Purpose-driven biomaterials research in liver-tissue engineering.

PubMed

Ananthanarayanan, Abhishek; Narmada, Balakrishnan Chakrapani; Mo, Xuejun; McMillian, Michael; Yu, Hanry

2011-03-01

Bottom-up engineering of microscale tissue ("microtissue") constructs to recapitulate partially the complex structure-function relationships of liver parenchyma has been realized through the development of sophisticated biomaterial scaffolds, liver-cell sources, and in vitro culture techniques. With regard to in vivo applications, the long-lived stem/progenitor cell constructs can improve cell engraftment, whereas the short-lived, but highly functional hepatocyte constructs stimulate host liver regeneration. With regard to in vitro applications, microtissue constructs are being adapted or custom-engineered into cell-based assays for testing acute, chronic and idiosyncratic toxicities of drugs or pathogens. Systems-level methods and computational models that represent quantitative relationships between biomaterial scaffolds, cells and microtissue constructs will further enable their rational design for optimal integration into specific biomedical applications. Copyright © 2010 Elsevier Ltd. All rights reserved.

CYP51 structures and structure-based development of novel, pathogen-specific inhibitory scaffolds.

PubMed

Hargrove, Tatiana Y; Kim, Kwangho; de Nazaré Correia Soeiro, Maria; da Silva, Cristiane França; Batista, Denise da Gama Jaen; Batista, Marcos Meuser; Yazlovitskaya, Eugenia M; Waterman, Michael R; Sulikowski, Gary A; Lepesheva, Galina I

2012-12-01

CYP51 (sterol 14α-demethylase) is a cytochrome P450 enzyme essential for sterol biosynthesis and the primary target for clinical and agricultural antifungal azoles. The azoles that are currently in clinical use for systemic fungal infections represent modifications of two basic scaffolds, ketoconazole and fluconazole, all of them being selected based on their antiparasitic activity in cellular experiments. By studying direct inhibition of CYP51 activity across phylogeny including human pathogens Trypanosoma brucei , Trypanosoma cruzi and Leishmania infantum , we identified three novel protozoa-specific inhibitory scaffolds, their inhibitory potency correlating well with antiprotozoan activity. VNI scaffold (carboxamide containing β-phenyl-imidazoles) is the most promising among them: killing T. cruzi amastigotes at low nanomolar concentration, it is also easy to synthesize and nontoxic. Oral administration of VNI (up to 400 mg/kg) neither leads to mortality nor reveals significant side effects up to 48 h post treatment using an experimental mouse model of acute toxicity. Trypanosomatidae CYP51 crystal structures determined in the ligand-free state and complexed with several azole inhibitors as well as a substrate analog revealed high rigidity of the CYP51 substrate binding cavity, which must be essential for the enzyme strict substrate specificity and functional conservation. Explaining profound potency of the VNI inhibitory scaffold, the structures also outline guidelines for its further development. First steps of the VNI scaffold optimization have been undertaken; the results presented here support the notion that CYP51 structure-based rational design of more efficient, pathogen-specific inhibitors represents a highly promising direction.

Design of Heteronuclear Metalloenzymes

PubMed Central

Bhagi-Damodaran, Ambika; Hosseinzadeh, Parisa; Mirts, Evan; Reed, Julian; Petrik, Igor D.; Lu, Yi

2016-01-01

Heteronuclear metalloenzymes catalyze some of the most fundamentally interesting and practically useful reactions in nature. However, the presence of two or more metal ions in close proximity in these enzymes makes them more difficult to prepare and study than homonuclear metalloenzymes. To meet these challenges, heteronuclear metal centers have been designed into small and stable proteins with rigid scaffolds to understand how these heteronuclear centers are constructed and the mechanism of their function. This chapter describes methods for designing heterobinuclear metal centers in a protein scaffold by giving specific examples of a few heme-nonheme bimetallic centers engineered in myoglobin and cytochrome c peroxidase. We provide step-by-step procedure on how to choose the protein scaffold, design a heterobinuclear metal center in the protein computationally, incorporate metal centers in the protein and characterize the resulting metalloprotein, both structurally and functionally. Finally, we discuss how an initial design can be further improved by rationally tuning its secondary coordination sphere, electron/proton transfer rates, and the substrate affinity. PMID:27586347

Differential Antibody Responses to Conserved HIV-1 Neutralizing Epitopes in the Context of Multivalent Scaffolds and Native-Like gp140 Trimers.

PubMed

Morris, Charles D; Azadnia, Parisa; de Val, Natalia; Vora, Nemil; Honda, Andrew; Giang, Erick; Saye-Francisco, Karen; Cheng, Yushao; Lin, Xiaohe; Mann, Colin J; Tang, Jeffrey; Sok, Devin; Burton, Dennis R; Law, Mansun; Ward, Andrew B; He, Linling; Zhu, Jiang

2017-02-28

Broadly neutralizing antibodies (bNAbs) have provided valuable insights into the humoral immune response to HIV-1. While rationally designed epitope scaffolds and well-folded gp140 trimers have been proposed as vaccine antigens, a comparative understanding of their antibody responses has not yet been established. In this study, we probed antibody responses to the N332 supersite and the membrane-proximal external region (MPER) in the context of heterologous protein scaffolds and native-like gp140 trimers. Ferritin nanoparticles and fragment crystallizable (Fc) regions were utilized as multivalent carriers to display scaffold antigens with grafted N332 and MPER epitopes, respectively. Trimeric scaffolds were also identified to stabilize the MPER-containing BG505 gp140.681 trimer in a native-like conformation. Following structural and antigenic evaluation, a subset of scaffold and trimer antigens was selected for immunization in BALB/c mice. Serum binding revealed distinct patterns of antibody responses to these two bNAb targets presented in different structural contexts. For example, the N332 nanoparticles elicited glycan epitope-specific antibody responses that could also recognize the native trimer, while a scaffolded BG505 gp140.681 trimer generated a stronger and more rapid antibody response to the trimer apex than its parent gp140.664 trimer. Furthermore, next-generation sequencing (NGS) of mouse splenic B cells revealed expansion of antibody lineages with long heavy-chain complementarity-determining region 3 (HCDR3) loops upon activation by MPER scaffolds, in contrast to the steady repertoires primed by N332 nanoparticles and a soluble gp140.664 trimer. These findings will facilitate the future development of a coherent vaccination strategy that combines both epitope-focused and trimer-based approaches. IMPORTANCE Both epitope-focused and trimer-based strategies are currently being explored in HIV-1 vaccine development, which aims to elicit broadly neutralizing antibodies (bNAbs) targeting conserved epitopes on the viral envelope (Env). However, little is known about the differences in antibody response to these bNAb targets presented by foreign scaffolds and native Env. In this study, a systematic effort was undertaken to design multivalent epitope scaffolds and soluble gp140.681 trimers with a complete antigenic surface, and to comparatively analyze the antibody responses elicited by these antigens to the N332 supersite and MPER in a mouse model. This study will inform both epitope-focused and trimer-based vaccine design and will facilitate integration of the two vaccine strategies. Copyright © 2017 Morris et al.

Generation and development of RNA ligase ribozymes with modular architecture through "design and selection".

PubMed

Fujita, Yuki; Ishikawa, Junya; Furuta, Hiroyuki; Ikawa, Yoshiya

2010-08-26

In vitro selection with long random RNA libraries has been used as a powerful method to generate novel functional RNAs, although it often requires laborious structural analysis of isolated RNA molecules. Rational RNA design is an attractive alternative to avoid this laborious step, but rational design of catalytic modules is still a challenging task. A hybrid strategy of in vitro selection and rational design has been proposed. With this strategy termed "design and selection," new ribozymes can be generated through installation of catalytic modules onto RNA scaffolds with defined 3D structures. This approach, the concept of which was inspired by the modular architecture of naturally occurring ribozymes, allows prediction of the overall architectures of the resulting ribozymes, and the structural modularity of the resulting ribozymes allows modification of their structures and functions. In this review, we summarize the design, generation, properties, and engineering of four classes of ligase ribozyme generated by design and selection.

Self-Assembled Proteins and Peptides as Scaffolds for Tissue Regeneration.

PubMed

Loo, Yihua; Goktas, Melis; Tekinay, Ayse B; Guler, Mustafa O; Hauser, Charlotte A E; Mitraki, Anna

2015-11-18

Self-assembling proteins and peptides are increasingly gaining interest for potential use as scaffolds in tissue engineering applications. They self-organize from basic building blocks under mild conditions into supramolecular structures, mimicking the native extracellular matrix. Their properties can be easily tuned through changes at the sequence level. Moreover, they can be produced in sufficient quantities with chemical synthesis or recombinant technologies to allow them to address homogeneity and standardization issues required for applications. Here. recent advances in self-assembling proteins, peptides, and peptide amphiphiles that form scaffolds suitable for tissue engineering are reviewed. The focus is on a variety of motifs, ranging from minimalistic dipeptides, simplistic ultrashort aliphatic peptides, and peptide amphiphiles to large "recombinamer" proteins. Special emphasis is placed on the rational design of self-assembling motifs and biofunctionalization strategies to influence cell behavior and modulate scaffold stability. Perspectives for combination of these "bottom-up" designer strategies with traditional "top-down" biofabrication techniques for new generations of tissue engineering scaffolds are highlighted. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure-Based Rational Design of a Toll-like Receptor 4 (TLR4) Decoy Receptor with High Binding Affinity for a Target Protein

PubMed Central

Lee, Sang-Chul; Hong, Seungpyo; Park, Keunwan; Jeon, Young Ho; Kim, Dongsup; Cheong, Hae-Kap; Kim, Hak-Sung

2012-01-01

Repeat proteins are increasingly attracting much attention as alternative scaffolds to immunoglobulin antibodies due to their unique structural features. Nonetheless, engineering interaction interface and understanding molecular basis for affinity maturation of repeat proteins still remain a challenge. Here, we present a structure-based rational design of a repeat protein with high binding affinity for a target protein. As a model repeat protein, a Toll-like receptor4 (TLR4) decoy receptor composed of leucine-rich repeat (LRR) modules was used, and its interaction interface was rationally engineered to increase the binding affinity for myeloid differentiation protein 2 (MD2). Based on the complex crystal structure of the decoy receptor with MD2, we first designed single amino acid substitutions in the decoy receptor, and obtained three variants showing a binding affinity (KD) one-order of magnitude higher than the wild-type decoy receptor. The interacting modes and contributions of individual residues were elucidated by analyzing the crystal structures of the single variants. To further increase the binding affinity, single positive mutations were combined, and two double mutants were shown to have about 3000- and 565-fold higher binding affinities than the wild-type decoy receptor. Molecular dynamics simulations and energetic analysis indicate that an additive effect by two mutations occurring at nearby modules was the major contributor to the remarkable increase in the binding affinities. PMID:22363519

Ligand-regulated peptides: a general approach for modulating protein-peptide interactions with small molecules.

PubMed

Binkowski, Brock F; Miller, Russell A; Belshaw, Peter J

2005-07-01

We engineered a novel ligand-regulated peptide (LiRP) system where the binding activity of intracellular peptides is controlled by a cell-permeable small molecule. In the absence of ligand, peptides expressed as fusions in an FKBP-peptide-FRB-GST LiRP scaffold protein are free to interact with target proteins. In the presence of the ligand rapamycin, or the nonimmunosuppressive rapamycin derivative AP23102, the scaffold protein undergoes a conformational change that prevents the interaction of the peptide with the target protein. The modular design of the scaffold enables the creation of LiRPs through rational design or selection from combinatorial peptide libraries. Using these methods, we identified LiRPs that interact with three independent targets: retinoblastoma protein, c-Src, and the AMP-activated protein kinase. The LiRP system should provide a general method to temporally and spatially regulate protein function in cells and organisms.

Rationally engineering natural protein assemblies in nanobiotechnology.

PubMed

Howorka, Stefan

2011-08-01

Multimeric protein assemblies are essential components in viruses, bacteria, eukaryotic cells, and organisms where they act as cytoskeletal scaffold, storage containers, or for directional transport. The bottom-up structures can be exploited in nanobiotechnology by harnessing their built-in properties and combining them with new functional modules. This review summarizes the design principles of natural protein assemblies, highlights recent progress in their structural elucidation, and shows how rational engineering can create new biomaterials for applications in vaccine development, biocatalysis, materials science, and synthetic biology. Copyright © 2011 Elsevier Ltd. All rights reserved.

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.

Sweetness prediction of natural compounds.

PubMed

Chéron, Jean-Baptiste; Casciuc, Iuri; Golebiowski, Jérôme; Antonczak, Serge; Fiorucci, Sébastien

2017-04-15

Based on the most exhaustive database of sweeteners with known sweetness values, a new quantitative structure-activity relationship model for sweetness prediction has been set up. Analysis of the physico-chemical properties of sweeteners in the database indicates that the structure of most potent sweeteners combines a hydrophobic scaffold functionalized by a limited number of hydrogen bond sites (less than 4 hydrogen bond donors and 10 acceptors), with a moderate molecular weight ranging from 350 to 450g·mol -1 . Prediction of sweetness, bitterness and toxicity properties of the largest database of natural compounds have been performed. In silico screening reveals that the majority of the predicted natural intense sweeteners comprise saponin or stevioside scaffolds. The model highlights that their sweetness potency is comparable to known natural sweeteners. The identified compounds provide a rational basis to initiate the design and chemosensory analysis of new low-calorie sweeteners. Copyright © 2016 Elsevier Ltd. All rights reserved.

Designing multi-targeted agents: An emerging anticancer drug discovery paradigm.

PubMed

Fu, Rong-Geng; Sun, Yuan; Sheng, Wen-Bing; Liao, Duan-Fang

2017-08-18

The dominant paradigm in drug discovery is to design ligands with maximum selectivity to act on individual drug targets. With the target-based approach, many new chemical entities have been discovered, developed, and further approved as drugs. However, there are a large number of complex diseases such as cancer that cannot be effectively treated or cured only with one medicine to modulate the biological function of a single target. As simultaneous intervention of two (or multiple) cancer progression relevant targets has shown improved therapeutic efficacy, the innovation of multi-targeted drugs has become a promising and prevailing research topic and numerous multi-targeted anticancer agents are currently at various developmental stages. However, most multi-pharmacophore scaffolds are usually discovered by serendipity or screening, while rational design by combining existing pharmacophore scaffolds remains an enormous challenge. In this review, four types of multi-pharmacophore modes are discussed, and the examples from literature will be used to introduce attractive lead compounds with the capability of simultaneously interfering with different enzyme or signaling pathway of cancer progression, which will reveal the trends and insights to help the design of the next generation multi-targeted anticancer agents. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Differential Antibody Responses to Conserved HIV-1 Neutralizing Epitopes in the Context of Multivalent Scaffolds and Native-Like gp140 Trimers

PubMed Central

Morris, Charles D.; Azadnia, Parisa; de Val, Natalia; Vora, Nemil; Honda, Andrew; Giang, Erick; Saye-Francisco, Karen; Cheng, Yushao; Lin, Xiaohe; Mann, Colin J.; Tang, Jeffrey; Sok, Devin; Burton, Dennis R.; Law, Mansun; Ward, Andrew B.

2017-01-01

ABSTRACT Broadly neutralizing antibodies (bNAbs) have provided valuable insights into the humoral immune response to HIV-1. While rationally designed epitope scaffolds and well-folded gp140 trimers have been proposed as vaccine antigens, a comparative understanding of their antibody responses has not yet been established. In this study, we probed antibody responses to the N332 supersite and the membrane-proximal external region (MPER) in the context of heterologous protein scaffolds and native-like gp140 trimers. Ferritin nanoparticles and fragment crystallizable (Fc) regions were utilized as multivalent carriers to display scaffold antigens with grafted N332 and MPER epitopes, respectively. Trimeric scaffolds were also identified to stabilize the MPER-containing BG505 gp140.681 trimer in a native-like conformation. Following structural and antigenic evaluation, a subset of scaffold and trimer antigens was selected for immunization in BALB/c mice. Serum binding revealed distinct patterns of antibody responses to these two bNAb targets presented in different structural contexts. For example, the N332 nanoparticles elicited glycan epitope-specific antibody responses that could also recognize the native trimer, while a scaffolded BG505 gp140.681 trimer generated a stronger and more rapid antibody response to the trimer apex than its parent gp140.664 trimer. Furthermore, next-generation sequencing (NGS) of mouse splenic B cells revealed expansion of antibody lineages with long heavy-chain complementarity-determining region 3 (HCDR3) loops upon activation by MPER scaffolds, in contrast to the steady repertoires primed by N332 nanoparticles and a soluble gp140.664 trimer. These findings will facilitate the future development of a coherent vaccination strategy that combines both epitope-focused and trimer-based approaches. PMID:28246356

Identification of shikimate kinase inhibitors among anti-Mycobacterium tuberculosis compounds by LC-MS.

PubMed

Simithy, Johayra; Reeve, Nathaniel; Hobrath, Judith V; Reynolds, Robert C; Calderón, Angela I

2014-03-01

Increasing drug resistance has challenged the control and treatment of tuberculosis, sparking recent interest in finding new antitubercular agents with different chemical scaffolds and mechanisms of action. Mycobacterium tuberculosis shikimate kinase (MtSK), an enzyme present in the shikimate pathway in bacteria, is essential for the survival of the tubercle bacillus, representing an ideal target for therapeutic intervention given its absence in mammals. In this study, a small library of 404 synthetic antimycobacterial compounds identified and supplied through the NIH Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) high throughput screening program against whole cell M. tuberculosis H37Rv was further screened using a mass spectrometry-based functional assay in order to identify a potential enzymatic target. Fourteen compounds containing an oxadiazole-amide or a 2-aminobenzothiazole core scaffold showed MtSK inhibitory activity at 50 μM, with the lowest giving an IC50 of 1.94 μM. Induced fit docking studies suggested that the scaffolds shared by these compounds fit well in the shikimate binding pocket of MtSK. In summary, we report new early discovery stage lead scaffolds targeting the essential protein MtSK that can be further pursued in a rational drug design program for the discovery of more selective antitubercular drugs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Asymmetric catalytic cascade reactions for constructing diverse scaffolds and complex molecules.

PubMed

Wang, Yao; Lu, Hong; Xu, Peng-Fei

2015-07-21

With the increasing concerns about chemical pollution and sustainability of resources, among the significant challenges facing synthetic chemists are the development and application of elegant and efficient methods that enable the concise synthesis of natural products, drugs, and related compounds in a step-, atom- and redox-economic manner. One of the most effective ways to reach this goal is to implement reaction cascades that allow multiple bond-forming events to occur in a single vessel. This Account documents our progress on the rational design and strategic application of asymmetric catalytic cascade reactions in constructing diverse scaffolds and synthesizing complex chiral molecules. Our research is aimed at developing robust cascade reactions for the systematic synthesis of a range of interesting molecules that contain structural motifs prevalent in natural products, pharmaceuticals, and biological probes. The strategies employed to achieve this goal can be classified into three categories: bifunctional base/Brønsted acid catalysis, covalent aminocatalysis/N-heterocyclic carbene catalysis, and asymmetric organocatalytic relay cascades. By the use of rationally designed substrates with properly reactive sites, chiral oxindole, chroman, tetrahydroquinoline, tetrahydrothiophene, and cyclohexane scaffolds were successfully assembled under bifunctional base/Brønsted acid catalysis from simple and readily available substances such as imines and nitroolefins. We found that some of these reactions are highly efficient since catalyst loadings as low as 1 mol % can promote the multistep sequences affording complex architectures with high stereoselectivities and yields. Furthermore, one of the bifunctional base/Brønsted acid-catalyzed cascade reactions for the synthesis of chiral cyclohexanes has been used as a key step in the construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of α-lycorane. Guided by the principles of covalent aminocatalysis and N-heterocyclic carbene catalysis, we synthesized chiral piperidine, indole, and cyclobutane derivatives. The synthesis of chiral cyclobutanes and pyrroloindolones showed unprecedented reactivity of substrates and catalysts. The development of the strategy of asymmetric organocatalytic relay cascades has provided a useful tool for the controlled synthesis of specific diastereomers in complex molecules. This Account gives a panoramic view and the logic of our research on the design, development, and applications of asymmetric catalytic cascade reactions that will potentially provide useful insights into exploring new reactions.

