenchymal stem cells (hMSCs) were used as the cell model to compare the biological properties of two composite scaffolds. The results demonstrated that cells could survive on all scaffolds, and showed a more flourishing living state on the composite scaffolds. The cell differentiation for 5% HA and 1% HNT scaffolds were significantly higher than other scaffolds, while the differentiation of 5% HNT scaffolds was lower than that of 1% HNT scaffolds mainly because of the reduced pore size and pore interconnectivity. Therefore, this study suggested that, with proper filler content and control of microstructure through processing, HNT could be a suitable substitute for HA for bone tissue engineering to reduce the cost and improve mechanical performance. Copyright © 2016. Published by Elsevier B.V.

Dual-source dual-power electrospinning and characteristics of multifunctional scaffolds for bone tissue engineering.

PubMed

Wang, Chong; Wang, Min

2012-10-01

Electrospun tissue engineering scaffolds are attractive due to their distinctive advantages over other types of scaffolds. As both osteoinductivity and osteoconductivity play crucial roles in bone tissue engineering, scaffolds possessing both properties are desirable. In this investigation, novel bicomponent scaffolds were constructed via dual-source dual-power electrospinning (DSDPES). One scaffold component was emulsion electrospun poly(D,L-lactic acid) (PDLLA) nanofibers containing recombinant human bone morphogenetic protein (rhBMP-2), and the other scaffold component was electrospun calcium phosphate (Ca-P) particle/poly(lactic-co-glycolic acid) (PLGA) nanocomposite fibers. The mass ratio of rhBMP-2/PDLLA fibers to Ca-P/PLGA fibers in bicomponent scaffolds could be controlled in the DSDPES process by adjusting the number of syringes used to supply solutions for electrospinning. Through process optimization, both types of fibers could be evenly distributed in bicomponent scaffolds. The structure and properties of each type of fibers in the scaffolds were studied. The morphological and structural properties and wettability of scaffolds were assessed. The effects of emulsion composition for rhBMP-2/PDLLA fibers and mass ratio of fibrous components in bicomponent scaffolds on in vitro release of rhBMP-2 from scaffolds were investigated. In vitro degradation of scaffolds was also studied by monitoring their morphological changes, weight losses and decreases in average molecular weight of fiber matrix polymers.

High porous titanium scaffolds showed higher compatibility than lower porous beta-tricalcium phosphate scaffolds for regulating human osteoblast and osteoclast differentiation.

PubMed

Hirota, Makoto; Hayakawa, Tohru; Shima, Takaki; Ametani, Akihiro; Tohnai, Iwai

2015-04-01

We compared osteoblast and osteoclast differentiation when using beta-tricalcium phosphate (βTCP) and titanium scaffolds by investigating human mesenchymal stem cells (hMSCs) and osteoclast progenitor cell activities. hMSCs were cultured for 7, 14, and 21days on titanium scaffolds with 60%, 73%, and 87% porosity and on βTCP scaffolds with 60% and 75% porosity. Human osteoclast progenitor cells were cultured with osteoblast for 14 and 21days on 87% titanium and 75% βTCP scaffolds. Viable cell numbers with 60% and 73% titanium were higher than with 87% titanium and βTCP scaffolds (P<0.05). An 87% titanium scaffold resulted in the highest osteocalcin production with calcification on day 14 (P<0.01) in titanium scaffolds. All titanium scaffolds resulted in higher osteocalcin production on days 7 and 14 compared to βTCP scaffolds (P<0.01). Osteoblasts cultured on 87% titanium scaffolds suppressed osteoclast differentiation on day 7 but enhanced osteoclast differentiation on day 14 compared to 75% βTCP scaffolds (P<0.01). These findings concluded that high porosity titanium scaffolds could enhance progression of hMSC/osteoblast differentiation and regulated osteoclast differentiation cooperating with osteoblast differentiation for calcification as compared with lower porous βTCP. Copyright © 2015 Elsevier B.V. All rights reserved.

Dynamic Scaffolding of Socially Regulated Learning in a Computer-Based Learning Environment

ERIC Educational Resources Information Center

Molenaar, Inge; Roda, Claudia; van Boxtel, Carla; Sleegers, Peter

2012-01-01

The aim of this study is to test the effects of dynamically scaffolding social regulation of middle school students working in a computer-based learning environment. Dyads in the scaffolding condition (N=56) are supported with computer-generated scaffolds and students in the control condition (N=54) do not receive scaffolds. The scaffolds are…

Prediction of scaffold proteins based on protein interaction and domain architectures.

PubMed

Oh, Kimin; Yi, Gwan-Su

2016-07-28

Scaffold proteins are known for being crucial regulators of various cellular functions by assembling multiple proteins involved in signaling and metabolic pathways. Identification of scaffold proteins and the study of their molecular mechanisms can open a new aspect of cellular systemic regulation and the results can be applied in the field of medicine and engineering. Despite being highlighted as the regulatory roles of dozens of scaffold proteins, there was only one known computational approach carried out so far to find scaffold proteins from interactomes. However, there were limitations in finding diverse types of scaffold proteins because their criteria were restricted to the classical scaffold proteins. In this paper, we will suggest a systematic approach to predict massive scaffold proteins from interactomes and to characterize the roles of scaffold proteins comprehensively. From a total of 10,419 basic scaffold protein candidates in protein interactomes, we classified them into three classes according to the structural evidences for scaffolding, such as domain architectures, domain interactions and protein complexes. Finally, we could define 2716 highly reliable scaffold protein candidates and their characterized functional features. To assess the accuracy of our prediction, the gold standard positive and negative data sets were constructed. We prepared 158 gold standard positive data and 844 gold standard negative data based on the functional information from Gene Ontology consortium. The precision, sensitivity and specificity of our testing was 80.3, 51.0, and 98.5 % respectively. Through the function enrichment analysis of highly reliable scaffold proteins, we could confirm the significantly enriched functions that are related to scaffold protein binding. We also identified functional association between scaffold proteins and their recruited proteins. Furthermore, we checked that the disease association of scaffold proteins is higher than kinases. In conclusion, we could predict larger volume of scaffold proteins and analyzed their functional characteristics. Deeper understandings about the roles of scaffold proteins from this study will provide a higher opportunity to find therapeutic or engineering applications of scaffold proteins using their functional characteristics.

Biomimetic composite coating on rapid prototyped scaffolds for bone tissue engineering.

PubMed

Arafat, M Tarik; Lam, Christopher X F; Ekaputra, Andrew K; Wong, Siew Yee; Li, Xu; Gibson, Ian

2011-02-01

The objective of this present study was to improve the functional performance of rapid prototyped scaffolds for bone tissue engineering through biomimetic composite coating. Rapid prototyped poly(ε-caprolactone)/tri-calcium phosphate (PCL/TCP) scaffolds were fabricated using the screw extrusion system (SES). The fabricated PCL/TCP scaffolds were coated with a carbonated hydroxyapatite (CHA)-gelatin composite via biomimetic co-precipitation. The structure of the prepared CHA-gelatin composite coating was studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Compressive mechanical testing revealed that the coating process did not have any detrimental effect on the mechanical properties of the scaffolds. The cell-scaffold interaction was studied by culturing porcine bone marrow stromal cells (BMSCs) on the scaffolds and assessing the proliferation and bone-related gene and protein expression capabilities of the cells. Confocal laser microscopy and SEM images of the cell-scaffold constructs showed a uniformly distributed cell sheet and accumulation of extracellular matrix in the interior of CHA-gelatin composite-coated PCL/TCP scaffolds. The proliferation rate of BMSCs on CHA-gelatin composite-coated PCL/TCP scaffolds was about 2.3 and 1.7 times higher than that on PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds, respectively, by day 10. Furthermore, reverse transcription polymerase chain reaction and Western blot analysis revealed that CHA-gelatin composite-coated PCL/TCP scaffolds stimulate osteogenic differentiation of BMSCs the most, compared with PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds. These results demonstrate that CHA-gelatin composite-coated rapid prototyped PCL/TCP scaffolds are promising for bone tissue engineering. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Bone tissue engineering scaffolding: computer-aided scaffolding techniques.

PubMed

Thavornyutikarn, Boonlom; Chantarapanich, Nattapon; Sitthiseripratip, Kriskrai; Thouas, George A; Chen, Qizhi

Tissue engineering is essentially a technique for imitating nature. Natural tissues consist of three components: cells, signalling systems (e.g. growth factors) and extracellular matrix (ECM). The ECM forms a scaffold for its cells. Hence, the engineered tissue construct is an artificial scaffold populated with living cells and signalling molecules. A huge effort has been invested in bone tissue engineering, in which a highly porous scaffold plays a critical role in guiding bone and vascular tissue growth and regeneration in three dimensions. In the last two decades, numerous scaffolding techniques have been developed to fabricate highly interconnective, porous scaffolds for bone tissue engineering applications. This review provides an update on the progress of foaming technology of biomaterials, with a special attention being focused on computer-aided manufacturing (Andrade et al. 2002) techniques. This article starts with a brief introduction of tissue engineering (Bone tissue engineering and scaffolds) and scaffolding materials (Biomaterials used in bone tissue engineering). After a brief reviews on conventional scaffolding techniques (Conventional scaffolding techniques), a number of CAM techniques are reviewed in great detail. For each technique, the structure and mechanical integrity of fabricated scaffolds are discussed in detail. Finally, the advantaged and disadvantage of these techniques are compared (Comparison of scaffolding techniques) and summarised (Summary).

Greater scaffold permeability promotes growth of osteoblastic cells in a perfused bioreactor.

PubMed

Fan, Jie; Jia, Xiaoling; Huang, Yan; Fu, Bingmei M; Fan, Yubo

2015-12-01

Pore size and porosity have been widely acknowledged as important structural factors in tissue-engineered scaffolds. In fact, scaffolds with similar pore size and porosity can provide important and varied permeability due to different pore shape, interconnectivity and tortuosity. However, the effects of scaffold permeability on seeded cells remains largely unknown during tissue regeneration in vitro. In this study, we measured the Darcy permeability (K) of tri-calcium phosphate scaffolds by distributed them into three groups: Low, Medium and High. As a result, the effects of scaffold permeability on cell proliferation, cellular activity and growth in the inner pores were investigated in perfused and static cultures in vitro. Results demonstrated that higher permeable scaffolds exhibited superior performance during bone regeneration in vitro and the advantages of higher scaffold permeability were amplified in perfused culture. Based on these findings, scaffold permeability should be considered in future scaffold fabrications. Copyright © 2013 John Wiley & Sons, Ltd.

Fabrication of chitin-chitosan/nano TiO2-composite scaffolds for tissue engineering applications.

PubMed

Jayakumar, R; Ramachandran, Roshni; Divyarani, V V; Chennazhi, K P; Tamura, H; Nair, S V

2011-03-01

In this study, we prepared chitin-chitosan/nano TiO(2) composite scaffolds using lyophilization technique for bone tissue engineering. The prepared composite scaffold was characterized using SEM, XRD, FTIR and TGA. In addition, swelling, degradation and biomineralization capability of the composite scaffolds were evaluated. The developed composite scaffold showed controlled swelling and degradation when compared to the control scaffold. Cytocompatibility of the scaffold was assessed by MTT assay and cell attachment studies using osteoblast-like cells (MG-63), fibroblast cells (L929) and human mesenchymal stem cells (hMSCs). Results indicated no sign of toxicity and cells were found attached to the pore walls within the scaffolds. These results suggested that the developed composite scaffold possess the prerequisites for tissue engineering scaffolds and it can be used for tissue engineering applications. Copyright © 2010 Elsevier B.V. All rights reserved.

Mechanical characterization of collagen-glycosaminoglycan scaffolds.

PubMed

Harley, Brendan A; Leung, Janet H; Silva, Emilio C C M; Gibson, Lorna J

2007-07-01

Tissue engineering scaffolds are used extensively as three-dimensional analogs of the extracellular matrix (ECM). However, less attention has been paid to characterizing the scaffold microstructure and mechanical properties than to the processing and bioactivity of scaffolds. Collagen-glycosaminoglycan (CG) scaffolds have long been utilized as ECM analogs for the regeneration of skin and are currently being considered for the regeneration of nerve and conjunctiva. Recently a series of CG scaffolds with a uniform pore microstructure has been developed with a range of sizes of equiaxed pores. Experimental characterization and theoretical modeling techniques have previously been used to describe the pore microstructure, specific surface area, cell attachment and permeability of these variants. The results of tensile and compressive tests on these CG scaffolds and of bending tests on the individual struts that define the scaffold network are reported here. The CG scaffold variants exhibited stress-strain behavior characteristic of low-density, open-cell foams with distinct linear elastic, collapse plateau and densification regimes. Scaffolds with equiaxed pores were found to be mechanically isotropic. The independent effects of hydration level, pore size, crosslink density and relative density on the mechanical properties was determined. Independent control over scaffold stiffness and pore size was obtained. Good agreement was observed between experimental results of scaffold mechanical characterization and low-density, open-cell foam model predictions for uniform scaffolds. The characterized scaffold variants provide a standardized framework with defined extracellular environments (microstructure, mechanics) for in vitro studies of the mechanical interactions between cells and scaffolds as well as in vivo tissue engineering studies.

ASTM international workshop on standards and measurements for tissue engineering scaffolds.

PubMed

Simon, Carl G; Yaszemski, Michael J; Ratcliffe, Anthony; Tomlins, Paul; Luginbuehl, Reto; Tesk, John A

2015-07-01

The "Workshop on Standards & Measurements for Tissue Engineering Scaffolds" was held on May 21, 2013 in Indianapolis, IN, and was sponsored by the ASTM International (ASTM). The purpose of the workshop was to identify the highest priority items for future standards work for scaffolds used in the development and manufacture of tissue engineered medical products (TEMPs). Eighteen speakers and 78 attendees met to assess current scaffold standards and to prioritize needs for future standards. A key finding was that the ASTM TEMPs subcommittees (F04.41-46) have many active "guide" documents for educational purposes, but few standard "test methods" or "practices." Overwhelmingly, the most clearly identified need was standards for measuring the structure of scaffolds, followed by standards for biological characterization, including in vitro testing, animal models and cell-material interactions. The third most pressing need was to develop standards for assessing the mechanical properties of scaffolds. Additional needs included standards for assessing scaffold degradation, clinical outcomes with scaffolds, effects of sterilization on scaffolds, scaffold composition, and drug release from scaffolds. Discussions highlighted the need for additional scaffold reference materials and the need to use them for measurement traceability. Workshop participants emphasized the need to promote the use of standards in scaffold fabrication, characterization, and commercialization. Finally, participants noted that standards would be more broadly accepted if their impact in the TEMPs community could be quantified. Many scaffold standard needs have been identified and focus is turning to generating these standards to support the use of scaffolds in TEMPs. © 2014 Wiley Periodicals, Inc.

Functionalization of chitosan/poly(lactic acid-glycolic acid) sintered microsphere scaffolds via surface heparinization for bone tissue engineering.

PubMed

Jiang, Tao; Khan, Yusuf; Nair, Lakshmi S; Abdel-Fattah, Wafa I; Laurencin, Cato T

2010-06-01

Scaffolds exhibiting biological recognition and specificity play an important role in tissue engineering and regenerative medicine. The bioactivity of scaffolds in turn influences, directs, or manipulates cellular responses. In this study, chitosan/poly(lactic acid-co-glycolic acid) (chitosan/PLAGA) sintered microsphere scaffolds were functionalized via heparin immobilization. Heparin was successfully immobilized on chitosan/PLAGA scaffolds with controllable loading efficiency. Mechanical testing showed that heparinization of chitosan/PLAGA scaffolds did not significantly alter the mechanical properties and porous structures. In addition, the heparinized chitosan/PLAGA scaffolds possessed a compressive modulus of 403.98 +/- 19.53 MPa and a compressive strength of 9.83 +/- 0.94 MPa, which are in the range of human trabecular bone. Furthermore, the heparinized chitosan/PLAGA scaffolds had an interconnected porous structure with a total pore volume of 30.93 +/- 0.90% and a median pore size of 172.33 +/- 5.89 mum. The effect of immobilized heparin on osteoblast-like MC3T3-E1 cell growth was investigated. MC3T3-E1 cells proliferated three dimensionally throughout the porous structure of the scaffolds. Heparinized chitosan/PLAGA scaffolds with low heparin loading (1.7 microg/scaffold) were shown to be capable of stimulating MC3T3-E1 cell proliferation by MTS assay and cell differentiation as evidenced by elevated osteocalcin expression when compared with nonheparinized chitosan/PLAGA scaffold and chitosan/PLAGA scaffold with high heparin loading (14.1 microg/scaffold). This study demonstrated the potential of functionalizing chitosan/PLAGA scaffolds via heparinization with improved cell functions for bone tissue engineering applications.

Synergistic Effect of Carbon Nanotubes and Graphene on Diopside Scaffolds.

PubMed

Liu, Tingting; Wu, Ping; Gao, Chengde; Feng, Pei; Xiao, Tao; Deng, Youwen; Shuai, Cijun; Peng, Shuping

2016-01-01

A synergetic effect between carbon nanotubes (CNTs) and graphene on diopside (Di) scaffolds was demonstrated. 3D network architecture in the matrix was formed through the 1D CNTs inlaid among the 2D graphene platelets (GNPs). The mechanical properties of the CNTs/GNPs/Di scaffolds were significantly improved compared with the CNTs/Di scaffolds and GNPs/Di scaffolds. In addition, the scaffolds exhibited excellent apatite-forming ability, a modest degradation rate, and stable mechanical properties in simulated body fluid (SBF). Moreover, cell culturing tests indicated that the scaffolds supported the cells attachment and proliferation. Taken together, the CNTs/GNPs/Di scaffolds offered great potential for bone tissue engineering.

[Research progress of articular cartilage scaffold for tissue engineering].

PubMed

Liu, Qingyu; Wang, Fuyou; Yang, Liu

2012-10-01

To review the research progress of articular cartilage scaffold materials and look into the future development prospects. Recent literature about articular cartilage scaffold for tissue engineering was reviewed, and the results from experiments and clinical application about natural and synthetic scaffold materials were analyzed. The design of articular cartilage scaffold for tissue engineering is vital to articular cartilage defects repair. The ideal scaffold can promote the progress of the cartilage repair, but the scaffold materials still have their limitations. It is necessary to pay more attention to the research of the articular cartilage scaffold, which is significant to the repair of cartilage defects in the future.

Fabrication and Mechanical Characterization of Hydrogel Infused Network Silk Scaffolds

PubMed Central

Kundanati, Lakshminath; Singh, Saket K.; Mandal, Biman B.; Murthy, Tejas G.; Gundiah, Namrata; Pugno, Nicola M.

2016-01-01

Development and characterization of porous scaffolds for tissue engineering and regenerative medicine is of great importance. In recent times, silk scaffolds were developed and successfully tested in tissue engineering and drug release applications. We developed a novel composite scaffold by mechanical infusion of silk hydrogel matrix into a highly porous network silk scaffold. The mechanical behaviour of these scaffolds was thoroughly examined for their possible use in load bearing applications. Firstly, unconfined compression experiments show that the denser composite scaffolds displayed significant enhancement in the elastic modulus as compared to either of the components. This effect was examined and further explained with the help of foam mechanics principles. Secondly, results from confined compression experiments that resemble loading of cartilage in confinement, showed nonlinear material responses for all scaffolds. Finally, the confined creep experiments were performed to calculate the hydraulic permeability of the scaffolds using soil mechanics principles. Our results show that composite scaffolds with some modifications can be a potential candidate for use of cartilage like applications. We hope such approaches help in developing novel scaffolds for tissue engineering by providing an understanding of the mechanics and can further be used to develop graded scaffolds by targeted infusion in specific regions. PMID:27681725

Gelatin Scaffolds with Controlled Pore Structure and Mechanical Property for Cartilage Tissue Engineering.

PubMed

Chen, Shangwu; Zhang, Qin; Nakamoto, Tomoko; Kawazoe, Naoki; Chen, Guoping

2016-03-01

Engineering of cartilage tissue in vitro using porous scaffolds and chondrocytes provides a promising approach for cartilage repair. However, nonuniform cell distribution and heterogeneous tissue formation together with weak mechanical property of in vitro engineered cartilage limit their clinical application. In this study, gelatin porous scaffolds with homogeneous and open pores were prepared using ice particulates and freeze-drying. The scaffolds were used to culture bovine articular chondrocytes to engineer cartilage tissue in vitro. The pore structure and mechanical property of gelatin scaffolds could be well controlled by using different ratios of ice particulates to gelatin solution and different concentrations of gelatin. Gelatin scaffolds prepared from ≥70% ice particulates enabled homogeneous seeding of bovine articular chondrocytes throughout the scaffolds and formation of homogeneous cartilage extracellular matrix. While soft scaffolds underwent cellular contraction, stiff scaffolds resisted cellular contraction and had significantly higher cell proliferation and synthesis of sulfated glycosaminoglycan. Compared with the gelatin scaffolds prepared without ice particulates, the gelatin scaffolds prepared with ice particulates facilitated formation of homogeneous cartilage tissue with significantly higher compressive modulus. The gelatin scaffolds with highly open pore structure and good mechanical property can be used to improve in vitro tissue-engineered cartilage.

Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold.

PubMed

Lin, Hsin-Yi; Chen, Hsin-Hung; Chang, Shih-Hsin; Ni, Tsung-Sheng

2013-01-01

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young's modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds' swelling ratios decreased by 55% after 60 min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.

Biomimetic fabrication of a three-level hierarchical calcium phosphate/collagen/hydroxyapatite scaffold for bone tissue engineering.

PubMed

Zhou, Changchun; Ye, Xingjiang; Fan, Yujiang; Ma, Liang; Tan, Yanfei; Qing, Fangzu; Zhang, Xingdong

2014-09-01

A three-level hierarchical calcium phosphate/collagen/hydroxyapatite (CaP/Col/HAp) scaffold for bone tissue engineering was developed using biomimetic synthesis. Porous CaP ceramics were first prepared as substrate materials to mimic the porous bone structure. A second-level Col network was then composited into porous CaP ceramics by vacuum infusion. Finally, a third-level HAp layer was achieved by biomimetic mineralization. The three-level hierarchical biomimetic scaffold was characterized using scanning electron microscopy, energy-dispersive x-ray spectra, x-ray diffraction and Fourier transform infrared spectroscopy, and the mechanical properties of the scaffold were evaluated using dynamic mechanical analysis. The results show that this scaffold exhibits a similar structure and composition to natural bone tissues. Furthermore, this three-level hierarchical biomimetic scaffold showed enhanced mechanical strength compared with pure porous CaP scaffolds. The biocompatibility and osteoinductivity of the biomimetic scaffolds were evaluated using in vitro and in vivo tests. Cell culture results indicated the good biocompatibility of this biomimetic scaffold. Faster and increased bone formation was observed in these scaffolds following a six-month implantation in the dorsal muscles of rabbits, indicating that this biomimetic scaffold exhibits better osteoinductivity than common CaP scaffolds.

A novel nano-structured porous polycaprolactone scaffold improves hyaline cartilage repair in a rabbit model compared to a collagen type I/III scaffold: in vitro and in vivo studies.

PubMed

Christensen, Bjørn Borsøe; Foldager, Casper Bindzus; Hansen, Ole Møller; Kristiansen, Asger Albæk; Le, Dang Quang Svend; Nielsen, Agnete Desirée; Nygaard, Jens Vinge; Bünger, Cody Erik; Lind, Martin

2012-06-01

To develop a nano-structured porous polycaprolactone (NSP-PCL) scaffold and compare the articular cartilage repair potential with that of a commercially available collagen type I/III (Chondro-Gide) scaffold. By combining rapid prototyping and thermally induced phase separation, the NSP-PCL scaffold was produced for matrix-assisted autologous chondrocyte implantation. Lyophilizing a water-dioxane-PCL solution created micro and nano-pores. In vitro: The scaffolds were seeded with rabbit chondrocytes and cultured in hypoxia for 6 days. qRT-PCR was performed using primers for sox9, aggrecan, collagen type 1 and 2. In vivo: 15 New Zealand White Rabbits received bilateral osteochondral defects in the femoral intercondylar grooves. Autologous chondrocytes were harvested 4 weeks prior to surgery. There were 3 treatment groups: (1) NSP-PCL scaffold without cells. (2) The Chondro-Gide scaffold with autologous chondrocytes and (3) NSP-PCL scaffold with autologous chondrocytes. Observation period was 13 weeks. Histological evaluation was made using the O'Driscoll score. In vitro: The expressions of sox9 and aggrecan were higher in the NSP-PCL scaffold, while expression of collagen 1 was lower compared to the Chondro-Gide scaffold. In vivo: Both NSP-PCL scaffolds with and without cells scored significantly higher than the Chondro-Gide scaffold when looking at the structural integrity and the surface regularity of the repair tissue. No differences were found between the NSP-PCL scaffold with and without cells. The NSP-PCL scaffold demonstrated higher in vitro expression of chondrogenic markers and had higher in vivo histological scores compared to the Chondro-Gide scaffold. The improved chondrocytic differentiation can potentially produce more hyaline cartilage during clinical cartilage repair. It appears to be a suitable cell-free implant for hyaline cartilage repair and could provide a less costly and more effective treatment option than the Chondro-Gide scaffold with cells.

Rapid prototyping for tissue-engineered bone scaffold by 3D printing and biocompatibility study.

PubMed

He, Hui-Yu; Zhang, Jia-Yu; Mi, Xue; Hu, Yang; Gu, Xiao-Yu

2015-01-01

The prototyping of tissue-engineered bone scaffold (calcined goat spongy bone-biphasic ceramic composite/PVA gel) by 3D printing was performed, and the biocompatibility of the fabricated bone scaffold was studied. Pre-designed STL file was imported into the GXYZ303010-XYLE 3D printing system, and the tissue-engineered bone scaffold was fabricated by 3D printing using gel extrusion. Rabbit bone marrow stromal cells (BMSCs) were cultured in vitro and then inoculated to the sterilized bone scaffold obtained by 3D printing. The growth of rabbit BMSCs on the bone scaffold was observed under the scanning electron microscope (SEM). The effect of the tissue-engineered bone scaffold on the proliferation and differentiation of rabbit BMSCs using MTT assay. Universal testing machine was adopted to test the tensile strength of the bone scaffold. The leachate of the bone scaffold was prepared and injected into the New Zealand rabbits. Cytotoxicity test, acute toxicity test, pyrogenic test and intracutaneous stimulation test were performed to assess the biocompatibility of the bone scaffold. Bone scaffold manufactured by 3D printing had uniform pore size with the porosity of about 68.3%. The pores were well interconnected, and the bone scaffold showed excellent mechanical property. Rabbit BMSCs grew and proliferated on the surface of the bone scaffold after adherence. MTT assay indicated that the proliferation and differentiation of rabbit BMSCs on the bone scaffold did not differ significantly from that of the cells in the control. In vivo experiments proved that the bone scaffold fabricated by 3D printing had no acute toxicity, pyrogenic reaction or stimulation. Bone scaffold manufactured by 3D printing allows the rabbit BMSCs to adhere, grow and proliferate and exhibits excellent biomechanical property and high biocompatibility. 3D printing has a good application prospect in the prototyping of tissue-engineered bone scaffold.