A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering

PubMed Central

Choy, Andrew Tsz Hang; Chan, Barbara Pui

2015-01-01

Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering. PMID:26115332

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

PubMed

Wen, Amy M; Steinmetz, Nicole F

2016-07-25

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.

Discovery of Highly Selective and Nanomolar Carbamate-Based Butyrylcholinesterase Inhibitors by Rational Investigation into Their Inhibition Mode.

PubMed

Sawatzky, Edgar; Wehle, Sarah; Kling, Beata; Wendrich, Jan; Bringmann, Gerhard; Sotriffer, Christoph A; Heilmann, Jörg; Decker, Michael

2016-03-10

Butyrylcholinesterase (BChE) is a promising target for the treatment of later stage cognitive decline in Alzheimer's disease. A set of pseudo-irreversible BChE inhibitors with high selectivity over hAChE was synthesized based on carbamates attached to tetrahydroquinazoline scaffolds with the 2-thiophenyl compound 2p as the most potent inhibitor of eqBChE (KC = 14.3 nM) and also of hBChE (KC = 19.7 nM). The inhibitors transfer the carbamate moiety onto the active site under release of the phenolic tetrahydroquinazoline scaffolds that themselves act as neuroprotectants. By combination of kinetic data with molecular docking studies, a plausible binding model was probed describing how the tetrahydroquinazoline scaffold guides the carbamate into a close position to the active site. The model explains the influence of the carrier scaffold onto the affinity of an inhibitor just before carbamate transfer. This strategy can be used to utilize the binding mode of other carbamate-based inhibitors.

Design of Bioinorganic Materials at the Interface of Coordination and Biosupramolecular Chemistry.

PubMed

Maity, Basudev; Ueno, Takafumi

2017-04-01

Protein assemblies have recently become known as potential molecular scaffolds for applications in materials science and bio-nanotechnology. Efforts to design protein assemblies for construction of protein-based hybrid materials with metal ions, metal complexes, nanomaterials and proteins now represent a growing field with a common aim of providing novel functions and mimicking natural functions. However, the important roles of protein assemblies in coordination and biosupramolecular chemistry have not been systematically investigated and characterized. In this personal account, we focus on our recent progress in rational design of protein assemblies using bioinorganic chemistry for (1) exploration of unnatural reactions, (2) construction of functional protein architectures, and (3) in vivo applications. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design of self-assembling beta-hairpin pepide-based hydrogels for tissue engineering applications

NASA Astrophysics Data System (ADS)

Butterick, Lisa Ann

The field of tissue engineering aims to repair damaged tissues and organs with diminished function. One approach used in tissue engineering is to introduce cells and/or growth factors to the damaged tissue in either one of two ways. The first method is an invasive procedure where cells are introduced to a preformed scaffold and cultured in vitro. The scaffold is then inserted into the host by making an incision at the site of interest, which must be as large as the preformed scaffold. The second method is a minimally invasive procedure where cells are suspended in a polymeric solution and injected via syringe. After leaving the syringe, the material undergoes a phase transition to form a hydrogel at the site of introduction. Regardless of the delivery mechanism employed, development of an appropriate scaffold conducive to cellular proliferation and extracellular matrix production is critical to the success of the implanted material in persuading the body to repair itself. In working toward this goal, we have developed a family of beta-hairpin peptides, based on the design MAX1, that undergoes intramolecular folding and self-assembly to form rigid hydrogels in response to changes in pH, ionic strength, and temperature. From a molecular design standpoint of view, site specific N-methylation of MAX1 was performed to determine the importance of forming hydrogen bonds during the self-assembly event and its effect on hydrogelation. The remainder of this thesis is dedicated to the development of materials and minimally methodologies to deliver gel/cell constructs via syringe to target sites to aid in tissue repair. A peptide, MAX7CNB was designed that undergoes folding and assembly in response to ultraviolet light to form hydrogel material. In addition, MAX8 was rationally designed to display the appropriate hydrogelation kinetics to achieve homogenous cellular encapsulation throughout the gel matrix. MAX8 gel/cell scaffolds can be easily delivered via syringe to secondary target sites while maintaining cellular homogeneity, viability and remain fixed at the site of introduction. Additionally, preliminary in vitro based studies employing mouse peritoneal macrophages suggest the MAX8 gels are non-inflammatory in nature and may not elicit an in vivo immune response upon implantation. It has been demonstrated throughout this thesis that by employing amino acids as fundamental building blocks, peptide sequences can be designed to undergo molecular recognition, resulting in hydrogel material for use in tissue engineering applications.

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

DNA rendering of polyhedral meshes at the nanoscale

NASA Astrophysics Data System (ADS)

Benson, Erik; Mohammed, Abdulmelik; Gardell, Johan; Masich, Sergej; Czeizler, Eugen; Orponen, Pekka; Högberg, Björn

2015-07-01

It was suggested more than thirty years ago that Watson-Crick base pairing might be used for the rational design of nanometre-scale structures from nucleic acids. Since then, and especially since the introduction of the origami technique, DNA nanotechnology has enabled increasingly more complex structures. But although general approaches for creating DNA origami polygonal meshes and design software are available, there are still important constraints arising from DNA geometry and sense/antisense pairing, necessitating some manual adjustment during the design process. Here we present a general method of folding arbitrary polygonal digital meshes in DNA that readily produces structures that would be very difficult to realize using previous approaches. The design process is highly automated, using a routeing algorithm based on graph theory and a relaxation simulation that traces scaffold strands through the target structures. Moreover, unlike conventional origami designs built from close-packed helices, our structures have a more open conformation with one helix per edge and are therefore stable under the ionic conditions usually used in biological assays.

DNA rendering of polyhedral meshes at the nanoscale.

PubMed

Benson, Erik; Mohammed, Abdulmelik; Gardell, Johan; Masich, Sergej; Czeizler, Eugen; Orponen, Pekka; Högberg, Björn

2015-07-23

It was suggested more than thirty years ago that Watson-Crick base pairing might be used for the rational design of nanometre-scale structures from nucleic acids. Since then, and especially since the introduction of the origami technique, DNA nanotechnology has enabled increasingly more complex structures. But although general approaches for creating DNA origami polygonal meshes and design software are available, there are still important constraints arising from DNA geometry and sense/antisense pairing, necessitating some manual adjustment during the design process. Here we present a general method of folding arbitrary polygonal digital meshes in DNA that readily produces structures that would be very difficult to realize using previous approaches. The design process is highly automated, using a routeing algorithm based on graph theory and a relaxation simulation that traces scaffold strands through the target structures. Moreover, unlike conventional origami designs built from close-packed helices, our structures have a more open conformation with one helix per edge and are therefore stable under the ionic conditions usually used in biological assays.

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.

Hit discovery of 4-amino-N-(4-(3-(trifluoromethyl)phenoxy)pyrimidin-5-yl)benzamide: A novel EGFR inhibitor from a designed small library.

PubMed

Elkamhawy, Ahmed; Paik, Sora; Hassan, Ahmed H E; Lee, Yong Sup; Roh, Eun Joo

2017-12-01

Searching for hit compounds within the huge chemical space resembles the attempt to find a needle in a haystack. Cheminformatics-guided selection of few representative molecules of a rationally designed virtual combinatorial library is a powerful tool to confront this challenge, speed up hit identification and cut off costs. Herein, this approach has been applied to identify hit compounds with novel scaffolds able to inhibit EGFR kinase. From a generated virtual library, six 4-aryloxy-5-aminopyrimidine scaffold-derived compounds were selected, synthesized and evaluated as hit EGFR inhibitors. 4-Aryloxy-5-benzamidopyrimidines inhibited EGFR with IC 50 1.05-5.37 μM. Cell-based assay of the most potent EGFR inhibitor hit (10ac) confirmed its cytotoxicity against different cancerous cells. In spite of no EGFR, HER2 or VEGFR1 inhibition was elicited by 4-aryloxy-5-(thio)ureidopyrimidine derivatives, cell-based evaluation suggested them as antiproliferative hits acting by other mechanism(s). Molecular docking study provided a plausible explanation of incapability of 4-aryloxy-5-(thio)ureidopyrimidines to inhibit EGFR and suggested a reasonable binding mode of 4-aryloxy-5-benzamidopyrimidines which provides a basis to develop more optimized ligands. Copyright © 2017 Elsevier Inc. All rights reserved.

Probing vocal fold fibroblast response to hyaluronan in 3D contexts.

PubMed

Munoz-Pinto, Dany J; Jimenez-Vergara, Andrea Carolina; Gelves, L Marcela; McMahon, Rebecca E; Guiza-Arguello, Viviana; Hahn, Mariah S

2009-11-01

A number of treatments are being investigated for vocal fold (VF) scar, including designer implants. The aim of the present study was to validate a 3D model system for probing the effects of various bioactive moieties on VF fibroblast (VFF) behavior toward rational implant design. We selected poly(ethylene glycol) diacrylate (PEGDA) hydrogels as our base-scaffold due to their broadly tunable material properties. However, since cells encapsulated in PEGDA hydrogels are generally forced to take on rounded/stellate morphologies, validation of PEGDA gels as a 3D VFF model system required that the present work directly parallel previous studies involving more permissive scaffolds. We therefore chose to focus on hyaluronan (HA), a polysaccharide that has been a particular focus of the VF community. Toward this end, porcine VFFs were encapsulated in PEGDA hydrogels containing consistent levels of high Mw HA (HA(HMW)), intermediate Mw HA (HA(IMW)), or the control polysaccharide, alginate, and cultured for 7 and 21 days. HA(HMW) promoted sustained increases in active ERK1/2 relative to HA(IMW). Furthermore, VFFs in HA(IMW) gels displayed a more myofibroblast-like phenotype, higher elastin production, and greater protein kinase C (PkC) levels at day 21 than VFFs in HA(HMW) and alginate gels. The present results are in agreement with a previous 3D study of VFF responses to HA(IMW) relative to alginate in collagen-based scaffolds permissive of cell elongation, indicating that PEGDA hydrogels may serve as an effective 3D model system for probing at least certain aspects of VFF behavior. Copyright 2009 Wiley Periodicals, Inc.

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

pH-Driven Reversible Self-Assembly of Micron-Scale DNA Scaffolds.

PubMed

Green, Leopold N; Amodio, Alessia; Subramanian, Hari K K; Ricci, Francesco; Franco, Elisa

2017-12-13

Inspired by cytoskeletal scaffolds that sense and respond dynamically to environmental changes and chemical inputs with a unique capacity for reconfiguration, we propose a strategy that allows the dynamic and reversible control of the growth and breakage of micron-scale synthetic DNA structures upon pH changes. We do so by rationally designing a pH-responsive system composed of synthetic DNA strands that act as pH sensors, regulators, and structural elements. Sensor strands can dynamically respond to pH changes and route regulatory strands to direct the self-assembly of structural elements into tubular structures. This example represents the first demonstration of the reversible assembly and disassembly of micron-scale DNA scaffolds using an external chemical input other than DNA. The capacity to reversibly modulate nanostructure size may promote the development of smart devices for catalysis or drug-delivery applications.

Student Award for Outstanding Research Winner in the Ph.D. Category for the 9th World Biomaterials Congress, Chengdu, China, June 1-5, 2012: The interplay of bone-like extracellular matrix and TNF-α signaling on in vitro osteogenic differentiation of mesenchymal stem cells.

PubMed

Mountziaris, Paschalia M; Tzouanas, Stephanie N; Mikos, Antonios G

2012-05-01

As an initial step in the development of a bone tissue engineering strategy to rationally control inflammation, we investigated the interplay of bone-like extracellular matrix (ECM) and varying doses of the inflammatory cytokine tumor necrosis factor alpha (TNF-α) on osteogenically differentiating mesenchymal stem cells (MSCs) cultured in vitro on 3D poly(ε-caprolactone) (PCL) microfiber scaffolds containing pregenerated bone-like ECM. To generate the ECM, PCL scaffolds were seeded with MSCs and cultured in medium containing the typically required osteogenic supplement dexamethasone. However, since dexamethasone antagonizes TNF-α, the interplay of ECM and TNF-α was investigated by culturing naïve MSCs on the decellularized scaffolds in the absence of dexamethasone. MSCs cultured on ECM-coated scaffolds continued to deposit mineralized matrix, a late stage marker of osteogenic differentiation. Mineralized matrix deposition was not adversely affected by exposure to TNF-α for 4-8 days, but was significantly reduced after continuous exposure to TNF-α over 16 days, which simulates the in vivo response, where brief TNF-α signaling stimulates bone regeneration, while prolonged exposure has damaging effects. This underscores the exciting potential of PCL/ECM constructs as a more clinically realistic in vitro culture model to facilitate the design of new bone tissue engineering strategies that rationally control inflammation to promote regeneration. Copyright © 2012 Wiley Periodicals, Inc.

A Framework for Designing Scaffolds That Improve Motivation and Cognition

PubMed Central

Belland, Brian R.; Kim, ChanMin; Hannafin, Michael J.

2013-01-01

A problematic, yet common, assumption among educational researchers is that when teachers provide authentic, problem-based experiences, students will automatically be engaged. Evidence indicates that this is often not the case. In this article, we discuss (a) problems with ignoring motivation in the design of learning environments, (b) problem-based learning and scaffolding as one way to help, (c) how scaffolding has strayed from what was originally equal parts motivational and cognitive support, and (d) a conceptual framework for the design of scaffolds that can enhance motivation as well as cognitive outcomes. We propose guidelines for the design of computer-based scaffolds to promote motivation and engagement while students are solving authentic problems. Remaining questions and suggestions for future research are then discussed. PMID:24273351

Evolutionary and molecular foundations of multiple contemporary functions of the nitroreductase superfamily

PubMed Central

Akiva, Eyal; Copp, Janine N.; Tokuriki, Nobuhiko; Babbitt, Patricia C.

2017-01-01

Insight regarding how diverse enzymatic functions and reactions have evolved from ancestral scaffolds is fundamental to understanding chemical and evolutionary biology, and for the exploitation of enzymes for biotechnology. We undertook an extensive computational analysis using a unique and comprehensive combination of tools that include large-scale phylogenetic reconstruction to determine the sequence, structural, and functional relationships of the functionally diverse flavin mononucleotide-dependent nitroreductase (NTR) superfamily (>24,000 sequences from all domains of life, 54 structures, and >10 enzymatic functions). Our results suggest an evolutionary model in which contemporary subgroups of the superfamily have diverged in a radial manner from a minimal flavin-binding scaffold. We identified the structural design principle for this divergence: Insertions at key positions in the minimal scaffold that, combined with the fixation of key residues, have led to functional specialization. These results will aid future efforts to delineate the emergence of functional diversity in enzyme superfamilies, provide clues for functional inference for superfamily members of unknown function, and facilitate rational redesign of the NTR scaffold. PMID:29078300

Advanced Bioinks for 3D Printing: A Materials Science Perspective.

PubMed

Chimene, David; Lennox, Kimberly K; Kaunas, Roland R; Gaharwar, Akhilesh K

2016-06-01

Advanced bioinks for 3D printing are rationally designed materials intended to improve the functionality of printed scaffolds outside the traditional paradigm of the "biofabrication window". While the biofabrication window paradigm necessitates compromise between suitability for fabrication and ability to accommodate encapsulated cells, recent developments in advanced bioinks have resulted in improved designs for a range of biofabrication platforms without this tradeoff. This has resulted in a new generation of bioinks with high print fidelity, shear-thinning characteristics, and crosslinked scaffolds with high mechanical strength, high cytocompatibility, and the ability to modulate cellular functions. In this review, we describe some of the promising strategies being pursued to achieve these goals, including multimaterial, interpenetrating network, nanocomposite, and supramolecular bioinks. We also provide an overview of current and emerging trends in advanced bioink synthesis and biofabrication, and evaluate the potential applications of these novel biomaterials to clinical use.

Rational Design of Si@SiO2/C Composites Using Sustainable Cellulose as a Carbon Resource for Anodes in Lithium-Ion Batteries.

PubMed

Shen, Dazhi; Huang, Chaofan; Gan, Lihui; Liu, Jian; Gong, Zhengliang; Long, Minnan

2018-03-07

In this work, we propose a novel and facile route for the rational design of Si@SiO 2 /C anode materials by using sustainable and environment-friendly cellulose as a carbon resource. To simultaneously obtain a SiO 2 layer and a carbon scaffold, a specially designed homogeneous cellulose solution and commercial Si nanopowder are used as the starting materials, and the cellulose/Si composite is directly assembled by an in situ regenerating method. Subsequently, Si@SiO 2 /C composite is obtained after carbonization. As expected, Si@SiO 2 is homogeneously encapsulated in the cellulose-derived carbon network. The obtained Si@SiO 2 /C composite shows a high reversible capacity of 1071 mA h g -1 at a current density of 420 mA g -1 and 70% capacity retention after 200 cycles. This novel, sustainable, and effective design is a promising approach to obtain high-performance and cost-effective composite anodes for practical applications.

Microstructure and compression properties of 3D powder printed Ti-6Al-4V scaffolds with designed porosity: Experimental and computational analysis.

PubMed

Barui, Srimanta; Chatterjee, Subhomoy; Mandal, Sourav; Kumar, Alok; Basu, Bikramjit

2017-01-01

The osseointegration of metallic implants depends on an effective balance among designed porosity to facilitate angiogenesis, tissue in-growth and bone-mimicking elastic modulus with good strength properties. While addressing such twin requirements, the present study demonstrates a low temperature additive manufacturing based processing strategy to fabricate Ti-6Al-4V scaffolds with designed porosity using inkjet-based 3D powder printing (3DPP). A novel starch-based aqueous binder was prepared and the physico-chemical parameters such as pH, viscosity, and surface tension were optimized for drop-on-demand (DOD) based thermal inkjet printing. Micro-computed tomography (micro-CT) of sintered scaffolds revealed a 57% total porosity in homogeneously porous scaffold and 45% in the gradient porous scaffold with 99% interconnectivity among the micropores. Under uniaxial compression testing, the strength of homogeneously porous and gradient porous scaffolds were ~47MPa and ~90MPa, respectively. The progressive failure in homogeneously porous scaffold was recorded. In parallel to experimental measurements, finite element (FE) analyses have been performed to study the stress distribution globally and also locally around the designed pores. Consistent with FE analyses, a higher elastic modulus was recorded with gradient porous scaffolds (~3GPa) than the homogenously porous scaffolds (~2GPa). While comparing with the existing literature reports, the present work, for the first time, establishes 'direct powder printing methodology' of Ti-6Al-4V porous scaffolds with biomedically relevant microstructural and mechanical properties. Also, a new FE analysis approach, based on the critical understanding of the porous architecture using micro-CT results, is presented to realistically predict the compression response of porous scaffolds. Copyright © 2016 Elsevier B.V. All rights reserved.

An easy-to-prepare mini-scaffold for DNA origami

NASA Astrophysics Data System (ADS)

Brown, S.; Majikes, J.; Martínez, A.; Girón, T. M.; Fennell, H.; Samano, E. C.; Labean, T. H.

2015-10-01

The DNA origami strategy for assembling designed supramolecular complexes requires ssDNA as a scaffold strand. A system is described that was designed approximately one third the length of the M13 bacteriophage genome for ease of ssDNA production. Folding of the 2404-base ssDNA scaffold into a variety of origami shapes with high assembly yields is demonstrated.The DNA origami strategy for assembling designed supramolecular complexes requires ssDNA as a scaffold strand. A system is described that was designed approximately one third the length of the M13 bacteriophage genome for ease of ssDNA production. Folding of the 2404-base ssDNA scaffold into a variety of origami shapes with high assembly yields is demonstrated. Electronic supplementary information (ESI) available: Flow chart of the production process, base sequences of the scaffold strand, and synthetic staple strands, as well as caDNAnao files for all three mini-M13 origami structures. See DOI: 10.1039/c5nr04921k

Use of an Improved Matching Algorithm to Select Scaffolds for Enzyme Design Based on a Complex Active Site Model.

PubMed

Huang, Xiaoqiang; Xue, Jing; Lin, Min; Zhu, Yushan

2016-01-01

Active site preorganization helps native enzymes electrostatically stabilize the transition state better than the ground state for their primary substrates and achieve significant rate enhancement. In this report, we hypothesize that a complex active site model for active site preorganization modeling should help to create preorganized active site design and afford higher starting activities towards target reactions. Our matching algorithm ProdaMatch was improved by invoking effective pruning strategies and the native active sites for ten scaffolds in a benchmark test set were reproduced. The root-mean squared deviations between the matched transition states and those in the crystal structures were < 1.0 Å for the ten scaffolds, and the repacking calculation results showed that 91% of the hydrogen bonds within the active sites are recovered, indicating that the active sites can be preorganized based on the predicted positions of transition states. The application of the complex active site model for de novo enzyme design was evaluated by scaffold selection using a classic catalytic triad motif for the hydrolysis of p-nitrophenyl acetate. Eighty scaffolds were identified from a scaffold library with 1,491 proteins and four scaffolds were native esterase. Furthermore, enzyme design for complicated substrates was investigated for the hydrolysis of cephalexin using scaffold selection based on two different catalytic motifs. Only three scaffolds were identified from the scaffold library by virtue of the classic catalytic triad-based motif. In contrast, 40 scaffolds were identified using a more flexible, but still preorganized catalytic motif, where one scaffold corresponded to the α-amino acid ester hydrolase that catalyzes the hydrolysis and synthesis of cephalexin. Thus, the complex active site modeling approach for de novo enzyme design with the aid of the improved ProdaMatch program is a promising approach for the creation of active sites with high catalytic efficiencies towards target reactions.

Use of an Improved Matching Algorithm to Select Scaffolds for Enzyme Design Based on a Complex Active Site Model

PubMed Central

Huang, Xiaoqiang; Xue, Jing; Lin, Min; Zhu, Yushan

2016-01-01

Active site preorganization helps native enzymes electrostatically stabilize the transition state better than the ground state for their primary substrates and achieve significant rate enhancement. In this report, we hypothesize that a complex active site model for active site preorganization modeling should help to create preorganized active site design and afford higher starting activities towards target reactions. Our matching algorithm ProdaMatch was improved by invoking effective pruning strategies and the native active sites for ten scaffolds in a benchmark test set were reproduced. The root-mean squared deviations between the matched transition states and those in the crystal structures were < 1.0 Å for the ten scaffolds, and the repacking calculation results showed that 91% of the hydrogen bonds within the active sites are recovered, indicating that the active sites can be preorganized based on the predicted positions of transition states. The application of the complex active site model for de novo enzyme design was evaluated by scaffold selection using a classic catalytic triad motif for the hydrolysis of p-nitrophenyl acetate. Eighty scaffolds were identified from a scaffold library with 1,491 proteins and four scaffolds were native esterase. Furthermore, enzyme design for complicated substrates was investigated for the hydrolysis of cephalexin using scaffold selection based on two different catalytic motifs. Only three scaffolds were identified from the scaffold library by virtue of the classic catalytic triad-based motif. In contrast, 40 scaffolds were identified using a more flexible, but still preorganized catalytic motif, where one scaffold corresponded to the α-amino acid ester hydrolase that catalyzes the hydrolysis and synthesis of cephalexin. Thus, the complex active site modeling approach for de novo enzyme design with the aid of the improved ProdaMatch program is a promising approach for the creation of active sites with high catalytic efficiencies towards target reactions. PMID:27243223

Computer-Aided Structure Based Drug Design Approaches for the Discovery of New Anti-CHIKV Agents.

PubMed

Jadav, Surender Singh; Sinha, Barij Nayan; Hilgenfeld, Rolf; Jayaprakash, Venkatesan

2017-11-10

Chikungunya is a viral infection caused by Chikungunya virus (CHIKV), an arbovirus transmitted through mosquito (Aedes aegypti and Aedes albopictus) bite. The virus from sylvatic cycle in Africa mutated to new vector adaptation and became one of the major emerging and re-emerging viral infections in the past decade, affecting more than 40 countries. Efforts are being made by many researches to develop means to prevent and control the infection through vaccines and vector control strategy. On the other hand, search for novel chemotherapeutic agents for the treatment of infected patients is on. Approach of repurposed drug is one way of identifying an existing drug for the treatment of CHIKV infection. Review the history of CHIKV nsp2 protease inhibitors derived through structure-based computer-aided drug design along with phytochemicals identified as anti-CHIKV agents. A survey on CHIKV inhibitors reported till date has been carriedout. The data obtained were organized and discussed under natural substances and synthetic derivatives obtained as result of rational design. The review provides a well organized content in chronological order that has highly significant information for medicinal chemist who wish to explore the area of Anti-CHIKV drug design and development. Natural compounds with different scaffolds provides an opportunity to explore Ligand based drug design (LBDD), while rational drug design approaches provides opportunity to explore the Structure based drug design. From the presented mini-review, readers can understand that this area is less explored and has lots of potential in anti-CHIKVviral drug design & development. of reported literature inferred that, unlike other viral proteases, the nsP2 protease can be targeted for CHIKV viral inhibition. The HTVS process for the identification of anti-CHIK agents provided a few successive validated lead compounds against CHIKV infections. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Solid-phase synthesis and screening of N-acylated polyamine (NAPA) combinatorial libraries for protein binding.

PubMed

Iera, Jaclyn A; Jenkins, Lisa M Miller; Kajiyama, Hiroshi; Kopp, Jeffrey B; Appella, Daniel H

2010-11-15

Inhibitors for protein-protein interactions are challenging to design, in part due to the unique and complex architectures of each protein's interaction domain. Most approaches to develop inhibitors for these interactions rely on rational design, which requires prior structural knowledge of the target and its ligands. In the absence of structural information, a combinatorial approach may be the best alternative to finding inhibitors of a protein-protein interaction. Current chemical libraries, however, consist mostly of molecules designed to inhibit enzymes. In this manuscript, we report the synthesis and screening of a library based on an N-acylated polyamine (NAPA) scaffold that we designed to have specific molecular features necessary to inhibit protein-protein interactions. Screens of the library identified a member with favorable binding properties to the HIV viral protein R (Vpr), a regulatory protein from HIV, that is involved in numerous interactions with other proteins critical for viral replication. Published by Elsevier Ltd.

Designing and Implementing Web-Based Scaffolding Tools for Technology-Enhanced Socioscientific Inquiry

ERIC Educational Resources Information Center

Shin, Suhkyung; Brush, Thomas A.; Glazewski, Krista D.

2017-01-01

This study explores how web-based scaffolding tools provide instructional support while implementing a socio-scientific inquiry (SSI) unit in a science classroom. This case study focused on how students used web-based scaffolding tools during SSI activities, and how students perceived the SSI unit and the scaffolding tools embedded in the SSI…

Rational Design of Porous Covalent Triazine-Based Framework Composites as Advanced Organic Lithium-Ion Battery Cathodes.

PubMed

Yuan, Ruoxin; Kang, Wenbin; Zhang, Chuhong

2018-06-02

In an effort to explore the use of organic high-performance lithium ion battery cathodes as an alternative to resolve the current bottleneck hampering the development of their inorganic counterparts, a rational strategy focusing on the optimal composition of covalent triazine-based frameworks (CTFs) with carbon-based materials of varied dimensionalities is delineated. Two-dimensional reduced graphene oxide (rGO) with a compatible structural conformation with the layered CTF is the most suitable scaffold for the tailored mesopores in the polymeric framework, providing outstanding energy storage ability. Through facile ionothermal synthesis and structure engineering, the obtained CTF-rGO composite possesses a high specific surface area of 1357.27 m²/g, and when used as a lithium ion battery cathode it delivers a large capacity of 235 mAh/g in 80 cycles at 0.1 A/g along with a stable capacity of 127 mAh/g over 2500 cycles at 5 A/g. The composite with modified pore structure shows drastically improved performance compared to a pristine CTF, especially at large discharge currents. The CTF-rGO composite with excellent capacity, stability, and rate performance shows great promise as an emerging high-performance cathode that could revolutionize the conventional lithium-ion battery industry.

Finding the perfect spot for fluorine: improving potency up to 40-fold during a rational fluorine scan of a Bruton's Tyrosine Kinase (BTK) inhibitor scaffold.

PubMed

Lou, Yan; Sweeney, Zachary K; Kuglstatter, Andreas; Davis, Dana; Goldstein, David M; Han, Xiaochun; Hong, Junbae; Kocer, Buelent; Kondru, Rama K; Litman, Renee; McIntosh, Joel; Sarma, Keshab; Suh, Judy; Taygerly, Joshua; Owens, Timothy D

2015-01-15

A rational fluorine scan based on co-crystal structures was explored to increase the potency of a series of selective BTK inhibitors. While fluorine substitution on a saturated bicyclic ring system yields no apparent benefit, the same operation on an unsaturated bicyclic ring can increase HWB activity by up to 40-fold. Comparison of co-crystal structures of parent molecules and fluorinated counterparts revealed the importance of placing fluorine at the optimal position to achieve favorable interactions with protein side chains. Copyright © 2014 Elsevier Ltd. All rights reserved.

Designing Online Problem Representation Engine for Conceptual Change

ERIC Educational Resources Information Center

Lee, Chwee Beng; Ling, Keck Voon

2012-01-01

Purpose: This paper aims to describe the web-based scaffold dynamic simulation system (PRES-on) designed for pre-service teachers. Design/methodology/approach: The paper describes the initial design of a web-based scaffold dynamic simulation system (PRES-on) as a cognitive tool for learners to represent problems. For the widespread use of the…

New paradigms in internal architecture design and freeform fabrication of tissue engineering porous scaffolds.

PubMed

Yoo, Dongjin

2012-07-01

Advanced additive manufacture (AM) techniques are now being developed to fabricate scaffolds with controlled internal pore architectures in the field of tissue engineering. In general, these techniques use a hybrid method which combines computer-aided design (CAD) with computer-aided manufacturing (CAM) tools to design and fabricate complicated three-dimensional (3D) scaffold models. The mathematical descriptions of micro-architectures along with the macro-structures of the 3D scaffold models are limited by current CAD technologies as well as by the difficulty of transferring the designed digital models to standard formats for fabrication. To overcome these difficulties, we have developed an efficient internal pore architecture design system based on triply periodic minimal surface (TPMS) unit cell libraries and associated computational methods to assemble TPMS unit cells into an entire scaffold model. In addition, we have developed a process planning technique based on TPMS internal architecture pattern of unit cells to generate tool paths for freeform fabrication of tissue engineering porous scaffolds. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

Rational protein design: developing next-generation biological therapeutics and nanobiotechnological tools.

PubMed

Wilson, Corey J

2015-01-01

Proteins are the most functionally diverse macromolecules observed in nature, participating in a broad array of catalytic, biosensing, transport, scaffolding, and regulatory functions. Fittingly, proteins have become one of the most promising nanobiotechnological tools to date, and through the use of recombinant DNA and other laboratory methods we have produced a vast number of biological therapeutics derived from human genes. Our emerging ability to rationally design proteins (e.g., via computational methods) holds the promise of significantly expanding the number and diversity of protein therapies and has opened the gateway to realizing true and uncompromised personalized medicine. In the last decade computational protein design has been transformed from a set of fundamental strategies to stringently test our understanding of the protein structure-function relationship, to practical tools for developing useful biological processes, nano-devices, and novel therapeutics. As protein design strategies improve (i.e., in terms of accuracy and efficiency) clinicians will be able to leverage individual genetic data and biological metrics to develop and deliver personalized protein therapeutics with minimal delay. © 2014 Wiley Periodicals, Inc.

Design, synthesis, and initial evaluation of D-glyceraldehyde crosslinked gelatin-hydroxyapatite as a potential bone graft substitute material

NASA Astrophysics Data System (ADS)

Florschutz, Anthony Vatroslav

Utilization of bone grafts for the treatment of skeletal pathology is a common practice in orthopaedic, craniomaxillofacial, dental, and plastic surgery. Autogenous bone graft is the established archetype but has disadvantages including donor site morbidity, limited supply, and prolonging operative time. In order to avoid these and other issues, bone graft substitute materials are becoming increasingly prevalent among surgeons for reconstructing skeletal defects and arthrodesis applications. Bone graft substitutes are biomaterials, biologics, and guided tissue/bone regenerative devices that can be used alone or in combinations as supplements or alternatives to autogenous bone graft. There is a growing interest and trend to specialize graft substitutes for specific indications and although there is good rationale for this indication-specific approach, the development and utility of a more universal bone graft substitute may provide a better answer for patients and surgeons. The aim of the present research focuses on the design, synthesis, and initial evaluation of D-glyceraldehyde crosslinked gelatin-hydroxyapatite composites for potential use as a bone graft substitutes. After initial establishment of rational material design, gelatinhydroxyapatite scaffolds were fabricated with different gelatin:hydroxyapatite ratios and crosslinking concentrations. The synthesized scaffolds were subsequently evaluated on the basis of their swelling behavior, porosity, density, percent composition, mechanical properties, and morphology and further assessed with respect to cell-biomaterial interaction and biomineralization in vitro. Although none of the materials achieved mechanical properties suitable for structural graft applications, a reproducible material design and synthesis was achieved with properties recognized to facilitate bone formation. Select scaffold formulations as well as a subset of scaffolds loaded with recombinant human bone morphogenetic protein-2 were implanted ectopically in a rodent animal model and histologically evaluated for biocompatibility, degradation, and bone formation in vivo. The gelatin-hydroxyapatite scaffolds retained dimensional structure over 28 days and did not elicit any undesirable systemic or local effects. Distinct areas of mineralization and osteoid/bone were noted in all the implanted scaffolds and quantitative differences were primarily dependent on the presence of hydroxyapatite.

Identification of Leishmania donovani Topoisomerase 1 inhibitors via intuitive scaffold hopping and bioisosteric modification of known Top 1 inhibitors

NASA Astrophysics Data System (ADS)

Mamidala, Rajinikanth; Majumdar, Papiya; Jha, Kunal Kumar; Bathula, Chandramohan; Agarwal, Rahul; Chary, M. Thirumala; Mazumdar, H. K.; Munshi, Parthapratim; Sen, Subhabrata

2016-05-01

A library of arylidenefuropyridinediones was discovered as potent inhibitors of Leishmania donovani Topoisomerase 1 (LdTop1) where the active molecules displayed considerable inhibition with single digit micromolar EC50 values. This molecular library was designed via intuitive scaffold hopping and bioisosteric modification of known topoisomerase 1 inhibitors such as camptothecin, edotecarin and etc. The design was rationalized by molecular docking analysis of the compound prototype with human topoisomerase 1 (HTop1) and Leishmania donovani topoisomerase 1(LdTop1). The most active compound 4 displayed no cytotoxicity against normal mammalian COS7 cell line (~100 fold less inhibition at the EC50). Similar to camptothecin, 4 interacted with free LdTop1 as observed in the preincubation DNA relaxation inhibition experiment. It also displayed anti-protozoal activity against Leishmania donovani promastigote. Crystal structure investigation of 4 and its molecular modelling with LdTop1 revealed putative binding sites in the enzyme that could be harnessed to generate molecules with better potency.

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.

Design of a Novel Two-Component Hybrid Dermal Scaffold for the Treatment of Pressure Sores.

PubMed

Sharma, Vaibhav; Kohli, Nupur; Moulding, Dale; Afolabi, Halimat; Hook, Lilian; Mason, Chris; García-Gareta, Elena

2017-11-01

The aim of this study is to design a novel two-component hybrid scaffold using the fibrin/alginate porous hydrogel Smart Matrix combined to a backing layer of plasma polymerized polydimethylsiloxane (Sil) membrane to make the fibrin-based dermal scaffold more robust for the treatment of the clinically challenging pressure sores. A design criteria are established, according to which the Sil membranes are punched to avoid collection of fluid underneath. Manual peel test shows that native silicone does not attach to the fibrin/alginate component while the plasma polymerized silicone membranes are firmly bound to fibrin/alginate. Structural characterization shows that the fibrin/alginate matrix is intact after the addition of the Sil membrane. By adding a Sil membrane to the original fibrin/alginate scaffold, the resulting two-component scaffolds have a significantly higher shear or storage modulus G'. In vitro cell studies show that dermal fibroblasts remain viable, proliferate, and infiltrate the two-component hybrid scaffolds during the culture period. These results show that the design of a novel two-component hybrid dermal scaffold is successful according to the proposed design criteria. To the best of the authors' knowledge, this is the first study that reports the combination of a fibrin-based scaffold with a plasma-polymerized silicone membrane. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-dimensional carbon architectures for electrochemical capacitors.

PubMed

Song, Yu; Liu, Tianyu; Qian, Fang; Zhu, Cheng; Yao, Bin; Duoss, Eric; Spadaccini, Christopher; Worsley, Marcus; Li, Yat

2018-01-01

Three-dimensional (3D) carbon-based materials are emerging as promising electrode candidates for energy storage devices. In comparison to the 1D and 2D structures, 3D morphology offers new opportunities in rational design and synthesis of novel architectures tailor-made for promoting electrochemical performance. The capability of building hierarchical porous structures with 3D configuration can significantly advance the performance of energy storage devices by simultaneously enhancing the ion-accessible surface area and ion diffusion. This feature article presents an overview of recent progress in design, synthesis and implementation of 3D carbon-based materials as electrodes for electrochemical capacitors. Synthesis methodologies of four types of 3D carbon-based electrodes: 3D exfoliated carbon structures, 3D graphene scaffolds, 3D hierarchical porous carbon foams, as well as 3D architectures with periodic pores derived from direct ink writing, are thoroughly discussed and highlighted with selected experimental works. Finally, key opportunities and challenges in which different 3D carbons can significantly impact the energy storage and conversion communities will be provided. Copyright © 2017 Elsevier Inc. All rights reserved.

Materials and fabrication of electrode scaffolds for deposition of MnO2 and their true performance in supercapacitors

NASA Astrophysics Data System (ADS)

Cao, Jianyun; Li, Xiaohong; Wang, Yaming; Walsh, Frank C.; Ouyang, Jia-Hu; Jia, Dechang; Zhou, Yu

2015-10-01

MnO2 is a promising electrode material for high energy supercapacitors because of its large pseudo-capacitance. However, MnO2 suffers from low electronic conductivity and poor cation diffusivity, which results in poor utilization and limited rate performance of traditional MnO2 powder electrodes, obtained by pressing a mixed paste of MnO2 powder, conductive additive and polymer binder onto metallic current collectors. Developing binder-free MnO2 electrodes by loading nanoscale MnO2 deposits on pre-fabricated device-ready electrode scaffolds is an effective way to achieve both high power and energy performance. These electrode scaffolds, with interconnected skeletons and pore structures, will not only provide mechanical support and electron collection as traditional current collectors but also fast ion transfer tunnels, leading to high MnO2 utilization and rate performance. This review covers design strategies, materials and fabrication methods for the electrode scaffolds. Rational evaluation of the true performance of these electrodes is carried out, which clarifies that some of the electrodes with as-claimed exceptional performances lack potential in practical applications due to poor mass loading of MnO2 and large dead volume of inert scaffold materials/void spaces in the electrode structure. Possible ways to meet this challenge and bring MnO2 electrodes from laboratory studies to real-world applications are considered.

CRISPR-FOCUS: A web server for designing focused CRISPR screening experiments.

PubMed

Cao, Qingyi; Ma, Jian; Chen, Chen-Hao; Xu, Han; Chen, Zhi; Li, Wei; Liu, X Shirley

2017-01-01

The recently developed CRISPR screen technology, based on the CRISPR/Cas9 genome editing system, enables genome-wide interrogation of gene functions in an efficient and cost-effective manner. Although many computational algorithms and web servers have been developed to design single-guide RNAs (sgRNAs) with high specificity and efficiency, algorithms specifically designed for conducting CRISPR screens are still lacking. Here we present CRISPR-FOCUS, a web-based platform to search and prioritize sgRNAs for CRISPR screen experiments. With official gene symbols or RefSeq IDs as the only mandatory input, CRISPR-FOCUS filters and prioritizes sgRNAs based on multiple criteria, including efficiency, specificity, sequence conservation, isoform structure, as well as genomic variations including Single Nucleotide Polymorphisms and cancer somatic mutations. CRISPR-FOCUS also provides pre-defined positive and negative control sgRNAs, as well as other necessary sequences in the construct (e.g., U6 promoters to drive sgRNA transcription and RNA scaffolds of the CRISPR/Cas9). These features allow users to synthesize oligonucleotides directly based on the output of CRISPR-FOCUS. Overall, CRISPR-FOCUS provides a rational and high-throughput approach for sgRNA library design that enables users to efficiently conduct a focused screen experiment targeting up to thousands of genes. (CRISPR-FOCUS is freely available at http://cistrome.org/crispr-focus/).