Selective laser sintering fabrication of nano-hydroxyapatite/poly-ε-caprolactone scaffolds for bone tissue engineering applications

PubMed Central

Xia, Yan; Zhou, Panyu; Cheng, Xiaosong; Xie, Yang; Liang, Chong; Li, Chao; Xu, Shuogui

2013-01-01

The regeneration of functional tissue in osseous defects is a formidable challenge in orthopedic surgery. In the present study, a novel biomimetic composite scaffold, here called nano-hydroxyapatite (HA)/poly-ε-caprolactone (PCL) was fabricated using a selective laser sintering technique. The macrostructure, morphology, and mechanical strength of the scaffolds were characterized. Scanning electronic microscopy (SEM) showed that the nano-HA/PCL scaffolds exhibited predesigned, well-ordered macropores and interconnected micropores. The scaffolds have a range of porosity from 78.54% to 70.31%, and a corresponding compressive strength of 1.38 MPa to 3.17 MPa. Human bone marrow stromal cells were seeded onto the nano-HA/PCL or PCL scaffolds and cultured for 28 days in vitro. As indicated by the level of cell attachment and proliferation, the nano-HA/PCL showed excellent biocompatibility, comparable to that of PCL scaffolds. The hydrophilicity, mineralization, alkaline phosphatase activity, and Alizarin Red S staining indicated that the nano-HA/PCL scaffolds are more bioactive than the PCL scaffolds in vitro. Measurements of recombinant human bone morphogenetic protein-2 (rhBMP-2) release kinetics showed that after nano-HA was added, the material increased the rate of rhBMP-2 release. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both nano-HA/PCL scaffolds and PCL scaffolds were implanted in rabbit femur defects for 3, 6, and 9 weeks. The wounds were studied radiographically and histologically. The in vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility. However, the nano-HA/PCL scaffolds enhanced the efficiency of new bone formation more than PCL scaffolds and fulfilled all the basic requirements of bone tissue engineering scaffolds. Thus, they show large potential for use in orthopedic and reconstructive surgery. PMID:24204147

Rapid prototyping for tissue-engineered bone scaffold by 3D printing and biocompatibility study

PubMed Central

He, Hui-Yu; Zhang, Jia-Yu; Mi, Xue; Hu, Yang; Gu, Xiao-Yu

2015-01-01

The prototyping of tissue-engineered bone scaffold (calcined goat spongy bone-biphasic ceramic composite/PVA gel) by 3D printing was performed, and the biocompatibility of the fabricated bone scaffold was studied. Pre-designed STL file was imported into the GXYZ303010-XYLE 3D printing system, and the tissue-engineered bone scaffold was fabricated by 3D printing using gel extrusion. Rabbit bone marrow stromal cells (BMSCs) were cultured in vitro and then inoculated to the sterilized bone scaffold obtained by 3D printing. The growth of rabbit BMSCs on the bone scaffold was observed under the scanning electron microscope (SEM). The effect of the tissue-engineered bone scaffold on the proliferation and differentiation of rabbit BMSCs using MTT assay. Universal testing machine was adopted to test the tensile strength of the bone scaffold. The leachate of the bone scaffold was prepared and injected into the New Zealand rabbits. Cytotoxicity test, acute toxicity test, pyrogenic test and intracutaneous stimulation test were performed to assess the biocompatibility of the bone scaffold. Bone scaffold manufactured by 3D printing had uniform pore size with the porosity of about 68.3%. The pores were well interconnected, and the bone scaffold showed excellent mechanical property. Rabbit BMSCs grew and proliferated on the surface of the bone scaffold after adherence. MTT assay indicated that the proliferation and differentiation of rabbit BMSCs on the bone scaffold did not differ significantly from that of the cells in the control. In vivo experiments proved that the bone scaffold fabricated by 3D printing had no acute toxicity, pyrogenic reaction or stimulation. Bone scaffold manufactured by 3D printing allows the rabbit BMSCs to adhere, grow and proliferate and exhibits excellent biomechanical property and high biocompatibility. 3D printing has a good application prospect in the prototyping of tissue-engineered bone scaffold. PMID:26380018

Injectable scaffolds: Preparation and application in dental and craniofacial regeneration

PubMed Central

Chang, Bei; Ahuja, Neelam; Ma, Chi; Liu, Xiaohua

2016-01-01

Injectable scaffolds are appealing for tissue regeneration because they offer many advantages over pre-formed scaffolds. This article provides a comprehensive review of the injectable scaffolds currently being investigated for dental and craniofacial tissue regeneration. First, we provide an overview of injectable scaffolding materials, including natural, synthetic, and composite biomaterials. Next, we discuss a variety of characteristic parameters and gelation mechanisms of the injectable scaffolds. The advanced injectable scaffolding systems developed in recent years are then illustrated. Furthermore, we summarize the applications of the injectable scaffolds for the regeneration of dental and craniofacial tissues that include pulp, dentin, periodontal ligament, temporomandibular joint, and alveolar bone. Finally, our perspectives on the injectable scaffolds for dental and craniofacial tissue regeneration are offered as signposts for the future advancement of this field. PMID:28649171

Effects of chitosan and bioactive glass modifications of knitted and rolled polylactide-based 96/4 L/D scaffolds on chondrogenic differentiation of adipose stem cells.

PubMed

Ahtiainen, Katja; Sippola, Laura; Nurminen, Manu; Mannerström, Bettina; Haimi, Suvi; Suuronen, Riitta; Hyttinen, Jari; Ylikomi, Timo; Kellomäki, Minna; Miettinen, Susanna

2015-01-01

The performance of biodegradable knitted and rolled 3-dimensional (3D) polylactide-based 96/4 scaffolds modified with bioactive glass (BaG) 13-93, chitosan and both was compared with regard to the viability, proliferation and chondrogenic differentiation of rabbit adipose stem cells (ASCs). Scaffold porosities were determined by micro-computed tomography (μCT). Water absorption and degradation of scaffolds were studied during 28-day hydrolysis in Tris-buffer. Viability, number and differentiation of ASCs in PLA96/4 scaffolds were examined in vitro. The dimensions of the scaffolds were maintained during hydrolysis and mass loss was detected only in the BaG13-93 containing scaffolds. ASCs adhered and proliferated on each scaffold type. Cell aggregation and expression of chondral matrix components improved in all scaffold types in chondrogenic medium. Signs of hypertrophy were detected in the modified scaffolds but not in the plain PLA96/4 scaffold. Chondrogenic differentiation was most enhanced in the presence of chitosan. These findings indicate that the plain P scaffold provided a good 3D-matrix for ASC proliferation whereas the addition of chitosan to the PLA96/4 scaffold induced chondrogenic differentiation independent of the medium. Accordingly, a PLA96/4 scaffold modified by chitosan could provide a functional and bioactive basis for tissue-engineered chondral implants. Copyright © 2012 John Wiley & Sons, Ltd.

Agent-based modeling of porous scaffold degradation and vascularization: Optimal scaffold design based on architecture and degradation dynamics.

PubMed

Mehdizadeh, Hamidreza; Bayrak, Elif S; Lu, Chenlin; Somo, Sami I; Akar, Banu; Brey, Eric M; Cinar, Ali

2015-11-01

A multi-layer agent-based model (ABM) of biomaterial scaffold vascularization is extended to consider the effects of scaffold degradation kinetics on blood vessel formation. A degradation model describing the bulk disintegration of porous hydrogels is incorporated into the ABM. The combined degradation-angiogenesis model is used to investigate growing blood vessel networks in the presence of a degradable scaffold structure. Simulation results indicate that higher porosity, larger mean pore size, and rapid degradation allow faster vascularization when not considering the structural support of the scaffold. However, premature loss of structural support results in failure for the material. A strategy using multi-layer scaffold with different degradation rates in each layer was investigated as a way to address this issue. Vascularization was improved with the multi-layered scaffold model compared to the single-layer model. The ABM developed provides insight into the characteristics that influence the selection of optimal geometric parameters and degradation behavior of scaffolds, and enables easy refinement of the model as new knowledge about the underlying biological phenomena becomes available. This paper proposes a multi-layer agent-based model (ABM) of biomaterial scaffold vascularization integrated with a structural-kinetic model describing bulk degradation of porous hydrogels to consider the effects of scaffold degradation kinetics on blood vessel formation. This enables the assessment of scaffold characteristics and in particular the disintegration characteristics of the scaffold on angiogenesis. Simulation results indicate that higher porosity, larger mean pore size, and rapid degradation allow faster vascularization when not considering the structural support of the scaffold. However, premature loss of structural support by scaffold disintegration results in failure of the material and disruption of angiogenesis. A strategy using multi-layer scaffold with different degradation rates in each layer was investigated as away to address this issue. Vascularization was improved with the multi-layered scaffold model compared to the single-layer model. The ABM developed provides insight into the characteristics that influence the selection of optimal geometric and degradation characteristics of tissue engineering scaffolds. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Development of model hydroxyapatite bone scaffolds with multiscale porosity for potential load bearing applications

NASA Astrophysics Data System (ADS)

Dellinger, Jennifer Gwynne

2005-11-01

Model hydroxyapatite (HA) bone scaffolds consisting of a latticed pattern of rods were fabricated by a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. An optimal HA paste formulation for this method was developed. Local porosity, i.e. microporosity (1--30 mum) and sintering porosity (less than 1 mum), were produced by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. Scaffolds with and without local porosity were evaluated with and without in vitro accelerated degradation. Percent weight loss of the scaffolds and calcium and phosphorus concentrations in solution increased with degradation time. After degradation, compressive strength and modulus decreased significantly for scaffolds with local porosity, but did not change significantly for scaffolds without local porosity. The compressive strength and modulus of scaffolds without local porosity were comparable to human cortical bone and were significantly greater than the scaffolds with local porosity. Micropores in HA disks caused surface pits that increased the surface roughness as compared to non-microporous HA disks. Mouse mesenchymal stem cells extended their cell processes into these microporous pits on HA disks in vitro. ALP expression was prolonged, cell attachment strength increased, and ECM production appeared greater on microporous HA disks compared to non-microporous HA disks and tissue culture treated polystyrene controls. Scaffolds with and without microporosity were implanted in goats bones. Microporous scaffolds with rhBMP-2 increased the percent of the scaffold filled with bone tissue compared to microporous scaffolds without rhBMP-2. Lamellar bone inside scaffolds was aligned near the rods junctions whereas lamellar bone was aligned in a more random configuration away from the rod junctions. Microporous scaffolds stained darkly with toluidine blue beneath areas of contact with new bone. This staining might indicate either extracellular matrix (ECM) in the rods or dye bound to the degrading scaffold. Although the presence of microporous topography alone did not influence bone healing in vivo, micropores were shown to provide tailorability of scaffold mechanical properties, provide a location for the storage and controlled release of a growth factor, and provide a location for bone integration inside the scaffold rods.

Soy Protein Scaffold Biomaterials for Tissue Engineering and Regenerative Medicine

NASA Astrophysics Data System (ADS)

Chien, Karen B.

Developing functional biomaterials using highly processable materials with tailorable physical and bioactive properties is an ongoing challenge in tissue engineering. Soy protein is an abundant, natural resource with potential use for regenerative medicine applications. Preliminary studies show that soy protein can be physically modified and fabricated into various biocompatible constructs. However, optimized soy protein structures for tissue regeneration (i.e. 3D porous scaffolds) have not yet been designed. Furthermore, little work has established the in vivo biocompatibility of implanted soy protein and the benefit of using soy over other proteins including FDA-approved bovine collagen. In this work, freeze-drying and 3D printing fabrication processes were developed using commercially available soy protein to create porous scaffolds that improve cell growth and infiltration compared to other soy biomaterials previously reported. Characterization of scaffold structure, porosity, and mechanical/degradation properties was performed. In addition, the behavior of human mesenchymal stem cells seeded on various designed soy scaffolds was analyzed. Biological characterization of the cell-seeded scaffolds was performed to assess feasibility for use in liver tissue regeneration. The acute and humoral response of soy scaffolds implanted in an in vivo mouse subcutaneous model was also investigated. All fabricated soy scaffolds were modified using thermal, chemical, and enzymatic crosslinking to change properties and cell growth behavior. 3D printing allowed for control of scaffold pore size and geometry. Scaffold structure, porosity, and degradation rate significantly altered the in vivo response. Freeze-dried soy scaffolds had similar biocompatibility as freeze-dried collagen scaffolds of the same protein content. However, the soy scaffolds degraded at a much faster rate, minimizing immunogenicity. Interestingly, subcutaneously implanted soy scaffolds affected blood glucose and insulin sensitivity levels. Furthermore, soy scaffolds implanted in the intraperitoneal cavity attached to adjacent liver tissue with no abnormalities. In vitro, soy scaffolds supported hMSC viability and transdifferentiation into hepatocyte-like cells. These results support the use of soy scaffolds for liver tissue engineering and for treating metabolic diseases. Based on achievable structural and mechanical properties, as well as systemic effects of ingested and degraded soy proteins, soy protein scaffolds may serve as new multifunctional biomaterials for tissue engineering and regenerative medicine.

Effects of the architecture of tissue engineering scaffolds on cell seeding and culturing.

PubMed

Melchels, Ferry P W; Barradas, Ana M C; van Blitterswijk, Clemens A; de Boer, Jan; Feijen, Jan; Grijpma, Dirk W

2010-11-01

The advance of rapid prototyping techniques has significantly improved control over the pore network architecture of tissue engineering scaffolds. In this work, we have assessed the influence of scaffold pore architecture on cell seeding and static culturing, by comparing a computer designed gyroid architecture fabricated by stereolithography with a random pore architecture resulting from salt leaching. The scaffold types showed comparable porosity and pore size values, but the gyroid type showed a more than 10-fold higher permeability due to the absence of size-limiting pore interconnections. The higher permeability significantly improved the wetting properties of the hydrophobic scaffolds and increased the settling speed of cells upon static seeding of immortalised mesenchymal stem cells. After dynamic seeding followed by 5 days of static culture gyroid scaffolds showed large cell populations in the centre of the scaffold, while salt-leached scaffolds were covered with a cell sheet on the outside and no cells were found in the scaffold centre. It was shown that interconnectivity of the pores and permeability of the scaffold prolonged the time of static culture before overgrowth of cells at the scaffold periphery occurred. Furthermore, novel scaffold designs are proposed to further improve the transport of oxygen and nutrients throughout the scaffolds and to create tissue engineering grafts with a designed, pre-fabricated vasculature. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Cell Population Kinetics of Collagen Scaffolds in Ex Vivo Oral Wound Repair

PubMed Central

Agis, Hermann; Collins, Amy; Taut, Andrei D.; Jin, Qiming; Kruger, Laura; Görlach, Christoph; Giannobile, William V.

2014-01-01

Biodegradable collagen scaffolds are used clinically for oral soft tissue augmentation to support wound healing. This study sought to provide a novel ex vivo model for analyzing healing kinetics and gene expression of primary human gingival fibroblasts (hGF) within collagen scaffolds. Sponge type and gel type scaffolds with and without platelet-derived growth factor-BB (PDGF) were assessed in an hGF containing matrix. Morphology was evaluated with scanning electron microscopy, and hGF metabolic activity using MTT. We quantitated the population kinetics within the scaffolds based on cell density and distance from the scaffold border of DiI-labled hGFs over a two-week observation period. Gene expression was evaluated with gene array and qPCR. The sponge type scaffolds showed a porous morphology. Absolute cell number and distance was higher in sponge type scaffolds when compared to gel type scaffolds, in particular during the first week of observation. PDGF incorporated scaffolds increased cell numbers, distance, and formazan formation in the MTT assay. Gene expression dynamics revealed the induction of key genes associated with the generation of oral tissue. DKK1, CYR61, CTGF, TGFBR1 levels were increased and integrin ITGA2 levels were decreased in the sponge type scaffolds compared to the gel type scaffold. The results suggest that this novel model of oral wound healing provides insights into population kinetics and gene expression dynamics of biodegradable scaffolds. PMID:25397671

Carbon nanotube (CNT) and nanofibrillated cellulose (NFC) reinforcement effect on thermoplastic polyurethane (TPU) scaffolds fabricated via phase separation using dimethyl sulfoxide (DMSO) as solvent.

PubMed

Mi, Hao-Yang; Jing, Xin; Salick, Max R; Cordie, Travis M; Turng, Lih-Sheng

2016-09-01

Although phase separation is a simple method of preparing tissue engineering scaffolds, it suffers from organic solvent residual in the scaffold. Searching for nontoxic solvents and developing effective solvent removal methods are current challenges in scaffold fabrication. In this study, thermoplastic polyurethane (TPU) scaffolds containing carbon nanotubes (CNTs) or nanofibrillated cellulose fibers (NFCs) were prepared using low toxicity dimethyl sulfoxide (DMSO) as a solvent. The effects of two solvent removal approaches on the final scaffold morphology were studied. The freeze drying method caused large pores, with small pores on the pore walls, which created connections between the pores. Meanwhile, the leaching and freeze drying method led to interconnected fine pores with smaller pore diameters. The nucleation effect of CNTs and the phase separation behavior of NFCs in the TPU solution resulted in significant differences in the microstructures of the resulting scaffolds. The mechanical performance of the nanocomposite scaffolds with different morphologies was investigated. Generally, the scaffolds with a fine pore structure showed higher compressive properties, and both the CNTs and NFCs improved the compressive properties of the scaffolds, with greater enhancement found in TPU/NFC nanocomposite scaffolds. In addition, all scaffolds showed good sustainability under cyclical load bearing, and the biocompatibility of the scaffolds was verified via 3T3 fibroblast cell culture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Embroidered polymer-collagen hybrid scaffold variants for ligament tissue engineering.

PubMed

Hoyer, M; Drechsel, N; Meyer, M; Meier, C; Hinüber, C; Breier, A; Hahner, J; Heinrich, G; Rentsch, C; Garbe, L-A; Ertel, W; Schulze-Tanzil, G; Lohan, A

2014-10-01

Embroidery techniques and patterns used for scaffold production allow the adaption of biomechanical scaffold properties. The integration of collagen into embroidered polylactide-co-caprolactone [P(LA-CL)] and polydioxanone (PDS) scaffolds could stimulate neo-tissue formation by anterior cruciate ligament (ACL) cells. Therefore, the aim of this study was to test embroidered P(LA-CL) and PDS scaffolds as hybrid scaffolds in combination with collagen hydrogel, sponge or foam for ligament tissue engineering. ACL cells were cultured on embroidered P(LA-CL) and PDS scaffolds without or with collagen supplementation. Cell adherence, vitality, morphology and ECM synthesis were analyzed. Irrespective of thread size, ACL cells seeded on P(LA-CL) scaffolds without collagen adhered and spread over the threads, whereas the cells formed clusters on PDS and larger areas remained cell-free. Using the collagen hydrogel, the scaffold colonization was limited by the gel instability. The collagen sponge layers integrated into the scaffolds were hardly penetrated by the cells. Collagen foams increased scaffold colonization in P(LA-CL) but did not facilitate direct cell-thread contacts in the PDS scaffolds. The results suggest embroidered P(LA-CL) scaffolds as a more promising basis for tissue engineering an ACL substitute than PDS due to superior cell attachment. Supplementation with a collagen foam presents a promising functionalization strategy. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci.

PubMed

Gao, Shuang; Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun; Xi, Tingfei; Guo, Quanyi

2017-02-01

The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96h, scaffolds crosslinked by GTA and EDAC could maintain their mass >70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49kPa in compression modulus and 12.81kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44kPa respectively. The same value of scaffolds crosslinked by 1.2mol/l EDAC were 1.49 and 532.50kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2mol/l EDAC was a preferable crosslinking condition. Copyright © 2016 Elsevier B.V. All rights reserved.

Biocompatibility and osteoconduction of macroporous silk fibroin implants in cortical defects in sheep.

PubMed

Uebersax, Lorenz; Apfel, Tanja; Nuss, Katja M R; Vogt, Rainer; Kim, Hyoen Yoo; Meinel, Lorenz; Kaplan, David L; Auer, Joerg A; Merkle, Hans P; von Rechenberg, Brigitte

2013-09-01

The goal of the presented study was to compare the biocompatibility and cellular responses to porous silk fibroin (SF) scaffolds produced in a water-based (UPW) or a solvent based process (HFIP) using two different SF sources. For that reason, four different SF scaffolds were implanted (n=6) into drill hole defects in the cancellous bone of the sheep tibia and humerus. The scaffolds were evaluated histologically for biocompatibility, cell-material interaction, and cellular ingrowth. New bone formation was observed macroscopically and histologically at 8 weeks after implantation. For semiquantitative evaluation, the investigated parameters were scored and statistically analyzed (factorial ANOVA). All implants showed good biocompatibility as evident by low infiltration of inflammatory cells and the absent encapsulation of the scaffolds in connective tissue. Multinuclear foreign body giant cells (MFGCs) and macrophages were present in all parts of the scaffold at the material surface and actively degrading the SF material. Cell ingrowth and vascularization were uniform across the scaffold. However, in HFIP scaffolds, local regions of void pores were present throughout the scaffold, probably due to the low pore interconnectivity in this scaffold type in contrast to UPW scaffolds. The amount of newly formed bone was very low in both scaffold types but was more abundant in the periphery than in the center of the scaffolds and for HFIP scaffolds mainly restricted to single pores. Copyright © 2013 Elsevier B.V. All rights reserved.

Three Dimensional Collagen Scaffold Promotes Intrinsic Vascularisation for Tissue Engineering Applications

PubMed Central

Chan, Elsa C.; Kuo, Shyh-Ming; Kong, Anne M.; Morrison, Wayne A.; Dusting, Gregory J.; Mitchell, Geraldine M.

2016-01-01

Here, we describe a porous 3-dimensional collagen scaffold material that supports capillary formation in vitro, and promotes vascularization when implanted in vivo. Collagen scaffolds were synthesized from type I bovine collagen and have a uniform pore size of 80 μm. In vitro, scaffolds seeded with primary human microvascular endothelial cells suspended in human fibrin gel formed CD31 positive capillary-like structures with clear lumens. In vivo, after subcutaneous implantation in mice, cell-free collagen scaffolds were vascularized by host neovessels, whilst a gradual degradation of the scaffold material occurred over 8 weeks. Collagen scaffolds, impregnated with human fibrinogen gel, were implanted subcutaneously inside a chamber enclosing the femoral vessels in rats. Angiogenic sprouts from the femoral vessels invaded throughout the scaffolds and these degraded completely after 4 weeks. Vascular volume of the resulting constructs was greater than the vascular volume of constructs from chambers implanted with fibrinogen gel alone (42.7±5.0 μL in collagen scaffold vs 22.5±2.3 μL in fibrinogen gel alone; p<0.05, n = 7). In the same model, collagen scaffolds seeded with human adipose-derived stem cells (ASCs) produced greater increases in vascular volume than did cell-free collagen scaffolds (42.9±4.0 μL in collagen scaffold with human ASCs vs 25.7±1.9 μL in collagen scaffold alone; p<0.05, n = 4). In summary, these collagen scaffolds are biocompatible and could be used to grow more robust vascularized tissue engineering grafts with improved the survival of implanted cells. Such scaffolds could also be used as an assay model for studies on angiogenesis, 3-dimensional cell culture, and delivery of growth factors and cells in vivo. PMID:26900837

Bone augmentation using a highly porous PLGA/β-TCP scaffold containing fibroblast growth factor-2.

PubMed

Yoshida, T; Miyaji, H; Otani, K; Inoue, K; Nakane, K; Nishimura, H; Ibara, A; Shimada, A; Ogawa, K; Nishida, E; Sugaya, T; Sun, L; Fugetsu, B; Kawanami, M

2015-04-01

Beta-tricalcium phosphate (β-TCP), a bio-absorbable ceramic, facilitates bone conductivity. We constructed a highly porous three-dimensional scaffold, using β-TCP, for bone tissue engineering and coated it with co-poly lactic acid/glycolic acid (PLGA) to improve the mechanical strength and biological performance. The aim of this study was to examine the effect of implantation of the PLGA/β-TCP scaffold loaded with fibroblast growth factor-2 (FGF-2) on bone augmentation. The β-TCP scaffold was fabricated by the replica method using polyurethane foam, then coated with PLGA. The PLGA/β-TCP scaffold was characterized by scanning electron miscroscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, compressive testing, cell culture and a subcutaneous implant test. Subsequently, a bone-forming test was performed using 52 rats. The β-TCP scaffold, PLGA-coated scaffold, and β-TCP and PLGA-coated scaffolds loaded with FGF-2, were implanted into rat cranial bone. Histological observations were made at 10 and 35 d postsurgery. SEM and TEM observations showed a thin PLGA layer on the β-TCP particles after coating. High porosity (> 90%) of the scaffold was exhibited after PLGA coating, and the compressive strength of the PLGA/β-TCP scaffold was six-fold greater than that of the noncoated scaffold. Good biocompatibility of the PLGA/β-TCP scaffold was found in the culture and implant tests. Histological samples obtained following implantation of PLGA/β-TCP scaffold loaded with FGF-2 showed significant bone augmentation. The PLGA coating improved the mechanical strength of β-TCP scaffolds while maintaining high porosity and tissue compatibility. PLGA/β-TCP scaffolds, in combination with FGF-2, are bioeffective for bone augmentation. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Synergistic Effect of Carbon Nanotubes and Graphene on Diopside Scaffolds

PubMed Central

Liu, Tingting; Wu, Ping; Gao, Chengde; Feng, Pei; Xiao, Tao; Deng, Youwen; Shuai, Cijun; Peng, Shuping

2016-01-01

A synergetic effect between carbon nanotubes (CNTs) and graphene on diopside (Di) scaffolds was demonstrated. 3D network architecture in the matrix was formed through the 1D CNTs inlaid among the 2D graphene platelets (GNPs). The mechanical properties of the CNTs/GNPs/Di scaffolds were significantly improved compared with the CNTs/Di scaffolds and GNPs/Di scaffolds. In addition, the scaffolds exhibited excellent apatite-forming ability, a modest degradation rate, and stable mechanical properties in simulated body fluid (SBF). Moreover, cell culturing tests indicated that the scaffolds supported the cells attachment and proliferation. Taken together, the CNTs/GNPs/Di scaffolds offered great potential for bone tissue engineering. PMID:27144173

Influence of electrospun scaffolds prepared from distinct polymers on proliferation and viability of endothelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matveeva, V. G., E-mail: matveeva-vg@mail.ru; Antonova, L. V., E-mail: antonova.la@mail.ru; Velikanova, E. A.

We compared electrospun nonwoven scaffolds from polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxybutyrate/valerate (PHBV)/polycaprolactone (PHBV/PCL). The surface of PHBV/PCL and PCL scaffolds was highly porous and consisted of randomly distributed fibers, whilst the surface of PLA scaffolds consisted of thin straight fibers, which located more sparsely, forming large pores. Culture of EA.hy 926 endothelial cells on these scaffolds during 7 days and further fluorescent microscopy demonstrated that the surface of PHBV/PCL scaffolds was most favorable for efficient adhesion, proliferation, and viability of endothelial cells. The lowest proliferation rate and cell viability were detected on PLA scaffolds. Therefore, PHBV/PCL electrospun nonwovenmore » scaffolds demonstrated the best results regarding endothelial cell proliferation and viability as compared to PCL and PLA scaffolds.« less

Use of Interim Scaffolding and Neotissue Development to Produce a Scaffold-Free Living Hyaline Cartilage Graft.

PubMed

Lau, Ting Ting; Leong, Wenyan; Peck, Yvonne; Su, Kai; Wang, Dong-An

2015-01-01

The fabrication of three-dimensional (3D) constructs relies heavily on the use of biomaterial-based scaffolds. These are required as mechanical supports as well as to translate two-dimensional cultures to 3D cultures for clinical applications. Regardless of the choice of scaffold, timely degradation of scaffolds is difficult to achieve and undegraded scaffold material can lead to interference in further tissue development or morphogenesis. In cartilage tissue engineering, hydrogel is the highly preferred scaffold material as it shares many similar characteristics with native cartilaginous matrix. Hence, we employed gelatin microspheres as porogens to create a microcavitary alginate hydrogel as an interim scaffold to facilitate initial chondrocyte 3D culture and to establish a final scaffold-free living hyaline cartilaginous graft (LhCG) for cartilage tissue engineering.