Structure-based discovery of pyrazolobenzothiazine derivatives as inhibitors of hepatitis C virus replication

PubMed Central

Barreca, Maria Letizia; Manfroni, Giuseppe; Leyssen, Pieter; Winquist, Johan; Kaushik-Basu, Neerja; Paeshuyse, Jan; Krishnan, Ramalingam; Iraci, Nunzio; Sabatini, Stefano; Tabarrini, Oriana; Basu, Amartya; Danielson, U. Helena; Neyts, Johan; Cecchetti, Violetta

2013-01-01

The NS5B RNA-dependent RNA polymerase is an attractive target for the development of novel and selective inhibitors of hepatitis C virus replication. In order to identify novel structural hits as anti-HCV agents, we performed structure-based virtual screening of our in-house library followed by rational drug design, organic synthesis and biological testing. These studies led to the identification of pyrazolobenzothiazine scaffold as a suitable template for obtaining novel anti-HCV agents targeting the NS5B polymerase. The best compound of this series was the meta-fluoro-N-1-phenyl pyrazolobenzothiazine derivative 4a, which exhibited an EC50= 3.6 µM, EC90= 25.6 µM and CC50 > 180 µM in the Huh 9–13 replicon system, thus providing a good starting point for further hit evolution. PMID:23409936

Computed tomography-based tissue-engineered scaffolds in craniomaxillofacial surgery.

PubMed

Smith, M H; Flanagan, C L; Kemppainen, J M; Sack, J A; Chung, H; Das, S; Hollister, S J; Feinberg, S E

2007-09-01

Tissue engineering provides an alternative modality allowing for decreased morbidity of donor site grafting and decreased rejection of less compatible alloplastic tissues. Using image-based design and computer software, a precisely sized and shaped scaffold for osseous tissue regeneration can be created via selective laser sintering. Polycaprolactone has been used to create a condylar ramus unit (CRU) scaffold for application in temporomandibular joint reconstruction in a Yucatan minipig animal model. Following sacrifice, micro-computed tomography and histology was used to demonstrate the efficacy of this particular scaffold design. A proof-of-concept surgery has demonstrated cartilaginous tissue regeneration along the articulating surface with exuberant osseous tissue formation. Bone volumes and tissue mineral density at both the 1 and 3 month time points demonstrated significant new bone growth interior and exterior to the scaffold. Computationally designed scaffolds can support masticatory function in a large animal model as well as both osseous and cartilage regeneration. Our group is continuing to evaluate multiple implant designs in both young and mature Yucatan minipig animals. 2007 John Wiley & Sons, Ltd.

Molecular and macro-scale analysis of enzyme-crosslinked silk hydrogels for rational biomaterial design.

PubMed

McGill, Meghan; Coburn, Jeannine M; Partlow, Benjamin P; Mu, Xuan; Kaplan, David L

2017-11-01

Silk fibroin-based hydrogels have exciting applications in tissue engineering and therapeutic molecule delivery; however, their utility is dependent on their diffusive properties. The present study describes a molecular and macro-scale investigation of enzymatically-crosslinked silk fibroin hydrogels, and demonstrates that these systems have tunable crosslink density and diffusivity. We developed a liquid chromatography tandem mass spectroscopy (LC-MS/MS) method to assess the quantity and order of covalent tyrosine crosslinks in the hydrogels. This analysis revealed between 28 and 56% conversion of tyrosine to dityrosine, which was dependent on the silk concentration and reactant concentration. The crosslink density was then correlated with storage modulus, revealing that both crosslinking and protein concentration influenced the mechanical properties of the hydrogels. The diffusive properties of the bulk material were studied by fluorescence recovery after photobleaching (FRAP), which revealed a non-linear relationship between silk concentration and diffusivity. As a result of this work, a model for synthesizing hydrogels with known crosslink densities and diffusive properties has been established, enabling the rational design of silk hydrogels for biomedical applications. Hydrogels from naturally-derived silk polymers offer versitile opportunities in the biomedical field, however, their design has largely been an empirical process. We present a fundamental study of the crosslink density, storage modulus, and diffusion behavior of enzymatically-crosslinked silk hydrogels to better inform scaffold design. These studies revealed unexpected non-linear trends in the crosslink density and diffusivity of silk hydrogels with respect to protein concentration and crosslink reagent concentration. This work demonstrates the tunable diffusivity and crosslinking in silk fibroin hydrogels, and enables the rational design of biomaterials. Further, the characterization methods presented have applications for other materials with dityrosine crosslinks, which are found in nature as post-translational modificaitons, as well as in engineered matrices such as tyramine-substituted hyaluronic acid and recombinant resilin. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Imidazopyridine-based inhibitors of glycogen synthase kinase 3: synthesis and evaluation of amide isostere replacements of the carboxamide scaffold.

PubMed

Yngve, Ulrika; Söderman, Peter; Svensson, Mats; Rosqvist, Susanne; Arvidsson, Per I

2012-11-01

In this study, we explored the effect of bioisostere replacement in a series of glycogen synthase kinase 3 (GSK3) inhibitors based on the imidazopyridine core. The synthesis and biological evaluation of a number of novel sulfonamide, 1,2,4-oxadiazole, and thiazole derivates as amide bioisosteres, as well as a computational rationalization of the obtained results are reported. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich.

A computational and cellular solids approach to the stiffness-based design of bone scaffolds.

PubMed

Norato, J A; Wagoner Johnson, A J

2011-09-01

We derive a cellular solids approach to the design of bone scaffolds for stiffness and pore size. Specifically, we focus on scaffolds made of stacked, alternating, orthogonal layers of hydroxyapatite rods, such as those obtained via micro-robotic deposition, and aim to determine the rod diameter, spacing and overlap required to obtain specified elastic moduli and pore size. To validate and calibrate the cellular solids model, we employ a finite element model and determine the effective scaffold moduli via numerical homogenization. In order to perform an efficient, automated execution of the numerical studies, we employ a geometry projection method so that analyses corresponding to different scaffold dimensions can be performed on a fixed, non-conforming mesh. Based on the developed model, we provide design charts to aid in the selection of rod diameter, spacing and overlap to be used in the robotic deposition to attain desired elastic moduli and pore size.

A novel method for biomaterial scaffold internal architecture design to match bone elastic properties with desired porosity.

PubMed

Lin, Cheng Yu; Kikuchi, Noboru; Hollister, Scott J

2004-05-01

An often-proposed tissue engineering design hypothesis is that the scaffold should provide a biomimetic mechanical environment for initial function and appropriate remodeling of regenerating tissue while concurrently providing sufficient porosity for cell migration and cell/gene delivery. To provide a systematic study of this hypothesis, the ability to precisely design and manufacture biomaterial scaffolds is needed. Traditional methods for scaffold design and fabrication cannot provide the control over scaffold architecture design to achieve specified properties within fixed limits on porosity. The purpose of this paper was to develop a general design optimization scheme for 3D internal scaffold architecture to match desired elastic properties and porosity simultaneously, by introducing the homogenization-based topology optimization algorithm (also known as general layout optimization). With an initial target for bone tissue engineering, we demonstrate that the method can produce highly porous structures that match human trabecular bone anisotropic stiffness using accepted biomaterials. In addition, we show that anisotropic bone stiffness may be matched with scaffolds of widely different porosity. Finally, we also demonstrate that prototypes of the designed structures can be fabricated using solid free-form fabrication (SFF) techniques.

3D braid scaffolds for regeneration of articular cartilage.

PubMed

Ahn, Hyunchul; Kim, Kyoung Ju; Park, Sook Young; Huh, Jeong Eun; Kim, Hyun Jeong; Yu, Woong-Ryeol

2014-06-01

Regenerating articular cartilage in vivo from cultured chondrocytes requires that the cells be cultured and implanted within a biocompatible, biodegradable scaffold. Such scaffolds must be mechanically stable; otherwise chondrocytes would not be supported and patients would experience severe pain. Here we report a new 3D braid scaffold that matches the anisotropic (gradient) mechanical properties of natural articular cartilage and is permissive to cell cultivation. To design an optimal structure, the scaffold unit cell was mathematically modeled and imported into finite element analysis. Based on this analysis, a 3D braid structure with gradient axial yarn distribution was designed and manufactured using a custom-built braiding machine. The mechanical properties of the 3D braid scaffold were evaluated and compared with simulated results, demonstrating that a multi-scale approach consisting of unit cell modeling and continuum analysis facilitates design of scaffolds that meet the requirements for mechanical compatibility with tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fracture behaviors of ceramic tissue scaffolds for load bearing applications

NASA Astrophysics Data System (ADS)

Entezari, Ali; Roohani-Esfahani, Seyed-Iman; Zhang, Zhongpu; Zreiqat, Hala; Dunstan, Colin R.; Li, Qing

2016-07-01

Healing large bone defects, especially in weight-bearing locations, remains a challenge using available synthetic ceramic scaffolds. Manufactured as a scaffold using 3D printing technology, Sr-HT-Gahnite at high porosity (66%) had demonstrated significantly improved compressive strength (53 ± 9 MPa) and toughness. Nevertheless, the main concern of ceramic scaffolds in general remains to be their inherent brittleness and low fracture strength in load bearing applications. Therefore, it is crucial to establish a robust numerical framework for predicting fracture strengths of such scaffolds. Since crack initiation and propagation plays a critical role on the fracture strength of ceramic structures, we employed extended finite element method (XFEM) to predict fracture behaviors of Sr-HT-Gahnite scaffolds. The correlation between experimental and numerical results proved the superiority of XFEM for quantifying fracture strength of scaffolds over conventional FEM. In addition to computer aided design (CAD) based modeling analyses, XFEM was conducted on micro-computed tomography (μCT) based models for fabricated scaffolds, which took into account the geometric variations induced by the fabrication process. Fracture strengths and crack paths predicted by the μCT-based XFEM analyses correlated well with relevant experimental results. The study provided an effective means for the prediction of fracture strength of porous ceramic structures, thereby facilitating design optimization of scaffolds.

Engineering structures and functions of mesenchymal stem cells by suspended large-area graphene nanopatterns

NASA Astrophysics Data System (ADS)

Kim, Jangho; Bae, Won-Gyu; Park, Subeom; Kim, Yeon Ju; Jo, Insu; Park, Sunho; Li Jeon, Noo; Kwak, Woori; Cho, Seoae; Park, Jooyeon; Kim, Hong Nam; Choi, Kyoung Soon; Seonwoo, Hoon; Choung, Yun-Hoon; Choung, Pill-Hoon; Hong, Byung Hee; Chung, Jong Hoon

2016-09-01

Inspired by the hierarchical nanofibrous and highly oriented structures of natural extracellular matrices, we report a rational design of chemical vapor deposition graphene-anchored scaffolds that provide both physical and chemical cues in a multilayered organization to control the adhesion and functions of cells for regenerative medicine. These hierarchical platforms are fabricated by transferring large graphene film onto nanogroove patterns. The top graphene layer exhibits planar morphology with slight roughness (∼20 nm between peaks) due to the underlying topography, which results in a suspended structure between the nanoridges. We demonstrate that the adhesion and differentiation of human mesenchymal stem cells were sensitively controlled and enhanced by the both the nanotopography and graphene cues in our scaffolds. Our results indicate that the layered physical and chemical cues can affect the apparent cell behaviors, and can synergistically enhance cell functionality. Therefore, these suspended graphene platforms may be used to advance regenerative medicine.

Synthesizing Results From Empirical Research on Computer-Based Scaffolding in STEM Education

PubMed Central

Belland, Brian R.; Walker, Andrew E.; Kim, Nam Ju; Lefler, Mason

2016-01-01

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. PMID:28344365

[Development of computer aided forming techniques in manufacturing scaffolds for bone tissue engineering].

PubMed

Wei, Xuelei; Dong, Fuhui

2011-12-01

To review recent advance in the research and application of computer aided forming techniques for constructing bone tissue engineering scaffolds. The literature concerning computer aided forming techniques for constructing bone tissue engineering scaffolds in recent years was reviewed extensively and summarized. Several studies over last decade have focused on computer aided forming techniques for bone scaffold construction using various scaffold materials, which is based on computer aided design (CAD) and bone scaffold rapid prototyping (RP). CAD include medical CAD, STL, and reverse design. Reverse design can fully simulate normal bone tissue and could be very useful for the CAD. RP techniques include fused deposition modeling, three dimensional printing, selected laser sintering, three dimensional bioplotting, and low-temperature deposition manufacturing. These techniques provide a new way to construct bone tissue engineering scaffolds with complex internal structures. With rapid development of molding and forming techniques, computer aided forming techniques are expected to provide ideal bone tissue engineering scaffolds.

Comparison of the mechanobiological performance of bone tissue scaffolds based on different unit cell geometries.

PubMed

Rodríguez-Montaño, Óscar L; Cortés-Rodríguez, Carlos Julio; Uva, Antonio E; Fiorentino, Michele; Gattullo, Michele; Monno, Giuseppe; Boccaccio, Antonio

2018-07-01

Enhancing the performance of scaffolds for bone regeneration requires a multidisciplinary approach involving competences in the fields of Biology, Medicine and Engineering. A number of studies have been conducted to investigate the influence of scaffolds design parameters on their mechanical and biological response. The possibilities offered by the additive manufacturing techniques to fabricate sophisticated and very complex microgeometries that until few years ago were just a geometrical abstraction, led many researchers to design scaffolds made from different unit cell geometries. The aim of this work is to find, based on mechanobiological criteria and for different load regimes, the optimal geometrical parameters of scaffolds made from beam-based repeating unit cells, namely, truncated cuboctahedron, truncated cube, rhombic dodecahedron and diamond. The performance, -expressed in terms of percentage of the scaffold volume occupied by bone-, of the scaffolds based on these unit cells was compared with that of scaffolds based on other unit cell geometries such as: hexahedron and rhombicuboctahedron. A very intriguing behavior was predicted for the truncated cube unit cell that allows the formation of large amounts of bone for low load values and of very small amounts for the medium-high ones. For high values of load, scaffolds made from hexahedron unit cells were predicted to favor the formation of the largest amounts of bone. In a clinical context where medical solutions become more and more customized, this study offers a support to the surgeon in the choice of the best scaffold to be implanted in a patient-specific anatomic region. Copyright © 2018 Elsevier Ltd. All rights reserved.

A Design Model of Distributed Scaffolding for Inquiry-Based Learning

NASA Astrophysics Data System (ADS)

Hsu, Ying-Shao; Lai, Ting-Ling; Hsu, Wei-Hsiu

2015-04-01

This study presents a series of three experiments that focus on how distributed scaffolding influences learners' conceptual understanding and reasoning from combined levels of triangulation, at the interactive level (discourses within a focus group) and the collective level (class). Three inquiry lessons on plate tectonics (LPT) were designed, implemented and redesigned to explore how students responded to the scaffoldings provided. The results show that the goal-oriented version (LPT3) was significantly more effective at helping students develop an understanding of plate tectonics and evidence-based reasoning than the teacher-led (LPT1) and deconstructed (LPT2) versions ( χ 2 = 11.56, p < 0.003). In LPT3, we can identify three key features of the scaffolding: an advanced organizer, deconstruction of complex tasks, and reflection on the whole inquiry cycle at the end of class time. In addition, LPT3 took much less teaching time. In other words, it appears to be effective and efficient, most likely due to synergies between teacher facilitation and lesson scaffolds. The empirical results clarify the functions of the design model proposed for distributed scaffolding: navigating inquiry, structuring tasks, supporting communication, and fostering reflection. Future studies should more closely evaluate the scaffolding system as a whole and synergies between different types of scaffolds for advancing learning.

Finite-element design and optimization of a three-dimensional tetrahedral porous titanium scaffold for the reconstruction of mandibular defects.

PubMed

Luo, Danmei; Rong, Qiguo; Chen, Quan

2017-09-01

Reconstruction of segmental defects in the mandible remains a challenge for maxillofacial surgery. The use of porous scaffolds is a potential method for repairing these defects. Now, additive manufacturing techniques provide a solution for the fabrication of porous scaffolds with specific geometrical shapes and complex structures. The goal of this study was to design and optimize a three-dimensional tetrahedral titanium scaffold for the reconstruction of mandibular defects. With a fixed strut diameter of 0.45mm and a mean cell size of 2.2mm, a tetrahedral structural porous scaffold was designed for a simulated anatomical defect derived from computed tomography (CT) data of a human mandible. An optimization method based on the concept of uniform stress was performed on the initial scaffold to realize a minimal-weight design. Geometric and mechanical comparisons between the initial and optimized scaffold show that the optimized scaffold exhibits a larger porosity, 81.90%, as well as a more homogeneous stress distribution. These results demonstrate that tetrahedral structural titanium scaffolds are feasible structures for repairing mandibular defects, and that the proposed optimization scheme has the ability to produce superior scaffolds for mandibular reconstruction with better stability, higher porosity, and less weight. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Uniform Surface Modification of 3D Bioglass®-Based Scaffolds with Mesoporous Silica Particles (MCM-41) for Enhancing Drug Delivery Capability

PubMed Central

Boccardi, Elena; Philippart, Anahí; Juhasz-Bortuzzo, Judith A.; Beltrán, Ana M.; Novajra, Giorgia; Vitale-Brovarone, Chiara; Spiecker, Erdmann; Boccaccini, Aldo R.

2015-01-01

The design and characterization of a new family of multifunctional scaffolds based on bioactive glass (BG) of 45S5 composition for bone tissue engineering and drug delivery applications are presented. These BG-based scaffolds are developed via a replication method of polyurethane packaging foam. In order to increase the therapeutic functionality, the scaffolds were coated with mesoporous silica particles (MCM-41), which act as an in situ drug delivery system. These sub-micron spheres are characterized by large surface area and pore volume with a narrow pore diameter distribution. The solution used for the synthesis of the silica mesoporous particles was designed to obtain a high-ordered mesoporous structure and spherical shape – both are key factors for achieving the desired controlled drug release. The MCM-41 particles were synthesized directly inside the BG-based scaffolds, and the drug-release capability of this combined system was evaluated. Moreover, the effect of MCM-41 particle coating on the bioactivity of the BG-based scaffolds was assessed. The results indicate that it is possible to obtain a multifunctional scaffold system characterized by high and interconnected porosity, high bioactivity, and sustained drug delivery capability. PMID:26594642

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.

Overcoming mutation-based resistance to antiandrogens with rational drug design

PubMed Central

Balbas, Minna D; Evans, Michael J; Hosfield, David J; Wongvipat, John; Arora, Vivek K; Watson, Philip A; Chen, Yu; Greene, Geoffrey L; Shen, Yang; Sawyers, Charles L

2013-01-01

The second-generation antiandrogen enzalutamide was recently approved for patients with castration-resistant prostate cancer. Despite its success, the duration of response is often limited. For previous antiandrogens, one mechanism of resistance is mutation of the androgen receptor (AR). To prospectively identify AR mutations that might confer resistance to enzalutamide, we performed a reporter-based mutagenesis screen and identified a novel mutation, F876L, which converted enzalutamide into an AR agonist. Ectopic expression of AR F876L rescued the growth inhibition of enzalutamide treatment. Molecular dynamics simulations performed on antiandrogen–AR complexes suggested a mechanism by which the F876L substitution alleviates antagonism through repositioning of the coactivator recruiting helix 12. This model then provided the rationale for a focused chemical screen which, based on existing antiandrogen scaffolds, identified three novel compounds that effectively antagonized AR F876L (and AR WT) to suppress the growth of prostate cancer cells resistant to enzalutamide. DOI: http://dx.doi.org/10.7554/eLife.00499.001 PMID:23580326

Scaffolding knowledge building in a Web-based communication and cultural competence program for international medical graduates.