Scaffolding for Argumentation in Hypothetical and Theoretical Biology Concepts

ERIC Educational Resources Information Center

Weng, Wan-Yun; Lin, Yu-Ren; She, Hsiao-Ching

2017-01-01

The present study investigated the effects of online argumentation scaffolding on students' argumentation involving hypothetical and theoretical biological concepts. Two types of scaffolding were developed in order to improve student argumentation: continuous scaffolding and withdraw scaffolding. A quasi-experimental design was used with four…

Fabrication and characterization of drug-loaded nano-hydroxyapatite/polyamide 66 scaffolds modified with carbon nanotubes and silk fibroin

PubMed Central

Yao, Meng-Zhu; Huang-Fu, Ming-Yi; Liu, Hui-Na; Wang, Xia-Rong; Sheng, Xiaoxia; Gao, Jian-Qing

2016-01-01

Nano-hydroxyapatite/polyamide 66 (nHA/PA66) porous scaffolds were fabricated by a phase inversion method. Carbon nanotubes (CNTs) and silk fibroin (SF) were used to modify the surface of the nHA/PA66 scaffolds by freeze-drying and cross-linking. Dexamethasone was absorbed to the CNTs to promote the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). The cell viability of BMSCs was investigated by changing the concentration of the CNT dispersion, and the most biocompatible scaffold was selected. In addition, the morphology and mechanical property of the scaffolds were investigated. The results showed that the nHA/PA66 scaffolds modified with CNTs and SF met the requirements of bone tissue engineering scaffolds. The dexamethasone-loaded CNT/SF-nHA/PA66 composite scaffold promoted the osteogenic differentiation of BMSCs, and the drug-loaded scaffolds are expected to function as effective bone tissue engineering scaffolds. PMID:27920525

Fast scaffolding with small independent mixed integer programs

PubMed Central

Salmela, Leena; Mäkinen, Veli; Välimäki, Niko; Ylinen, Johannes; Ukkonen, Esko

2011-01-01

Motivation: Assembling genomes from short read data has become increasingly popular, but the problem remains computationally challenging especially for larger genomes. We study the scaffolding phase of sequence assembly where preassembled contigs are ordered based on mate pair data. Results: We present MIP Scaffolder that divides the scaffolding problem into smaller subproblems and solves these with mixed integer programming. The scaffolding problem can be represented as a graph and the biconnected components of this graph can be solved independently. We present a technique for restricting the size of these subproblems so that they can be solved accurately with mixed integer programming. We compare MIP Scaffolder to two state of the art methods, SOPRA and SSPACE. MIP Scaffolder is fast and produces better or as good scaffolds as its competitors on large genomes. Availability: The source code of MIP Scaffolder is freely available at http://www.cs.helsinki.fi/u/lmsalmel/mip-scaffolder/. Contact: leena.salmela@cs.helsinki.fi PMID:21998153

[Research progress of cell-scaffold complex in tendon tissue engineering].

PubMed

Zhu, Ying; Li, Min

2013-04-01

To review the research progress of cell-scaffold complex in the tendon tissue engineering. Recent literature concerning cell-scaffold complex in the tendon tissue engineering was reviewed, the research situation of the cell-scaffold complex was elaborated in the aspects of seed cells, scaffolds, cell culture, and application. In tendon tissue engineering, a cell-scaffold complex is built by appropriate seed cells and engineered scaffolds. Experiments showed that modified seed cells had better therapeutic effects. Further, scaffold functionality could be improved through surface modification, growth factor cure, mechanical stimulation, and contact guidance. Among these methods, mechanical stimulation revealed the most significant results in promoting cell proliferation and function. Through a variety of defect models, it is demonstrated that the use of cell-scaffold complex could achieve satisfactory results for tendon regeneration. The cell-scaffold complex for tendon tissue engineering is a popular research topic. Although it has not yet met the requirement of clinical use, it has broad application prospects.

Scaffold-Focused Virtual Screening: Prospective Application to the Discovery of TTK Inhibitors

PubMed Central

2013-01-01

We describe and apply a scaffold-focused virtual screen based upon scaffold trees to the mitotic kinase TTK (MPS1). Using level 1 of the scaffold tree, we perform both 2D and 3D similarity searches between a query scaffold and a level 1 scaffold library derived from a 2 million compound library; 98 compounds from 27 unique top-ranked level 1 scaffolds are selected for biochemical screening. We show that this scaffold-focused virtual screen prospectively identifies eight confirmed active compounds that are structurally differentiated from the query compound. In comparison, 100 compounds were selected for biochemical screening using a virtual screen based upon whole molecule similarity resulting in 12 confirmed active compounds that are structurally similar to the query compound. We elucidated the binding mode for four of the eight confirmed scaffold hops to TTK by determining their protein–ligand crystal structures; each represents a ligand-efficient scaffold for inhibitor design. PMID:23672464

Accelerated healing of full-thickness wounds by genipin-crosslinked silk sericin/PVA scaffolds.

PubMed

Aramwit, Pornanong; Siritienthong, Tippawan; Srichana, Teerapol; Ratanavaraporn, Juthamas

2013-01-01

Silk sericin has recently been studied for its advantageous biological properties, including its ability to promote wound healing. This study developed a delivery system to accelerate the healing of full-thickness wounds. Three-dimensional scaffolds were fabricated from poly(vinyl alcohol) (PVA), glycerin (as a plasticizer) and genipin (as a crosslinking agent), with or without sericin. The physical and biological properties of the genipin-crosslinked sericin/PVA scaffolds were investigated and compared with those of scaffolds without sericin. The genipin-crosslinked sericin/PVA scaffolds exhibited a higher compressive modulus and greater swelling in water than the scaffolds without sericin. Sericin also exhibited controlled release from the scaffolds. The genipin-crosslinked sericin/PVA scaffolds promoted the attachment and proliferation of L929 mouse fibroblasts. After application to full-thickness rat wounds, the wounds treated with genipin-crosslinked sericin/PVA scaffolds showed a significantly greater reduction in wound size, collagen formation and epithelialization compared with the control scaffolds without sericin but lower numbers of macrophages and multinucleated giant cells. These results indicate that the delivery of sericin from the novel genipin-crosslinked scaffolds efficiently healed the wound. Therefore, these genipin-crosslinked sericin/PVA scaffolds represent a promising candidate for the accelerated healing of full-thickness wounds. Copyright © 2013 S. Karger AG, Basel.

Tough and flexible CNT-polymeric hybrid scaffolds for engineering cardiac constructs.

PubMed

Kharaziha, Mahshid; Shin, Su Ryon; Nikkhah, Mehdi; Topkaya, Seda Nur; Masoumi, Nafiseh; Annabi, Nasim; Dokmeci, Mehmet R; Khademhosseini, Ali

2014-08-01

In the past few years, a considerable amount of effort has been devoted toward the development of biomimetic scaffolds for cardiac tissue engineering. However, most of the previous scaffolds have been electrically insulating or lacked the structural and mechanical robustness to engineer cardiac tissue constructs with suitable electrophysiological functions. Here, we developed tough and flexible hybrid scaffolds with enhanced electrical properties composed of carbon nanotubes (CNTs) embedded aligned poly(glycerol sebacate):gelatin (PG) electrospun nanofibers. Incorporation of varying concentrations of CNTs from 0 to 1.5% within the PG nanofibrous scaffolds (CNT-PG scaffolds) notably enhanced fiber alignment and improved the electrical conductivity and toughness of the scaffolds while maintaining the viability, retention, alignment, and contractile activities of cardiomyocytes (CMs) seeded on the scaffolds. The resulting CNT-PG scaffolds resulted in stronger spontaneous and synchronous beating behavior (3.5-fold lower excitation threshold and 2.8-fold higher maximum capture rate) compared to those cultured on PG scaffold. Overall, our findings demonstrated that aligned CNT-PG scaffold exhibited superior mechanical properties with enhanced CM beating properties. It is envisioned that the proposed hybrid scaffolds can be useful for generating cardiac tissue constructs with improved organization and maturation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electron Beam Sterilization Does Not Have a Detrimental Effect on the Ability of Extracellular Matrix Scaffolds to Support In Vivo Ligament Healing

PubMed Central

Proffen, Benedikt L.; Perrone, Gabriel S.; Fleming, Braden C.; Sieker, Jakob T.; Kramer, Joshua; Hawes, Michael L.; Badger, Gary J.; Murray, Martha M.

2015-01-01

Purpose Extra-cellular matrix (ECM) scaffolds have been used to enhance anterior cruciate ligament (ACL) repair in large animal models. To translate this technology to clinical care, identifying a method, which effectively sterilizes the material without significantly impairing in vivo function, is desirable. Methods 16 Yorkshire pigs underwent ACL transection and were randomly assigned to bridge-enhanced ACL repair – primary suture repair of the ACL with addition of autologous blood soaked ECM scaffold - with either 1) an aseptically processed ECM scaffold, or 2) an electron beam irradiated ECM scaffold. Primary outcome measures included sterility of the scaffold and biomechanical properties of the scaffold itself and the repaired ligament at eight weeks after surgery. Results Scaffolds treated with 15kGy electron beam irradiation had no bacterial or fungal growth noted, while aseptically processed scaffolds had bacterial growth in all tested samples. The mean biomechanical properties of the scaffold and healing ligament were lower in the electron beam group; however, differences were not statistically significant. Conclusions Electron beam irradiation was able to effectively sterilize the scaffolds. In addition, this technique had only a minimal impact on the in vivo function of the scaffolds when used for ligament healing in the porcine model. PMID:25676876

Improvement of Physical and Wound Adhesion Properties of Silk Sericin and Polyvinyl Alcohol Dressing Using Glycerin.

PubMed

Aramwit, Pornanong; Ratanavaraporn, Juthamas; Siritientong, Tippawan

2015-08-01

This study aimed to use glycerin to improve physical and wound adhesion properties of a wound dressing made of silk sericin and polyvinyl alcohol (PVA). Glycerin of a natural-derived plasticizer was used to modify the properties of silk sericin/PVA scaffolds. Various concentrations of glycerin were mixed with silk sericin and PVA and then fabricated into the scaffolds by a freeze-drying technique. The control study was performed to examine the properties of the silk sericin/PVA scaffolds with and without glycerin. Physical, mechanical, wound adhesion properties, the release profile of silk sericin, and in vivo safety of the silk sericin/PVA scaffolds with and without glycerin were investigated. The silk sericin/PVA scaffolds with glycerin exhibited more homogenous structure, less compressive modulus, higher Young modulus and elongation percentage, and a higher degree of crosslinking compared with the scaffold without glycerin. The silk sericin/PVA scaffold with 2% wt/vol glycerin showed more controlled release of silk sericin than the other scaffolds. The sustained release of silk sericin from the scaffold with glycerin would be advantageous for long-term healing of wounds. The silk sericin/PVA scaffold with 2% (wt/vol) glycerin was less adhesive to the wound compared with the scaffold without glycerin. Furthermore, the implantation of silk sericin/PVA scaffolds with 2% (wt/vol) glycerin did not cause any irritation to the tissue. The silk sericin/PVA scaffolds with glycerin were introduced as a biocompatible, more flexible, and less adhesive wound dressing than the scaffold without glycerin.

Fabrication and characterization of novel nano-biocomposite scaffold of chitosan-gelatin-alginate-hydroxyapatite for bone tissue engineering.

PubMed

Sharma, Chhavi; Dinda, Amit Kumar; Potdar, Pravin D; Chou, Chia-Fu; Mishra, Narayan Chandra

2016-07-01

A novel nano-biocomposite scaffold was fabricated in bead form by applying simple foaming method, using a combination of natural polymers-chitosan, gelatin, alginate and a bioceramic-nano-hydroxyapatite (nHAp). This approach of combining nHAp with natural polymers to fabricate the composite scaffold, can provide good mechanical strength and biological property mimicking natural bone. Environmental scanning electron microscopy (ESEM) images of the nano-biocomposite scaffold revealed the presence of interconnected pores, mostly spread over the whole surface of the scaffold. The nHAp particulates have covered the surface of the composite matrix and made the surface of the scaffold rougher. The scaffold has a porosity of 82% with a mean pore size of 112±19.0μm. Swelling and degradation studies of the scaffold showed that the scaffold possesses excellent properties of hydrophilicity and biodegradability. Short term mechanical testing of the scaffold does not reveal any rupturing after agitation under physiological conditions, which is an indicative of good mechanical stability of the scaffold. In vitro cell culture studies by seeding osteoblast cells over the composite scaffold showed good cell viability, proliferation rate, adhesion and maintenance of osteoblastic phenotype as indicated by MTT assay, ESEM of cell-scaffold construct, histological staining and gene expression studies, respectively. Thus, it could be stated that the nano-biocomposite scaffold of chitosan-gelatin-alginate-nHAp has the paramount importance for applications in bone tissue-engineering in future regenerative therapies. Copyright © 2016 Elsevier B.V. All rights reserved.

ASTM International Workshop on Standards & Measurements for Tissue Engineering Scaffolds

PubMed Central

Simon, Carl G.; Yaszemski, Michael J.; Ratcliffe, Anthony; Tomlins, Paul; Luginbuehl, Reto; Tesk, John A.

2016-01-01

The “Workshop on Standards & Measurements for Tissue Engineering Scaffolds” was held on May 21, 2013 in Indianapolis, IN and was sponsored by the ASTM International (ASTM). The purpose of the workshop was to identify the highest priority items for future standards work for scaffolds used in the development and manufacture of tissue engineered medical products (TEMPs). Eighteen speakers and 78 attendees met to assess current scaffold standards and to prioritize needs for future standards. A key finding was that the ASTM TEMPs subcommittees (F04.41-46) have many active “guide” documents for educational purposes, but that few standard “test methods” or “practices” have been published. Overwhelmingly, the most clearly identified need was standards for measuring the structure of scaffolds, followed by standards for biological characterization, including in vitro testing, animal models and cell-material interactions. The third most pressing need was to develop standards for assessing the mechanical properties of scaffolds. Additional needs included standards for assessing scaffold degradation, clinical outcomes with scaffolds, effects of sterilization on scaffolds, scaffold composition and drug release from scaffolds. Discussions also highlighted the need for additional scaffold reference materials and the need to use them for measurement traceability. Finally, dialogue emphasized the needs to promote the use of standards in scaffold fabrication, characterization, and commercialization and to assess the use and impact of standards in the TEMPs community. Many scaffold standard needs have been identified and focus should now turn to generating these standards to support the use of scaffolds in TEMPs. PMID:25220952

Influence of Additive Manufactured Scaffold Architecture on the Distribution of Surface Strains and Fluid Flow Shear Stresses and Expected Osteochondral Cell Differentiation.

PubMed

Hendrikson, Wim J; Deegan, Anthony J; Yang, Ying; van Blitterswijk, Clemens A; Verdonschot, Nico; Moroni, Lorenzo; Rouwkema, Jeroen

2017-01-01

Scaffolds for regenerative medicine applications should instruct cells with the appropriate signals, including biophysical stimuli such as stress and strain, to form the desired tissue. Apart from that, scaffolds, especially for load-bearing applications, should be capable of providing mechanical stability. Since both scaffold strength and stress-strain distributions throughout the scaffold depend on the scaffold's internal architecture, it is important to understand how changes in architecture influence these parameters. In this study, four scaffold designs with different architectures were produced using additive manufacturing. The designs varied in fiber orientation, while fiber diameter, spacing, and layer height remained constant. Based on micro-CT (μCT) scans, finite element models (FEMs) were derived for finite element analysis (FEA) and computational fluid dynamics (CFD). FEA of scaffold compression was validated using μCT scan data of compressed scaffolds. Results of the FEA and CFD showed a significant impact of scaffold architecture on fluid shear stress and mechanical strain distribution. The average fluid shear stress ranged from 3.6 mPa for a 0/90 architecture to 6.8 mPa for a 0/90 offset architecture, and the surface shear strain from 0.0096 for a 0/90 offset architecture to 0.0214 for a 0/90 architecture. This subsequently resulted in variations of the predicted cell differentiation stimulus values on the scaffold surface. Fluid shear stress was mainly influenced by pore shape and size, while mechanical strain distribution depended mainly on the presence or absence of supportive columns in the scaffold architecture. Together, these results corroborate that scaffold architecture can be exploited to design scaffolds with regions that guide specific tissue development under compression and perfusion. In conjunction with optimization of stimulation regimes during bioreactor cultures, scaffold architecture optimization can be used to improve scaffold design for tissue engineering purposes.

Osteoinduction and proliferation of bone-marrow stromal cells in three-dimensional poly (ε-caprolactone)/ hydroxyapatite/collagen scaffolds.

PubMed

Wang, Ting; Yang, Xiaoyan; Qi, Xin; Jiang, Chaoyin

2015-05-08

Osteoinduction and proliferation of bone-marrow stromal cells (BMSCs) in three-dimensional (3D) poly(ε-caprolactone) (PCL) scaffolds have not been studied throughly and are technically challenging. This study aimed to optimize nanocomposites of 3D PCL scaffolds to provide superior adhesion, proliferation and differentiation environment for BMSCs in this scenario. BMSCs were isolated and cultured in a novel 3D tissue culture poly(ε-caprolactone) (PCL) scaffold coated with poly-lysine, hydroxyapatite (HAp), collagen and HAp/collagen. Cell morphology was observed and BMSC biomarkers for osteogenesis, osteoblast differentiation and activation were analyzed. Scanning Electron Microscope (SEM) micrographs showed that coating materials were uniformly deposited on the surface of PCL scaffolds and BMSCs grew and aggregated to form clusters during 3D culture. Both mRNA and protein levels of the key players of osteogenesis and osteoblast differentiation and activation, including runt-related transcription factor 2 (Runx2), alkaline phosphates (ALP), osterix, osteocalcin, and RANKL, were significantly higher in BMSCs seeded in PCL scaffolds coated with HAp or HAp/collagen than those seeded in uncoated PCL scaffolds, whereas the expression levels were not significantly different in collagen or poly-lysine coated PCL scaffolds. In addition, poly-lysine, collagen, HAp/collagen, and HAp coated PCL scaffolds had significantly more viable cells than uncoated PCL scaffolds, especially scaffolds with HAp/collagen and collagen-alone coatings. That BMSCs in HAp or HAp/collagen PCL scaffolds had remarkably higher ALP activities than those in collagen-coated alone or uncoated PCL scaffolds indicating higher osteogenic differentiation levels of BMSCs in HAp or HAp/collagen PCL scaffolds. Moreover, morphological changes of BMSCs after four-week of 3D culture confirmed that BMSCs successfully differentiated into osteoblast with spread-out phenotype in HAp/collagen coated PCL scaffolds. This study showed a proof of concept for preparing biomimetic 3D poly (ε-caprolactone)/ hydroxyapatite/collagen scaffolds with excellent osteoinduction and proliferation capacity for bone regeneration.

Cytotoxicity assessment of polyhydroxybutyrate/chitosan/nano- bioglass nanofiber scaffolds by stem cells from human exfoliated deciduous teeth stem cells from dental pulp of exfoliated deciduous tooth

PubMed Central

Hashemi-Beni, Batool; Khoroushi, Maryam; Foroughi, Mohammad Reza; Karbasi, Saeed; Khademi, Abbas Ali

2018-01-01

Background: The aim of this study was to compare the cytotoxicity and the biocompatibility of three different nanofibers scaffolds after seeding of stem cells harvested from human deciduous dental pulp. Given the importance of scaffold and its features in tissue engineering, this study demonstrated the construction of polyhydroxybutyrate (PHB)/chitosan/nano-bioglass (nBG) nanocomposite scaffold using electrospinning method. Materials and Methods: This experimental study was conducted on normal exfoliated deciduous incisors obtained from 6-year-old to 11-year-old healthy children. The dental pulp was extracted from primary incisor teeth which are falling aseptically. After digesting the tissue with 4 mg/ml of type I collagenase, the cells were cultured in medium solution. Identification of stem cells from human exfoliated deciduous teeth was performed by flowcytometry using CD19, CD14, CD146, and CD90 markers. Then, 1 × 104 stem cells were seeded on the scaffold with a diameter of 10 mm × 0.3 mm. Cell viability was evaluated on days 3, 5, and 7 through methyl thiazol tetrazolium techniques (P < 0.05) on different groups that they are groups included (1) PHB scaffold (G1), (2) PHB/chitosan scaffold (G2), (3) the optimal PHB/chitosan/nBG scaffold (G3), (4) mineral trioxide aggregate (MTA), and (5) the G3 + MTA scaffold (G3 + MTA). Data were analyzed with two-way ANOVA at significance level of P < 0.05. Results: The results indicated that the PHB/chitosan/nBG scaffold and PHB/chitosan/nBG scaffold + MTA groups showed significant difference compared with the PHB/chitosan scaffold and PHB scaffold groups on the 7th day (P < 0.05). Conclusion: Thus, it can be concluded that the scaffold with nBG nanoparticles is more biocompatible than the other scaffolds and can be considered as a suitable scaffold for growth and proliferation of stem cells. PMID:29576778

Cytotoxicity assessment of polyhydroxybutyrate/chitosan/nano- bioglass nanofiber scaffolds by stem cells from human exfoliated deciduous teeth stem cells from dental pulp of exfoliated deciduous tooth.

PubMed

Hashemi-Beni, Batool; Khoroushi, Maryam; Foroughi, Mohammad Reza; Karbasi, Saeed; Khademi, Abbas Ali

2018-01-01

The aim of this study was to compare the cytotoxicity and the biocompatibility of three different nanofibers scaffolds after seeding of stem cells harvested from human deciduous dental pulp. Given the importance of scaffold and its features in tissue engineering, this study demonstrated the construction of polyhydroxybutyrate (PHB)/chitosan/nano-bioglass (nBG) nanocomposite scaffold using electrospinning method. This experimental study was conducted on normal exfoliated deciduous incisors obtained from 6-year-old to 11-year-old healthy children. The dental pulp was extracted from primary incisor teeth which are falling aseptically. After digesting the tissue with 4 mg/ml of type I collagenase, the cells were cultured in medium solution. Identification of stem cells from human exfoliated deciduous teeth was performed by flowcytometry using CD19, CD14, CD146, and CD90 markers. Then, 1 × 10 4 stem cells were seeded on the scaffold with a diameter of 10 mm × 0.3 mm. Cell viability was evaluated on days 3, 5, and 7 through methyl thiazol tetrazolium techniques ( P < 0.05) on different groups that they are groups included (1) PHB scaffold (G1), (2) PHB/chitosan scaffold (G2), (3) the optimal PHB/chitosan/nBG scaffold (G3), (4) mineral trioxide aggregate (MTA), and (5) the G3 + MTA scaffold (G3 + MTA). Data were analyzed with two-way ANOVA at significance level of P < 0.05. The results indicated that the PHB/chitosan/nBG scaffold and PHB/chitosan/nBG scaffold + MTA groups showed significant difference compared with the PHB/chitosan scaffold and PHB scaffold groups on the 7 th day ( P < 0.05). Thus, it can be concluded that the scaffold with nBG nanoparticles is more biocompatible than the other scaffolds and can be considered as a suitable scaffold for growth and proliferation of stem cells.

Biodegradable and biocompatible high elastic chitosan scaffold is cell-friendly both in vitro and in vivo

PubMed Central

Lin, Xianfeng; Yang, Lin; Wang, Qiang; Wang, Zhengke; Shan, Zhi; Li, Shengyun; Wang, Jiying; Fan, Shunwu; Hu, Qiaoling

2017-01-01

Biodegradable and biocompatible macromolecule chitosan has been favored for a variety of clinical applications. We reported herein the fabrication of a novel chitosan scaffold with high elasticity. This scaffold can be easily compressed and thus enable the insertion of such scaffold into surgical lesions during minimal invasive surgeries. In addition, this novel scaffold can restore its shape when released. We evidenced that this high elastic scaffold has better biocompatibility than traditional chitosan scaffold. Therefore, this new chitosan material might lead to the manufacture of a variety of novel biodegradable biomedical materials and devices. PMID:28103580

Fabrication of functional PLGA-based electrospun scaffolds and their applications in biomedical engineering.

PubMed

Zhao, Wen; Li, Jiaojiao; Jin, Kaixiang; Liu, Wenlong; Qiu, Xuefeng; Li, Chenrui

2016-02-01

Electrospun PLGA-based scaffolds have been applied extensively in biomedical engineering, such as tissue engineering and drug delivery system. Due to lack of the recognition sites on cells, hydropholicity and single-function, the applications of PLGA fibrous scaffolds are limited. In order to tackle these issues, many works have been done to obtain functional PLGA-based scaffolds, including surface modifications, the fabrication of PLGA-based composite scaffolds and drug-loaded scaffolds. The functional PLGA-based scaffolds have significantly improved cell adhesion, attachment and proliferation. Moreover, the current study has summarized the applications of functional PLGA-based scaffolds in wound dressing, vascular and bone tissue engineering area as well as drug delivery system. Copyright © 2015 Elsevier B.V. All rights reserved.

Alendronate-Eluting Biphasic Calcium Phosphate (BCP) Scaffolds Stimulate Osteogenic Differentiation

PubMed Central

Kim, Sung Eun; Lee, Deok-Won; Kang, Eun Young; Jeong, Won Jae; Lee, Boram; Jeong, Myeong Seon; Kim, Hak Jun; Park, Kyeongsoon; Song, Hae-Ryong

2015-01-01

Biphasic calcium phosphate (BCP) scaffolds have been widely used in orthopedic and dental fields as osteoconductive bone substitutes. However, BCP scaffolds are not satisfactory for the stimulation of osteogenic differentiation and maturation. To enhance osteogenic differentiation, we prepared alendronate- (ALN-) eluting BCP scaffolds. The coating of ALN on BCP scaffolds was confirmed by scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). An in vitro release study showed that release of ALN from ALN-eluting BCP scaffolds was sustained for up to 28 days. In vitro results revealed that MG-63 cells grown on ALN-eluting BCP scaffolds exhibited increased ALP activity and calcium deposition and upregulated gene expression of Runx2, ALP, OCN, and OPN compared with the BCP scaffold alone. Therefore, this study suggests that ALN-eluting BCP scaffolds have the potential to effectively stimulate osteogenic differentiation. PMID:26221587

A bioprosthetic ovary created using 3D printed microporous scaffolds restores ovarian function in sterilized mice.

PubMed

Laronda, Monica M; Rutz, Alexandra L; Xiao, Shuo; Whelan, Kelly A; Duncan, Francesca E; Roth, Eric W; Woodruff, Teresa K; Shah, Ramille N

2017-05-16

Emerging additive manufacturing techniques enable investigation of the effects of pore geometry on cell behavior and function. Here, we 3D print microporous hydrogel scaffolds to test how varying pore geometry, accomplished by manipulating the advancing angle between printed layers, affects the survival of ovarian follicles. 30° and 60° scaffolds provide corners that surround follicles on multiple sides while 90° scaffolds have an open porosity that limits follicle-scaffold interaction. As the amount of scaffold interaction increases, follicle spreading is limited and survival increases. Follicle-seeded scaffolds become highly vascularized and ovarian function is fully restored when implanted in surgically sterilized mice. Moreover, pups are born through natural mating and thrive through maternal lactation. These findings present an in vivo functional ovarian implant designed with 3D printing, and indicate that scaffold pore architecture is a critical variable in additively manufactured scaffold design for functional tissue engineering.

A gelatin composite scaffold strengthened by drug-loaded halloysite nanotubes.

PubMed

Ji, Lijun; Qiao, Wei; Zhang, Yuheng; Wu, Huayu; Miao, Shiyong; Cheng, Zhilin; Gong, Qianming; Liang, Ji; Zhu, Aiping

2017-09-01

Mechanical properties and anti-infection are two of the most concerned issues for artificial bone grafting materials. Bone regeneration porous scaffolds with sustained drug release were developed by freeze-drying the mixture of nanosized drug-loaded halloysite nanotubes (HNTs) and gelatin. The scaffolds showed porous structure and excellent biocompatibility. The mechanical properties of the obtained composite scaffolds were enhanced significantly by HNTs to >300%, comparing to those of gelatin scaffold, and match to those of natural cancellous bones. The ibuprofen-loaded HNTs incorporated in the scaffolds allowed extended drug release over 100h, comparing to 8h when directly mixed the drug into the gelatin scaffold. The biological properties of the composite scaffolds were investigated by culturing MG63 cells on them. The HNTs/gelatin scaffolds with excellent mechanical properties and sustained drug release could be a promising artificial bone grating material. Copyright © 2017 Elsevier B.V. All rights reserved.

Does the tissue engineering architecture of poly(3-hydroxybutyrate) scaffold affects cell-material interactions?

PubMed

Masaeli, Elahe; Morshed, Mohammad; Rasekhian, Parsa; Karbasi, Saeed; Karbalaie, Khadije; Karamali, Fereshte; Abedi, Daryoush; Razavi, Shahnaz; Jafarian-Dehkordi, Abbas; Nasr-Esfahani, Mohammad Hossein; Baharvand, Hossein

2012-07-01

A critical element in tissue engineering involves the fabrication of a three-dimensional scaffold. The scaffold provides a space for new tissue formation, supports cellular ingrowth, and proliferation and mimics many roles of the extracellular matrix. Poly(3-hydroxybutyrate) (PHB) is the most thoroughly investigated member of the polyhydroxyalkanoates (PHAs) family that has various degrees of biocompatibility and biodegradability for tissue engineering applications. In this study, we fabricated PHB scaffolds by utilizing electrospinning and salt-leaching procedures. The behavior of monkey epithelial kidney cells (Vero) and mouse mesenchymal stem cells (mMSCs) on these scaffolds was compared by the MTS assay and scanning electron microscopy. Additionally, this study investigated the mechanical and physical properties of these scaffolds by measuring tensile strength and modulus, dynamic contact angle and porosity. According to our results, the salt-leached scaffolds showed more wettability and permeability, but inferior mechanical properties when compared with nanofibrous scaffolds. In terms of cell response, salt-leached scaffolds showed enhanced Vero cell proliferation, whereas both scaffolds responded similarly in the case of mMSCs proliferation. In brief, nanofibrous scaffolds can be a better substrate for cell attachment and morphology. Copyright © 2012 Wiley Periodicals, Inc.

Influence of crosslinking on the mechanical behavior of 3D printed alginate scaffolds: Experimental and numerical approaches.

PubMed

Naghieh, Saman; Karamooz-Ravari, Mohammad Reza; Sarker, M D; Karki, Eva; Chen, Xiongbiao

2018-04-01

Tissue scaffolds fabricated by three-dimensional (3D) bioprinting are attracting considerable attention for tissue engineering applications. Because the mechanical properties of hydrogel scaffolds should match the damaged tissue, changing various parameters during 3D bioprinting has been studied to manipulate the mechanical behavior of the resulting scaffolds. Crosslinking scaffolds using a cation solution (such as CaCl 2 ) is also important for regulating the mechanical properties, but has not been well documented in the literature. Here, the effect of varied crosslinking agent volume and crosslinking time on the mechanical behavior of 3D bioplotted alginate scaffolds was evaluated using both experimental and numerical methods. Compression tests were used to measure the elastic modulus of each scaffold, then a finite element model was developed and a power model used to predict scaffold mechanical behavior. Results showed that crosslinking time and volume of crosslinker both play a decisive role in modulating the mechanical properties of 3D bioplotted scaffolds. Because mechanical properties of scaffolds can affect cell response, the findings of this study can be implemented to modulate the elastic modulus of scaffolds according to the intended application. Copyright © 2018 Elsevier Ltd. All rights reserved.

A novel albumin-based tissue scaffold for autogenic tissue engineering applications.

PubMed

Li, Pei-Shan; Lee, I-Liang; Yu, Wei-Lin; Sun, Jui-Sheng; Jane, Wann-Neng; Shen, Hsin-Hsin

2014-07-18

Tissue scaffolds provide a framework for living tissue regeneration. However, traditional tissue scaffolds are exogenous, composed of metals, ceramics, polymers, and animal tissues, and have a defined biocompatibility and application. This study presents a new method for obtaining a tissue scaffold from blood albumin, the major protein in mammalian blood. Human, bovine, and porcine albumin was polymerised into albumin polymers by microbial transglutaminase and was then cast by freeze-drying-based moulding to form albumin tissue scaffolds. Scanning electron microscopy and material testing analyses revealed that the albumin tissue scaffold possesses an extremely porous structure, moderate mechanical strength, and resilience. Using a culture of human mesenchymal stem cells (MSCs) as a model, we showed that MSCs can be seeded and grown in the albumin tissue scaffold. Furthermore, the albumin tissue scaffold can support the long-term osteogenic differentiation of MSCs. These results show that the albumin tissue scaffold exhibits favourable material properties and good compatibility with cells. We propose that this novel tissue scaffold can satisfy essential needs in tissue engineering as a general-purpose substrate. The use of this scaffold could lead to the development of new methods of artificial fabrication of autogenic tissue substitutes.

Three-Dimensional Printing of Hollow-Struts-Packed Bioceramic Scaffolds for Bone Regeneration.

PubMed

Luo, Yongxiang; Zhai, Dong; Huan, Zhiguang; Zhu, Haibo; Xia, Lunguo; Chang, Jiang; Wu, Chengtie

2015-11-04

Three-dimensional printing technologies have shown distinct advantages to create porous scaffolds with designed macropores for application in bone tissue engineering. However, until now, 3D-printed bioceramic scaffolds only possessing a single type of macropore have been reported. Generally, those scaffolds with a single type of macropore have relatively low porosity and pore surfaces, limited delivery of oxygen and nutrition to surviving cells, and new bone tissue formation in the center of the scaffolds. Therefore, in this work, we present a useful and facile method for preparing hollow-struts-packed (HSP) bioceramic scaffolds with designed macropores and multioriented hollow channels via a modified coaxial 3D printing strategy. The prepared HSP scaffolds combined high porosity and surface area with impressive mechanical strength. The unique hollow-struts structures of bioceramic scaffolds significantly improved cell attachment and proliferation and further promoted formation of new bone tissue in the center of the scaffolds, indicating that HSP ceramic scaffolds can be used for regeneration of large bone defects. In addition, the strategy can be used to prepare other HSP ceramic scaffolds, indicating a universal application for tissue engineering, mechanical engineering, catalysis, and environmental materials.

Development of a biodegradable scaffold with interconnected pores by heat fusion and its application to bone tissue engineering.

PubMed

Shin, Michael; Abukawa, Harutsugi; Troulis, Maria J; Vacanti, Joseph P

2008-03-01

Tissue engineering has been proposed as an approach to alleviate the shortage of donor tissue and organs by combining cells and a biodegradable scaffold as a temporary extracellular matrix. While numerous scaffold fabrication methods have been proposed, tissue formation is typically limited to the surface of the scaffolds in bone tissue engineering applications due to early calcification on the surface. To improve tissue formation, a novel scaffold with a hierarchical interconnected pore structure on two distinct length scales has been developed. Here we present the fabrication process and the application of the scaffold to bone tissue engineering. Porous poly(lactide-co-glycolide) (PLGA) scaffolds were made by combining solvent casting/particulate leaching with heat fusion. Porcine bone marrow-derived mesenchymal stem cells (MSCs) were differentiated into osteoblasts and cultured on these scaffolds in vitro for 2, 4, and 6 weeks. Subsequently, the constructs were assessed using histology and scanning electron microscopy. The bone marrow-derived osteoblasts attached well on these scaffolds. Cells were observed throughout the scaffolds. These initial results show promise for this scaffold to aid in the regeneration of bone. (c) 2007 Wiley Periodicals, Inc.

A green salt-leaching technique to produce sericin/PVA/glycerin scaffolds with distinguished characteristics for wound-dressing applications.

PubMed

Aramwit, Pornanong; Ratanavaraporn, Juthamas; Ekgasit, Sanong; Tongsakul, Duangta; Bang, Nipaporn

2015-05-01

Sericin/PVA/glycerin scaffolds could be fabricated using the freeze-drying technique; they showed good physical and biological properties and can be applied as wound dressings. However, freeze-drying is an energy- and time-consuming process with a high associated cost. In this study, an alternative, solvent-free, energy- and time-saving, low-cost salt-leaching technique is introduced as a green technology to produce sericin/PVA/glycerin scaffolds. We found that sericin/PVA/glycerin scaffolds were successfully fabricated without any crosslinking using a salt-leaching technique. The salt-leached sericin/PVA/glycerin scaffolds had a porous structure with pore interconnectivity. The sericin in the salt-leached scaffolds had a crystallinity that was as high as that of the freeze-dried scaffolds. Compared to the freeze-dried scaffolds with the same composition, the salt-leached sericin/PVA/glycerin scaffolds has larger pores, a lower Young's modulus, and faster rates of biodegradation and sericin release. When cultured with L929 mouse fibroblast cells, a higher number of cells were found in the salt-leached scaffolds. Furthermore, the salt-leached scaffolds were less adhesive to the wound, which would reduce pain upon removal. Therefore, salt-leached sericin/PVA/glycerin scaffolds with distinguished characteristics were introduced as another choice of wound dressing, and their production process was simpler, more energy efficient, and saved time and money compared to the freeze-dried scaffolds. © 2014 Wiley Periodicals, Inc.

Design and characterization of microcapsules-integrated collagen matrixes as multifunctional three-dimensional scaffolds for soft tissue engineering.

PubMed

Del Mercato, Loretta L; Passione, Laura Gioia; Izzo, Daniela; Rinaldi, Rosaria; Sannino, Alessandro; Gervaso, Francesca

2016-09-01

Three-dimensional (3D) porous scaffolds based on collagen are promising candidates for soft tissue engineering applications. The addition of stimuli-responsive carriers (nano- and microparticles) in the current approaches to tissue reconstruction and repair brings about novel challenges in the design and conception of carrier-integrated polymer scaffolds. In this study, a facile method was developed to functionalize 3D collagen porous scaffolds with biodegradable multilayer microcapsules. The effects of the capsule charge as well as the influence of the functionalization methods on the binding efficiency to the scaffolds were studied. It was found that the binding of cationic microcapsules was higher than that of anionic ones, and application of vacuum during scaffolds functionalization significantly hindered the attachment of the microcapsules to the collagen matrix. The physical properties of microcapsules-integrated scaffolds were compared to pristine scaffolds. The modified scaffolds showed swelling ratios, weight losses and mechanical properties similar to those of unmodified scaffolds. Finally, in vitro diffusional tests proved that the collagen scaffolds could stably retain the microcapsules over long incubation time in Tris-HCl buffer at 37°C without undergoing morphological changes, thus confirming their suitability for tissue engineering applications. The obtained results indicate that by tuning the charge of the microcapsules and by varying the fabrication conditions, collagen scaffolds patterned with high or low number of microcapsules can be obtained, and that the microcapsules-integrated scaffolds fully retain their original physical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesizing Results From Empirical Research on Computer-Based Scaffolding in STEM Education: A Meta-Analysis.

PubMed

Belland, Brian R; Walker, Andrew E; Kim, Nam Ju; Lefler, Mason

2017-04-01

Computer-based scaffolding assists students as they generate solutions to complex problems, goals, or tasks, helping increase and integrate their higher order skills in the process. However, despite decades of research on scaffolding in STEM (science, technology, engineering, and mathematics) education, no existing comprehensive meta-analysis has synthesized the results of these studies. This review addresses that need by synthesizing the results of 144 experimental studies (333 outcomes) on the effects of computer-based scaffolding designed to assist the full range of STEM learners (primary through adult education) as they navigated ill-structured, problem-centered curricula. Results of our random effect meta-analysis (a) indicate that computer-based scaffolding showed a consistently positive (ḡ = 0.46) effect on cognitive outcomes across various contexts of use, scaffolding characteristics, and levels of assessment and (b) shed light on many scaffolding debates, including the roles of customization (i.e., fading and adding) and context-specific support. Specifically, scaffolding's influence on cognitive outcomes did not vary on the basis of context-specificity, presence or absence of scaffolding change, and logic by which scaffolding change is implemented. Scaffolding's influence was greatest when measured at the principles level and among adult learners. Still scaffolding's effect was substantial and significantly greater than zero across all age groups and assessment levels. These results suggest that scaffolding is a highly effective intervention across levels of different characteristics and can largely be designed in many different ways while still being highly effective.

[Mechanical properties of polylactic acid/beta-tricalcium phosphate composite scaffold with double channels based on three-dimensional printing technique].

PubMed

Lian, Qin; Zhuang, Pei; Li, Changhai; Jin, Zhongmin; Li, Dichen

2014-03-01

To improve the poor mechanical strength of porous ceramic scaffold, an integrated method based on three-dimensional (3-D) printing technique is developed to incorporate the controlled double-channel porous structure into the polylactic acid/beta-tricalcium phosphate (PLA/beta-TCP) reinforced composite scaffolds (double-channel composite scaffold) to improve their tissue regeneration capability and the mechanical properties. The designed double-channel structure inside the ceramic scaffold consisted of both primary and secondary micropipes, which parallel but un-connected. The set of primary channels was used for cell ingrowth, while the set of secondary channels was used for the PLA perfusion. Integration technology of 3-D printing technique and gel-casting was firstly used to fabricate the double-channel ceramic scaffolds. PLA/beta-TCP composite scaffolds were obtained by the polymer gravity perfusion process to pour PLA solution into the double-channel ceramic scaffolds through the secondary channel set. Microscope, porosity, and mechanical experiments for the standard samples were used to evaluate the composite properties. The ceramic scaffold with only the primary channel (single-channel scaffold) was also prepared as a control. Morphology observation results showed that there was no PLA inside the primary channels of the double-channel composite scaffolds but a dense interface layer between PLA and beta-TCP obviously formed on the inner wall of the secondary channels by the PLA penetration during the perfusion process. Finite element simulation found that the compressive strength of the double-channel composite scaffold was less than that of the single-channel scaffold; however, mechanical tests found that the maximum compressive strength of the double-channel composite scaffold [(21.25 +/- 1.15) MPa] was higher than that of the single-channel scaffold[ (9.76 +/- 0.64) MPa]. The double-channel composite scaffolds fabricated by 3-D printing technique have controlled complex micropipes and can significantly enhance mechanical properties, which is a promising strategy to solve the contradiction of strength and high-porosity of the ceramic scaffolds for the bone tissue engineering application.

The development of computer-aided system for tissue scaffolds (CASTS) system for functionally graded tissue-engineering scaffolds.

PubMed

Sudarmadji, Novella; Chua, Chee Kai; Leong, Kah Fai

2012-01-01

Computer-aided system for tissue scaffolds (CASTS) is an in-house parametric library of polyhedral units that can be assembled into customized tissue scaffolds. Thirteen polyhedral configurations are available to select, depending on the biological and mechanical requirements of the target tissue/organ. Input parameters include the individual polyhedral units and overall scaffold block as well as the scaffold strut diameter. Taking advantage of its repeatability and reproducibility, the scaffold file is then converted into .STL file and fabricated using selective laser sintering, a rapid prototyping system. CASTS seeks to fulfill anatomical, biological, and mechanical requirements of the target tissue/organ. Customized anatomical scaffold shape is achieved through a Boolean operation between the scaffold block and the tissue defect image. Biological requirements, such as scaffold pore size and porosity, are unique for different type of cells. Matching mechanical properties, such as stiffness and strength, between the scaffold and target organ is very important, particularly in the regeneration of load-bearing organ, i.e., bone. This includes mimicking the compressive stiffness variation across the bone to prevent stress shielding and ensuring that the scaffold can withstand the load normally borne by the bone. The stiffness variation is tailored by adjusting the scaffold porosity based on the porosity-stiffness relationship of the CASTS scaffolds. Two types of functional gradients based on the gradient direction include radial and axial/linear gradient. Radial gradient is useful in the case of regenerating a section of long bones while the gradient in linear direction can be used in short or irregular bones. Stiffness gradient in the radial direction is achieved by using cylindrical unit cells arranged in a concentric manner, in which the porosity decreases from the center of the structure toward the outside radius, making the scaffold stiffer at the outer radius and more porous at the center of the scaffold. On the other hand, the linear gradient is accomplished by varying the strut diameter along the gradient direction. The parameters to vary in both gradient types are the strut diameter, the unit cell dimension, and the boundaries between two scaffold regions with different stiffness.

Hydroxyapatite reinforced collagen scaffolds with improved architecture and mechanical properties.

PubMed

Kane, Robert J; Weiss-Bilka, Holly E; Meagher, Matthew J; Liu, Yongxing; Gargac, Joshua A; Niebur, Glen L; Wagner, Diane R; Roeder, Ryan K

2015-04-01

Hydroxyapatite (HA) reinforced collagen scaffolds have shown promise for synthetic bone graft substitutes and tissue engineering scaffolds. Freeze-dried HA-collagen scaffolds are readily fabricated and have exhibited osteogenicity in vivo, but are limited by an inherent scaffold architecture that results in a relatively small pore size and weak mechanical properties. In order to overcome these limitations, HA-collagen scaffolds were prepared by compression molding HA reinforcements and paraffin microspheres within a suspension of concentrated collagen fibrils (∼ 180 mg/mL), cross-linking the collagen matrix, and leaching the paraffin porogen. HA-collagen scaffolds exhibited an architecture with high porosity (85-90%), interconnected pores ∼ 300-400 μm in size, and struts ∼ 3-100 μm in thickness containing 0-80 vol% HA whisker or powder reinforcements. HA reinforcement enabled a compressive modulus of up to ∼ 1 MPa, which was an order of magnitude greater than unreinforced collagen scaffolds. The compressive modulus was also at least one order of magnitude greater than comparable freeze-dried HA-collagen scaffolds and two orders of magnitude greater than absorbable collagen sponges used clinically. Moreover, scaffolds reinforced with up to 60 vol% HA exhibited fully recoverable elastic deformation upon loading to 50% compressive strain for at least 100,000 cycles. Thus, the scaffold mechanical properties were well-suited for surgical handling, fixation, and bearing osteogenic loads during bone regeneration. The scaffold architecture, permeability, and composition were shown to be conducive to the infiltration and differentiation of adipose-derive stromal cells in vitro. Acellular scaffolds were demonstrated to induce angiogenesis and osteogenesis after subcutaneous ectopic implantation by recruiting endogenous cell populations, suggesting that the scaffolds were osteoinductive. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A novel route in bone tissue engineering: magnetic biomimetic scaffolds.

PubMed

Bock, N; Riminucci, A; Dionigi, C; Russo, A; Tampieri, A; Landi, E; Goranov, V A; Marcacci, M; Dediu, V

2010-03-01

In recent years, interest in tissue engineering and its solutions has increased considerably. In particular, scaffolds have become fundamental tools in bone graft substitution and are used in combination with a variety of bio-agents. However, a long-standing problem in the use of these conventional scaffolds lies in the impossibility of re-loading the scaffold with the bio-agents after implantation. This work introduces the magnetic scaffold as a conceptually new solution. The magnetic scaffold is able, via magnetic driving, to attract and take up in vivo growth factors, stem cells or other bio-agents bound to magnetic particles. The authors succeeded in developing a simple and inexpensive technique able to transform standard commercial scaffolds made of hydroxyapatite and collagen in magnetic scaffolds. This innovative process involves dip-coating of the scaffolds in aqueous ferrofluids containing iron oxide nanoparticles coated with various biopolymers. After dip-coating, the nanoparticles are integrated into the structure of the scaffolds, providing the latter with magnetization values as high as 15 emu g(-)(1) at 10 kOe. These values are suitable for generating magnetic gradients, enabling magnetic guiding in the vicinity and inside the scaffold. The magnetic scaffolds do not suffer from any structural damage during the process, maintaining their specific porosity and shape. Moreover, they do not release magnetic particles under a constant flow of simulated body fluids over a period of 8 days. Finally, preliminary studies indicate the ability of the magnetic scaffolds to support adhesion and proliferation of human bone marrow stem cells in vitro. Hence, this new type of scaffold is a valuable candidate for tissue engineering applications, featuring a novel magnetic guiding option. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Evaluation of Osteoconductive Scaffolds in the Canine Femoral Multi-Defect Model

PubMed Central

Luangphakdy, Viviane; Walker, Esteban; Shinohara, Kentaro; Pan, Hui; Hefferan, Theresa; Bauer, Thomas W.; Stockdale, Linda; Saini, Sunil; Dadsetan, Mahrokh; Runge, M. Brett; Vasanji, Amit; Griffith, Linda; Yaszemski, Michael

2013-01-01

Treatment of large segmental bone defects remains an unsolved clinical challenge, despite a wide array of existing bone graft materials. This project was designed to rapidly assess and compare promising biodegradable osteoconductive scaffolds for use in the systematic development of new bone regeneration methodologies that combine scaffolds, sources of osteogenic cells, and bioactive scaffold modifications. Promising biomaterials and scaffold fabrication methods were identified in laboratories at Rutgers, MIT, Integra Life Sciences, and Mayo Clinic. Scaffolds were fabricated from various materials, including poly(L-lactide-co-glycolide) (PLGA), poly(L-lactide-co-ɛ-caprolactone) (PLCL), tyrosine-derived polycarbonate (TyrPC), and poly(propylene fumarate) (PPF). Highly porous three-dimensional (3D) scaffolds were fabricated by 3D printing, laser stereolithography, or solvent casting followed by porogen leaching. The canine femoral multi-defect model was used to systematically compare scaffold performance and enable selection of the most promising substrate(s) on which to add cell sourcing options and bioactive surface modifications. Mineralized cancellous allograft (MCA) was used to provide a comparative reference to the current clinical standard for osteoconductive scaffolds. Percent bone volume within the defect was assessed 4 weeks after implantation using both MicroCT and limited histomorphometry. Bone formed at the periphery of all scaffolds with varying levels of radial ingrowth. MCA produced a rapid and advanced stage of bone formation and remodeling throughout the defect in 4 weeks, greatly exceeding the performance of all polymer scaffolds. Two scaffold constructs, TyrPCPL/TCP and PPF4SLA/HAPLGA Dip, proved to be significantly better than alternative PLGA and PLCL scaffolds, justifying further development. MCA remains the current standard for osteoconductive scaffolds. PMID:23215980

Evaluation of osteoconductive scaffolds in the canine femoral multi-defect model.

PubMed

Luangphakdy, Viviane; Walker, Esteban; Shinohara, Kentaro; Pan, Hui; Hefferan, Theresa; Bauer, Thomas W; Stockdale, Linda; Saini, Sunil; Dadsetan, Mahrokh; Runge, M Brett; Vasanji, Amit; Griffith, Linda; Yaszemski, Michael; Muschler, George F

2013-03-01

Treatment of large segmental bone defects remains an unsolved clinical challenge, despite a wide array of existing bone graft materials. This project was designed to rapidly assess and compare promising biodegradable osteoconductive scaffolds for use in the systematic development of new bone regeneration methodologies that combine scaffolds, sources of osteogenic cells, and bioactive scaffold modifications. Promising biomaterials and scaffold fabrication methods were identified in laboratories at Rutgers, MIT, Integra Life Sciences, and Mayo Clinic. Scaffolds were fabricated from various materials, including poly(L-lactide-co-glycolide) (PLGA), poly(L-lactide-co-ɛ-caprolactone) (PLCL), tyrosine-derived polycarbonate (TyrPC), and poly(propylene fumarate) (PPF). Highly porous three-dimensional (3D) scaffolds were fabricated by 3D printing, laser stereolithography, or solvent casting followed by porogen leaching. The canine femoral multi-defect model was used to systematically compare scaffold performance and enable selection of the most promising substrate(s) on which to add cell sourcing options and bioactive surface modifications. Mineralized cancellous allograft (MCA) was used to provide a comparative reference to the current clinical standard for osteoconductive scaffolds. Percent bone volume within the defect was assessed 4 weeks after implantation using both MicroCT and limited histomorphometry. Bone formed at the periphery of all scaffolds with varying levels of radial ingrowth. MCA produced a rapid and advanced stage of bone formation and remodeling throughout the defect in 4 weeks, greatly exceeding the performance of all polymer scaffolds. Two scaffold constructs, TyrPC(PL)/TCP and PPF4(SLA)/HA(PLGA) (Dip), proved to be significantly better than alternative PLGA and PLCL scaffolds, justifying further development. MCA remains the current standard for osteoconductive scaffolds.

Improving the permeability of lyophilized collagen-hydroxyapatite scaffolds for cell-based bone regeneration with a gelatin porogen.

PubMed

Villa, Max M; Wang, Liping; Huang, Jianping; Rowe, David W; Wei, Mei

2016-11-01

Bone tissue engineering using biomaterial scaffolds and culture-expanded osteoprogenitor cells has been demonstrated in several studies; however, it is not yet a clinical reality. One challenge is the optimal design of scaffolds for cell delivery and the identification of scaffold parameters that can delineate success and failure in vivo. Motivated by a previous experiment in which a batch of lyophilized collagen-hydroxyapatite (HA) scaffolds displayed modest bone formation in vivo, despite having large pores and high porosity, we began to investigate the effect of scaffold permeability on bone formation. Herein, we fabricated scaffolds with a permeability of 2.17 ± 1.63 × 10 -9 m 4 /(N s) and fourfold higher using a sacrificial gelatin porogen. Scaffolds were seeded with mouse bone marrow stromal cells carrying a fluorescent reporter for osteoblast differentiation and implanted into critical-size calvarial defects in immunodeficient mice. The porogen scaffold group containing a 1:1 ratio of solids to beads was significantly more radiopaque than the scaffold group without the bead porogen 3 weeks after implantation. Quantitative histomorphometry uncovered the same trend between the 1:1 group and scaffolds without porogen found in the radiographic data; however, this was not statistically significant here. Taken together, the X-ray and histology suggest that the 1:1 ratio of porogen to scaffold solids, resulting in a fourfold increase in permeability, may enhance bone formation when compared to scaffolds without porogen. Scaffold permeability can be a useful quality control measure before implantation and this practice should improve the consistency and efficacy of cell-based bone tissue engineering. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1580-1590, 2016. © 2015 Wiley Periodicals, Inc.

Indirect three-dimensional printing of synthetic polymer scaffold based on thermal molding process.

PubMed

Park, Jeong Hun; Jung, Jin Woo; Kang, Hyun-Wook; Cho, Dong-Woo

2014-06-01

One of the major issues in tissue engineering has been the development of three-dimensional (3D) scaffolds, which serve as a structural template for cell growth and extracellular matrix formation. In scaffold-based tissue engineering, 3D printing (3DP) technology has been successfully applied for the fabrication of complex 3D scaffolds by using both direct and indirect techniques. In principle, direct 3DP techniques rely on the straightforward utilization of the final scaffold materials during the actual scaffold fabrication process. In contrast, indirect 3DP techniques use a negative mold based on a scaffold design, to which the desired biomaterial is cast and then sacrificed to obtain the final scaffold. Such indirect 3DP techniques generally impose a solvent-based process for scaffold fabrication, resulting in a considerable increase in the fabrication time and poor mechanical properties. In addition, the internal architecture of the resulting scaffold is affected by the properties of the biomaterial solution. In this study, we propose an advanced indirect 3DP technique using projection-based micro-stereolithography and an injection molding system (IMS) in order to address these challenges. The scaffold was fabricated by a thermal molding process using IMS to overcome the limitation of the solvent-based molding process in indirect 3DP techniques. The results indicate that the thermal molding process using an IMS has achieved a substantial reduction in scaffold fabrication time and has also provided the scaffold with higher mechanical modulus and strength. In addition, cell adhesion and proliferation studies have indicated no significant difference in cell activity between the scaffolds prepared by solvent-based and thermal molding processes.

Fabrication of 3D porous SF/β-TCP hybrid scaffolds for bone tissue reconstruction.

PubMed

Park, Hyun Jung; Min, Kyung Dan; Lee, Min Chae; Kim, Soo Hyeon; Lee, Ok Joo; Ju, Hyung Woo; Moon, Bo Mi; Lee, Jung Min; Park, Ye Ri; Kim, Dong Wook; Jeong, Ju Yeon; Park, Chan Hum

2016-07-01

Bio-ceramic is a biomaterial actively studied in the field of bone tissue engineering. But, only certain ceramic materials can resolve the corrosion problem and possess the biological affinity of conventional metal biomaterials. Therefore, the recent development of composites of hybrid composites and polymers has been widely studied. In this study, we aimed to select the best scaffold of silk fibroin and β-TCP hybrid for bone tissue engineering. We fabricated three groups of scaffold such as SF (silk fibroin scaffold), GS (silk fibroin/small granule size of β-TCP scaffold) and GM (silk fibroin/medium granule size of β-TCP scaffold), and we compared the characteristics of each group. During characterization of the scaffold, we used scanning electron microscopy (SEM) and a Fourier transform infrared spectroscopy (FTIR) for structural analysis. We compared the physiological properties of the scaffold regarding the swelling ratio, water uptake and porosity. To evaluate the mechanical properties, we examined the compressive strength of the scaffold. During in vitro testing, we evaluated cell attachment and cell proliferation (CCK-8). Finally, we confirmed in vivo new bone regeneration from the implanted scaffolds using histological staining and micro-CT. From these evaluations, the fabricated scaffold demonstrated high porosity with good inter-pore connectivity, showed good biocompatibility and high compressive strength and modulus. In particular, the present study indicates that the GM scaffold using β-TCP accelerates new bone regeneration of implanted scaffolds. Accordingly, our scaffold is expected to act a useful application in the field of bone tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1779-1787, 2016. © 2016 Wiley Periodicals, Inc.

Preparation of aminated chitosan/alginate scaffold containing halloysite nanotubes with improved cell attachment.