PubMed

Lax, Leila R; Russell, M Lynn; Nelles, Laura J; Smith, Cathy M

2009-10-01

Professional behaviors, tacitly understood by Canadian-trained physicians, are difficult to teach and often create practice barriers for IMGs. The purpose of this design research study was to develop a Web-based program simulating Canadian medical literacy and culture, and to evaluate strategies of scaffolding individual knowledge building. Study 1 (N = 20) examined usability and pedagogic design. Studies 2 (N = 39) and 3 (N = 33) examined case participation patterns. Model design was validated in Study 1. Studies 2 and 3 demonstrated high levels of participation, on unprompted third tries, on knowledge tests. Recursive patterns were strongest on Reflective Exercises. Five strategies scaffolded knowledge building: (1) video simulations, (2) contextualized resources, (3) concurrent feedback, (4) Reflective Exercises, and (5) commentaries prompting "reflection on reflection." Scaffolded design supports complex knowledge building. These findings are concurrent with educational research on the importance of recursion and revision of knowledge for improvable and relational understanding.

Beyond small molecule SAR – using the dopamine D3 receptor crystal structure to guide drug design

PubMed Central

Keck, Thomas M.; Burzynski, Caitlin; Shi, Lei; Newman, Amy Hauck

2016-01-01

The dopamine D3 receptor is a target of pharmacotherapeutic interest in a variety of neurological disorders including schizophrenia, restless leg syndrome, and drug addiction. The high protein sequence homology between the D3 and D2 receptors has posed a challenge to developing D3 receptor-selective ligands whose behavioral actions can be attributed to D3 receptor engagement, in vivo. However, through primarily small molecule structure-activity relationship (SAR) studies, a variety of chemical scaffolds have been discovered over the past two decades that have resulted in several D3 receptor-selective ligands with high affinity and in vivo activity. Nevertheless, viable clinical candidates remain limited. The recent determination of the high-resolution crystal structure of the D3 receptor has invigorated structure-based drug design, providing refinements to the molecular dynamic models and testable predictions about receptor-ligand interactions. This review will highlight recent preclinical and clinical studies demonstrating potential utility of D3 receptor-selective ligands in the treatment of addiction. In addition, new structure-based rational drug design strategies for D3 receptor-selective ligands that complement traditional small molecule SAR to improve the selectivity and directed efficacy profiles are examined. PMID:24484980

The Molecular Basis for Dual Fatty Acid Amide Hydrolase (FAAH)/Cyclooxygenase (COX) Inhibition.

PubMed

Palermo, Giulia; Favia, Angelo D; Convertino, Marino; De Vivo, Marco

2016-06-20

The design of multitarget-directed ligands is a promising strategy for discovering innovative drugs. Here, we report a mechanistic study that clarifies key aspects of the dual inhibition of the fatty acid amide hydrolase (FAAH) and the cyclooxygenase (COX) enzymes by a new multitarget-directed ligand named ARN2508 (2-[3-fluoro-4-[3-(hexylcarbamoyloxy)phenyl]phenyl]propanoic acid). This potent dual inhibitor combines, in a single scaffold, the pharmacophoric elements often needed to block FAAH and COX, that is, a carbamate moiety and the 2-arylpropionic acid functionality, respectively. Molecular modeling and molecular dynamics simulations suggest that ARN2508 uses a noncovalent mechanism of inhibition to block COXs, while inhibiting FAAH via the acetylation of the catalytic Ser241, in line with previous experimental evidence for covalent FAAH inhibition. This study proposes the molecular basis for the dual FAAH/COX inhibition by this novel hybrid scaffold, stimulating further experimental studies and offering new insights for the rational design of novel anti-inflammatory agents that simultaneously act on FAAH and COX. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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.

Biocompatible, biodegradable polymer-based, lighter than or light as water scaffolds for tissue engineering and methods for preparation and use thereof

NASA Technical Reports Server (NTRS)

Khan, Mohammed Yusuf (Inventor); Laurencin, Cato T. (Inventor); Lu, Helen H. (Inventor); Botchwey, Edward (Inventor); Pollack, Solomon R. (Inventor); Levine, Elliot (Inventor)

2012-01-01

Scaffolds for tissue engineering prepared from biocompatible, biodegradable polymer-based, lighter than or light as water microcarriers and designed for cell culturing in vitro in a rotating bioreactor are provided. Methods for preparation and use of these scaffolds as tissue engineering devices are also provided.

Dispensing-based bioprinting of mechanically-functional hybrid scaffolds with vessel-like channels for tissue engineering applications - A brief review.

PubMed

Naghieh, Saman; Sarker, Md; Izadifar, Mohammad; Chen, Xiongbiao

2018-02-01

Over the past decades, significant progress has been achieved in the field of tissue engineering (TE) to restore/repair damaged tissues or organs and, in this regard, scaffolds made from biomaterials have played a critical role. Notably, recent advances in biomaterials and three-dimensional (3D) printing have enabled the manipulation of two or more biomaterials of distinct, yet complementary, mechanical and/or biological properties to form so-called hybrid scaffolds mimicking native tissues. Among various biomaterials, hydrogels synthesized to incorporate living cells and/or biological molecules have dominated due to their hydrated tissue-like environment. Moreover, dispensing-based bioprinting has evolved to the point that it can now be used to create hybrid scaffolds with complex structures. However, the complexities associated with multi-material bioprinting and synthesis of hydrogels used for hybrid scaffolds pose many challenges for their fabrication. This paper presents a brief review of dispensing-based bioprinting of hybrid scaffolds for TE applications. The focus is on the design and fabrication of hybrid scaffolds, including imaging techniques, potential biomaterials, physical architecture, mechanical properties, cell viability, and the importance of vessel-like channels. The key issues and challenges for dispensing-based bioprinting of hybrid scaffolds are also identified and discussed along with recommendations for future research directions. Addressing these issues will significantly enhance the design and fabrication of hybrid scaffolds to and pave the way for translating them into clinical applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Effect of Various Media Scaffolding on Increasing Understanding of Students' Geometry Concepts

ERIC Educational Resources Information Center

Sutiarso, Sugeng; Coesamin, M.; Nurhanurawati

2018-01-01

This study is a quasi-experimental research with pretest-posttest control group design, which aims to determine (1) the tendency of students in using various media scaffolding based on gender, and (2) effect of media scaffolding on increasing understanding of students' geometry concepts. Media scaffolding used this study is chart, props, and…

Review: Polymeric-Based 3D Printing for Tissue Engineering.

PubMed

Wu, Geng-Hsi; Hsu, Shan-Hui

Three-dimensional (3D) printing, also referred to as additive manufacturing, is a technology that allows for customized fabrication through computer-aided design. 3D printing has many advantages in the fabrication of tissue engineering scaffolds, including fast fabrication, high precision, and customized production. Suitable scaffolds can be designed and custom-made based on medical images such as those obtained from computed tomography. Many 3D printing methods have been employed for tissue engineering. There are advantages and limitations for each method. Future areas of interest and progress are the development of new 3D printing platforms, scaffold design software, and materials for tissue engineering applications.

Bioreactor Based Bone Tissue Engineering: Influence of Wall Collision on Osteoblast Cultured on Polymeric Microcarrier Scaffolds in Rotating Bioreactors

DTIC Science & Technology

2005-01-01

heavier than water (HTW; density > I g/cm 3) scaffolds were fabricated by sintering HTW microspheres of 85:15 poly (lactide-co-glycolide) ( PLAGA ), and...mixed scaffolds were designed by mixing lighter than water (LTW; density < 1 g/cm 3) and HTW microspheres of PLAGA . We quantified average velocities of...differentiation. In previous studies, we have described the development of novel poly(lactide-co-glycolide) ( PLAGA ) microsphere based mixed scaffolds that

Innovation and design of a web-based pain education interprofessional resource.

PubMed

Lax, Leila; Watt-Watson, Judy; Lui, Michelle; Dubrowski, Adam; McGillion, Michael; Hunter, Judith; Maclennan, Cameron; Knickle, Kerry; Robb, Anja; Lapeyre, Jaime

2011-01-01

The present article describes educational innovation processes and design of a web-based pain interprofessional resource for prelicensure health science students in universities across Canada. Operationalization of educational theory in design coupled with formative evaluation of design are discussed, along with strategies that support collaborative innovation. Educational design was driven by content, theory and evaluation. Pain misbeliefs and teaching points along the continuum from acute to persistent pain were identified. Knowledge-building theory, situated learning, reflection and novel designs for cognitive scaffolding were then employed. Design research principles were incorporated to inform iterative and ongoing design. An authentic patient case was constructed, situated in interprofessional complex care to highlight learning objectives related to pre-operative, postoperative and treatment up to one year, for a surgical cancer patient. Pain mechanisms, assessment and management framed content creation. Knowledge building scaffolds were used, which included video simulations, embedded resources, concurrent feedback, practice-based reflective exercises and commentaries. Scaffolds were refined to specifically support knowledge translation. Illustrative commentaries were designed to explicate pain misbeliefs and best practices. Architecture of the resource was mapped; a multimedia, interactive prototype was created. This pain education resource was developed primarily for individual use, with extensions for interprofessional collective discourse. Translation of curricular content scripts into representation maps supported the collaborative design process by establishing a common visual language. The web-based prototype will be formatively and summatively evaluated to assess pedagogic design, knowledge-translation scaffolds, pain knowledge gains, relevance, feasibility and fidelity of this educational innovation.

Designing of PLA scaffolds for bone tissue replacement fabricated by ordinary commercial 3D printer.

PubMed

Gregor, Aleš; Filová, Eva; Novák, Martin; Kronek, Jakub; Chlup, Hynek; Buzgo, Matěj; Blahnová, Veronika; Lukášová, Věra; Bartoš, Martin; Nečas, Alois; Hošek, Jan

2017-01-01

The primary objective of Tissue engineering is a regeneration or replacement of tissues or organs damaged by disease, injury, or congenital anomalies. At present, Tissue engineering repairs damaged tissues and organs with artificial supporting structures called scaffolds. These are used for attachment and subsequent growth of appropriate cells. During the cell growth gradual biodegradation of the scaffold occurs and the final product is a new tissue with the desired shape and properties. In recent years, research workplaces are focused on developing scaffold by bio-fabrication techniques to achieve fast, precise and cheap automatic manufacturing of these structures. Most promising techniques seem to be Rapid prototyping due to its high level of precision and controlling. However, this technique is still to solve various issues before it is easily used for scaffold fabrication. In this article we tested printing of clinically applicable scaffolds with use of commercially available devices and materials. Research presented in this article is in general focused on "scaffolding" on a field of bone tissue replacement. Commercially available 3D printer and Polylactic acid were used to create originally designed and possibly suitable scaffold structures for bone tissue engineering. We tested printing of scaffolds with different geometrical structures. Based on the osteosarcoma cells proliferation experiment and mechanical testing of designed scaffold samples, it will be stated that it is likely not necessary to keep the recommended porosity of the scaffold for bone tissue replacement at about 90%, and it will also be clarified why this fact eliminates mechanical properties issue. Moreover, it is demonstrated that the size of an individual pore could be double the size of the recommended range between 0.2-0.35 mm without affecting the cell proliferation. Rapid prototyping technique based on Fused deposition modelling was used for the fabrication of designed scaffold structures. All the experiments were performed in order to show how to possibly solve certain limitations and issues that are currently reported by research workplaces on the field of scaffold bio-fabrication. These results should provide new valuable knowledge for further research.

Electro fluido dynamic techniques to design instructive biomaterials for tissue engineering and drug delivery

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

Guarino, Vincenzo, E-mail: vguarino@unina.it; Altobelli, Rosaria; Cirillo, Valentina

A large variety of processes and tools is continuously investigated to discover new solutions to design instructive materials with controlled chemical, physical and biological properties for tissue engineering and drug delivery. Among them, electro fluido dynamic techniques (EFDTs) are emerging as an interesting strategy, based on highly flexible and low-cost processes, to revisit old biomaterial’s manufacturing approach by utilizing electrostatic forces as the driving force for the fabrication of 3D architectures with controlled physical and chemical functionalities to guide in vitro and in vivo cell activities. By a rational selection of polymer solution properties and process conditions, EFDTs allow tomore » produce fibres and/or particles at micro and/or nanometric size scale which may be variously assembled by tailored experimental setups, thus giving the chance to generate a plethora of different 3D devices able to incorporate biopolymers (i.e., proteins, polysaccharides) or active molecules (e.g., drugs) for different applications. Here, we focus on the optimization of basic EFDTs - namely electrospinning, electrospraying and electrodynamic atomization - to develop active platforms (i.e., monocomponent, protein and drug loaded scaffolds and µ-scaffolds) made of synthetic (PCL, PLGA) or natural (chitosan, alginate) polymers. In particular, we investigate how to set materials and process parameters to impart specific morphological, biochemical or physical cues to trigger all the fundamental cell–biomaterial and cell– cell cross-talking elicited during regenerative processes, in order to reproduce the complex microenvironment of native or pathological tissues.« less

Electro fluido dynamic techniques to design instructive biomaterials for tissue engineering and drug delivery

NASA Astrophysics Data System (ADS)

Guarino, Vincenzo; Altobelli, Rosaria; Cirillo, Valentina; Ambrosio, Luigi

2015-12-01

A large variety of processes and tools is continuously investigated to discover new solutions to design instructive materials with controlled chemical, physical and biological properties for tissue engineering and drug delivery. Among them, electro fluido dynamic techniques (EFDTs) are emerging as an interesting strategy, based on highly flexible and low-cost processes, to revisit old biomaterial's manufacturing approach by utilizing electrostatic forces as the driving force for the fabrication of 3D architectures with controlled physical and chemical functionalities to guide in vitro and in vivo cell activities. By a rational selection of polymer solution properties and process conditions, EFDTs allow to produce fibres and/or particles at micro and/or nanometric size scale which may be variously assembled by tailored experimental setups, thus giving the chance to generate a plethora of different 3D devices able to incorporate biopolymers (i.e., proteins, polysaccharides) or active molecules (e.g., drugs) for different applications. Here, we focus on the optimization of basic EFDTs - namely electrospinning, electrospraying and electrodynamic atomization - to develop active platforms (i.e., monocomponent, protein and drug loaded scaffolds and µ-scaffolds) made of synthetic (PCL, PLGA) or natural (chitosan, alginate) polymers. In particular, we investigate how to set materials and process parameters to impart specific morphological, biochemical or physical cues to trigger all the fundamental cell-biomaterial and cell- cell cross-talking elicited during regenerative processes, in order to reproduce the complex microenvironment of native or pathological tissues.

Student Self-Efficacy in Introductory Project-Based Learning Courses

NASA Astrophysics Data System (ADS)

Pleiss, Geoffrey; Zastavker, Yevgeniya V.

2012-02-01

This study investigates first-year engineering students' self-efficacy in two introductory Project-Based Learning (PjBL) courses -- Physics (Mechanics) Laboratory and Engineering Design -- taught at a small technical institution. Twelve students participated in semi-structured open-ended interviews about their experiences in both courses. Analysis was performed using grounded theory. Results indicate that students had lower self-efficacy in Physics Lab than in Engineering Design. In Physics Lab, students reported high levels of faculty-supported scaffolding related to final project deliverables, which in turn established perceptions of an outcome-based course emphasis. Conversely, in Engineering Design, students observed high levels of scaffolding related to the intermediate project deliverables, highlighting process-centered aspects of the course. Our analyses indicate that this difference in student perceptions of course emphases -- resulting from the differences in scaffolding -- is a primary factor for the discrepancy in self-efficacy between Physics Lab and Engineering Design. Future work will examine how other variables (e.g., academic background, perception of community, gender) affect students' self-efficacy and perception of scaffolding in these PjBL courses.

The Guareschi Pyridine Scaffold as a Valuable Platform for the Identification of Selective PI3K Inhibitors.

PubMed

Galli, Ubaldina; Ciraolo, Elisa; Massarotti, Alberto; Margaria, Jean Piero; Sorba, Giovanni; Hirsch, Emilio; Tron, Gian Cesare

2015-09-18

A novel series of 4-aryl-3-cyano-2-(3-hydroxyphenyl)-6-morpholino-pyridines have been designed as potential phosphatidylinositol-3-kinase (PI3K) inhibitors. The compounds have been synthesized using the Guareschi reaction to prepare the key 4-aryl-3-cyano-2,6-dihydroxypyridine intermediate. A different selectivity according to the nature of the aryl group has been observed. Compound 9b is a selective inhibitor against the PI3Kα isoform, maintaining a good inhibitory activity. Docking studies were also performed in order to rationalize its profile of selectivity.

Three-dimensional quantitative structure-activity relationship study on antioxidant capacity of curcumin analogues

NASA Astrophysics Data System (ADS)

Chen, Bohong; Zhu, Zhibo; Chen, Min; Dong, Wenqi; Li, Zhen

2014-03-01

A comparative molecular similarity indices analysis (CoMSIA) was performed on a set of 27 curcumin-like diarylpentanoid analogues with the radical scavenging activities. A significant cross-validated correlation coefficient Q2 (0.784), SEP (0.042) for CoMSIA were obtained, indicating the statistical significance of the correlation. Further we adopt a rational approach toward the selection of substituents at various positions in our scaffold,and finally find the favored and disfavoured regions for the enhanced antioxidative activity. The results have been used as a guide to design compounds that, potentially, have better activity against oxidative damage.

Diverted organic synthesis (DOS): accessing a new, natural product inspired, neurotrophically active scaffold through an intramolecular Pauson-Khand reaction.

PubMed

Mehta, Goverdhan; Samineni, Ramesh; Srihari, Pabbaraja; Reddy, R Gajendra; Chakravarty, Sumana

2012-09-14

Drawing inspiration from the impressive neurotrophic activity exhibited by the natural product paecilomycine A, we have designed a new natural product-like scaffold employing an intramolecular Pauson-Khand reaction. Several compounds based on the new designer scaffold exhibited promising neurotrophic activity and are worthy of further biological evaluation. Our findings also highlight the importance of a DOS strategy in creating useful therapeutical leads.

Characterization of a Honeycomb-Like Scaffold With Dielectrophoresis-Based Patterning for Tissue Engineering.

PubMed

Huan, Zhijie; Chu, Henry K; Yang, Jie; Sun, Dong

2017-04-01

Seeding and patterning of cells with an engineered scaffold is a critical process in artificial tissue construction and regeneration. To date, many engineered scaffolds exhibit simple intrinsic designs, which fail to mimic the geometrical complexity of native tissues. In this study, a novel scaffold that can automatically seed cells into multilayer honeycomb patterns for bone tissue engineering application was designed and examined. The scaffold incorporated dielectrophoresis for noncontact manipulation of cells and intrinsic honeycomb architectures were integrated in each scaffold layer. When a voltage was supplied to the stacked scaffold layers, three-dimensional electric fields were generated, thereby manipulating cells to form into honeycomb-like cellular patterns for subsequent culture. The biocompatibility of the scaffold material was confirmed through the cell viability test. Experiments were conducted to evaluate the cell viability during DEP patterning at different voltage amplitudes, frequencies, and manipulating time. Three different mammalian cells were examined and the effects of the cell size and the cell concentration on the resultant cellular patterns were evaluated. Results showed that the proposed scaffold structure was able to construct multilayer honeycomb cellular patterns in a manner similar to the natural tissue. This honeycomb-like scaffold and the dielectrophoresis-based patterning technique examined in this study could provide the field with a promising tool to enhance seeding and patterning of a wide range of cells for the development of high-quality artificial tissues.

Molecular Basis of C–N Bond Cleavage by the Glycyl Radical Enzyme Choline Trimethylamine-Lyase

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

Bodea, Smaranda; Funk, Michael A.; Balskus, Emily P.

We report that deamination of choline catalyzed by the glycyl radical enzyme choline trimethylamine-lyase (CutC) has emerged as an important route for the production of trimethylamine, a microbial metabolite associated with both human disease and biological methane production. Here, we have determined five high-resolution X-ray structures of wild-type CutC and mechanistically informative mutants in the presence of choline. Within an unexpectedly polar active site, CutC orients choline through hydrogen bonding with a putative general base, and through close interactions between phenolic and carboxylate oxygen atoms of the protein scaffold and the polarized methyl groups of the trimethylammonium moiety. These structuralmore » data, along with biochemical analysis of active site mutants, support a mechanism that involves direct elimination of trimethylamine. Lastly, this work broadens our understanding of radical-based enzyme catalysis and will aid in the rational design of inhibitors of bacterial trimethylamine production.« less

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.

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.

The Role of Technology-Based Scaffolding in Problem-Based Online Asynchronous Discussion

ERIC Educational Resources Information Center

Ak, Serife

2016-01-01

This study examined the effects of technology-based scaffolds that were composed through the use of the seven-stage, problem-based learning strategy on knowledge construction in a problem-based online asynchronous discussion. In a quasi-experimental setting, 60 students in an undergraduate Instructional Technology and Material Design course were…

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

Unit cell-based computer-aided manufacturing system for tissue engineering.

PubMed

Kang, Hyun-Wook; Park, Jeong Hun; Kang, Tae-Yun; Seol, Young-Joon; Cho, Dong-Woo

2012-03-01

Scaffolds play an important role in the regeneration of artificial tissues or organs. A scaffold is a porous structure with a micro-scale inner architecture in the range of several to several hundreds of micrometers. Therefore, computer-aided construction of scaffolds should provide sophisticated functionality for porous structure design and a tool path generation strategy that can achieve micro-scale architecture. In this study, a new unit cell-based computer-aided manufacturing (CAM) system was developed for the automated design and fabrication of a porous structure with micro-scale inner architecture that can be applied to composite tissue regeneration. The CAM system was developed by first defining a data structure for the computing process of a unit cell representing a single pore structure. Next, an algorithm and software were developed and applied to construct porous structures with a single or multiple pore design using solid freeform fabrication technology and a 3D tooth/spine computer-aided design model. We showed that this system is quite feasible for the design and fabrication of a scaffold 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

Computer aided design of architecture of degradable tissue engineering scaffolds.

PubMed

Heljak, M K; Kurzydlowski, K J; Swieszkowski, W

2017-11-01

One important factor affecting the process of tissue regeneration is scaffold stiffness loss, which should be properly balanced with the rate of tissue regeneration. The aim of the research reported here was to develop a computer tool for designing the architecture of biodegradable scaffolds fabricated by melt-dissolution deposition systems (e.g. Fused Deposition Modeling) to provide the required scaffold stiffness at each stage of degradation/regeneration. The original idea presented in the paper is that the stiffness of a tissue engineering scaffold can be controlled during degradation by means of a proper selection of the diameter of the constituent fibers and the distances between them. This idea is based on the size-effect on degradation of aliphatic polyesters. The presented computer tool combines a genetic algorithm and a diffusion-reaction model of polymer hydrolytic degradation. In particular, we show how to design the architecture of scaffolds made of poly(DL-lactide-co-glycolide) with the required Young's modulus change during hydrolytic degradation.

Innovation and design of a web-based pain education interprofessional resource

PubMed Central

Lax, Leila; Watt-Watson, Judy; Lui, Michelle; Dubrowski, Adam; McGillion, Michael; Hunter, Judith; MacLennan, Cameron; Knickle, Kerry; Robb, Anja; Lapeyre, Jaime

2011-01-01

INTRODUCTION: The present article describes educational innovation processes and design of a web-based pain interprofessional resource for prelicensure health science students in universities across Canada. Operationalization of educational theory in design coupled with formative evaluation of design are discussed, along with strategies that support collaborative innovation. METHODS: Educational design was driven by content, theory and evaluation. Pain misbeliefs and teaching points along the continuum from acute to persistent pain were identified. Knowledge-building theory, situated learning, reflection and novel designs for cognitive scaffolding were then employed. Design research principles were incorporated to inform iterative and ongoing design. RESULTS: An authentic patient case was constructed, situated in inter-professional complex care to highlight learning objectives related to pre-operative, postoperative and treatment up to one year, for a surgical cancer patient. Pain mechanisms, assessment and management framed content creation. Knowledge building scaffolds were used, which included video simulations, embedded resources, concurrent feedback, practice-based reflective exercises and commentaries. Scaffolds were refined to specifically support knowledge translation. Illustrative commentaries were designed to explicate pain misbeliefs and best practices. Architecture of the resource was mapped; a multimedia, interactive prototype was created. This pain education resource was developed primarily for individual use, with extensions for interprofessional collective discourse. DISCUSSION: Translation of curricular content scripts into representation maps supported the collaborative design process by establishing a common visual language. The web-based prototype will be formatively and summatively evaluated to assess pedagogic design, knowledge-translation scaffolds, pain knowledge gains, relevance, feasibility and fidelity of this educational innovation. PMID:22184552

Rational design of small-molecule stabilizers of spermine synthase dimer by virtual screening and free energy-based approach.

PubMed

Zhang, Zhe; Martiny, Virginie; Lagorce, David; Ikeguchi, Yoshihiko; Alexov, Emil; Miteva, Maria A

2014-01-01

Snyder-Robinson Syndrome (SRS) is a rare mental retardation disorder which is caused by the malfunctioning of an enzyme, the spermine synthase (SMS), which functions as a homo-dimer. The malfunctioning of SMS in SRS patients is associated with several identified missense mutations that occur away from the active site. This investigation deals with a particular SRS-causing mutation, the G56S mutation, which was shown computationally and experimentally to destabilize the SMS homo-dimer and thus to abolish SMS enzymatic activity. As a proof-of-concept, we explore the possibility to restore the enzymatic activity of the malfunctioning SMS mutant G56S by stabilizing the dimer through small molecule binding at the mutant homo-dimer interface. For this purpose, we designed an in silico protocol that couples virtual screening and a free binding energy-based approach to identify potential small-molecule binders on the destabilized G56S dimer, with the goal to stabilize it and thus to increase SMS G56S mutant activity. The protocol resulted in extensive list of plausible stabilizers, among which we selected and tested 51 compounds experimentally for their capability to increase SMS G56S mutant enzymatic activity. In silico analysis of the experimentally identified stabilizers suggested five distinctive chemical scaffolds. This investigation suggests that druggable pockets exist in the vicinity of the mutation sites at protein-protein interfaces which can be used to alter the disease-causing effects by small molecule binding. The identified chemical scaffolds are drug-like and can serve as original starting points for development of lead molecules to further rescue the disease-causing effects of the Snyder-Robinson syndrome for which no efficient treatment exists up to now.

A Design Model of Distributed Scaffolding for Inquiry-Based Learning

ERIC Educational Resources Information Center

Hsu, Ying-Shao; Lai, Ting-Ling; Hsu, Wei-Hsiu

2015-01-01

This study presents a series of three experiments that focus on how distributed scaffolding influences learners' conceptual understanding and reasoning from combined levels of triangulation, at the interactive level (discourses within a focus group) and the collective level (class). Three inquiry lessons on plate tectonics (LPT) were designed,…

Tunable signal processing in synthetic MAP kinase cascades.

PubMed

O'Shaughnessy, Ellen C; Palani, Santhosh; Collins, James J; Sarkar, Casim A

2011-01-07

The flexibility of MAPK cascade responses enables regulation of a vast array of cell fate decisions, but elucidating the mechanisms underlying this plasticity is difficult in endogenous signaling networks. We constructed insulated mammalian MAPK cascades in yeast to explore how intrinsic and extrinsic perturbations affect the flexibility of these synthetic signaling modules. Contrary to biphasic dependence on scaffold concentration, we observe monotonic decreases in signal strength as scaffold concentration increases. We find that augmenting the concentration of sequential kinases can enhance ultrasensitivity and lower the activation threshold. Further, integrating negative regulation and concentration variation can decouple ultrasensitivity and threshold from the strength of the response. Computational analyses show that cascading can generate ultrasensitivity and that natural cascades with different kinase concentrations are innately biased toward their distinct activation profiles. This work demonstrates that tunable signal processing is inherent to minimal MAPK modules and elucidates principles for rational design of synthetic signaling systems. Copyright © 2011 Elsevier Inc. All rights reserved.

Comprehensive computational design of ordered peptide macrocycles

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

Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram Khipple

Mixed chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to-date, but there is currently no way to systematically search through the structural space spanned by such compounds for new drug candidates. Natural proteins do not provide a useful guide: peptide macrocycles lack regular secondary structures and hydrophobic cores and have different backbone torsional constraints. Hence the development of new peptide macrocycles has been approached by modifying natural products or using library selection methods; the former is limited by the small number of known structures, and the latter by the limited size and diversity accessible throughmore » library-based methods. To overcome these limitations, here we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L and D amino acids. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. We synthesize and characterize by NMR twelve 7-10 residue macrocycles, 9 of which have structures very close to the design models in solution. NMR structures of three 11-14 residue bicyclic designs are also very close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide based macrocycles unparalleled for other molecular systems, and vastly increase the available starting scaffolds for both rational drug design and library selection methods.« less

An Insilico Design of Nanoclay Based Nanocomposites and Scaffolds in Bone Tissue Engineering

NASA Astrophysics Data System (ADS)

Sharma, Anurag

A multiscale in silico approach to design polymer nanocomposites and scaffolds for bone tissue engineering applications is described in this study. This study focuses on the role of biomaterials design and selection, structural integrity and mechanical properties evolution during degradation and tissue regeneration in the successful design of polymer nanocomposite scaffolds. Polymer nanocomposite scaffolds are synthesized using aminoacid modified montmorillonite nanoclay with biomineralized hydroxyapatite and polycaprolactone (PCL/in situ HAPclay). Representative molecular models of polymer nanocomposite system are systematically developed using molecular dynamics (MD) technique and successfully validated using material characterization techniques. The constant force steered molecular dynamics (fSMD) simulation results indicate a two-phase nanomechanical behavior of the polymer nanocomposite. The MD and fSMD simulations results provide quantitative contributions of molecular interactions between different constituents of representative models and their effect on nanomechanical responses of nanoclay based polymer nanocomposite system. A finite element (FE) model of PCL/in situ HAPclay scaffold is built using micro-computed tomography images and bridging the nanomechanical properties obtained from fSMD simulations into the FE model. A new reduction factor, K is introduced into modeling results to consider the effect of wall porosity of the polymer scaffold. The effect of accelerated degradation under alkaline conditions and human osteoblast cells culture on the evolution of mechanical properties of scaffolds are studied and the damage mechanics based analytical models are developed. Finally, the novel multiscale models are developed that incorporate the complex molecular and microstructural properties, mechanical properties at nanoscale and structural levels and mechanical properties evolution during degradation and tissue formation in the polymer nanocomposite scaffold. Overall, this study provides a leap into methodologies for in silico design of biomaterials for bone tissue engineering applications. Furthermore, as a part of this work, a molecular dynamics study of rice DNA in the presence of single walled carbon nanotube is carried out to understand the role played by molecular interactions in the conformation changes of rice DNA. The simulations results showed wrapping of DNA onto SWCNT, breaking and forming of hydrogen bonds due to unzipping of Watson-Crick (WC) nucleobase pairs and forming of new non-WC nucleobase pairs in DNA.

Validating continuous digital light processing (cDLP) additive manufacturing accuracy and tissue engineering utility of a dye-initiator package.

PubMed

Wallace, Jonathan; Wang, Martha O; Thompson, Paul; Busso, Mallory; Belle, Vaijayantee; Mammoser, Nicole; Kim, Kyobum; Fisher, John P; Siblani, Ali; Xu, Yueshuo; Welter, Jean F; Lennon, Donald P; Sun, Jiayang; Caplan, Arnold I; Dean, David

2014-03-01

This study tested the accuracy of tissue engineering scaffold rendering via the continuous digital light processing (cDLP) light-based additive manufacturing technology. High accuracy (i.e., <50 µm) allows the designed performance of features relevant to three scale spaces: cell-scaffold, scaffold-tissue, and tissue-organ interactions. The biodegradable polymer poly (propylene fumarate) was used to render highly accurate scaffolds through the use of a dye-initiator package, TiO2 and bis (2,4,6-trimethylbenzoyl)phenylphosphine oxide. This dye-initiator package facilitates high accuracy in the Z dimension. Linear, round, and right-angle features were measured to gauge accuracy. Most features showed accuracies between 5.4-15% of the design. However, one feature, an 800 µm diameter circular pore, exhibited a 35.7% average reduction of patency. Light scattered in the x, y directions by the dye may have reduced this feature's accuracy. Our new fine-grained understanding of accuracy could be used to make further improvements by including corrections in the scaffold design software. Successful cell attachment occurred with both canine and human mesenchymal stem cells (MSCs). Highly accurate cDLP scaffold rendering is critical to the design of scaffolds that both guide bone regeneration and that fully resorb. Scaffold resorption must occur for regenerated bone to be remodeled and, thereby, achieve optimal strength.

Design and characterization of a biodegradable composite scaffold for ligament tissue engineering.

PubMed

Hayami, James W S; Surrao, Denver C; Waldman, Stephen D; Amsden, Brian G

2010-03-15

Herein we report on the development and characterization of a biodegradable composite scaffold for ligament tissue engineering based on the fundamental morphological features of the native ligament. An aligned fibrous component was used to mimic the fibrous collagen network and a hydrogel component to mimic the proteoglycan-water matrix of the ligament. The composite scaffold was constructed from cell-adherent, base-etched, electrospun poly(epsilon-caprolactone-co-D,L-lactide) (PCLDLLA) fibers embedded in a noncell-adherent photocrosslinked N-methacrylated glycol chitosan (MGC) hydrogel seeded with primary ligament fibroblasts. Base etching improved cellular adhesion to the PCLDLLA material. Cells within the MGC hydrogel remained viable (72 +/- 4%) during the 4-week culture period. Immunohistochemistry staining revealed ligament ECM markers collagen type I, collagen type III, and decorin organizing and accumulating along the PCLDLLA fibers within the composite scaffolds. On the basis of these results, it was determined that the composite scaffold design was a viable alternative to the current approaches used for ligament tissue engineering and merits further study. (c) 2009 Wiley Periodicals, Inc.

Design control for clinical translation of 3D printed modular scaffolds.

PubMed

Hollister, Scott J; Flanagan, Colleen L; Zopf, David A; Morrison, Robert J; Nasser, Hassan; Patel, Janki J; Ebramzadeh, Edward; Sangiorgio, Sophia N; Wheeler, Matthew B; Green, Glenn E

2015-03-01

The primary thrust of tissue engineering is the clinical translation of scaffolds and/or biologics to reconstruct tissue defects. Despite this thrust, clinical translation of tissue engineering therapies from academic research has been minimal in the 27 year history of tissue engineering. Academic research by its nature focuses on, and rewards, initial discovery of new phenomena and technologies in the basic research model, with a view towards generality. Translation, however, by its nature must be directed at specific clinical targets, also denoted as indications, with associated regulatory requirements. These regulatory requirements, especially design control, require that the clinical indication be precisely defined a priori, unlike most academic basic tissue engineering research where the research target is typically open-ended, and furthermore requires that the tissue engineering therapy be constructed according to design inputs that ensure it treats or mitigates the clinical indication. Finally, regulatory approval dictates that the constructed system be verified, i.e., proven that it meets the design inputs, and validated, i.e., that by meeting the design inputs the therapy will address the clinical indication. Satisfying design control requires (1) a system of integrated technologies (scaffolds, materials, biologics), ideally based on a fundamental platform, as compared to focus on a single technology, (2) testing of design hypotheses to validate system performance as opposed to mechanistic hypotheses of natural phenomena, and (3) sequential testing using in vitro, in vivo, large preclinical and eventually clinical tests against competing therapies, as compared to single experiments to test new technologies or test mechanistic hypotheses. Our goal in this paper is to illustrate how design control may be implemented in academic translation of scaffold based tissue engineering therapies. Specifically, we propose to (1) demonstrate a modular platform approach founded on 3D printing for developing tissue engineering therapies and (2) illustrate the design control process for modular implementation of two scaffold based tissue engineering therapies: airway reconstruction and bone tissue engineering based spine fusion.

Design Control for Clinical Translation of 3D Printed Modular Scaffolds

PubMed Central

Hollister, Scott J.; Flanagan, Colleen L.; Zopf, David A.; Morrison, Robert J.; Nasser, Hassan; Patel, Janki J.; Ebramzadeh, Edward; Sangiorgio, Sophia N.; Wheeler, Matthew B.; Green, Glenn E.

2015-01-01

The primary thrust of tissue engineering is the clinical translation of scaffolds and/or biologics to reconstruct tissue defects. Despite this thrust, clinical translation of tissue engineering therapies from academic research has been minimal in the 27 year history of tissue engineering. Academic research by its nature focuses on, and rewards, initial discovery of new phenomena and technologies in the basic research model, with a view towards generality. Translation, however, by its nature must be directed at specific clinical targets, also denoted as indications, with associated regulatory requirements. These regulatory requirements, especially design control, require that the clinical indication be precisely defined a priori, unlike most academic basic tissue engineering research where the research target is typically open-ended, and furthermore requires that the tissue engineering therapy be constructed according to design inputs that ensure it treats or mitigates the clinical indication. Finally, regulatory approval dictates that the constructed system be verified, i.e., proven that it meets the design inputs, and validated, i.e., that by meeting the design inputs the therapy will address the clinical indication. Satisfying design control requires (1) a system of integrated technologies (scaffolds, materials, biologics), ideally based on a fundamental platform, as compared to focus on a single technology, (2) testing of design hypotheses to validate system performance as opposed to mechanistic hypotheses of natural phenomena, and (3) sequential testing using in vitro, in vivo, large preclinical and eventually clinical tests against competing therapies, as compared to single experiments to test new technologies or test mechanistic hypotheses. Our goal in this paper is to illustrate how design control may be implemented in academic translation of scaffold based tissue engineering therapies. Specifically, we propose to (1) demonstrate a modular platform approach founded on 3D printing for developing tissue engineering therapies and (2) illustrate the design control process for modular implementation of two scaffold based tissue engineering therapies: airway reconstruction and bone tissue engineering based spine fusion. PMID:25666115

Nanostructured thick 3D nanofibrous scaffold can induce bone.

PubMed

Eap, Sandy; Morand, David; Clauss, François; Huck, Olivier; Stoltz, Jean-François; Lutz, Jean-Christophe; Gottenberg, Jacques-Eric; Benkirane-Jessel, Nadia; Keller, Laetitia; Fioretti, Florence

2015-01-01

Designing unique nanostructured biomimetic materials is a new challenge in modern regenerative medicine. In order to develop functional substitutes for damaged organs or tissues, several methods have been used to create implants able to regenerate robust and durable bone. Electrospinning produces nonwoven scaffolds based on polymer nanofibers mimicking the fibrillar organization of bone extracellular matrix. Here, we describe a biomimetic 3D thick nanofibrous scaffold obtained by electrospinning of the biodegradable, bioresorbable and FDA-approved polymer, poly(ε-caprolactone). Such scaffold presents a thickness reaching one centimeter. We report here the demonstration that the designed nanostructured implant is able to induce in vivo bone regeneration.

Structure-Activity Relationship Analysis of 3-phenylcoumarin-Based Monoamine Oxidase B Inhibitors

NASA Astrophysics Data System (ADS)

Rauhamäki, Sanna; Postila, Pekka A.; Niinivehmas, Sanna; Kortet, Sami; Schildt, Emmi; Pasanen, Mira; Manivannan, Elangovan; Ahinko, Mira; Koskimies, Pasi; Nyberg, Niina; Huuskonen, Pasi; Multamäki, Elina; Pasanen, Markku; Juvonen, Risto O.; Raunio, Hannu; Huuskonen, Juhani; Pentikäinen, Olli T.