PubMed

Amir Afshar, Hamideh; Ghaee, Azadeh

2016-10-20

The chemical nature of biomaterials play important role in cell attachment, proliferation and migration in tissue engineering. Chitosan and alginate are biodegradable and biocompatible polymers used as scaffolds for various medical and clinical applications. Amine groups of chitosan scaffolds play an important role in cell attachment and water adsorption but also associate with alginate carboxyl groups via electrostatic interactions and hydrogen bonding, consequently the activity of amine groups in the scaffold decreases. In this study, chitosan/alginate/halloysite nanotube (HNTs) composite scaffolds were prepared using a freeze-drying method. Amine treatment on the scaffold occurred through chemical methods, which in turn caused the hydroxyl groups to be replaced with carboxyl groups in chitosan and alginate, after which a reaction between ethylenediamine, 1-ethyl-3,(3-dimethylaminopropyl) carbodiimide (EDC) and scaffold triggered the amine groups to connect to the carboxyl groups of chitosan and alginate. The chemical structure, morphology and mechanical properties of the composite scaffolds were investigated by FTIR, CHNS, SEM/EDS and compression tests. The electrostatic attraction and hydrogen bonding between chitosan, alginate and halloysite was confirmed by FTIR spectroscopy. Chitosan/alginate/halloysite scaffolds exhibit significant enhancement in compressive strength compared with chitosan/alginate scaffolds. CHNS and EDS perfectly illustrate that amine groups were effectively introduced in the aminated scaffold. The growth and cell attachment of L929 cells as well as the cytotoxicity of the scaffolds were investigated by SEM and Alamar Blue (AB). The results indicated that the aminated chitosan/alginate/halloysite scaffold has better cell growth and cell adherence in comparison to that of chitosan/alginate/halloysite samples. Aminated chitosan/alginate/halloysite composite scaffolds exhibit great potential for applications in tissue engineering, ideally in cell culture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Construction of a 3D rGO-collagen hybrid scaffold for enhancement of the neural differentiation of mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Guo, Weibo; Wang, Shu; Yu, Xin; Qiu, Jichuan; Li, Jianhua; Tang, Wei; Li, Zhou; Mou, Xiaoning; Liu, Hong; Wang, Zhonglin

2016-01-01

The cell-material interface is one of the most important considerations in designing a high-performance tissue engineering scaffold because the surface of the scaffold can determine the fate of stem cells. A conductive surface is required for a scaffold to direct stem cells toward neural differentiation. However, most conductive polymers are toxic and not amenable to biological degradation, which restricts the design of neural tissue engineering scaffolds. In this study, we used a bioactive three-dimensional (3D) porcine acellular dermal matrix (PADM), which is mainly composed of type I collagen, as a basic material and successfully assembled a layer of reduced graphene oxide (rGO) nanosheets on the surface of the PADM channels to obtain a porous 3D, biodegradable, conductive and biocompatible PADM-rGO hybrid neural tissue engineering scaffold. Compared with the PADM scaffold, assembling the rGO into the scaffold did not induce a significant change in the microstructure but endowed the PADM-rGO hybrid scaffold with good conductivity. A comparison of the neural differentiation of rat bone-marrow-derived mesenchymal stem cells (MSCs) was performed by culturing the MSCs on PADM and PADM-rGO scaffolds in neuronal culture medium, followed by the determination of gene expression and immunofluorescence staining. The results of both the gene expression and protein level assessments suggest that the rGO-assembled PADM scaffold may promote the differentiation of MSCs into neuronal cells with higher protein and gene expression levels after 7 days under neural differentiation conditions. This study demonstrated that the PADM-rGO hybrid scaffold is a promising scaffold for neural tissue engineering; this scaffold can not only support the growth of MSCs at a high proliferation rate but also enhance the differentiation of MSCs into neural cells.The cell-material interface is one of the most important considerations in designing a high-performance tissue engineering scaffold because the surface of the scaffold can determine the fate of stem cells. A conductive surface is required for a scaffold to direct stem cells toward neural differentiation. However, most conductive polymers are toxic and not amenable to biological degradation, which restricts the design of neural tissue engineering scaffolds. In this study, we used a bioactive three-dimensional (3D) porcine acellular dermal matrix (PADM), which is mainly composed of type I collagen, as a basic material and successfully assembled a layer of reduced graphene oxide (rGO) nanosheets on the surface of the PADM channels to obtain a porous 3D, biodegradable, conductive and biocompatible PADM-rGO hybrid neural tissue engineering scaffold. Compared with the PADM scaffold, assembling the rGO into the scaffold did not induce a significant change in the microstructure but endowed the PADM-rGO hybrid scaffold with good conductivity. A comparison of the neural differentiation of rat bone-marrow-derived mesenchymal stem cells (MSCs) was performed by culturing the MSCs on PADM and PADM-rGO scaffolds in neuronal culture medium, followed by the determination of gene expression and immunofluorescence staining. The results of both the gene expression and protein level assessments suggest that the rGO-assembled PADM scaffold may promote the differentiation of MSCs into neuronal cells with higher protein and gene expression levels after 7 days under neural differentiation conditions. This study demonstrated that the PADM-rGO hybrid scaffold is a promising scaffold for neural tissue engineering; this scaffold can not only support the growth of MSCs at a high proliferation rate but also enhance the differentiation of MSCs into neural cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06602f

Formation of Neural Networks in 3D Scaffolds Fabricated by Means of Laser Microstereolithography.

PubMed

Vedunova, M V; Timashev, P S; Mishchenko, T A; Mitroshina, E V; Koroleva, A V; Chichkov, B N; Panchenko, V Ya; Bagratashvili, V N; Mukhina, I V

2016-08-01

We developed and tested new 3D scaffolds for neurotransplantation. Scaffolds of predetermined architectonic were prepared using microstereolithography technique. Scaffolds were highly biocompatible with the nervous tissue cells. In vitro studies showed that the material of fabricated scaffolds is not toxic for dissociated brain cells and promotes the formation of functional neural networks in the matrix. These results demonstrate the possibility of fabrication of tissue-engineering constructs for neurotransplantation based on created scaffolds.

Efficacy of chitosan and sodium alginate scaffolds for repair of spinal cord injury in rats

PubMed Central

Yao, Zi-ang; Chen, Feng-jia; Cui, Hong-li; Lin, Tong; Guo, Na; Wu, Hai-ge

2018-01-01

Spinal cord injury results in the loss of motor and sensory pathways and spontaneous regeneration of adult mammalian spinal cord neurons is limited. Chitosan and sodium alginate have good biocompatibility, biodegradability, and are suitable to assist the recovery of damaged tissues, such as skin, bone and nerve. Chitosan scaffolds, sodium alginate scaffolds and chitosan-sodium alginate scaffolds were separately transplanted into rats with spinal cord hemisection. Basso-Beattie-Bresnahan locomotor rating scale scores and electrophysiological results showed that chitosan scaffolds promoted recovery of locomotor capacity and nerve transduction of the experimental rats. Sixty days after surgery, chitosan scaffolds retained the original shape of the spinal cord. Compared with sodium alginate scaffolds- and chitosan-sodium alginate scaffolds-transplanted rats, more neurofilament-H-immunoreactive cells (regenerating nerve fibers) and less glial fibrillary acidic protein-immunoreactive cells (astrocytic scar tissue) were observed at the injury site of experimental rats in chitosan scaffold-transplanted rats. Due to the fast degradation rate of sodium alginate, sodium alginate scaffolds and composite material scaffolds did not have a supporting and bridging effect on the damaged tissue. Above all, compared with sodium alginate and composite material scaffolds, chitosan had better biocompatibility, could promote the regeneration of nerve fibers and prevent the formation of scar tissue, and as such, is more suitable to help the repair of spinal cord injury. PMID:29623937

Partially nanofibrous architecture of 3D tissue engineering scaffolds.

PubMed

Wei, Guobao; Ma, Peter X

2009-11-01

An ideal tissue-engineering scaffold should provide suitable pores and appropriate pore surface to induce desired cellular activities and to guide 3D tissue regeneration. In the present work, we have developed macroporous polymer scaffolds with varying pore wall architectures from smooth (solid), microporous, partially nanofibrous, to entirely nanofibrous ones. All scaffolds are designed to have well-controlled interconnected macropores, resulting from leaching sugar sphere template. We examine the effects of material composition, solvent, and phase separation temperature on the pore surface architecture of 3D scaffolds. In particular, phase separation of PLLA/PDLLA or PLLA/PLGA blends leads to partially nanofibrous scaffolds, in which PLLA forms nanofibers and PDLLA or PLGA forms the smooth (solid) surfaces on macropore walls, respectively. Specific surface areas are measured for scaffolds with similar macroporosity but different macropore wall architectures. It is found that the pore wall architecture predominates the total surface area of the scaffolds. The surface area of a partially nanofibrous scaffold increases linearly with the PLLA content in the polymer blend. The amounts of adsorbed proteins from serum increase with the surface area of the scaffolds. These macroporous scaffolds with adjustable pore wall surface architectures may provide a platform for investigating the cellular responses to pore surface architecture, and provide us with a powerful tool to develop superior scaffolds for various tissue-engineering applications.

Improvement of biomaterials used in tissue engineering by an ageing treatment.

PubMed

Acevedo, Cristian A; Díaz-Calderón, Paulo; Enrione, Javier; Caneo, María J; Palacios, Camila F; Weinstein-Oppenheimer, Caroline; Brown, Donald I

2015-04-01

Biomaterials based on crosslinked sponges of biopolymers have been extensively used as scaffolds to culture mammal cells. It is well known that single biopolymers show significant change over time due to a phenomenon called physical ageing. In this research, it was verified that scaffolds used for skin tissue engineering (based on gelatin, chitosan and hyaluronic acid) express an ageing-like phenomenon. Treatments based on ageing of scaffolds improve the behavior of skin-cells for tissue engineering purposes. Physical ageing of dry scaffolds was studied by differential scanning calorimetry and was modeled with ageing kinetic equations. In addition, the physical properties of wet scaffolds also changed with the ageing treatments. Scaffolds were aged up to 3 weeks, and then skin-cells (fibroblasts) were seeded on them. Results indicated that adhesion, migration, viability, proliferation and spreading of the skin-cells were affected by the scaffold ageing. The best performance was obtained with a 2-week aged scaffold (under cell culture conditions). The cell viability inside the scaffold was increased from 60% (scaffold without ageing treatment) to 80%. It is concluded that biopolymeric scaffolds can be modified by means of an ageing treatment, which changes the behavior of the cells seeded on them. The ageing treatment under cell culture conditions might become a bioprocess to improve the scaffolds used for tissue engineering and regenerative medicine.

Chitosan-Based Bilayer Hydroxyapatite Nanorod Composite Scaffolds for Osteochondral Regeneration

NASA Astrophysics Data System (ADS)

Swanson, Shawn

Osteochondral defects involve injury to bone and cartilage. As articular cartilage is worn down, bone in the joint begins to rub together, causing bone spurs. This is known as osteoarthritis, and is a common issue among the aging population. This problem presents an interesting opportunity for tissue engineering. Tissue engineering is an approach to treatment of tissue defects where synthetic, three dimensional (3-D) scaffolds are implanted in a defect to facilitate healing. The osteochondral scaffold consists of two regions in the form of a bilayer scaffold- one to mimic bone with osteoconductive properties, and one to mimic cartilage with biomimetic properties. One approach to improving the osteoconductivity of tissue engineering scaffolds is the addition of hydroxyapatite (HAp), the main mineral phase in bone. HAp with nanorod morphology is desirable because it is biomimetic for the calcium phosphate found in bone. Incorporating HAp nanorods in bone tissue engineering scaffolds to form a composite material may increase scaffold osteoconductivity. The cartilage scaffold is fabricated from chitosan and hyaluronic acid (HA). HA is a known component of cartilage and thus is biomimetic. The bilayer scaffolds were seeded with osteoblast-like MG-63 cells to investigate cell migration and were evaluated with Alamar Blue proliferation assay. The cells successfully migrated to the bone region of the scaffold, indicating that the bilayer scaffold provides a promising osteochondral scaffold.

The Osteogenesis of Bone Marrow Stem Cells on mPEG-PCL-mPEG/Hydroxyapatite Composite Scaffold via Solid Freeform Fabrication

PubMed Central

Liao, Han-Tsung; Jiang, Cho-Pei

2014-01-01

The study described a novel bone tissue scaffold fabricated by computer-aided, air pressure-aided deposition system to control the macro- and microstructure precisely. The porcine bone marrow stem cells (PBMSCs) seeded on either mPEG-PCL-mPEG (PCL) or mPEG-PCL-mPEG/hydroxyapatite (PCL/HA) composite scaffold were cultured under osteogenic medium to test the ability of osteogenesis in vitro. The experimental outcomes indicated that both scaffolds possessed adequate pore size, porosity, and hydrophilicity for the attachment and proliferation of PBMSCs and the PBMSCs expressed upregulated genes of osteogensis and angiogenesis in similar manner on both scaffolds. The major differences between these two types of the scaffolds were the addition of HA leading to higher hardness of PCL/HA scaffold, cell proliferation, and VEGF gene expression in PCL/HA scaffold. However, the in vivo bone forming efficacy between PBMSCs seeded PCL and PCL/HA scaffold was different from the in vitro results. The outcome indicated that the PCL/HA scaffold which had bone-mimetic environment due to the addition of HA resulted in better bone regeneration and mechanical strength than those of PCL scaffold. Therefore, providing a bone-mimetic scaffold is another crucial factor for bone tissue engineering in addition to the biocompatibility, 3D architecture with high porosity, and interpored connection. PMID:24868523

Hyaluronic acid doped-poly(3,4-ethylenedioxythiophene)/chitosan/gelatin (PEDOT-HA/Cs/Gel) porous conductive scaffold for nerve regeneration.

PubMed

Wang, Shuping; Guan, Shui; Zhu, Zhibo; Li, Wenfang; Liu, Tianqing; Ma, Xuehu

2017-02-01

Conducting polymer, as a "smart" biomaterial, has been increasingly used to construct tissue engineered scaffold for nerve tissue regeneration. In this study, a novel porous conductive scaffold was prepared by incorporating conductive hyaluronic acid (HA) doped-poly(3,4-ethylenedioxythiophene) (PEDOT-HA) nanoparticles into a chitosan/gelatin (Cs/Gel) matrix. The physicochemical characteristics of Cs/Gel scaffold with 0-10wt% PEDOT-HA were analyzed and the results indicated that the incorporation of PEDOT-HA into scaffold increased the electrical and mechanical properties while decreasing the porosity and water absorption. Moreover, in vitro biodegradation of scaffold displayed a declining trend with the PEDOT-HA content increased. About the biocompatibility of conductive scaffold, neuron-like rat phaeochromocytoma (PC12) cells were cultured in scaffold to evaluate cell adhesion and growth. 8% PEDOT-HA/Cs/Gel scaffold had a higher cell adhesive efficiency and cell viability than the other conductive scaffolds. Furthermore, cells in the scaffold with 8wt% PEDOT-HA expressed higher synapse growth gene of GAP43 and SYP compared with Cs/Gel control group. These results suggest that 8%PEDOT-HA/Cs/Gel scaffold is an attractive cell culture conductive substrate which could support cell adhesion, survival, proliferation, and synapse growth for the application in nerve tissue regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

Biodegradable lysine-derived polyurethane scaffolds promote healing in a porcine full-thickness excisional wound model

PubMed Central

Adolph, Elizabeth J.; Pollins, Alonda C.; Cardwell, Nancy L.; Davidson, Jeffrey M.; Guelcher, Scott A.; Nanney, Lillian B.

2014-01-01

Lysine-derived polyurethane scaffolds (LTI-PUR) support cutaneous wound healing in loose-skinned small animal models. Due to the physiological and anatomical similarities of human and pig skin we investigated the capacity of LTI-PUR scaffolds to support wound healing in a porcine excisional wound model. Modifications to scaffold design included the addition of carboxymethylcellulose (CMC) as a porogen to increase interconnectivity and an additional plasma treatment (Plasma) to decrease surface hydrophobicity. All LTI-PUR scaffold and formulations supported cellular infiltration and were biodegradable. At 15 days, CMC and Plasma scaffolds simulated increased macrophages more so than LTI PUR or no treatment. This response was consistent with macrophage-mediated oxidative degradation of the lysine component of the scaffolds. Cell proliferation was similar in control and scaffold treated wounds at 8 and 15 days. Neither apoptosis nor blood vessel area density showed significant differences in the presence of any of the scaffold variations compared to untreated wounds, providing further evidence that these synthetic biomaterials had no adverse effects on those pivotal wound healing processes. During the critical phase of granulation tissue formation in full thickness porcine excisional wounds, LTI-PUR scaffolds supported tissue infiltration, while undergoing biodegradation. Modifications to scaffold fabrication modify the reparative process. This study emphasizes the biocompatibility and favorable cellular responses of PUR scaffolding formulations in a clinically relevant animal model. PMID:25290884

Nano-biphasic calcium phosphate/polyvinyl alcohol composites with enhanced bioactivity for bone repair via low-temperature three-dimensional printing and loading with platelet-rich fibrin

PubMed Central

Wang, Chunmei; Zhang, Shuaishuai; Li, Donglin; Wang, Jimeng; Cao, Tianqing; Bi, Long; Pei, Guoxian

2018-01-01

Background and aim As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals. Methods Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures. Results The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits. Conclusion These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects. PMID:29416332

Nano-biphasic calcium phosphate/polyvinyl alcohol composites with enhanced bioactivity for bone repair via low-temperature three-dimensional printing and loading with platelet-rich fibrin.

PubMed

Song, Yue; Lin, Kaifeng; He, Shu; Wang, Chunmei; Zhang, Shuaishuai; Li, Donglin; Wang, Jimeng; Cao, Tianqing; Bi, Long; Pei, Guoxian

2018-01-01

As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals. Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures. The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits. These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects.

Evaluation of 3D-Printed Polycaprolactone Scaffolds Coated with Freeze-Dried Platelet-Rich Plasma for Bone Regeneration.

PubMed

Li, Junda; Chen, Meilin; Wei, Xiaoying; Hao, Yishan; Wang, Jinming

2017-07-19

Three-dimensional printing is one of the most promising techniques for the manufacturing of scaffolds for bone tissue engineering. However, a pure scaffold is limited by its biological properties. Platelet-rich plasma (PRP) has been shown to have the potential to improve the osteogenic effect. In this study, we improved the biological properties of scaffolds by coating 3D-printed polycaprolactone (PCL) scaffolds with freeze-dried and traditionally prepared PRP, and we evaluated these scaffolds through in vitro and in vivo experiments. In vitro, we evaluated the interaction between dental pulp stem cells (DPSCs) and the scaffolds by measuring cell proliferation, alkaline phosphatase (ALP) activity, and osteogenic differentiation. The results showed that freeze-dried PRP significantly enhanced ALP activity and the mRNA expression levels of osteogenic genes (ALP, RUNX2 (runt-related gene-2), OCN (osteocalcin), OPN (osteopontin)) of DPSCs ( p < 0.05). In vivo, 5 mm calvarial defects were created, and the PRP-PCL scaffolds were implanted. The data showed that compared with traditional PRP-PCL scaffolds or bare PCL scaffolds, the freeze-dried PRP-PCL scaffolds induced significantly greater bone formation ( p < 0.05). All these data suggest that coating 3D-printed PCL scaffolds with freeze-dried PRP can promote greater osteogenic differentiation of DPSCs and induce more bone formation, which may have great potential in future clinical applications.

Bone engineering in dog mandible: Coculturing mesenchymal stem cells with endothelial progenitor cells in a composite scaffold containing vascular endothelial growth factor.

PubMed

Khojasteh, Arash; Fahimipour, Farahnaz; Jafarian, Mohammad; Sharifi, Davoud; Jahangir, Shahrbanoo; Khayyatan, Fahimeh; Baghaban Eslaminejad, Mohamadreza

2017-10-01

We sought to assess the effects of coculturing mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) in the repair of dog mandible bone defects. The cells were delivered in β-tricalcium phosphate scaffolds coated with poly lactic co-glycolic acid microspheres that gradually release vascular endothelial growth factor (VEGF). The complete scaffold and five partial scaffolds were implanted in bilateral mandibular body defects in eight beagles. The scaffolds were examined histologically and morphometrically 8 weeks after implantation. Histologic staining of the decalcified scaffolds demonstrated that bone formation was greatest in the VEGF/MSC scaffold (63.42 ± 1.67), followed by the VEGF/MSC/EPC (47.8 ± 1.87) and MSC/EPC (45.21 ± 1.6) scaffolds, the MSC scaffold (34.59 ± 1.49), the VEGF scaffold (20.03 ± 1.29), and the untreated scaffold (7.24 ± 0.08). Hence, the rate of new bone regeneration was highest in scaffolds containing MSC, either mixed with EPC or incorporating VEGF. Adding both EPC and VEGF with the MSC was not necessary. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1767-1777, 2017. © 2016 Wiley Periodicals, Inc.

The effect of controlled release of PDGF-BB from heparin-conjugated electrospun PCL/gelatin scaffolds on cellular bioactivity and infiltration

PubMed Central

Lee, Jongman; Yoo, James J.; Atala, Anthony; Lee, Sang Jin

2013-01-01

Heparin-conjugated electrospun poly(ε-caprolactone) (PCL)/gelatin scaffolds were developed to provide controlled release of platelet-derived growth factor-BB (PDGF-BB) and allow prolonged bioactivity of this molecule. A mixture of PCL and gelatin was electrospun into three different morphologies. Next, heparin molecules were conjugated to the reactive surface of the scaffolds. This heparin-conjugated scaffold allowed the immobilization of PDGF-BB via electrostatic interaction. In vitro PDGF-BB release profiles indicated that passive physical adsorption of PDGF-BB to non-heparinized scaffolds resulted in an initial burst release of PDGF-BB within 5 days, which then leveled off. However, electrostatic interaction between PDGF-BB and the heparin-conjugated scaffolds gave rise to a sustained release of PDGF-BB over the course of 20 days without an initial burst. Moreover, PDGF-BB that was strongly bound to the heparin-conjugated scaffolds enhanced smooth muscle cell (SMC) proliferation. In addition, scaffolds composed of 3.0 µm diameter fibers that were immobilized with PDGF-BB accelerated SMC infiltration into the scaffold when compared to scaffolds composed of smaller diameter fibers or scaffolds that did not release PDGF-BB. We concluded that the combination of the large pore structure in the scaffolds and the heparin-mediated delivery of PDGF-BB provided the most effective cellular interactions through synergistic physical and chemical cues. PMID:22770570

An Adaptive Scaffolding E-Learning System for Middle School Students' Physics Learning

ERIC Educational Resources Information Center

Chen, Ching-Huei

2014-01-01

This study presents a framework that utilizes cognitive and motivational aspects of learning to design an adaptive scaffolding e-learning system. It addresses scaffolding processes and conditions for designing adaptive scaffolds. The features and effectiveness of this adaptive scaffolding e-learning system are discussed and evaluated. An…

Teenaged Internet Tutors' Use of Scaffolding with Older Learners

ERIC Educational Resources Information Center

Tambaum, Tiina

2017-01-01

This study analyses how teenaged instructors paired with older learners make use of scaffolding. Video data were categorised according to 15 types of direct scaffolding tactics, indirect scaffolding, and unused scaffolding opportunities. The results show that a teenager who is unprepared for the role of an instructor of Internet skills for older…

Accounting for structural compliance in nanoindentation measurements of bioceramic bone scaffolds

Treesearch

Juan Vivanco; Joseph E. Jakes; Josh Slane; Heidi-Lynn Ploeg

2014-01-01

Structural properties have been shown to be critical in the osteoconductive capacity and strength of bioactive ceramic bone scaffolds. Given the cellular foam-like structure of bone scaffolds, nanoindentation has been used as a technique to assess the mechanical properties of individual components of the scaffolds. Nevertheless, nanoindents placed on scaffolds may...

Effects of Argument Scaffolding and Source Credibility on Science Text Comprehension

ERIC Educational Resources Information Center

Lin, Tzu-Jung; Horng, Ruey-Yun; Anderson, Richard C.

2014-01-01

This study investigated the effects of argument scaffolding and source credibility on science text comprehension. Eighty-seven college students were randomly assigned to an argument scaffolding activity, or no scaffolding, and read 2 science texts, attributed to a high- or a low-credibility source. The argument-scaffolding group recalled less…

In vitro evaluation of chitosan/poly(lactic acid-glycolic acid) sintered microsphere scaffolds for bone tissue engineering.

PubMed

Jiang, Tao; Abdel-Fattah, Wafa I; Laurencin, Cato T

2006-10-01

A three-dimensional (3-D) scaffold is one of the major components in many tissue engineering approaches. We developed novel 3-D chitosan/poly(lactic acid-glycolic acid) (PLAGA) composite porous scaffolds by sintering together composite chitosan/PLAGA microspheres for bone tissue engineering applications. Pore sizes, pore volume, and mechanical properties of the scaffolds can be manipulated by controlling fabrication parameters, including sintering temperature and sintering time. The sintered microsphere scaffolds had a total pore volume between 28% and 37% with median pore size in the range 170-200microm. The compressive modulus and compressive strength of the scaffolds are in the range of trabecular bone making them suitable as scaffolds for load-bearing bone tissue engineering. In addition, MC3T3-E1 osteoblast-like cells proliferated well on the composite scaffolds as compared to PLAGA scaffolds. It was also shown that the presence of chitosan on microsphere surfaces increased the alkaline phosphatase activity of the cells cultured on the composite scaffolds and up-regulated gene expression of alkaline phosphatase, osteopontin, and bone sialoprotein.

Development of Novel Biocomposite Scaffold of Chitosan-Gelatin/Nanohydroxyapatite for Potential Bone Tissue Engineering Applications

NASA Astrophysics Data System (ADS)

Dan, Yang; Liu, Ouyang; Liu, Yong; Zhang, Yuan-Yuan; Li, Shuai; Feng, Xiao-bo; Shao, Zeng-wu; Yang, Cao; Yang, Shu-Hua; Hong, Ji-bo

2016-11-01

In this study, a three-dimensional chitosan-gelatin/nanohydroxyapatite (ChG/nHaP) scaffold was successfully fabricated and characterized in terms of swelling, degradation, cell proliferation, cell attachment, and mineralization characterizations. The ChG/nHaP scaffold was fabricated with a mean pore size of 100-180 μm. Our results showed that the physicochemical and biological properties of the scaffolds were affected by the presence of HaP. The swelling and degradation characteristics of the ChG scaffold were remarkably decreased by the addition of HaP. On the other hand, the presence of HaP remarkably improved the MC3T3-E1 cell attachment and cell growth in the scaffold membrane. The biocompatible nature of the ChG/nHaP scaffold leads to the development of finely scaled mineral deposits on the scaffold membrane. Thus, HaP played an important role in improving the biological performance of the scaffold. Therefore, the ChG/nHaP scaffold could be applied as a suitable material for bone tissue engineering applications.

Comparative study of chitosan and chitosan-gelatin scaffold for tissue engineering

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Dehiya, Brijnandan S.; Sindhu, Anil

2017-12-01

A number of orthopedic disorders and bone defect issues are solved by scaffold-based therapy in tissue engineering. The biocompatibility of chitosan (polysaccharide) and its similarity with glycosaminoglycan makes it a bone-grafting material. The current work focus on the synthesis of chitosan and chitosan-gelatin scaffold for hard tissue engineering. The chitosan and chitosan-gelatin scaffold have shown improved specific surface area, density, porosity, mechanical properties, biodegradability and absorption. These scaffolds can lead to the development or artificial fabrication of hard tissue alternates. The porous scaffold samples were prepared by freeze-drying method. The microstructure, mechanical and degradable properties of chitosan and chitosan-gelatin scaffolds were analyzed and results revealed that the scaffolds prepared from chitosan-gelatin can be utilized as a useful matrix for tissue engineering.

Influence of Additive Manufactured Scaffold Architecture on the Distribution of Surface Strains and Fluid Flow Shear Stresses and Expected Osteochondral Cell Differentiation

PubMed Central

Hendrikson, Wim J.; Deegan, Anthony J.; Yang, Ying; van Blitterswijk, Clemens A.; Verdonschot, Nico; Moroni, Lorenzo; Rouwkema, Jeroen

2017-01-01

Scaffolds for regenerative medicine applications should instruct cells with the appropriate signals, including biophysical stimuli such as stress and strain, to form the desired tissue. Apart from that, scaffolds, especially for load-bearing applications, should be capable of providing mechanical stability. Since both scaffold strength and stress–strain distributions throughout the scaffold depend on the scaffold’s internal architecture, it is important to understand how changes in architecture influence these parameters. In this study, four scaffold designs with different architectures were produced using additive manufacturing. The designs varied in fiber orientation, while fiber diameter, spacing, and layer height remained constant. Based on micro-CT (μCT) scans, finite element models (FEMs) were derived for finite element analysis (FEA) and computational fluid dynamics (CFD). FEA of scaffold compression was validated using μCT scan data of compressed scaffolds. Results of the FEA and CFD showed a significant impact of scaffold architecture on fluid shear stress and mechanical strain distribution. The average fluid shear stress ranged from 3.6 mPa for a 0/90 architecture to 6.8 mPa for a 0/90 offset architecture, and the surface shear strain from 0.0096 for a 0/90 offset architecture to 0.0214 for a 0/90 architecture. This subsequently resulted in variations of the predicted cell differentiation stimulus values on the scaffold surface. Fluid shear stress was mainly influenced by pore shape and size, while mechanical strain distribution depended mainly on the presence or absence of supportive columns in the scaffold architecture. Together, these results corroborate that scaffold architecture can be exploited to design scaffolds with regions that guide specific tissue development under compression and perfusion. In conjunction with optimization of stimulation regimes during bioreactor cultures, scaffold architecture optimization can be used to improve scaffold design for tissue engineering purposes. PMID:28239606

Mesoporous bioactive glass nanolayer-functionalized 3D-printed scaffolds for accelerating osteogenesis and angiogenesis

NASA Astrophysics Data System (ADS)

Zhang, Yali; Xia, Lunguo; Zhai, Dong; Shi, Mengchao; Luo, Yongxiang; Feng, Chun; Fang, Bing; Yin, Jingbo; Chang, Jiang; Wu, Chengtie

2015-11-01

The hierarchical microstructure, surface and interface of biomaterials are important factors influencing their bioactivity. Porous bioceramic scaffolds have been widely used for bone tissue engineering by optimizing their chemical composition and large-pore structure. However, the surface and interface of struts in bioceramic scaffolds are often ignored. The aim of this study is to incorporate hierarchical pores and bioactive components into the bioceramic scaffolds by constructing nanopores and bioactive elements on the struts of scaffolds and further improve their bone-forming activity. Mesoporous bioactive glass (MBG) modified β-tricalcium phosphate (MBG-β-TCP) scaffolds with a hierarchical pore structure and a functional strut surface (~100 nm of MBG nanolayer) were successfully prepared via 3D printing and spin coating. The compressive strength and apatite-mineralization ability of MBG-β-TCP scaffolds were significantly enhanced as compared to β-TCP scaffolds without the MBG nanolayer. The attachment, viability, alkaline phosphatase (ALP) activity, osteogenic gene expression (Runx2, BMP2, OPN and Col I) and protein expression (OPN, Col I, VEGF, HIF-1α) of rabbit bone marrow stromal cells (rBMSCs) as well as the attachment, viability and angiogenic gene expression (VEGF and HIF-1α) of human umbilical vein endothelial cells (HUVECs) in MBG-β-TCP scaffolds were significantly upregulated compared with conventional bioactive glass (BG)-modified β-TCP (BG-β-TCP) and pure β-TCP scaffolds. Furthermore, MBG-β-TCP scaffolds significantly enhanced the formation of new bone in vivo as compared to BG-β-TCP and β-TCP scaffolds. The results suggest that application of the MBG nanolayer to modify 3D-printed bioceramic scaffolds offers a new strategy to construct hierarchically porous scaffolds with significantly improved physicochemical and biological properties, such as mechanical properties, osteogenesis, angiogenesis and protein expression for bone tissue engineering applications, in which the incorporation of nanostructures and bioactive components into the scaffold struts synergistically play a key role in the improved bone formation.

Novel layered double hydroxides-hydroxyapatite/gelatin bone tissue engineering scaffolds: Fabrication, characterization, and in vivo study.

PubMed

Fayyazbakhsh, Fateme; Solati-Hashjin, Mehran; Keshtkar, Abbas; Shokrgozar, Mohammad Ali; Dehghan, Mohammad Mehdi; Larijani, Bagher

2017-07-01

Developing porous biodegradable scaffolds through simple methods is one of the main approaches of bone tissue engineering (BTE). In this work, a novel BTE composite containing layered double hydroxides (LDH), hydroxyapatite (HA) and gelatin (GEL) was fabricated using co-precipitation and solvent-casting methods. Physiochemical characterizations showed that the chemical composition and microstructure of the scaffolds were similar to the natural spongy bone. Interconnected macropores ranging over 100 to 600μm were observed for both scaffolds while the porosity of 90±0.12% and 92.11±0.15%, as well as, Young's modulus of 19.8±0.41 and 12.5±0.35GPa were reported for LDH/GEL and LDH-HA/GEL scaffolds, respectively. The scaffolds were degraded in deionized water after a month. The SEM images revealed that between two scaffolds, the LDH-HA/GEL with needle-like secondary HA crystals showed better bioactivity. According to the alkaline phosphatase activity and Alizarin red staining results, LDH-HA/GEL scaffolds demonstrated better bone-specific activities comparing to LDH/Gel scaffold as well as control sample (P<0.05). The rabbit adipose stem cells (ASCs) were extracted and cultured, then seeded on the LDH-HA/GEL scaffolds after confluence. Three groups of six adult rabbits were prepared: the scaffold+ASCs group, the empty scaffold group and the control group. The critical defects were made on the left radius and the scaffolds with or without ASCs were implanted there while the control group was left without any treatment. All animals were sacrificed after 12weeks. Histomorphometric results showed that the regeneration of defects was accelerated by scaffold implantation but ASC-seeding significantly improved the quality of new bone formation (P<0.05). The results confirmed the good performance of LDH-HA/GEL scaffold to induce bone regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Design of a bioresorbable polymeric scaffold for osteoblast culture

NASA Astrophysics Data System (ADS)

Ditaranto, Vincent M., Jr.

Bioresorbable polymeric scaffolds were designed for the purpose of growing rat osteosarcoma cells (ROS 17/2.8) using the compression molding method. The material used in the construction of the scaffolds was a mixture of polycaprolactone (PCL), Hydroxyapatite (HA), Glycerin (GL) and salt (NaCl) for porosity. The concentration of the several materials utilized, was determined by volume. Past research at the University of Massachusetts Lowell (UML) has successfully utilized the compression molding method for the construction of scaffolds, but was unable to accomplish the goal of long term cell survival and complete cellular proliferation throughout a three dimensional scaffold. This research investigated various concentrations of the materials and molding temperatures used for the manufacture of scaffolds in order to improve the scaffold design and address those issues. The design of the scaffold using the compression molding process is detailed in the Method and Materials section of this thesis. The porogen (salt) used for porosity was suspected as a possible source of contamination causing cell apoptosis in past studies. This research addressed the issues for cell survival and proliferation throughout a three dimensional scaffold. The leaching of the salt was one major design modification. This research successfully used ultrasonic leaching in addition to the passive method. Prior to cell culture, the scaffolds were irradiated to 2.75 Mrad, with cobalt-60 gamma radionuclide. The tissue culture consisted of two trials: (1) cell culture in scaffolds cleaned with passive leaching; (2) cell culture with scaffolds cleaned with ultrasonic leaching. Cell survival and proliferation was accomplished only with the addition of ultrasonic leaching of the scaffolds. Analysis of the scaffolds included Scanning Electron Microscopy (SEM), Nikon light microscopy and x-ray mapping of the calcium, sodium and chloride ion distribution. The cells were analyzed by Environmental Scanning Electron Microscopy (ESEM) and Nikon light microscopy. The high magnification of ESEM up to 60,000 x revealed an unexpected discovery. The osteoblasts appeared to be remodeling the PCL scaffold shown in the last two figures of this research.

Versatile three-dimensional virus-based template for dye-sensitized solar cells with improved electron transport and light harvesting.

PubMed

Chen, Po-Yen; Dang, Xiangnan; Klug, Matthew T; Qi, Jifa; Dorval Courchesne, Noémie-Manuelle; Burpo, Fred J; Fang, Nicholas; Hammond, Paula T; Belcher, Angela M

2013-08-27

By genetically encoding affinity for inorganic materials into the capsid proteins of the M13 bacteriophage, the virus can act as a template for the synthesis of nanomaterial composites for use in various device applications. Herein, the M13 bacteriophage is employed to build a multifunctional and three-dimensional scaffold capable of improving both electron collection and light harvesting in dye-sensitized solar cells (DSSCs). This has been accomplished by binding gold nanoparticles (AuNPs) to the virus proteins and encapsulating the AuNP-virus complexes in TiO2 to produce a plasmon-enhanced and nanowire (NW)-based photoanode. The NW morphology exhibits an improved electron diffusion length compared to traditional nanoparticle-based DSSCs, and the AuNPs increase the light absorption of the dye-molecules through the phenomenon of localized surface plasmon resonance. Consequently, we report a virus-templated and plasmon-enhanced DSSC with an efficiency of 8.46%, which is achieved through optimizing both the NW morphology and the concentration of AuNPs loaded into the solar cells. In addition, we propose a theoretical model that predicts the experimentally observed trends of plasmon enhancement.

Design and synthesis of nonionic copolypeptide hydrogels with reversible thermoresponsive and tunable physical properties.

PubMed

Zhang, Shanshan; Alvarez, Daniel J; Sofroniew, Michael V; Deming, Timothy J

2015-04-13

Polypeptide-based formulations that undergo liquid to hydrogel transitions upon change in temperature have become desirable targets since they can be mixed with cells or injected into tissues as liquids, and subsequently transform into rigid scaffolds or depots. Such materials have been challenging to prepare using synthetic polypeptides, especially when reversible gelation and tunable physical properties are desired. Here, we designed and prepared new nonionic diblock copolypeptide hydrogels (DCH) containing hydrophilic poly(γ-[2-(2-methoxyethoxy)ethyl]-rac-glutamate) and hydrophobic poly(l-leucine) segments, named DCHEO, and also further incorporated copolypeptide domains into DCHEO to yield unprecedented thermoresponsive DCH, named DCHT. Although previous attempts to prepare nonionic hydrogels composed solely of synthetic polypeptides have been unsuccessful, our designs yielded materials with highly reversible thermal transitions and tunable properties. Nonionic, thermoresponsive DCHT were found to support the viability of suspended mesenchymal stem cells in vitro and were able to dissolve and provide prolonged release of both hydrophilic and hydrophobic molecules. The versatility of these materials was further demonstrated by the independent molecular tuning of DCHT liquid viscosity at room temperature and DCHT hydrogel stiffness at elevated temperature, as well as the DCHT liquid to hydrogel transition temperature itself.

Type IV Collagens and Basement Membrane Diseases: Cell Biology and Pathogenic Mechanisms.

PubMed

Mao, Mao; Alavi, Marcel V; Labelle-Dumais, Cassandre; Gould, Douglas B

2015-01-01

Basement membranes are highly specialized extracellular matrices. Once considered inert scaffolds, basement membranes are now viewed as dynamic and versatile environments that modulate cellular behaviors to regulate tissue development, function, and repair. Increasing evidence suggests that, in addition to providing structural support to neighboring cells, basement membranes serve as reservoirs of growth factors that direct and fine-tune cellular functions. Type IV collagens are a major component of all basement membranes. They evolved along with the earliest multicellular organisms and have been integrated into diverse fundamental biological processes as time and evolution shaped the animal kingdom. The roles of basement membranes in humans are as complex and diverse as their distributions and molecular composition. As a result, basement membrane defects result in multisystem disorders with ambiguous and overlapping boundaries that likely reflect the simultaneous interplay and integration of multiple cellular pathways and processes. Consequently, there will be no single treatment for basement membrane disorders, and therapies are likely to be as varied as the phenotypes. Understanding tissue-specific pathology and the underlying molecular mechanism is the present challenge; personalized medicine will rely upon understanding how a given mutation impacts diverse cellular functions. Copyright © 2015 Elsevier Inc. All rights reserved.

Lipid composition dictates serum stability of reconstituted high-density lipoproteins: implications for in vivo applications.

PubMed

Gilmore, Sean F; Carpenter, Timothy S; Ingólfsson, Helgi I; Peters, Sandra K G; Henderson, Paul T; Blanchette, Craig D; Fischer, Nicholas O

2018-04-26

Nanolipoprotein particles (NLPs) are reconstituted high-density lipoproteins, consisting of a phospholipid bilayer stabilized by an apolipoprotein scaffold protein. This class of nanoparticle has been a vital tool in the study of membrane proteins, and in recent years has been increasingly used for in vivo applications. Previous work demonstrated that the composition of the lipid bilayer component affects the stability of these particles in serum solutions. In the current study, NLPs assembled with phosphatidylcholine lipids featuring different acyl chain structures were systematically tested to understand the effect that lipid composition has on NLP stability in both neat serum and cell culture media supplemented with 10% serum by volume. The time at which 50% of the particles dissociate, as well as the fraction of the initial population that remains resistant to dissociation, were correlated to key parameters obtained from all-atom simulations of the corresponding lipid bilayers. A significant correlation was observed between the compressibility modulus of the lipid bilayer and particle stability in these complex biological milieu. These results can be used as a reference to tune the stability of these versatile biological nanoparticles for in vitro and in vivo applications.

Trichocyanines: a Red-Hair-Inspired Modular Platform for Dye-Based One-Time-Pad Molecular Cryptography.

PubMed

Leone, Loredana; Pezzella, Alessandro; Crescenzi, Orlando; Napolitano, Alessandra; Barone, Vincenzo; d'Ischia, Marco

2015-06-01

Current molecular cryptography (MoCryp) systems are almost exclusively based on DNA chemistry and reports of cryptography technologies based on other less complex chemical systems are lacking. We describe herein, as proof of concept, the prototype of the first asymmetric MoCryp system, based on an 8-compound set of a novel bioinspired class of cyanine-type dyes called trichocyanines. These novel acidichromic cyanine-type dyes inspired by red hair pigments were synthesized and characterized with the aid of density functional theory (DFT) calculations. Trichocyanines consist of a modular scaffold easily accessible via an expedient condensation of 3-phenyl- or 3-methyl-2H-1,4-benzothiazines with N-dimethyl- or o-methoxyhydroxy-substituted benzaldehyde or cinnamaldehyde derivatives. The eight representative members synthesized herein can be classified as belonging to two three-state systems tunable through four different control points. This versatile dye platform can generate an expandable palette of colors and appears to be specifically suited to implement an unprecedented single-use asymmetric molecular cryptography system. With this system, we intend to pioneer the translation of digital public-key cryptography into a chemical-coding one-time-pad-like system.

Trichocyanines: a Red-Hair-Inspired Modular Platform for Dye-Based One-Time-Pad Molecular Cryptography

PubMed Central

Leone, Loredana; Pezzella, Alessandro; Crescenzi, Orlando; Napolitano, Alessandra; Barone, Vincenzo; d’Ischia, Marco

2015-01-01

Current molecular cryptography (MoCryp) systems are almost exclusively based on DNA chemistry and reports of cryptography technologies based on other less complex chemical systems are lacking. We describe herein, as proof of concept, the prototype of the first asymmetric MoCryp system, based on an 8-compound set of a novel bioinspired class of cyanine-type dyes called trichocyanines. These novel acidichromic cyanine-type dyes inspired by red hair pigments were synthesized and characterized with the aid of density functional theory (DFT) calculations. Trichocyanines consist of a modular scaffold easily accessible via an expedient condensation of 3-phenyl- or 3-methyl-2H-1,4-benzothiazines with N-dimethyl- or o-methoxyhydroxy-substituted benzaldehyde or cinnamaldehyde derivatives. The eight representative members synthesized herein can be classified as belonging to two three-state systems tunable through four different control points. This versatile dye platform can generate an expandable palette of colors and appears to be specifically suited to implement an unprecedented single-use asymmetric molecular cryptography system. With this system, we intend to pioneer the translation of digital public-key cryptography into a chemical-coding one-time-pad-like system. PMID:26246999

Unidirectionally aligned line patterns driven by entropic effects on faceted surfaces

PubMed Central

Hong, Sung Woo; Huh, June; Gu, Xiaodan; Lee, Dong Hyun; Jo, Won Ho; Park, Soojin; Xu, Ting; Russell, Thomas P.

2012-01-01

A simple, versatile approach to the directed self-assembly of block copolymers into a macroscopic array of unidirectionally aligned cylindrical microdomains on reconstructed faceted single crystal surfaces or on flexible, inexpensive polymeric replicas was discovered. High fidelity transfer of the line pattern generated from the microdomains to a master mold is also shown. A single-grained line patterns over arbitrarily large surface areas without the use of top-down techniques is demonstrated, which has an order parameter typically in excess of 0.97 and a slope error of 1.1 deg. This degree of perfection, produced in a short time period, has yet to be achieved by any other methods. The exceptional alignment arises from entropic penalties of chain packing in the facets coupled with the bending modulus of the cylindrical microdomains. This is shown, theoretically, to be the lowest energy state. The atomic crystalline ordering of the substrate is transferred, over multiple length scales, to the block copolymer microdomains, opening avenues to large-scale roll-to-roll type and nanoimprint processing of perfectly patterned surfaces and as templates and scaffolds for magnetic storage media, polarizing devices, and nanowire arrays. PMID:22307591

Using droplet-on-demand based printing to guide self-assembly in a peptide-protein based bioink

NASA Astrophysics Data System (ADS)

Hedegaard, Clara; Collin, Estelle; Redondo-Gomez, Carlos; Nguyen, Luong T. H.; Ng, Kee Woei; Castrejon-Pita, Alfonso A.; Castrejon-Pita, J. Rafael; Mata, Alvaro

2017-11-01

Tissue engineering aims to capture details of the extracellular matrix (ECM) that stimulate tissue regeneration. Advanced biofabrication techniques have enabled structural complexity, however they are restricted by the choice of material due to stringent printing requirements, leading to a lack of nanoscale control and molecular versatility. In this project, we exploit the dynamics of droplet fluid interactions combined with the co-assembly of peptide amphiphiles (PAs) with biomolecules/proteins to develop a new approach to droplet-based biofabrication. A custom-made droplet generator was developed and used to controllably dispense droplets of PA into a protein solution resulting in gel formation within milliseconds. Taking advantage of the interfacial and inertial forces during the droplet/liquid interaction, it is possible to control the co-assembly kinetics, to give rise to aligned or disordered nanofibers, hydrogel structures of different geometries and sizes, surface topographies, and higher-ordered structures made from multiple hydrogels. The process allows multiple cell types to be spatially distributed on the outside or embedded within the ECM mimetic scaffolds, whilst exhibiting high cell viability (>88%). ERC Starting Grant (STROFUNSCAFF), FP7-PEOPLE-2013-CIG Biomorph and the Royal Society.

Synthesis, characterization and toxicity studies of pyridinecarboxaldehydes and L-tryptophan derived Schiff bases and corresponding copper (II) complexes.

PubMed

Malakyan, Margarita; Babayan, Nelly; Grigoryan, Ruzanna; Sarkisyan, Natalya; Tonoyan, Vahan; Tadevosyan, Davit; Matosyan, Vladimir; Aroutiounian, Rouben; Arakelyan, Arsen

2016-01-01

Schiff bases and their metal-complexes are versatile compounds exhibiting a broad range of biological activities and thus actively used in the drug development process. The aim of the present study was the synthesis and characterization of new Schiff bases and their copper (II) complexes, derived from L-tryptophan and isomeric (2-; 3-; 4-) pyridinecarboxaldehydes, as well as the assessment of their toxicity in vitro . The optimal conditions of the Schiff base synthesis resulting in up to 75-85% yield of target products were identified. The structure-activity relationship analysis indicated that the location of the carboxaldehyde group at 2-, 3- or 4-position with regard to nitrogen of the pyridine ring in aldehyde component of the L-tryptophan derivative Schiff bases and corresponding copper complexes essentially change the biological activity of the compounds. The carboxaldehyde group at 2- and 4-positions leads to the higher cytotoxic activity, than that of at 3-position, and the presence of the copper in the complexes increases the cytotoxicity. Based on toxicity classification data, the compounds with non-toxic profile were identified, which can be used as new entities in the drug development process using Schiff base scaffold.

Molecular threading and tunable molecular recognition on DNA origami nanostructures.

PubMed

Wu, Na; Czajkowsky, Daniel M; Zhang, Jinjin; Qu, Jianxun; Ye, Ming; Zeng, Dongdong; Zhou, Xingfei; Hu, Jun; Shao, Zhifeng; Li, Bin; Fan, Chunhai

2013-08-21

The DNA origami technology holds great promise for the assembly of nanoscopic technological devices and studies of biochemical reactions at the single-molecule level. For these, it is essential to establish well controlled attachment of functional materials to predefined sites on the DNA origami nanostructures for reliable measurements and versatile applications. However, the two-sided nature of the origami scaffold has shown limitations in this regard. We hypothesized that holes of the commonly used two-dimensional DNA origami designs are large enough for the passage of single-stranded (ss)-DNA. Sufficiently long ssDNA initially located on one side of the origami should thus be able to "thread" to the other side through the holes in the origami sheet. By using an origami sheet attached with patterned biotinylated ssDNA spacers and monitoring streptavidin binding with atomic force microscopic (AFM) imaging, we provide unambiguous evidence that the biotin ligands positioned on one side have indeed threaded through to the other side. Our finding reveals a previously overlooked critical design feature that should provide new interpretations to previous experiments and new opportunities for the construction of origami structures with new functional capabilities.

Synthesis, characterization and toxicity studies of pyridinecarboxaldehydes and L-tryptophan derived Schiff bases and corresponding copper (II) complexes

PubMed Central

Malakyan, Margarita; Babayan, Nelly; Grigoryan, Ruzanna; Sarkisyan, Natalya; Tonoyan, Vahan; Tadevosyan, Davit; Matosyan, Vladimir; Aroutiounian, Rouben; Arakelyan, Arsen

2016-01-01

Schiff bases and their metal-complexes are versatile compounds exhibiting a broad range of biological activities and thus actively used in the drug development process. The aim of the present study was the synthesis and characterization of new Schiff bases and their copper (II) complexes, derived from L-tryptophan and isomeric (2-; 3-; 4-) pyridinecarboxaldehydes, as well as the assessment of their toxicity in vitro. The optimal conditions of the Schiff base synthesis resulting in up to 75-85% yield of target products were identified. The structure-activity relationship analysis indicated that the location of the carboxaldehyde group at 2-, 3- or 4-position with regard to nitrogen of the pyridine ring in aldehyde component of the L-tryptophan derivative Schiff bases and corresponding copper complexes essentially change the biological activity of the compounds. The carboxaldehyde group at 2- and 4-positions leads to the higher cytotoxic activity, than that of at 3-position, and the presence of the copper in the complexes increases the cytotoxicity. Based on toxicity classification data, the compounds with non-toxic profile were identified, which can be used as new entities in the drug development process using Schiff base scaffold. PMID:28344771

25 years and still going strong: 2'-O-(pyren-1-yl)methylribonucleotides - versatile building blocks for applications in molecular biology, diagnostics and materials science.

PubMed

Hrdlicka, Patrick J; Karmakar, Saswata

2017-11-29

Oligonucleotides (ONs) modified with 2'-O-(pyren-1-yl)methylribonucleotides have been explored for a range of applications in molecular biology, nucleic acid diagnostics, and materials science for more than 25 years. The first part of this review provides an overview of synthetic strategies toward 2'-O-(pyren-1-yl)methylribonucleotides and is followed by a summary of biophysical properties of nucleic acid duplexes modified with these building blocks. Insights from structural studies are then presented to rationalize the reported properties. In the second part, applications of ONs modified with 2'-O-(pyren-1-yl)methyl-RNA monomers are reviewed, which include detection of RNA targets, discrimination of single nucleotide polymorphisms, formation of self-assembled pyrene arrays on nucleic acid scaffolds, the study of charge transfer phenomena in nucleic acid duplexes, and sequence-unrestricted recognition of double-stranded DNA. The predictable binding mode of the pyrene moiety, coupled with the microenvironment-dependent properties and synthetic feasibility, render 2'-O-(pyren-1-yl)methyl-RNA monomers as a promising class of pyrene-functionalized nucleotide building blocks for new applications in molecular biology, nucleic acid diagnostics, and materials science.

Organic Light-Emitting Transistors: Materials, Device Configurations, and Operations.

PubMed

Zhang, Congcong; Chen, Penglei; Hu, Wenping

2016-03-09

Organic light-emitting transistors (OLETs) represent an emerging class of organic optoelectronic devices, wherein the electrical switching capability of organic field-effect transistors (OFETs) and the light-generation capability of organic light-emitting diodes (OLEDs) are inherently incorporated in a single device. In contrast to conventional OFETs and OLEDs, the planar device geometry and the versatile multifunctional nature of OLETs not only endow them with numerous technological opportunities in the frontier fields of highly integrated organic electronics, but also render them ideal scientific scaffolds to address the fundamental physical events of organic semiconductors and devices. This review article summarizes the recent advancements on OLETs in light of materials, device configurations, operation conditions, etc. Diverse state-of-the-art protocols, including bulk heterojunction, layered heterojunction and laterally arranged heterojunction structures, as well as asymmetric source-drain electrodes, and innovative dielectric layers, which have been developed for the construction of qualified OLETs and for shedding new and deep light on the working principles of OLETs, are highlighted by addressing representative paradigms. This review intends to provide readers with a deeper understanding of the design of future OLETs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[BIOCOMPATIBILITY OF POLY-LACTIDE-CO-GLYCOLIDE/COLLAGEN TYPE I SCAFFOLD WITH RAT VAGINAL EPITHELIAL CELLS].

PubMed

Li, Yachai; Huang, Xianghua; Zhang, Mingle; Li, Yanan; Chen, Yexing; Jia, Jingfei

2015-09-01

To explore the biocompatibility of the poly-lactide-co-glycolide (PLGA)/collagen type I scaffold with rat vaginal epithelial cells, and the feasibility of using PLGA/collagen type I as scaffold to reconstruct vagina by the tissue engineering. PLGA/collagen type I scaffold was prepared with PLGA covered polylysine and collagen type I. The vaginal epithelial cells of Sprague Dawley rat of 10-12 weeks old were cultured by enzyme digestion method. The vaginal epithelial cells of passage 2 were cultured in the leaching liquor of scaffold for 48 hours to detect its cytotoxicity by MTT. The vaginal epithelial cells were inoculated on the PLGA/collagen type I scaffold (experimental group) and PLGA scaffold (control group) to calculate the cell adhesion rate. Epithelial cells-scaffold complexes were implanted subcutaneously on the rat back. At 2, 4, and 8 weeks after implantation, the epithelial cells-scaffold complexes were harvested to observe the cell growth by HE staining and immunohistochemical analysis. The epithelial cells-scaffold complexes were transplanted to reconstruct vagina in 6 rats with vaginal defect. After 3 and 6 months, the vaginal length was measured and the appearance was observed. The neovagina tissues were harvested for histological evaluation after 6 months. The epithelial cells grew and proliferated well in the leaching liquor of PLGA/collagen type I scaffold, and the cytotoxicity was at grade 1. The cell adhesion rate on the PLGA/collagen type I scaffold was 71.8%±9.2%, which significantly higher than that on the PLGA scaffold (63.4%±5.7%) (t=2.195, P=0.005). The epithelial cells could grow and adhere to the PLGA/collagen type I scaffolds. At 2 weeks after implanted subcutaneously, the epithelial cells grew and proliferated in the pores of scaffolds, and the fibroblasts were observed. At 4 weeks, 1-3 layers epithelium formed on the surface of scaffold. At 8 weeks, the epithelial cells increased and arranged regularly, which formed the membrane-like layer on the scaffold. The keratin expression of the epithelium was positive. At 3 months after transplantation in situ, the vaginal mucosa showed pink and lustrous epithelialization, and the majority of scaffold degraded. After 6 months, the neovagina length was 1.2 cm, without obvious stenosis; the vaginal mucosa had similar appearance and epithelial layer to normal vagina, but it had less duplicature; there were nail-like processes in the basal layer, but the number was less than that of normal vagina. The immunohistochemistry staining for keratin was positive. The PLGA/collagen type I scaffolds have good cytocompatibility with the epithelial cells, and can be used as the biodegradable polymer scaffold of the vaginal tissue engineering.

The effect of sterilization methods on the physical properties of silk sericin scaffolds.