2018-03-01

Monoamine oxidase B (MAO-B) catalyzes deamination of monoamines such as neurotransmitters dopamine and norepinephrine. Accordingly, small-molecule MAO-B inhibitors potentially alleviate the symptoms of dopamine-linked neuropathologies such as depression or Parkinson’s disease. Coumarin with a functionalized 3-phenyl ring system is a promising scaffold for building potent MAO-B inhibitors. Here, a vast set of 3-phenylcoumarin derivatives was designed using virtual combinatorial chemistry or rationally de novo and synthesized using microwave chemistry. The derivatives inhibited the MAO-B at 100 nM - 1 µM. The IC50 value of the most potent derivative 1 was 56 nM. A docking-based structure-activity relationship analysis summarizes the atom-level determinants of the MAO-B inhibition by the derivatives. Finally, the cross-reactivity of the derivatives was tested against monoamine oxidase A and a specific subset of enzymes linked to estradiol metabolism, known to have coumarin-based inhibitors. Overall, the results indicate that the 3-phenylcoumarins, especially derivative 1, present unique pharmacological features worth considering in future drug development.

Current strategies in multiphasic scaffold design for osteochondral tissue engineering: A review.

PubMed

Yousefi, Azizeh-Mitra; Hoque, Md Enamul; Prasad, Rangabhatala G S V; Uth, Nicholas

2015-07-01

The repair of osteochondral defects requires a tissue engineering approach that aims at mimicking the physiological properties and structure of two different tissues (cartilage and bone) using specifically designed scaffold-cell constructs. Biphasic and triphasic approaches utilize two or three different architectures, materials, or composites to produce a multilayered construct. This article gives an overview of some of the current strategies in multiphasic/gradient-based scaffold architectures and compositions for tissue engineering of osteochondral defects. In addition, the application of finite element analysis (FEA) in scaffold design and simulation of in vitro and in vivo cell growth outcomes has been briefly covered. FEA-based approaches can potentially be coupled with computer-assisted fabrication systems for controlled deposition and additive manufacturing of the simulated patterns. Finally, a summary of the existing challenges associated with the repair of osteochondral defects as well as some recommendations for future directions have been brought up in the concluding section of this article. © 2014 Wiley Periodicals, Inc.

Multiscale Poly-(ϵ-caprolactone) Scaffold Mimicking Nonlinearity in Tendon Tissue Mechanics

PubMed Central

Banik, Brittany L.; Lewis, Gregory S.; Brown, Justin L.

2016-01-01

Regenerative medicine plays a critical role in the future of medicine. However, challenges remain to balance stem cells, biomaterial scaffolds, and biochemical factors to create successful and effective scaffold designs. This project analyzes scaffold architecture with respect to mechanical capability and preliminary mesenchymal stem cell response for tendon regeneration. An electrospun fiber scaffold with tailorable properties based on a “Chinese-fingertrap” design is presented. The unique criss-crossed fiber structures demonstrate non-linear mechanical response similar to that observed in native tendon. Mechanical testing revealed that optimizing the fiber orientation resulted in the characteristic “S”-shaped curve, demonstrating a toe region and linear elastic region. This project has promising research potential across various disciplines: vascular engineering, nerve regeneration, and ligament and tendon tissue engineering. PMID:27141530

Exploring Scaffolding Modes in PjBL: A Professional Development Course to Promote In-Service Teachers' Technology Integration

ERIC Educational Resources Information Center

Chen, Ching-Huei

2017-01-01

This study investigated in-service teachers' learning experiences in a scaffolded project-based learning environment. The participants were fifty-five teachers enrolled in a graduate-level learning-by-doing design course. The participants subsequently responded to a survey on the effects of different modes of scaffolds and were interviewed with…

Highly porous scaffolds of PEDOT:PSS for bone tissue engineering.

PubMed

Guex, Anne Géraldine; Puetzer, Jennifer L; Armgarth, Astrid; Littmann, Elena; Stavrinidou, Eleni; Giannelis, Emmanuel P; Malliaras, George G; Stevens, Molly M

2017-10-15

Conjugated polymers have been increasingly considered for the design of conductive materials in the field of regenerative medicine. However, optimal scaffold properties addressing the complexity of the desired tissue still need to be developed. The focus of this study lies in the development and evaluation of a conductive scaffold for bone tissue engineering. In this study PEDOT:PSS scaffolds were designed and evaluated in vitro using MC3T3-E1 osteogenic precursor cells, and the cells were assessed for distinct differentiation stages and the expression of an osteogenic phenotype. Ice-templated PEDOT:PSS scaffolds presented high pore interconnectivity with a median pore diameter of 53.6±5.9µm and a total pore surface area of 7.72±1.7m 2 ·g -1 . The electrical conductivity, based on I-V curves, was measured to be 140µS·cm -1 with a reduced, but stable conductivity of 6.1µS·cm -1 after 28days in cell culture media. MC3T3-E1 gene expression levels of ALPL, COL1A1 and RUNX2 were significantly enhanced after 4weeks, in line with increased extracellular matrix mineralisation, and osteocalcin deposition. These results demonstrate that a porous material, based purely on PEDOT:PSS, is suitable as a scaffold for bone tissue engineering and thus represents a promising candidate for regenerative medicine. Tissue engineering approaches have been increasingly considered for the repair of non-union fractions, craniofacial reconstruction or large bone defect replacements. The design of complex biomaterials and successful engineering of 3-dimensional tissue constructs is of paramount importance to meet this clinical need. Conductive scaffolds, based on conjugated polymers, present interesting candidates to address the piezoelectric properties of bone tissue and to induce enhanced osteogenesis upon implantation. However, conductive scaffolds have not been investigated in vitro in great measure. To this end, we have developed a highly porous, electrically conductive scaffold based on PEDOT:PSS, and provide evidence that this purely synthetic material is a promising candidate for bone tissue engineering. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Design, synthesis, biological evaluation and docking study of 5-oxo-4,5-dihydropyrano[3,2-c]chromene derivatives as acetylcholinesterase and butyrylcholinesterase inhibitors.

PubMed

Khoobi, Mehdi; Alipour, Masoumeh; Sakhteman, Amirhossein; Nadri, Hamid; Moradi, Alireza; Ghandi, Mehdi; Emami, Saeed; Foroumadi, Alireza; Shafiee, Abbas

2013-10-01

A series of fused coumarins namely 5-oxo-4,5-dihydropyrano[3,2-c]chromenes linked to N-benzylpyridinium scaffold were synthesized and evaluated as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. The 1-(4-fluorobenzyl)pyridinium derivative 6g showed the most potent anti-AChE activity (IC50 value=0.038 μM) and the highest AChE/BuChE selectivity (SI>48). The docking study permitted us to rationalize the observed structure-affinity relationships and to detect possible binding modes. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Poly(ester-urethane) scaffolds: effect of structure on properties and osteogenic activity of stem cells.

PubMed

Kiziltay, Aysel; Marcos-Fernandez, Angel; San Roman, Julio; Sousa, Rui A; Reis, Rui L; Hasirci, Vasif; Hasirci, Nesrin

2015-08-01

The present study aimed to investigate the effect of structure (design and porosity) on the matrix stiffness and osteogenic activity of stem cells cultured on poly(ester-urethane) (PEU) scaffolds. Different three-dimensional (3D) forms of scaffold were prepared from lysine-based PEU using traditional salt-leaching and advanced bioplotting techniques. The resulting scaffolds were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury porosimetry and mechanical testing. The scaffolds had various pore sizes with different designs, and all were thermally stable up to 300 °C. In vitro tests, carried out using rat bone marrow stem cells (BMSCs) for bone tissue engineering, demonstrated better viability and higher cell proliferation on bioplotted scaffolds compared to salt-leached ones, most probably due to their larger and interconnected pores and stiffer nature, as shown by higher compressive moduli, which were measured by compression testing. Similarly, SEM, von Kossa staining and EDX analyses indicated higher amounts of calcium deposition on bioplotted scaffolds during cell culture. It was concluded that the design with larger interconnected porosity and stiffness has an effect on the osteogenic activity of the stem cells. Copyright © 2013 John Wiley & Sons, Ltd.

Supramolecular Architectures and Mimics of Complex Natural Folds Derived from Rationally Designed alpha-Helical Protein Structures

NASA Astrophysics Data System (ADS)

Tavenor, Nathan Albert

Protein-based supramolecular polymers (SMPs) are a class of biomaterials which draw inspiration from and expand upon the many examples of complex protein quaternary structures observed in nature: collagen, microtubules, viral capsids, etc. Designing synthetic supramolecular protein scaffolds both increases our understanding of natural superstructures and allows for the creation of novel materials. Similar to small-molecule SMPs, protein-based SMPs form due to self-assembly driven by intermolecular interactions between monomers, and monomer structure determines the properties of the overall material. Using protein-based monomers takes advantage of the self-assembly and highly specific molecular recognition properties encodable in polypeptide sequences to rationally design SMP architectures. The central hypothesis underlying our work is that alpha-helical coiled coils, a well-studied protein quaternary folding motif, are well-suited to SMP design through the addition of synthetic linkers at solvent-exposed sites. Through small changes in the structures of the cross-links and/or peptide sequence, we have been able to control both the nanoscale organization and the macroscopic properties of the SMPs. Changes to the linker and hydrophobic core of the peptide can be used to control polymer rigidity, stability, and dimensionality. The gaps in knowledge that this thesis sought to fill on this project were 1) the relationship between the molecular structure of the cross-linked polypeptides and the macroscopic properties of the SMPs and 2) a means of creating materials exhibiting multi-dimensional net or framework topologies. Separate from the above efforts on supramolecular architectures was work on improving backbone modification strategies for an alpha-helix in the context of a complex protein tertiary fold. Earlier work in our lab had successfully incorporated unnatural building blocks into every major secondary structure (beta-sheet, alpha-helix, loops and beta-turns) of a small protein with a tertiary fold. Although the tertiary fold of the native sequence was mimicked by the resulting artificial protein, the thermodynamic stability was greatly compromised. Most of this energetic penalty derived from the modifications present in the alpha-helix. The contribution within this thesis was direct comparison of several alpha-helical design strategies and establishment of the thermodynamic consequences of each.

Additive manufacturing and mechanical characterization of graded porosity scaffolds designed based on triply periodic minimal surface architectures.

PubMed

Afshar, M; Anaraki, A Pourkamali; Montazerian, H; Kadkhodapour, J

2016-09-01

Since the advent of additive manufacturing techniques, triply periodic minimal surfaces have emerged as a novel tool for designing porous scaffolds. Whereas scaffolds are expected to provide multifunctional performance, spatially changing pore patterns have been a promising approach to integrate mechanical characteristics of different architectures into a unique scaffold. Smooth morphological variations are also frequently seen in nature particularly in bone and cartilage structures and can be inspiring for designing of artificial tissues. In this study, we carried out experimental and numerical procedures to uncover the mechanical properties and deformation mechanisms of linearly graded porosity scaffolds for two different mathematically defined pore structures. Among TPMS-based scaffolds, P and D surfaces were subjected to gradient modeling to explore the mechanical responses for stretching and bending dominated deformations, respectively. Moreover, the results were compared to their corresponding uniform porosity structures. Mechanical properties were found to be by far greater for the stretching dominated structure (P-Surface). For bending dominated architecture (D-Surface), although there was no global fracture for uniform structures, graded structure showed a brittle fracture at 0.08 strain. A layer by layer deformation mechanism for stretching dominated structure was observed. For bending dominated scaffolds, deformation was accompanied by development of 45° shearing bands. Finite element simulations were also performed and the results showed a good agreement with the experimental observations. Copyright © 2016 Elsevier Ltd. All rights reserved.

A new rational-based optimal design strategy of ship structure based on multi-level analysis and super-element modeling method

NASA Astrophysics Data System (ADS)

Sun, Li; Wang, Deyu

2011-09-01

A new multi-level analysis method of introducing the super-element modeling method, derived from the multi-level analysis method first proposed by O. F. Hughes, has been proposed in this paper to solve the problem of high time cost in adopting a rational-based optimal design method for ship structural design. Furthermore, the method was verified by its effective application in optimization of the mid-ship section of a container ship. A full 3-D FEM model of a ship, suffering static and quasi-static loads, was used as the analyzing object for evaluating the structural performance of the mid-ship module, including static strength and buckling performance. Research results reveal that this new method could substantially reduce the computational cost of the rational-based optimization problem without decreasing its accuracy, which increases the feasibility and economic efficiency of using a rational-based optimal design method in ship structural design.

A brief review of extrusion-based tissue scaffold bio-printing.

PubMed

Ning, Liqun; Chen, Xiongbiao

2017-08-01

Extrusion-based bio-printing has great potential as a technique for manipulating biomaterials and living cells to create three-dimensional (3D) scaffolds for damaged tissue repair and function restoration. Over the last two decades, advances in both engineering techniques and life sciences have evolved extrusion-based bio-printing from a simple technique to one able to create diverse tissue scaffolds from a wide range of biomaterials and cell types. However, the complexities associated with synthesis of materials for bio-printing and manipulation of multiple materials and cells in bio-printing pose many challenges for scaffold fabrication. This paper presents an overview of extrusion-based bio-printing for scaffold fabrication, focusing on the prior-printing considerations (such as scaffold design and materials/cell synthesis), working principles, comparison to other techniques, and to-date achievements. This paper also briefly reviews the recent development of strategies with regard to hydrogel synthesis, multi-materials/cells manipulation, and process-induced cell damage in extrusion-based bio-printing. The key issue and challenges for extrusion-based bio-printing are also identified and discussed along with recommendations for future, aimed at developing novel biomaterials and bio-printing systems, creating patterned vascular networks within scaffolds, and preserving the cell viability and functions in scaffold bio-printing. The address of these challenges will significantly enhance the capability of extrusion-based bio-printing. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

LARGE STRAIN STIMULATION PROMOTES EXTRACELLULAR MATRIX PRODUCTION AND STIFFNESS IN AN ELASTOMERIC SCAFFOLD MODEL

PubMed Central

D’more, Antonio; Soares, Joao; Stella, John A.; Zhang, Will; Amoroso, Nicholas J.; Mayer, John E.; Wagner, William R.; Sacks, Michael S.

2016-01-01

Mechanical conditioning of engineered tissue constructs is widely recognized as one of the most relevant methods to enhance tissue accretion and microstructure, leading to improved mechanical behaviors. The understanding of the underlying mechanisms remains rather limited, restricting the development of in silico models of these phenomena, and the translation of engineered tissues into clinical application. In the present study, we examined the role of large strip-biaxial strains (up to 50%) on ECM synthesis by vascular smooth muscle cells (VSMCs) micro-integrated into electrospun polyester urethane urea (PEUU) constructs over the course of 3 weeks. Experimental results indicated that VSMC biosynthetic behavior was quite sensitive to tissue strain maximum level, and that collagen was the primary ECM component synthesized. Moreover, we found that while a 30% peak strain level achieved maximum ECM synthesis rate, further increases in strain level lead to a reduction in ECM biosynthesis. Subsequent mechanical analysis of the formed collagen fiber network was performed by removing the scaffold mechanical responses using a strain-energy based approach, showing that the de-novo collagen also demonstrated mechanical behaviors substantially better than previously obtained with small strain training and comparable to mature collagenous tissues. We conclude that the application of large deformations can play a critical role not only in the quantity of ECM synthesis (i.e. the rate of mass production), but also on the modulation of the stiffness of the newly formed ECM constituents. The improved understanding of the process of growth and development of ECM in these mechano-sensitive cell-scaffold systems will lead to more rational design and manufacturing of engineered tissues operating under highly demanding mechanical environments. PMID:27344402

Rational Design of Novel Allosteric Dihydrofolate Reductase Inhibitors Showing Antibacterial Effects on Drug-Resistant Escherichia coli Escape Variants.

PubMed

Srinivasan, Bharath; Rodrigues, João V; Tonddast-Navaei, Sam; Shakhnovich, Eugene; Skolnick, Jeffrey

2017-07-21

In drug discovery, systematic variations of substituents on a common scaffold and bioisosteric replacements are often used to generate diversity and obtain molecules with better biological effects. However, this could saturate the small-molecule diversity pool resulting in drug resistance. On the other hand, conventional drug discovery relies on targeting known pockets on protein surfaces leading to drug resistance by mutations of critical pocket residues. Here, we present a two-pronged strategy of designing novel drugs that target unique pockets on a protein's surface to overcome the above problems. Dihydrofolate reductase, DHFR, is a critical enzyme involved in thymidine and purine nucleotide biosynthesis. Several classes of compounds that are structural analogues of the substrate dihydrofolate have been explored for their antifolate activity. Here, we describe 10 novel small-molecule inhibitors of Escherichia coli DHFR, EcDHFR, belonging to the stilbenoid, deoxybenzoin, and chalcone family of compounds discovered by a combination of pocket-based virtual ligand screening and systematic scaffold hopping. These inhibitors show a unique uncompetitive or noncompetitive inhibition mechanism, distinct from those reported for all known inhibitors of DHFR, indicative of binding to a unique pocket distinct from either substrate or cofactor-binding pockets. Furthermore, we demonstrate that rescue mutants of EcDHFR, with reduced affinity to all known classes of DHFR inhibitors, are inhibited at the same concentration as the wild-type. These compounds also exhibit antibacterial activity against E. coli harboring the drug-resistant variant of DHFR. This discovery is the first report on a novel class of inhibitors targeting a unique pocket on EcDHFR.

Design and criteria of electrospun fibrous scaffolds for the treatment of spinal cord injury

PubMed Central

Vigani, Barbara; Rossi, Silvia; Sandri, Giuseppina; Bonferoni, Maria Cristina; Ferrari, Franca

2017-01-01

The complex pathophysiology of spinal cord injury may explain the current lack of an effective therapeutic approach for the regeneration of damaged neuronal cells and the recovery of motor functions. Many efforts have been performed to design and develop suitable scaffolds for spinal cord regeneration, keeping in mind that the reconstruction of a pro-regenerative environment is the key challenge for an effective neurogenesis. The aim of this review is to outline the main features of an ideal scaffold, based on biomaterials, produced by the electrospinning technique and intended for the spinal cord regeneration. An overview of the polymers more investigated in the production of neural fibrous scaffolds is also provided. PMID:29239316

Understanding Cognitive Engagement in Online Discussion: Use of a Scaffolded, Audio-Based Argumentation Activity

ERIC Educational Resources Information Center

Oh, Eunjung Grace; Kim, Hyun Song

2016-01-01

The purpose of this paper is to explore how adult learners engage in asynchronous online discussion through the implementation of an audio-based argumentation activity. The study designed scaffolded audio-based argumentation activities to promote students' cognitive engagement. The research was conducted in an online graduate course at a liberal…

Biomimetic nanoclay scaffolds for bone tissue engineering

NASA Astrophysics Data System (ADS)

Ambre, Avinash Harishchandra

Tissue engineering offers a significant potential alternative to conventional methods for rectifying tissue defects by evoking natural regeneration process via interactions between cells and 3D porous scaffolds. Imparting adequate mechanical properties to biodegradable scaffolds for bone tissue engineering is an important challenge and extends from molecular to macroscale. This work focuses on the use of sodium montmorillonite (Na-MMT) to design polymer composite scaffolds having enhanced mechanical properties along with multiple interdependent properties. Materials design beginning at the molecular level was used in which Na-MMT clay was modified with three different unnatural amino acids and further characterized using Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD). Based on improved bicompatibility with human osteoblasts (bone cells) and intermediate increase in d-spacing of MMT clay (shown by XRD), 5-aminovaleric acid modified clay was further used to prepare biopolymer (chitosan-polygalacturonic acid complex) scaffolds. Osteoblast proliferation in biopolymer scaffolds containing 5-aminovaleric acid modified clay was similar to biopolymer scaffolds containing hydroxyapatite (HAP). A novel process based on biomineralization in bone was designed to prepare 5-aminovaleric acid modified clay capable of imparting multiple properties to the scaffolds. Bone-like apatite was mineralized in modified clay and a novel nanoclay-HAP hybrid (in situ HAPclay) was obtained. FTIR spectroscopy indicated a molecular level organic-inorganic association between the intercalated 5-aminovaleric acid and mineralized HAP. Osteoblasts formed clusters on biopolymer composite films prepared with different weight percent compositions of in situ HAPclay. Human MSCs formed mineralized nodules on composite films and mineralized extracellular matrix (ECM) in composite scaffolds without the use of osteogenic supplements. Polycaprolactone (PCL), a synthetic polymer, was used for preparing composites (films and scaffolds) containing in situ HAPclay. Composite films showed significantly improved nanomechanical properties. Human MSCs formed mineralized ECM on films in absence of osteogenic supplements and were able to infiltrate the scaffolds. Atomic force microscopy imaging of mineralized ECM formed on composite films showed similarities in dimensions, arrangement of collagen and apatite with their natural bone counterparts. This work indicates the potential of in situ HAPclay to impart polymeric scaffolds with osteoinductive, osteoconductive abilities and improve their mechanical properties besides emphasizing nanoclays as cell-instructive materials.