PubMed

Siritientong, Tippawan; Srichana, Teerapol; Aramwit, Pornanong

2011-06-01

Protein-based biomaterials respond differently to sterilization methods. Since protein is a complex structure, heat, or irradiation may result in the loss of its physical or biological properties. Recent investigations have shown that sericin, a degumming silk protein, can be successfully formed into a 3-D scaffolds after mixing with other polymers which can be applied in skin tissue engineering. The objective of this study was to investigate the effectiveness of ethanol, ethylene oxide (EtO) and gamma irradiation on the sterilization of sericin scaffolds. The influence of these sterilization methods on the physical properties such as pore size, scaffold dimensions, swelling and mechanical properties, as well as the amount of sericin released from sericin/polyvinyl alcohol/glycerin scaffolds, were also investigated. Ethanol treatment was ineffective for sericin scaffold sterilization whereas gamma irradiation was the most effective technique for scaffold sterilization. Moreover, ethanol also caused significant changes in pore size resulting from shrinkage of the scaffold. Gamma-irradiated samples exhibited the highest swelling property, but they also lost the greatest amount of weight after immersion for 24 h compared with scaffolds obtained from other sterilization methods. The results of the maximum stress test and Young's modulus showed that gamma-irradiated and ethanol-treated scaffolds are more flexible than the EtO-treated and untreated scaffolds. The amount of sericin released, which was related to its collagen promoting effect, was highest from the gamma-irradiated scaffold. The results of this study indicate that gamma irradiation should have the greatest potential for sterilizing sericin scaffolds for skin tissue engineering.

Development of ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffolds for accelerated healing of full-thickness wounds.

PubMed

Siritienthong, Tippawan; Ratanavaraporn, Juthamas; Aramwit, Pornanong

2012-12-15

Silk sericin has been recently reported for its advantageous biological properties to promote wound healing. In this study, we established that the ethyl alcohol (EtOH) could be used to precipitate sericin and form the stable sericin/polyvinyl alcohol (PVA) scaffolds without the crosslinking. The sericin/PVA scaffolds were fabricated via freeze-drying and subsequently precipitating in various concentrations of EtOH. The EtOH-precipitated sericin/PVA scaffolds showed denser structure, higher compressive modulus, but lower water swelling ability than the non-precipitated scaffolds. Sericin could be released from the EtOH-precipitated sericin/PVA scaffolds in a sustained manner. After cultured with L929 mouse fibroblasts, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed the highest potential to promote cell proliferation. After applied to the full-thickness wounds of rats, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed significantly higher percentage of wound size reduction and higher extent of type III collagen formation and epithelialization, compared with the control scaffolds without sericin. The accelerated wound healing by the 70 vol% EtOH-precipitated sericin/PVA scaffolds was possibly due to (1) the bioactivity of sericin itself to promote wound healing, (2) the sustained release of precipitated sericin from the scaffolds, and (3) the activation and recruitment of wound healing-macrophages by sericin to the wounds. This finding suggested that the EtOH-precipitated sericin/PVA scaffolds were more effective for the wound healing, comparing with the EtOH-precipitated PVA scaffolds without sericin. Copyright © 2012 Elsevier B.V. All rights reserved.

A parts list for fungal cellulosomes revealed by comparative genomics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haitjema, Charles H.; Gilmore, Sean P.; Henske, John K.

Cellulosomes are large, multi-protein complexes that tether plant biomass degrading enzymes together for improved hydrolysis1. These complexes were first described in anaerobic bacteria where species specific dockerin domains mediate assembly of enzymes onto complementary cohesin motifs interspersed within non-catalytic protein scaffolds1. The versatile protein assembly mechanism conferred by the bacterial cohesin-dockerin interaction is now a standard design principle for synthetic protein-scale pathways2,3. For decades, analogous structures have been reported in the early branching anaerobic fungi, which are known to assemble by sequence divergent non-catalytic dockerin domains (NCDD)4. However, the enzyme components, modular assembly mechanism, and functional role of fungal cellulosomesmore » remain unknown5,6. Here, we describe the comprehensive set of proteins critical to fungal cellulosome assembly, including novel, conserved scaffolding proteins unique to the Neocallimastigomycota. High quality genomes of the anaerobic fungi Anaeromyces robustus, Neocallimastix californiae and Piromyces finnis were assembled with long-read, single molecule technology to overcome their repeat-richness and extremely low GC content. Genomic analysis coupled with proteomic validation revealed an average 320 NCDD-containing proteins per fungal strain that were overwhelmingly carbohydrate active enzymes (CAZymes), with 95 large fungal scaffoldins identified across 4 genera that contain a conserved amino acid sequence repeat that binds to NCDDs. Fungal dockerin and scaffoldin domains have no similarity to their bacterial counterparts, yet several catalytic domains originated via horizontal gene transfer with gut bacteria. Though many catalytic domains are shared with bacteria, the biocatalytic activity of anaerobic fungi is expanded by the inclusion of GH3, GH6, and GH45 enzymes in the enzyme complexes. Collectively, these findings suggest that the fungal cellulosome is an evolutionarily chimeric structure – an independently evolved fungal complex that co-opted useful activities from bacterial neighbors within the gut microbiome.« less

Electrodeposited nickel-cobalt sulfide nanosheet on polyacrylonitrile nanofibers: a binder-free electrode for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Kamran Sami, Syed; Siddiqui, Saqib; Tajmeel Feroze, Muhammad; Chung, Chan-Hwa

2017-11-01

To pursue high-performance energy storage devices with both high energy density and power density, one-dimensional (1D) nanostructures play a key role in the development of functional devices including energy conversion, energy storage, and environmental devices. The polyacrylonitrile (PAN) nanofibers were obtained by the versatile electrospinning method. An ultra-thin nickel-cobalt sulfide (NiCoS) layer was conformably electrodeposited on a self-standing PAN nanofibers by cyclic voltammetry to fabricate the light-weighted porous electrodes for supercapacitors. The porous web of PAN nanofibers acts as a high-surface-area scaffold with significant electrochemical performance, while the electrodeposition of metal sulfide nanosheet further enhances the specific capacitance. The fabricated NiCoS on PAN (NiCoS/PAN) nanofibers exhibits a very high capacitance of 1513 F g-1 at 5 A g-1 in 1 M potassium chloride (KCl) aqueous electrolyte with superior rate capability and excellent electrochemical stability as a hybrid electrode. The high capacitance of the NiCoS is attributed to the large surface area of the electrospun PAN nanofibers scaffold, which has offered a large number of active sites for possible redox reaction of ultra-thin NiCoS layer. Benefiting from the compositional features and electrode architectures, the hybrid electrode of NiCoS/PAN nanofibers shows greatly improved electrochemical performance with an ultra-high capacitance (1124 F g-1 at 50 A g-1). Moreover, a binder-free asymmetric supercapacitor device is also fabricated by using NiCoS/PAN nanofibers as the positive electrode and activated carbon (MSP-20) on PAN nanofibers as the negative electrode; this demonstrates high energy density of 56.904 W h kg-1 at a power density of 1.445 kW kg-1, and it still delivers the energy density of 33.3923 W h kg-1 even at higher power density of 16.5013 kW kg-1.

PDZ affinity chromatography: a general method for affinity purification of proteins based on PDZ domains and their ligands.

PubMed

Walkup, Ward G; Kennedy, Mary B

2014-06-01

PDZ (PSD-95, DiscsLarge, ZO1) domains function in nature as protein binding domains within scaffold and membrane-associated proteins. They comprise ∼90 residues and make specific, high affinity interactions with complementary C-terminal peptide sequences, with other PDZ domains, and with phospholipids. We hypothesized that the specific, strong interactions of PDZ domains with their ligands would make them well suited for use in affinity chromatography. Here we describe a novel affinity chromatography method applicable for the purification of proteins that contain PDZ domain-binding ligands, either naturally or introduced by genetic engineering. We created a series of affinity resins comprised of PDZ domains from the scaffold protein PSD-95, or from neuronal nitric oxide synthase (nNOS), coupled to solid supports. We used them to purify heterologously expressed neuronal proteins or protein domains containing endogenous PDZ domain ligands, eluting the proteins with free PDZ domain peptide ligands. We show that Proteins of Interest (POIs) lacking endogenous PDZ domain ligands can be engineered as fusion products containing C-terminal PDZ domain ligand peptides or internal, N- or C-terminal PDZ domains and then can be purified by the same method. Using this method, we recovered recombinant GFP fused to a PDZ domain ligand in active form as verified by fluorescence yield. Similarly, chloramphenicol acetyltransferase (CAT) and β-Galactosidase (LacZ) fused to a C-terminal PDZ domain ligand or an N-terminal PDZ domain were purified in active form as assessed by enzymatic assay. In general, PDZ domains and ligands derived from PSD-95 were superior to those from nNOS for this method. PDZ Domain Affinity Chromatography promises to be a versatile and effective method for purification of a wide variety of natural and recombinant proteins. Copyright © 2014 Elsevier Inc. All rights reserved.

Towards the creation of decellularized organ constructs using irreversible electroporation and active mechanical perfusion

PubMed Central

2010-01-01

Background Despite advances in transplant surgery and general medicine, the number of patients awaiting transplant organs continues to grow, while the supply of organs does not. This work outlines a method of organ decellularization using non-thermal irreversible electroporation (N-TIRE) which, in combination with reseeding, may help supplement the supply of organs for transplant. Methods In our study, brief but intense electric pulses were applied to porcine livers while under active low temperature cardio-emulation perfusion. Histological analysis and lesion measurements were used to determine the effects of the pulses in decellularizing the livers as a first step towards the development of extracellular scaffolds that may be used with stem cell reseeding. A dynamic conductivity numerical model was developed to simulate the treatment parameters used and determine an irreversible electroporation threshold. Results Ninety-nine individual 1000 V/cm 100-μs square pulses with repetition rates between 0.25 and 4 Hz were found to produce a lesion within 24 hours post-treatment. The livers maintained intact bile ducts and vascular structures while demonstrating hepatocytic cord disruption and cell delamination from cord basal laminae after 24 hours of perfusion. A numerical model found an electric field threshold of 423 V/cm under specific experimental conditions, which may be used in the future to plan treatments for the decellularization of entire organs. Analysis of the pulse repetition rate shows that the largest treated area and the lowest interstitial density score was achieved for a pulse frequency of 1 Hz. After 24 hours of perfusion, a maximum density score reduction of 58.5 percent had been achieved. Conclusions This method is the first effort towards creating decellularized tissue scaffolds that could be used for organ transplantation using N-TIRE. In addition, it provides a versatile platform to study the effects of pulse parameters such as pulse length, repetition rate, and field strength on whole organ structures. PMID:21143979

Modulation of gene expression using electrospun scaffolds with templated architecture.

PubMed

Karchin, A; Wang, Y-N; Sanders, J E

2012-06-01

The fabrication of biomimetic scaffolds is a critical component to fulfill the promise of functional tissue-engineered materials. We describe herein a simple technique, based on printed circuit board manufacturing, to produce novel templates for electrospinning scaffolds for tissue-engineering applications. This technique facilitates fabrication of electrospun scaffolds with templated architecture, which we defined as a scaffold's bulk mechanical properties being driven by its fiber architecture. Electrospun scaffolds with templated architectures were characterized with regard to fiber alignment and mechanical properties. Fast Fourier transform analysis revealed a high degree of fiber alignment along the conducting traces of the templates. Mechanical testing showed that scaffolds demonstrated tunable mechanical properties as a function of templated architecture. Fibroblast-seeded scaffolds were subjected to a peak strain of 3 or 10% at 0.5 Hz for 1 h. Exposing seeded scaffolds to the low strain magnitude (3%) significantly increased collagen I gene expression compared to the high strain magnitude (10%) in a scaffold architecture-dependent manner. These experiments indicate that scaffolds with templated architectures can be produced, and modulation of gene expression is possible with templated architectures. This technology holds promise for the long-term goal of creating tissue-engineered replacements with the biomechanical and biochemical make-up of native tissues. Copyright © 2012 Wiley Periodicals, Inc.

Magnetic responsive hydroxyapatite composite scaffolds construction for bone defect reparation.

PubMed

Zeng, Xiao Bo; Hu, Hao; Xie, Li Qin; Lan, Fang; Jiang, Wen; Wu, Yao; Gu, Zhong Wei

2012-01-01

In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. A type of magnetic scaffold composed of magnetic nanoparticles (MNPs) and hydroxyapatite (HA) for bone repair has been developed by our research group. In this study, to investigate the influence of the MNP content (in the scaffolds) on the cell behaviors and the interactions between the magnetic scaffold and the exterior magnetic field, a series of MNP-HA magnetic scaffolds with different MNP contents (from 0.2% to 2%) were fabricated by immersing HA scaffold into MNP colloid. ROS 17/2.8 and MC3T3-E1 cells were cultured on the scaffolds in vitro, with and without an exterior magnetic field, respectively. The cell adhesion, proliferation and differentiation were evaluated via scanning electron microscopy; confocal laser scanning microscopy; and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), alkaline phosphatase, and bone gla protein activity tests. The results demonstrated the positive influence of the magnetic scaffolds on cell adhesion, proliferation, and differentiation. Further, a higher amount of MNPs on the magnetic scaffolds led to more significant stimulation. The magnetic scaffold can respond to the exterior magnetic field and engender some synergistic effect to intensify the stimulating effect of a magnetic field to the proliferation and differentiation of cells.

Novel fiber-based pure chitosan scaffold for tendon augmentation: biomechanical and cell biological evaluation.

PubMed

Nowotny, J; Aibibu, D; Farack, J; Nimtschke, U; Hild, M; Gelinsky, M; Kasten, P; Cherif, Ch

2016-07-01

One possibility to improve the mechanical properties after tendon ruptures is augmentation with a scaffold. Based on wet spinning technology, chitosan fibres were processed to a novel pure high-grade multifilament yarn with reproducible quality. The fibres were braided to obtain a 3D tendon scaffold. The CS fibres and scaffolds were evaluated biomechanically and compared to human supraspinatus (SSP) tendons. For the cytobiological characterization, in vitro cell culture experiments with human mesenchymal stem cells (hMSC) were performed. Three types of 3D circular braided scaffolds were fabricated. Significantly, higher ultimate stress values were measured for scaffold with larger filament yarn, compared to scaffold with smaller filament yarn. During cultivation over 28 days, the cells showed in dependence of isolation method and/or donor a doubling or tripling of the cell number or even a six-fold increase on the CS scaffold, which was comparable to the control (polystyrene) or in the case of cells obtained from human biceps tendon even higher proliferation rates. After 14 days, the scaffold surface was covered homogeneously with a cell layer. In summary, the present work demonstrates that braided chitosan scaffolds constitute a straightforward approach for designing tendon analogues, maintaining important flexibility in scaffold design and providing favourable mechanical properties of the resulting construct.

3D printing of photocurable poly(glycerol sebacate) elastomers.

PubMed

Yeh, Yi-Cheun; Highley, Christopher B; Ouyang, Liliang; Burdick, Jason A

2016-10-07

Three-dimensional (3D) printed scaffolds have great potential in biomedicine; however, it is important that we are able to design such scaffolds with a range of diverse properties towards specific applications. Here, we report the extrusion-based 3D printing of biodegradable and photocurable acrylated polyglycerol sebacate (Acr-PGS) to fabricate scaffolds with elastic properties. Two Acr-PGS macromers were synthesized with varied molecular weights and viscosity, which were then blended to obtain photocurable macromer inks with a range of viscosities. The quality of extruded and photocured scaffolds was dependent on the initial ink viscosity, with flow of printed material resulting in a loss of structural resolution or sample breaking observed with too low or too high viscosity inks, respectively. However, scaffolds with high print resolution and up to ten layers were fabricated with an optimal ink viscosity. The mechanical properties of printed scaffolds were dependent on printing density, where the scaffolds with lower printing density possessed lower moduli and failure properties than higher density scaffolds. The 3D printed scaffolds supported the culture of 3T3 fibroblasts and both spreading and proliferation were observed, indicating that 3D printed Acr-PGS scaffolds are cytocompatible. These results demonstrate that Acr-PGS is a promising material for the fabrication of elastomeric scaffolds for biomedical applications.

Degradability, biocompatibility, and osteogenesis of biocomposite scaffolds containing nano magnesium phosphate and wheat protein both in vitro and in vivo for bone regeneration.

PubMed

Xia, Yan; Zhou, Panyu; Wang, Fei; Qiu, Chao; Wang, Panfeng; Zhang, Yuntong; Zhao, Liming; Xu, Shuogui

2016-01-01

In this study, bioactive scaffold of nano magnesium phosphate (nMP)/wheat protein (WP) composite (MWC) was fabricated. The results revealed that the MWC scaffolds had interconnected not only macropores (sized 400-600 μm) but also micropores (sized 10-20 μm) on the walls of macropores. The MWC scaffolds containing 40 w% nMP had an appropriate degradability in phosphate-buffered saline and produced a weak alkaline microenvironment. In cell culture experiments, the results revealed that the MWC scaffolds significantly promoted the MC3T3-E1 cell proliferation, differentiation, and growth into the scaffolds. The results of synchrotron radiation microcomputed tomography and analysis of the histological sections of the in vivo implantation revealed that the MWC scaffolds evidently improved the new bone formation and bone defects repair as compared with WP scaffolds. Moreover, it was found that newly formed bone tissue continued to increase with the gradual reduction of materials residual in the MWC scaffolds. Furthermore, the immunohistochemical analysis further offered the evidence of the stimulatory effects of MWC scaffolds on osteogenic-related cell differentiation and new bone regeneration. The results indicated that MWC scaffolds with good biocompability and degradability could promote osteogenesis in vivo, which would have potential for bone tissue repair.

Strong and biocompatible three-dimensional porous silk fibroin/graphene oxide scaffold prepared by phase separation.

PubMed

Wang, Shu-Dong; Ma, Qian; Wang, Ke; Ma, Pi-Bo

2018-05-01

Silk fibroin (SF) is blended with graphene oxide (GO) to prepare the strong and biocompatible three dimensional porous SF/GO blended scaffold via phase separation. GO could be well dispersed in SF solution and GO could also be well distributed in the SF scaffold. Furthermore, the introduction of GO can lead to structural change in the bended scaffold. Higher concentration of GO resulted in more compact structure and smaller pore size of the composite scaffolds without decreasing their porosity. Scanning electron microscopy and energy dispersive spectrometry results also reveal that SF and GO are homogeneous blended together. Analysis of chemical structures of the scaffold shows that addition of GO do not affect the crystalline structure of SF and it is evenly blended with SF. The blended scaffold has significantly higher breaking strength than the pure SF scaffold. In vitro study indicates that both pure SF scaffold and SF/GO composite scaffold support growth and proliferation of MC3T3-E1 osteoprogenitor cells. However, the addition of GO contribute to the proliferation of MC3T3-E1 osteoprogenitor. The testing results show that the blended scaffold is an appropriate candidate for tissue engineering. Copyright © 2018 Elsevier B.V. All rights reserved.

Sensate Scaffolds Can Reliably Detect Joint Loading

PubMed Central

Bliss, C. L.; Szivek, J. A.; Tellis, B. C.; Margolis, D. S.; Schnepp, A. B.; Ruth, J. T.

2008-01-01

Treatment of cartilage defects is essential to the prevention of osteoarthritis. Scaffold-based cartilage tissue engineering shows promise as a viable technique to treat focal defects. Added functionality can be achieved by incorporating strain gauges into scaffolds, thereby providing a real-time diagnostic measurement of joint loading. Strain-gauged scaffolds were placed into the medial femoral condyles of 14 adult canine knees and benchtop tested. Loads between 75 and 130 N were applied to the stifle joints at 30°, 50°, and 70° of flexion. Strain-gauged scaffolds were able to reliably assess joint loading at all applied flexion angles and loads. Pressure sensitive films were used to determine joint surface pressures during loading and to assess the effect of scaffold placement on joint pressures. A comparison of peak pressures in control knees and joints with implanted scaffolds, as well as a comparison of pressures before and after scaffold placement, showed that strain-gauged scaffold implantation did not significantly alter joint pressures. Future studies could possibly use strain-gauged scaffolds to clinically establish normal joint loads and to determine loads that are damaging to both healthy and tissue-engineered cartilage. Strain-gauged scaffolds may significantly aid the development of a functional engineered cartilage tissue substitute as well as provide insight into the native environment of cartilage. PMID:16941586

The Role of Previous Mother-Child Scaffolding in Head Start Children's Structuring of Problem-Solving Tasks with a Peer

ERIC Educational Resources Information Center

Hustedt, Jason T.

2015-01-01

This study further extends scaffolding research to mother-child dyads (N = 51) in poverty, examining relationships between maternal scaffolding and 4-year-old Head Start children's own later scaffolding behaviors. At Time 1, experimental group children received maternal scaffolding during problem-solving tasks, whereas control group children…

Copper-releasing, boron-containing bioactive glass-based scaffolds coated with alginate for bone tissue engineering.

PubMed

Erol, M M; Mouriňo, V; Newby, P; Chatzistavrou, X; Roether, J A; Hupa, L; Boccaccini, Aldo R

2012-02-01

The aim of this study was to synthesize and characterize new boron-containing bioactive glass-based scaffolds coated with alginate cross-linked with copper ions. A recently developed bioactive glass powder with nominal composition (wt.%) 65 SiO2, 15 CaO, 18.4 Na2O, 0.1 MgO and 1.5 B2O3 was fabricated as porous scaffolds by the foam replica method. Scaffolds were alginate coated by dipping them in alginate solution. Scanning electron microscopy investigations indicated that the alginate effectively attached on the surface of the three-dimensional scaffolds leading to a homogeneous coating. It was confirmed that the scaffold structure remained amorphous after the sintering process and that the alginate coating improved the scaffold bioactivity and mechanical properties. Copper release studies showed that the alginate-coated scaffolds allowed controlled release of copper ions. The novel copper-releasing composite scaffolds represent promising candidates for bone regeneration. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fabrication of triple-layered bifurcated vascular scaffold with a certain degree of three-dimensional structure

NASA Astrophysics Data System (ADS)

Liu, Yuanyuan; Jiang, Weijian; Yang, Yang; Pu, Huayan; Peng, Yan; Xin, Liming; Zhang, Yi; Sun, Yu

2018-01-01

Constructing vascular scaffolds is important in tissue engineering. However, scaffolds with characteristics such as multiple layers and a certain degree of spatial morphology still cannot be readily constructed by current vascular scaffolds fabrication techniques. This paper presents a three-layered bifurcated vascular scaffold with a curved structure. The technique combines 3D printed molds and casting hydrogel and fugitive ink to create vessel-mimicking constructs with customizable structural parameters. Compared with other fabrication methods, the technique can create more native-like 3D geometries. The diameter and wall thickness of the fabricated constructs can be independently controlled, providing a feasible approach for vascular scaffold construction. Enzymatically-crosslinked gelatin was used as the scaffold material. The morphology and mechanical properties were evaluated. Human umbilical cord derived endothelial cells (HUVECs) were seeded on the scaffolds and cultured for 72 h. Cell viability and morphology were assessed. The results showed that the proposed process had good application potentials, and will hopefully provide a feasible approach for constructing vascular scaffolds.

Chitosan-chitin nanocrystal composite scaffolds for tissue engineering.

PubMed

Liu, Mingxian; Zheng, Huanjun; Chen, Juan; Li, Shuangli; Huang, Jianfang; Zhou, Changren

2016-11-05

Chitin nanocrystals (CNCs) with length and width of 300 and 20nm were uniformly dispersed in chitosan (CS) solution. The CS/CNCs composite scaffolds prepared utilizing a dispersion-based freeze dry approach exhibit significant enhancement in compressive strength and modulus compared with pure CS scaffold both in dry and wet state. A well-interconnected porous structure with size in the range of 100-200μm and over 80% porosity are found in the composite scaffolds. The crystal structure of CNCs is retained in the composite scaffolds. The incorporation of CNCs leads to increase in the scaffold density and decrease in the water swelling ratio. Moreover, the composite scaffolds are successfully applied as scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs images reveal that CNCs can markedly promote the cell adhesion and proliferation of the osteoblast on CS. The biocompatible composite scaffolds with enhanced mechanical properties have potential application in bone tissue engineering. Copyright © 2016 Elsevier Ltd. All rights reserved.

Graphene Oxide Hybridized nHAC/PLGA Scaffolds Facilitate the Proliferation of MC3T3-E1 Cells

NASA Astrophysics Data System (ADS)

Liang, Chunyong; Luo, Yongchao; Yang, Guodong; Xia, Dan; Liu, Lei; Zhang, Xiaomin; Wang, Hongshui

2018-01-01

Biodegradable porous biomaterial scaffolds play a critical role in bone regeneration. In this study, the porous nano-hydroxyapatite/collagen/poly(lactic-co-glycolic acid)/graphene oxide (nHAC/PLGA/GO) composite scaffolds containing different amount of GO were fabricated by freeze-drying method. The results show that the synthesized scaffolds possess a three-dimensional porous structure. GO slightly improves the hydrophilicity of the scaffolds and reinforces their mechanical strength. Young's modulus of the 1.5 wt% GO incorporated scaffold is greatly increased compared to the control sample. The in vitro experiments show that the nHAC/PLGA/GO (1.5 wt%) scaffolds significantly cell adhesion and proliferation of osteoblast cells (MC3T3-E1). This present study indicates that the nHAC/PLGA/GO scaffolds have excellent cytocompatibility and bone regeneration ability, thus it has high potential to be used as scaffolds in the field of bone tissue engineering.

Cytocompatibility of electrospun nanofiber tubular scaffolds for small diameter tissue engineering blood vessels.

PubMed

Xiang, Ping; Li, Min; Zhang, Chao-ying; Chen, Deng-long; Zhou, Zhi-hua

2011-10-01

A tubular scaffold was fabricated by using electrospun polymer solution blends of pNSR32 (recombinant spider silk protein), PCL (polycaprolactone) and Gt (gelatin). The physicochemical properties and cytocompatibility of these scaffolds were investigated. Afterwards, the pNSR32/PCL/Gt tubular scaffold (inner diameter=3mm) showed high porosity of 86.2 ± 2.9%, pore size of 2423 ± 979nm and average fibre diameter of 166 ± 85nm. Water uptake and contact angle of the scaffolds reached 112.0 ± 4.4% and 45.7 ± 13.7°, respectively. SDRAECs (Sprague Dawley Rat Aortic Endothelial Cells) grew and proliferated well and phenotype could be maintained on the composite scaffolds after they had been cultured on the composite scaffolds for 7 days. Compared with pure PCL scaffolds a greater density of viable cells was seen on the composites, especially the pNSR32/PCL/Gt scaffolds. Copyright © 2011 Elsevier B.V. All rights reserved.

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

PubMed Central

Jung, Hyun-Do; Lee, Hyun; Kim, Hyoun-Ee; Koh, Young-Hag; Song, Juha

2015-01-01

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification. PMID:26709604

3D printed alendronate-releasing poly(caprolactone) porous scaffolds enhance osteogenic differentiation and bone formation in rat tibial defects.

PubMed

Kim, Sung Eun; Yun, Young-Pil; Shim, Kyu-Sik; Kim, Hak-Jun; Park, Kyeongsoon; Song, Hae-Ryong

2016-09-29

The aim of this study was to evaluate the in vitro osteogenic effects and in vivo new bone formation of three-dimensional (3D) printed alendronate (Aln)-releasing poly(caprolactone) (PCL) (Aln/PCL) scaffolds in rat tibial defect models. 3D printed Aln/PCL scaffolds were fabricated via layer-by-layer deposition. The fabricated Aln/PCL scaffolds had high porosity and an interconnected pore structure and showed sustained Aln release. In vitro studies showed that MG-63 cells seeded on the Aln/PCL scaffolds displayed increased alkaline phosphatase (ALP) activity and calcium content in a dose-dependent manner when compared with cell cultures in PCL scaffolds. In addition, in vivo animal studies and histologic evaluation showed that Aln/PCL scaffolds implanted in a rat tibial defect model markedly increased new bone formation and mineralized bone tissues in a dose-dependent manner compared to PCL-only scaffolds. Our results show that 3D printed Aln/PCL scaffolds are promising templates for bone tissue engineering applications.

Polymer-Ceramic Composite Scaffolds: The Effect of Hydroxyapatite and β-tri-Calcium Phosphate

PubMed Central

Caetano, Guilherme; Vyas, Cian; Diver, Carl; Bártolo, Paulo

2018-01-01

The design of bioactive scaffolds with improved mechanical and biological properties is an important topic of research. This paper investigates the use of polymer-ceramic composite scaffolds for bone tissue engineering. Different ceramic materials (hydroxyapatite (HA) and β-tri-calcium phosphate (TCP)) were mixed with poly-ε-caprolactone (PCL). Scaffolds with different material compositions were produced using an extrusion-based additive manufacturing system. The produced scaffolds were physically and chemically assessed, considering mechanical, wettability, scanning electron microscopy and thermal gravimetric tests. Cell viability, attachment and proliferation tests were performed using human adipose derived stem cells (hADSCs). Results show that scaffolds containing HA present better biological properties and TCP scaffolds present improved mechanical properties. It was also possible to observe that the addition of ceramic particles had no effect on the wettability of the scaffolds. PMID:29342890

Fabrication and characterization of a rapid prototyped tissue engineering scaffold with embedded multicomponent matrix for controlled drug release.

PubMed

Chen, Muwan; Le, Dang Q S; Hein, San; Li, Pengcheng; Nygaard, Jens V; Kassem, Moustapha; Kjems, Jørgen; Besenbacher, Flemming; Bünger, Cody

2012-01-01

Bone tissue engineering implants with sustained local drug delivery provide an opportunity for better postoperative care for bone tumor patients because these implants offer sustained drug release at the tumor site and reduce systemic side effects. A rapid prototyped macroporous polycaprolactone scaffold was embedded with a porous matrix composed of chitosan, nanoclay, and β-tricalcium phosphate by freeze-drying. This composite scaffold was evaluated on its ability to deliver an anthracycline antibiotic and to promote formation of mineralized matrix in vitro. Scanning electronic microscopy, confocal imaging, and DNA quantification confirmed that immortalized human bone marrow-derived mesenchymal stem cells (hMSC-TERT) cultured in the scaffold showed high cell viability and growth, and good cell infiltration to the pores of the scaffold. Alkaline phosphatase activity and osteocalcin staining showed that the scaffold was osteoinductive. The drug-release kinetics was investigated by loading doxorubicin into the scaffold. The scaffolds comprising nanoclay released up to 45% of the drug for up to 2 months, while the scaffold without nanoclay released 95% of the drug within 4 days. Therefore, this scaffold can fulfill the requirements for both bone tissue engineering and local sustained release of an anticancer drug in vitro. These results suggest that the scaffold can be used clinically in reconstructive surgery after bone tumor resection. Moreover, by changing the composition and amount of individual components, the scaffold can find application in other tissue engineering areas that need local sustained release of drug.

Enhanced osteogenic potential of human mesenchymal stem cells on electrospun nanofibrous scaffolds prepared from eri-tasar silk fibroin.

PubMed

Panda, Niladri Nath; Biswas, Amit; Pramanik, Krishna; Jonnalagadda, Sriramakamal

2015-07-01

This study evaluated the mechanical properties and osteogenic potential of a silk fibroin scaffold prepared from a 70:30 blend of Eri (Philosamia ricini) and Tasar (Antheraea mylitta) silk, respectively (ET scaffolds). An electrospinning process was used to prepare uniformly blended, fibrous scaffolds of nanoscale dimensions, as confirmed by scanning and transmission electron microscopy (fiber diameter < 300 nm). Similarly prepared scaffolds derived from gelatin and Bombyx mori (BM) silk fibroin were used as controls. Mechanical testing and atomic force microscopy showed that the ET scaffolds had significantly higher tensile strength (1.83 ± 0.13 MPa) and surface roughness (0.44 μm) compared with BM (1.47 ± 0.10 MPa; 0.37 μm) and gelatin scaffolds (0.6 ± 0.07 MPa; 0.28 μm). All scaffolds were exposed to mesenchymal stem cells isolated to human chord blood (hMSCs) for up to 28 days in vitro. Alamar blue and alkaline phosphatase assay showed greater attachment and proliferation for both ET and BM scaffolds compared with gelatin. The ET scaffolds also promoted greater differentiation of the attached hMSCs as evidenced by higher expression of RunX2, osteocalcin, and CD29/CD44 expression. ET scaffolds also showed significantly higher mineralization, as evidenced by glycosaminoglycan assay, alizarin red staining, and elemental analysis of crystalline composites isolated from the scaffolds. © 2014 Wiley Periodicals, Inc.

A comparison study between electrospun polycaprolactone and piezoelectric poly(3-hydroxybutyrate-co-3-hydroxyvalerate) scaffolds for bone tissue engineering.

PubMed

Gorodzha, Svetlana N; Muslimov, Albert R; Syromotina, Dina S; Timin, Alexander S; Tcvetkov, Nikolai Y; Lepik, Kirill V; Petrova, Aleksandra V; Surmeneva, Maria A; Gorin, Dmitry A; Sukhorukov, Gleb B; Surmenev, Roman A

2017-12-01

In this study, bone scaffolds composed of polycaprolactone (PCL), piezoelectric poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a combination of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and silicate containing hydroxyapatite (PHBV-SiHA) were successfully fabricated by a conventional electrospinning process. The morphological, chemical, wetting and biological properties of the scaffolds were examined. All fabricated scaffolds are composed of randomly oriented fibres with diameters from 800nm to 12μm. Fibre size increased with the addition of SiHA to PHBV scaffolds. Moreover, fibre surface roughness in the case of hybrid scaffolds was also increased. XRD, FTIR and Raman spectroscopy were used to analyse the chemical composition of the scaffolds, and contact angle measurements were performed to reveal the wetting behaviour of the synthesized materials. To determine the influence of the piezoelectric nature of PHBV in combination with SiHA nanoparticles on cell attachment and proliferation, PCL (non-piezoelectric), pure PHBV, and PHBV-SiHA scaffolds were seeded with human mesenchymal stem cells (hMSCs). In vitro study on hMSC adhesion, viability, spreading and osteogenic differentiation showed that the PHBV-SiHA scaffolds had the largest adhesion and differentiation abilities compared with other scaffolds. Moreover, the piezoelectric PHBV scaffolds have demonstrated better calcium deposition potential compared with non-piezoelectric PCL. The results of the study revealed pronounced advantages of hybrid PHBV-SiHA scaffolds to be used in bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Strategies for neurotrophin-3 and chondroitinase ABC release from freeze-cast chitosan-alginate nerve-guidance scaffolds.

PubMed

Francis, Nicola L; Hunger, Philipp M; Donius, Amalie E; Wegst, Ulrike G K; Wheatley, Margaret A

2017-01-01

Freeze casting, or controlled unidirectional solidification, can be used to fabricate chitosan-alginate (C-A) scaffolds with highly aligned porosity that are suitable for use as nerve-guidance channels. To augment the guidance of growth across a spinal cord injury lesion, these scaffolds are now evaluated in vitro to assess their ability to release neurotrophin-3 (NT-3) and chondroitinase ABC (chABC) in a controlled manner. Protein-loaded microcapsules were incorporated into C-A scaffolds prior to freeze casting without affecting the original scaffold architecture. In vitro protein release was not significantly different when comparing protein loaded directly into the scaffolds with release from scaffolds containing incorporated microcapsules. NT-3 was released from the C-A scaffolds for 8 weeks in vitro, while chABC was released for up to 7 weeks. Low total percentages of protein released from the scaffolds over this time period were attributed to limitation of diffusion by the interpenetrating polymer network matrix of the scaffold walls. NT-3 and chABC released from the scaffolds retained bioactivity, as determined by a neurite outgrowth assay, and the promotion of neurite growth across an inhibitory barrier of chondroitin sulphate proteoglycans. This demonstrates the potential of these multifunctional scaffolds for enhancing axonal regeneration through growth-inhibiting glial scars via the sustained release of chABC and NT-3. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Bone regeneration by nanohydroxyapatite/chitosan/poly(lactide-co-glycolide) scaffolds seeded with human umbilical cord mesenchymal stem cells in the calvarial defects of the nude mice.

PubMed

Wang, Fei; Su, Xiao-Xia; Guo, Yu-Cheng; Li, Ang; Zhang, Yin-Cheng; Zhou, Hong; Qiao, Hu; Guan, Li-Min; Zou, Min; Si, Xin-Qin

2015-01-01

In the preliminary study, we have found an excellent osteogenic property of nanohydroxyapatite/chitosan/poly(lactide-co-glycolide) (nHA/CS/PLGA) scaffolds seeded with human umbilical cord mesenchymal stem cells (hUCMSCs) in vitro and subcutaneously in the nude mice. The aim of this study was to further evaluate the osteogenic capacity of nHA/CS/PLGA scaffolds seeded with hUCMSCs in the calvarial defects of the nude mice. Totally 108 nude mice were included and divided into 6 groups: PLGA scaffolds + hUCMSCs; nHA/PLGA scaffolds + hUCMSCs; CS/PLGA scaffolds + hUCMSCs; nHA/CS/PLGA scaffolds + hUCMSCs; nHA/CS/PLGA scaffolds without seeding; the control group (no scaffolds) (n = 18). The scaffolds were implanted into the calvarial defects of nude mice. The amount of new bones was evaluated by fluorescence labeling, H&E staining, and Van Gieson staining at 4 and 8 weeks, respectively. The results demonstrated that the amount of new bones was significantly increased in the group of nHA/CS/PLGA scaffolds seeded with hUCMSCs (p < 0.01). On the basis of previous studies in vitro and in subcutaneous implantation of the nude mice, the results revealed that the nHA and CS also enhanced the bone regeneration by nHA/CS/PLGA scaffolds seeded with hUCMSCs in the calvarial defects of the nude mice at early stage.

Fabrication and characterization of a rapid prototyped tissue engineering scaffold with embedded multicomponent matrix for controlled drug release

PubMed Central

Chen, Muwan; Le, Dang QS; Hein, San; Li, Pengcheng; Nygaard, Jens V; Kassem, Moustapha; Kjems, Jørgen; Besenbacher, Flemming; Bünger, Cody

2012-01-01

Bone tissue engineering implants with sustained local drug delivery provide an opportunity for better postoperative care for bone tumor patients because these implants offer sustained drug release at the tumor site and reduce systemic side effects. A rapid prototyped macroporous polycaprolactone scaffold was embedded with a porous matrix composed of chitosan, nanoclay, and β-tricalcium phosphate by freeze-drying. This composite scaffold was evaluated on its ability to deliver an anthracycline antibiotic and to promote formation of mineralized matrix in vitro. Scanning electronic microscopy, confocal imaging, and DNA quantification confirmed that immortalized human bone marrow-derived mesenchymal stem cells (hMSC-TERT) cultured in the scaffold showed high cell viability and growth, and good cell infiltration to the pores of the scaffold. Alkaline phosphatase activity and osteocalcin staining showed that the scaffold was osteoinductive. The drug-release kinetics was investigated by loading doxorubicin into the scaffold. The scaffolds comprising nanoclay released up to 45% of the drug for up to 2 months, while the scaffold without nanoclay released 95% of the drug within 4 days. Therefore, this scaffold can fulfill the requirements for both bone tissue engineering and local sustained release of an anticancer drug in vitro. These results suggest that the scaffold can be used clinically in reconstructive surgery after bone tumor resection. Moreover, by changing the composition and amount of individual components, the scaffold can find application in other tissue engineering areas that need local sustained release of drug. PMID:22904634

Fabrication of channeled scaffolds with ordered array of micro-pores through microsphere leaching and indirect Rapid Prototyping technique.

PubMed

Tan, J Y; Chua, C K; Leong, K F

2013-02-01

Advanced scaffold fabrication techniques such as Rapid Prototyping (RP) are generally recognized to be advantageous over conventional fabrication methods in terms architectural control and reproducibility. Yet, most RP techniques tend to suffer from resolution limitations which result in scaffolds with uncontrollable, random-size pores and low porosity, albeit having interconnected channels which is characteristically present in most RP scaffolds. With the increasing number of studies demonstrating the profound influences of scaffold pore architecture on cell behavior and overall tissue growth, a scaffold fabrication method with sufficient architectural control becomes imperative. The present study demonstrates the use of RP fabrication techniques to create scaffolds having interconnected channels as well as controllable micro-size pores. Adopted from the concepts of porogen leaching and indirect RP techniques, the proposed fabrication method uses monodisperse microspheres to create an ordered, hexagonal closed packed (HCP) array of micro-pores that surrounds the existing channels of the RP scaffold. The pore structure of the scaffold is shaped using a single sacrificial construct which comprises the microspheres and a dissolvable RP mold that were sintered together. As such, the size of pores as well as the channel configuration of the scaffold can be tailored based on the design of the RP mold and the size of microspheres used. The fabrication method developed in this work can be a promising alternative way of preparing scaffolds with customized pore structures that may be required for specific studies concerning cell-scaffold interactions.

Improvement of mechanical strength and osteogenic potential of calcium sulfate-based hydroxyapatite 3-dimensional printed scaffolds by ε-polycarbonate coating.

PubMed

Kim, Beom-Su; Yang, Sun-Sik; Park, Ho; Lee, Se-Hwan; Cho, Young-Sam; Lee, Jun

2017-09-01

Powder-based three-dimensional (3D) printing is an excellent method to fabricate complex-shaped scaffolds for tissue engineering. However, their lower mechanical strength restricts their application in bone tissue engineering. Here, we created a 3D-printed scaffold coated with a ε-polycaprolactone (PCL) polymer solution (5 and 10 w/v %) to improve the mechanical strength of the scaffold. The 3D scaffold was fabricated from calcium sulfate hemihydrate powder (CaSO 4 -1/2 H 2 O), transformed into hydroxyapatite (HAp) by treatment with a hydrothermal reaction in an NH 4 H 2 PO 4 solution. The surface properties and composition of the scaffold were evaluated using scanning electron microscopy and X-ray diffraction analysis. We demonstrated that the 3D scaffold coated with PCL had an improved mechanical modulus. Coating with 5 and 10% PCL increased the compressive strength significantly, by about 2-fold and 4-fold, respectively, compared with that of uncoated scaffolds. However, the porosity was reduced significantly by coating with 10% PCL. In vitro biological evaluation demonstrated that MG-63 cells adhered well and proliferated on the 3D scaffold coated with PCL, and the scaffold was not cytotoxic. In addition, alkaline phosphatase activity and real time polymerase chain reaction demonstrated that osteoblast differentiation also improved in the PCL-coated 3D scaffolds. These results indicated that PCL polymer coating could improve the compressive strength and biocompatibility of 3D HAp scaffolds for bone tissue engineering applications.

Synthesis of and in vitro and in vivo evaluation of a novel TGF-β1-SF-CS three-dimensional scaffold for bone tissue engineering.

PubMed

Tong, Shuang; Xu, Da-Peng; Liu, Zi-Mei; Du, Yang; Wang, Xu-Kai

2016-08-01

The role of transforming growth factor-β1 (TGF-β1) in normal human fracture healing has been previously demonstrated. The objective of the present study was to examine the biocompatibility of TGF-β1-silk fibroin-chitosan (TGF-β1-SF-CS) three-dimensional (3D) scaffolds in order to construct an ideal scaffold for bone tissue engineering. We added TGF-β1 directly to the SF-CS scaffold to construct a 3D scaffold for the first time, to the best of our knowledge, and performed evaluations to determine whether it may have potential applications as a growth factor delivery device. Bone marrow-derived mesenchymal stem cells (BMSCs) were seeded on the TGF-β1-SF-CS scaffolds and the silk fibroin-chitosan (SF-CS) scaffolds. On the TGF-β1‑SF-CS and the SF-CS scaffolds, the cell adhesion rate increased in a time‑dependent manner. Using a Cell Counting Kit-8 (CCK-8) assay and analyzing the alkaline phosphatase (ALP) expression proved that TGF-β1 significantly enhanced the growth and proliferation of BMSCs on the SF-CS scaffolds in a time-dependent manner. To examine the in vivo biocompatibility and osteogenesis of the TGF-β1‑SF-CS scaffolds, the TGF-β1-SF-CS scaffolds and the SF-CS scaffolds were implanted in rabbit mandibles and studied histologically and microradiographically. The 3D computed tomography (CT) scan and histological examinations of the samples showed that the TGF-β1-SF-CS scaffolds exhibited good biocompatibility and extensive osteoconductivity with the host bone after 8 weeks. Moreover, the introduction of TGF-β1 to the SF-CS scaffolds markedly enhanced the efficiency of new bone formation, and this was confirmed using bone mineral density (BMD) and biomechanical evaluation, particularly at 8 weeks after implantation. We demonstrated that the TGF-β1‑SF-CS scaffolds possessed as good biocompatibility and osteogenesis as the hybrid ones. Taken together, these findings indicate that the TGF-β1-SF-CS scaffolds fulfilled the basic requirements of bone tissue engineering, and have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery. Thus, TGF-β1-SF-CS composite scaffolds represent a promising, novel type of scaffold for use in bone tissue engineering.

3D printed porous polycaprolactone/oyster shell powder (PCL/OSP) scaffolds for bone tissue engineering

NASA Astrophysics Data System (ADS)

Luo, Wenfeng; Zhang, Shuangying; Lan, Yuewei; Huang, Chen; Wang, Chao; Lai, Xuexu; Chen, Hanwei; Ao, Ningjian

2018-04-01

In this work, oyster shell powder (OSP) was used as the bio-filler and combined with polycaprolactone (PCL) through melt blending methodology. The PCL and PCL/OSP scaffolds were prepared using additive manufacturing process. All the 3D printed scaffolds hold a highly porosity and interconnected pore structures. OSP particles are dispersed in the polymer matrix, which helped to improve the degree of crystallinity and mineralization ability of the scaffolds. There was no significant cytotoxicity of the prepared scaffolds towards MG-63 cells, and all the scaffolds showed a well ALP activity. Therefore, PCL/OSP scaffolds had a high potential to be employed in the bone tissue engineering.

Suspended, Shrinkage-Free, Electrospun PLGA Nanofibrous Scaffold for Skin Tissue Engineering.

PubMed

Ru, Changhai; Wang, Feilong; Pang, Ming; Sun, Lining; Chen, Ruihua; Sun, Yu

2015-05-27

Electrospinning is a technique for creating continuous nanofibrous networks that can architecturally be similar to the structure of extracellular matrix (ECM). However, the shrinkage of electrospun mats is unfavorable for the triggering of cell adhesion and further growth. In this work, electrospun PLGA nanofiber assemblies are utilized to create a scaffold. Aided by a polypropylene auxiliary supporter, the scaffold is able to maintain long-term integrity without dimensional shrinkage. This scaffold is also able to suspend in cell culture medium; hence, keratinocyte cells seeded on the scaffold are exposed to air as required in skin tissue engineering. Experiments also show that human skin keratinocytes can proliferate on the scaffold and infiltrate into the scaffold.

Study on a hydroxypropyl chitosan-gelatin based scaffold for corneal stroma tissue engineering

NASA Astrophysics Data System (ADS)

Wang, Shilu; Liu, Wanshun; Han, Baoqin; Yang, Lingling

2009-07-01

Hydroxypropyl chitosan (HPCTS) was crosslinked with gelatin (GEL) and chondroitin sulfate (CS) by 1,4-butanediol diglycidyl ether to synthesize a scaffold. In this study, this scaffold was tested in physical and biological characteristics as a bioactive corneal stroma surrogate. The results showed the scaffold exhibited 83-88% light transmission values at wavelengths of visible light. Besides that, the scaffold had 96% water content and allowed NaCl and glucose to permeate. Moreover, it was suitable for keratocytes growing on its surface. In the biological part, we compared the scaffold with CS-free ones to investigate the potential effect of CS and found out that CS notablely improved cell compatibility of the scaffold.

Thermal Stability and Surface Wettability Studies of Polylactic Acid/Halloysite Nanotube Nanocomposite Scaffold for Tissue Engineering Studies

NASA Astrophysics Data System (ADS)

Nizar, M. Mohd; Hamzah, M. S. A.; Razak, S. I. Abd; Mat Nayan, N. H.

2018-03-01

This paper reports the preliminary study about the incorporation of halloysite nanotubes (HNT) into polylactic acid (PLA) scaffold to improve the thermal resistance and surface wettability properties. The fabrication of the porous scaffold requires a simple yet effective technique with low-cost materials within freeze extraction method. The thermal stability of PLA/HNT scaffold compared to neat PLA scaffold achieved with increased content of HNT by 5 wt%. Moreover, the surface wettability of the scaffold also shows a positive impact with high content of HNT by 5 wt%. This new nanocomposite scaffold may have high potential as a suitable template for tissue regeneration.

Fabrication of three-dimensional collagen scaffold using an inverse mould-leaching process.

PubMed

Ahn, SeungHyun; Lee, SuYeon; Cho, Youngseok; Chun, Wook; Kim, GeunHyung

2011-09-01

Natural biopolymers, such as collagen or chitosan, are considered ideal for biomedical scaffolds. However, low processability of the materials has hindered the fabrication of designed pore structures controlled by various solid freeform-fabrication methods. A new technique to fabricate a biomedical three-dimensional collagen scaffold, supplemented with a sacrificial poly(ethylene oxide) mould is proposed. The fabricated collagen scaffold shows a highly porous surface and a three-dimensional structure with high porosity as well as mechanically stable structure. To show its feasibility for biomedical applications, fibroblasts/keratinocytes were co-cultured on the scaffold, and the cell proliferation and cell migration of the scaffold was more favorable than that obtained with a spongy-type collagen scaffold.

Scaffolding under the Microscope: Applying Self-Regulation and Other-Regulation Perspectives to a Scaffolded Task

ERIC Educational Resources Information Center

Leith, Georgia; Yuill, Nicola; Pike, Alison

2018-01-01

Background: Typical scaffolding coding schemes provide overall scores to compare across a sample. As such, insights into the scaffolding process can be obscured: the child's contribution to the learning; the particular skills being taught and learned; and the overall changes in amount of scaffolding over the course of the task. Aims: This study…

In vivo bone formation by human marrow stromal cells in biodegradable scaffolds that release dexamethasone and ascorbate-2-phosphate.

PubMed

Kim, Hyongbum; Suh, Hwal; Jo, Sangmee Ahn; Kim, Hyun Woo; Lee, Jung Min; Kim, Eun Hae; Reinwald, Yvonne; Park, Sang-Hyug; Min, Byoung-Hyun; Jo, Inho

2005-07-15

An unsolved problem with stem cell-based engineering of bone tissue is how to provide a microenvironment that promotes the osteogenic differentiation of multipotent stem cells. Previously, we fabricated porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds that released biologically active dexamethasone (Dex) and ascorbate-2-phosphate (AsP), and that acted as osteogenic scaffolds. To determine whether these osteogenic scaffolds can be used for bone formation in vivo, we seeded multipotent human marrow stromal cells (hMSCs) onto the scaffolds and implanted them subcutaneously into athymic mice. Higher alkaline phosphatase expression was observed in hMSCs in the osteogenic scaffolds compared with that of hMSCs in control scaffolds. Furthermore, there was more calcium deposition and stronger von Kossa staining in the osteogenic scaffolds, which suggested that there was enhanced mineralized bone formation. We failed to detect cartilage in the osteogenic scaffolds (negative Safranin O staining), which implied that there was intramembranous ossification. This is the first study to demonstrate the successful formation of mineralized bone tissue in vivo by hMSCs in PLGA scaffolds that release Dex and AsP.

Improving bone repair of femoral and radial defects in rabbit by incorporating PRP into PLGA/CPC composite scaffold with unidirectional pore structure.

PubMed

He, Fupo; Chen, Yan; Li, Jiyan; Lin, Bomiao; Ouyang, Yi; Yu, Bo; Xia, Yuanyou; Yu, Bo; Ye, Jiandong

2015-04-01

In this study, a platelet-rich plasma poly(lactic-co-glycolic acid) (PRP-PLGA)/calcium phosphate cement (CPC) composite scaffold was prepared by incorporating PRP into PLGA/CPC scaffold with unidirectional pore structure, which was fabricated by the unidirectional freeze casting of CPC slurry and the following infiltration of PLGA. The results from in vitro cell experiments and in vivo implantation in femoral defects manifested that incorporation of PRP into PLGA/CPC scaffold improved in vitro cell response (cell attachment, proliferation, and differentiation), and markedly boosted bone formation, angiogenesis and material degradation. The incorporation of PRP into scaffold showed more outstanding improvement in osteogenesis as the scaffolds were used to repair the segmental radial defects, especially at the early stage. The new bone tissues grew along the unidirectional lamellar pores of scaffold. At 12 weeks postimplantation, the segmental radial defects treated with PRP-PLGA/CPC scaffold had almost recuperated, whereas treated with the scaffold without PRP was far from healed. Taken together, the PRP-PLGA/CPC scaffold with unidirectional pore structure is a promising candidate to repair bone defects at various sites. © 2014 Wiley Periodicals, Inc.

Effect of pore architecture and stacking direction on mechanical properties of solid freeform fabrication-based scaffold for bone tissue engineering.

PubMed

Lee, Jung-Seob; Cha, Hwang Do; Shim, Jin-Hyung; Jung, Jin Woo; Kim, Jong Young; Cho, Dong-Woo

2012-07-01

Fabrication of a three-dimensional (3D) scaffold with increased mechanical strength may be an essential requirement for more advanced bone tissue engineering scaffolds. Various material- and chemical-based approaches have been explored to enhance the mechanical properties of engineered bone tissue scaffolds. In this study, the effects of pore architecture and stacking direction on the mechanical and cell proliferation properties of a scaffold were investigated. The 3D scaffold was prepared using solid freeform fabrication technology with a multihead deposition system. Various types of scaffolds with different pore architectures (lattice, stagger, and triangle types) and stacking directions (horizontal and vertical directions) were fabricated with a blend of polycaprolactone and poly lactic-co-glycolic acid. In compression tests, the triangle-type scaffold was the strongest among the experimental groups. Stacking direction affected the mechanical properties of scaffolds. An in vitro cell counting kit-8 assay showed no significant differences in optical density depending on the different pore architectures and stacking directions. In conclusion, mechanical properties of scaffolds can be enhanced by controlling pore architecture and stacking direction. Copyright © 2012 Wiley Periodicals, Inc.

Inquiry-based science education: scaffolding pupils' self-directed learning in open inquiry

NASA Astrophysics Data System (ADS)

van Uum, Martina S. J.; Verhoeff, Roald P.; Peeters, Marieke

2017-12-01

This paper describes a multiple case study on open inquiry-based learning in primary schools. During open inquiry, teachers often experience difficulties in balancing support and transferring responsibility to pupils' own learning. To facilitate teachers in guiding open inquiry, we developed hard and soft scaffolds. The hard scaffolds consisted of documents with explanations and/or exercises regarding difficult parts of the inquiry process. The soft scaffolds included explicit references to and additional explanations of the hard scaffolds. We investigated how teacher implementation of these scaffolds contributed to pupils' self-directed learning during open inquiry. Four classes of pupils, aged 10-11, were observed while they conducted an inquiry lesson module of about 10 lessons in their classrooms. Data were acquired via classroom observations, audio recordings, and interviews with teachers and pupils. The results show that after the introduction of the hard scaffolds by the teacher, pupils were able and willing to apply them to their investigations. Combining hard scaffolds with additional soft scaffolding promoted pupils' scientific understanding and contributed to a shared guidance of the inquiry process by the teacher and her pupils. Our results imply that the effective use of scaffolds is an important element to be included in teacher professionalisation.

3D Printing of Scaffolds for Tissue Regeneration Applications.

PubMed

Do, Anh-Vu; Khorsand, Behnoush; Geary, Sean M; Salem, Aliasger K

2015-08-26

The current need for organ and tissue replacement, repair, and regeneration for patients is continually growing such that supply is not meeting demand primarily due to a paucity of donors as well as biocompatibility issues leading to immune rejection of the transplant. In order to overcome these drawbacks, scientists have investigated the use of scaffolds as an alternative to transplantation. These scaffolds are designed to mimic the extracellular matrix (ECM) by providing structural support as well as promoting attachment, proliferation, and differentiation with the ultimate goal of yielding functional tissues or organs. Initial attempts at developing scaffolds were problematic and subsequently inspired an interest in 3D printing as a mode for generating scaffolds. Utilizing three-dimensional printing (3DP) technologies, ECM-like scaffolds can be produced with a high degree of complexity, where fine details can be included at a micrometer level. In this Review, the criteria for printing viable and functional scaffolds, scaffolding materials, and 3DP technologies used to print scaffolds for tissue engineering are discussed. Creating biofunctional scaffolds could potentially help to meet the demand by patients for tissues and organs without having to wait or rely on donors for transplantation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.