Structural basis for ligand recognition at the benzodiazepine binding site of GABAA alpha 3 receptor, and pharmacophore-based virtual screening approach.

PubMed

Vijayan, R S K; Ghoshal, Nanda

2008-10-01

Given the heterogeneity of GABA(A) receptor, the pharmacological significance of identifying subtype selective modulators is increasingly being recognized. Thus, drugs selective for GABA(A) alpha(3) receptors are expected to display fewer side effects than the drugs presently in clinical use. Hence we carried out 3D QSAR (three-dimensional quantitative structure-activity relationship) studies on a series of novel GABA(A) alpha(3) subtype selective modulators to gain more insight into subtype affinity. To identify the 3D functional attributes required for subtype selectivity, a chemical feature-based pharmacophore, primarily based on selective ligands representing diverse structural classes was generated. The obtained pseudo receptor model of the benzodiazepine binding site revealed a binding mode akin to "Message-Address" concept. Scaffold hopping was carried out across multi-conformational May Bridge database for the identification of novel chemotypes. Further a focused data reduction approach was employed to choose a subset of enriched compounds based on "Drug likeness" and "Similarity-based" methods. These results taken together could provide impetus for rational design and optimization of more selective and high affinity leads with a potential to have decreased adverse effects.

Identifying the binding mode of a molecular scaffold

NASA Astrophysics Data System (ADS)

Chema, Doron; Eren, Doron; Yayon, Avner; Goldblum, Amiram; Zaliani, Andrea

2004-01-01

We describe a method for docking of a scaffold-based series and present its advantages over docking of individual ligands, for determining the binding mode of a molecular scaffold in a binding site. The method has been applied to eight different scaffolds of protein kinase inhibitors (PKI). A single analog of each of these eight scaffolds was previously crystallized with different protein kinases. We have used FlexX to dock a set of molecules that share the same scaffold, rather than docking a single molecule. The main mode of binding is determined by the mode of binding of the largest cluster among the docked molecules that share a scaffold. Clustering is based on our `nearest single neighbor' method [J. Chem. Inf. Comput. Sci., 43 (2003) 208-217]. Additional criteria are applied in those cases in which more than one significant binding mode is found. Using the proposed method, most of the crystallographic binding modes of these scaffolds were reconstructed. Alternative modes, that have not been detected yet by experiments, could also be identified. The method was applied to predict the binding mode of an additional molecular scaffold that was not yet reported and the predicted binding mode has been found to be very similar to experimental results for a closely related scaffold. We suggest that this approach be used as a virtual screening tool for scaffold-based design processes.

Preliminary Results of Implantation in Animal Model and Osteoblast Culture Evaluation of Prototypes of Biomimetic Multispiked Connecting Scaffold for Noncemented Stemless Resurfacing Hip Arthroplasty Endoprostheses

PubMed Central

Uklejewski, Ryszard; Rogala, Piotr; Winiecki, Mariusz; Kędzia, Andrzej; Ruszkowski, Piotr

2013-01-01

We present the new fixation method for RHA (resurfacing hip arthroplasty) endoprostheses by means of the biomimetic multispiked connecting scaffold (MSC-Scaffold). Such connecting scaffold can generate new type of RHA endoprostheses, that is stemless and fixed entirely without cement. The preprototypes of this MSC-Scaffold were manufactured with modern additive laser additive technology (SLM). The pilot surgical implantations in animal model (two laboratory swine) of MSC-Scaffold preprototypes have showed after two months neither implant loosening, migration, and nor other early complications. From the results of performed histopathological evaluation of the periscaffold spikes bone tissue and 10-day culture of human osteoblasts (NHOst) we can conclude that (1) the scaffolding effect was obtained and (2) to improve the osseointegration of the scaffold spikes, their material surface should be physicochemically modified (e.g., with hydroxyapatite). Some histopathological findings in the periscaffold domain near the MSC-Scaffold spikes bases (fibrous connective tissue and metallic particles near the MSC-Scaffold spikes bases edges) prompt considering the necessity to optimize the design of the MSC-Scaffold in the regions of its interspike space near the spikes bases edges, to provide more room for new bone formation in this region and for indispensable post-processing (glass pearl blasting) after the SLM manufacturing. PMID:23984397

The concept of template-based de novo design from drug-derived molecular fragments and its application to TAR RNA.

PubMed

Schüller, Andreas; Suhartono, Marcel; Fechner, Uli; Tanrikulu, Yusuf; Breitung, Sven; Scheffer, Ute; Göbel, Michael W; Schneider, Gisbert

2008-02-01

Principles of fragment-based molecular design are presented and discussed in the context of de novo drug design. The underlying idea is to dissect known drug molecules in fragments by straightforward pseudo-retro-synthesis. The resulting building blocks are then used for automated assembly of new molecules. A particular question has been whether this approach is actually able to perform scaffold-hopping. A prospective case study illustrates the usefulness of fragment-based de novo design for finding new scaffolds. We were able to identify a novel ligand disrupting the interaction between the Tat peptide and TAR RNA, which is part of the human immunodeficiency virus (HIV-1) mRNA. Using a single template structure (acetylpromazine) as reference molecule and a topological pharmacophore descriptor (CATS), new chemotypes were automatically generated by our de novo design software Flux. Flux features an evolutionary algorithm for fragment-based compound assembly and optimization. Pharmacophore superimposition and docking into the target RNA suggest perfect matching between the template molecule and the designed compound. Chemical synthesis was straightforward, and bioactivity of the designed molecule was confirmed in a FRET assay. This study demonstrates the practicability of de novo design to generating RNA ligands containing novel molecular scaffolds.

Load-adaptive scaffold architecturing: a bioinspired approach to the design of porous additively manufactured scaffolds with optimized mechanical properties.

PubMed

Rainer, Alberto; Giannitelli, Sara M; Accoto, Dino; De Porcellinis, Stefano; Guglielmelli, Eugenio; Trombetta, Marcella

2012-04-01

Computer-Aided Tissue Engineering (CATE) is based on a set of additive manufacturing techniques for the fabrication of patient-specific scaffolds, with geometries obtained from medical imaging. One of the main issues regarding the application of CATE concerns the definition of the internal architecture of the fabricated scaffolds, which, in turn, influences their porosity and mechanical strength. The present study envisages an innovative strategy for the fabrication of highly optimized structures, based on the a priori finite element analysis (FEA) of the physiological load set at the implant site. The resulting scaffold micro-architecture does not follow a regular geometrical pattern; on the contrary, it is based on the results of a numerical study. The algorithm was applied to a solid free-form fabrication process, using poly(ε-caprolactone) as the starting material for the processing of additive manufactured structures. A simple and intuitive geometry was chosen as a proof-of-principle application, on which finite element simulations and mechanical testing were performed. Then, to demonstrate the capability in creating mechanically biomimetic structures, the proximal femur subjected to physiological loading conditions was considered and a construct fitting a femur head portion was designed and manufactured.

Geometric modeling of space-optimal unit-cell-based tissue engineering scaffolds

NASA Astrophysics Data System (ADS)

Rajagopalan, Srinivasan; Lu, Lichun; Yaszemski, Michael J.; Robb, Richard A.

2005-04-01

Tissue engineering involves regenerating damaged or malfunctioning organs using cells, biomolecules, and synthetic or natural scaffolds. Based on their intended roles, scaffolds can be injected as space-fillers or be preformed and implanted to provide mechanical support. Preformed scaffolds are biomimetic "trellis-like" structures which, on implantation and integration, act as tissue/organ surrogates. Customized, computer controlled, and reproducible preformed scaffolds can be fabricated using Computer Aided Design (CAD) techniques and rapid prototyping devices. A curved, monolithic construct with minimal surface area constitutes an efficient substrate geometry that promotes cell attachment, migration and proliferation. However, current CAD approaches do not provide such a biomorphic construct. We address this critical issue by presenting one of the very first physical realizations of minimal surfaces towards the construction of efficient unit-cell based tissue engineering scaffolds. Mask programmability, and optimal packing density of triply periodic minimal surfaces are used to construct the optimal pore geometry. Budgeted polygonization, and progressive minimal surface refinement facilitate the machinability of these surfaces. The efficient stress distributions, as deduced from the Finite Element simulations, favor the use of these scaffolds for orthopedic applications.

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.

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

A Scaffolding Strategy to Develop Handheld Sensor-Based Vocabulary Games for Improving Students' Learning Motivation and Performance

ERIC Educational Resources Information Center

Huang, Yong-Ming; Huang, Yueh-Min

2015-01-01

Vocabulary is the foundation for students who learn a foreign language. Nevertheless, students may be bored by the painstaking process of rote learning. To this end, this study designed a handheld sensor-based vocabulary game based on a scaffolding strategy for improving students' motivation and achievement in vocabulary learning. On the one hand,…

A TPMS-based method for modeling porous scaffolds for bionic bone tissue engineering.

PubMed

Shi, Jianping; Zhu, Liya; Li, Lan; Li, Zongan; Yang, Jiquan; Wang, Xingsong

2018-05-09

In the field of bone defect repair, gradient porous scaffolds have received increased attention because they provide a better environment for promoting tissue regeneration. In this study, we propose an effective method to generate bionic porous scaffolds based on the TPMS (triply periodic minimal surface) and SF (sigmoid function) methods. First, cortical bone morphological features (e.g., pore size and distribution) were determined for several regions of a rabbit femoral bone by analyzing CT-scans. A finite element method was used to evaluate the mechanical properties of the bone at these respective areas. These results were used to place different TPMS substructures into one scaffold domain with smooth transitions. The geometrical parameters of the scaffolds were optimized to match the elastic properties of a human bone. With this proposed method, a functional gradient porous scaffold could be designed and produced by an additive manufacturing method.

Solid freeform-fabricated scaffolds designed to carry multicellular mesenchymal stem cell spheroids for cartilage regeneration.

PubMed

Huang, G S; Tseng, C S; Linju Yen, B; Dai, L G; Hsieh, P S; Hsu, S-h

2013-10-13

Three-dimensional (3D) cellular spheroids have recently emerged as a new trend to replace suspended single cells in modern cell-based therapies because of their greater regeneration capacities in vitro. They may lose the 3D structure during a change of microenvironment, which poses challenges to their translation in vivo. Besides, the conventional microporous scaffolds may have difficulty in accommodating these relatively large spheroids. Here we revealed a novel design of microenvironment for delivering and sustaining the 3D spheroids. Biodegradable scaffolds with macroporosity to accommodate mesenchymal stem cell (MSC) spheroids were made by solid freeform fabrication (SFF) from the solution of poly(D,L-lactide-co-glycolide). Their internal surface was modified with chitosan following air plasma treatment in order to preserve the morphology of the spheroids. It was demonstrated that human MSC spheroids loaded in SFF scaffolds produced a significantly larger amount of cartilage-associated extracellular matrix in vitro and in NOD/SCID mice compared to single cells in the same scaffolds. Implantation of MSC spheroid-loaded scaffolds into the chondral defects of rabbit knees showed superior cartilage regeneration. This study establishes new perspectives in designing the spheroid-sustaining microenvironment within a tissue engineering scaffold for in vivo applications.

Structural and material approaches to bone tissue engineering in powder-based three-dimensional printing.

PubMed

Butscher, A; Bohner, M; Hofmann, S; Gauckler, L; Müller, R

2011-03-01

This article reviews the current state of knowledge concerning the use of powder-based three-dimensional printing (3DP) for the synthesis of bone tissue engineering scaffolds. 3DP is a solid free-form fabrication (SFF) technique building up complex open porous 3D structures layer by layer (a bottom-up approach). In contrast to traditional fabrication techniques generally subtracting material step by step (a top-down approach), SFF approaches allow nearly unlimited designs and a large variety of materials to be used for scaffold engineering. Today's state of the art materials, as well as the mechanical and structural requirements for bone scaffolds, are summarized and discussed in relation to the technical feasibility of their use in 3DP. Advances in the field of 3DP are presented and compared with other SFF methods. Existing strategies on material and design control of scaffolds are reviewed. Finally, the possibilities and limiting factors are addressed and potential strategies to improve 3DP for scaffold engineering are proposed. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Exploring the Effect of Embedded Scaffolding Within Curricular Tasks on Third-Grade Students' Model-Based Explanations about Hydrologic Cycling

NASA Astrophysics Data System (ADS)

Zangori, Laura; Forbes, Cory T.; Schwarz, Christina V.

2015-10-01

Opportunities to generate model-based explanations are crucial for elementary students, yet are rarely foregrounded in elementary science learning environments despite evidence that early learners can reason from models when provided with scaffolding. We used a quasi-experimental research design to investigate the comparative impact of a scaffold test condition consisting of embedded physical scaffolds within a curricular modeling task on third-grade (age 8-9) students' formulation of model-based explanations for the water cycle. This condition was contrasted to the control condition where third-grade students used a curricular modeling task with no embedded physical scaffolds. Students from each condition ( n scaffold = 60; n unscaffold = 56) generated models of the water cycle before and after completion of a 10-week water unit. Results from quantitative analyses suggest that students in the scaffolded condition represented and linked more subsurface water process sequences with surface water process sequences than did students in the unscaffolded condition. However, results of qualitative analyses indicate that students in the scaffolded condition were less likely to build upon these process sequences to generate model-based explanations and experienced difficulties understanding their models as abstracted representations rather than recreations of real-world phenomena. We conclude that embedded curricular scaffolds may support students to consider non-observable components of the water cycle but, alone, may be insufficient for generation of model-based explanations about subsurface water movement.

Fragment virtual screening based on Bayesian categorization for discovering novel VEGFR-2 scaffolds.

PubMed

Zhang, Yanmin; Jiao, Yu; Xiong, Xiao; Liu, Haichun; Ran, Ting; Xu, Jinxing; Lu, Shuai; Xu, Anyang; Pan, Jing; Qiao, Xin; Shi, Zhihao; Lu, Tao; Chen, Yadong

2015-11-01

The discovery of novel scaffolds against a specific target has long been one of the most significant but challengeable goals in discovering lead compounds. A scaffold that binds in important regions of the active pocket is more favorable as a starting point because scaffolds generally possess greater optimization possibilities. However, due to the lack of sufficient chemical space diversity of the databases and the ineffectiveness of the screening methods, it still remains a great challenge to discover novel active scaffolds. Since the strengths and weaknesses of both fragment-based drug design and traditional virtual screening (VS), we proposed a fragment VS concept based on Bayesian categorization for the discovery of novel scaffolds. This work investigated the proposal through an application on VEGFR-2 target. Firstly, scaffold and structural diversity of chemical space for 10 compound databases were explicitly evaluated. Simultaneously, a robust Bayesian classification model was constructed for screening not only compound databases but also their corresponding fragment databases. Although analysis of the scaffold diversity demonstrated a very unevenly distribution of scaffolds over molecules, results showed that our Bayesian model behaved better in screening fragments than molecules. Through a literature retrospective research, several generated fragments with relatively high Bayesian scores indeed exhibit VEGFR-2 biological activity, which strongly proved the effectiveness of fragment VS based on Bayesian categorization models. This investigation of Bayesian-based fragment VS can further emphasize the necessity for enrichment of compound databases employed in lead discovery by amplifying the diversity of databases with novel structures.

A design protocol for tailoring ice-templated scaffold structure

PubMed Central

Pawelec, K. M.; Husmann, A.; Best, S. M.; Cameron, R. E.

2014-01-01

In this paper, we show, for the first time, the key link between scaffold architecture and latent heat evolution during the production of porous biomedical collagen structures using freeze-drying. Collagen scaffolds are used widely in the biomedical industry for the repair and reconstruction of skeletal tissues and organs. Freeze-drying of collagen slurries is a standard industrial process, and, until now, the literature has sought to characterize the influence of set processing parameters including the freezing protocol and weight percentage of collagen. However, we are able to demonstrate, by monitoring the local thermal events within the slurry during solidification, that nucleation, growth and annealing processes can be controlled, and therefore we are able to control the resulting scaffold architecture. Based on our correlation of thermal profile measurements with scaffold architecture, we hypothesize that there is a link between the fundamental freezing of ice and the structure of scaffolds, which suggests that this concept is applicable not only for collagen but also for ceramics and pharmaceuticals. We present a design protocol of strategies for tailoring the ice-templated scaffold structure. PMID:24402916

Tissue Engineered Bone Using Polycaprolactone Scaffolds Made by Selective Laser Sintering

DTIC Science & Technology

2005-01-01

temporo - mandibular joint (TMJ) pose many challenges for bone tissue engineering. Adverse reactions to alloplastic, non- biological materials result in...producing a prototype mandibular condyle scaffold based on an actual pig condyle. INTRODUCTION Repair and reconstruction of complex joints such as the...computed tomography (CT) data with a designed porous architecture to build a complex scaffold that mimics a mandibular condyle. Results show that

Biofunctionalized peptide-based hydrogels provide permissive scaffolds to attract neurite outgrowth from spiral ganglion neurons.

PubMed

Frick, Claudia; Müller, Marcus; Wank, Ute; Tropitzsch, Anke; Kramer, Benedikt; Senn, Pascal; Rask-Andersen, Helge; Wiesmüller, Karl-Heinz; Löwenheim, Hubert

2017-01-01

Cochlear implants (CI) allow for hearing rehabilitation in patients with sensorineural hearing loss or deafness. Restricted CI performance results from the spatial gap between spiral ganglion neurons and the CI, causing current spread that limits spatially restricted stimulation and impairs frequency resolution. This may be substantially improved by guiding peripheral processes of spiral ganglion neurons towards and onto the CI electrode contacts. An injectable, peptide-based hydrogel was developed which may provide a permissive scaffold to facilitate neurite growth towards the CI. To test hydrogel capacity to attract spiral ganglion neurites, neurite outgrowth was quantified in an in vitro model using a custom-designed hydrogel scaffold and PuraMatrix ® . Neurite attachment to native hydrogels is poor, but significantly improved by incorporation of brain-derived neurotrophic factor (BDNF), covalent coupling of the bioactive laminin epitope IKVAV and the incorporation a full length laminin to hydrogel scaffolds. Incorporation of full length laminin protein into a novel custom-designed biofunctionalized hydrogel (IKVAV-GGG-SIINFEKL) allows for neurite outgrowth into the hydrogel scaffold. The study demonstrates that peptide-based hydrogels can be specifically biofunctionalized to provide a permissive scaffold to attract neurite outgrowth from spiral ganglion neurons. Such biomaterials appear suitable to bridge the spatial gap between neurons and the CI. Copyright © 2016 Elsevier B.V. All rights reserved.

Structure Based Library Design (SBLD) for new 1,4-dihydropyrimidine scaffold as simultaneous COX-1/COX-2 and 5-LOX inhibitors.

PubMed

Lokwani, Deepak; Azad, Rajaram; Sarkate, Aniket; Reddanna, Pallu; Shinde, Devanand

2015-08-01

The various scaffolds containing 1,4-dihydropyrimidine ring were designed by considering the environment of the active site of COX-1/COX-2 and 5-LOX enzymes. The structure-based library design approach, including the focused library design (Virtual Combinatorial Library Design) and virtual screening was used to select the 1,4-dihydropyrimidine scaffold for simultaneous inhibition of both enzyme pathways (COX-1/COX-2 and 5-LOX). The virtual library on each 1,4-dihydropyrimidine scaffold was enumerated in two alternative ways. In first way, the chemical reagents at R groups were filtered by docking of scaffold with single position substitution, that is, only at R1, or R2, or R3, … Rn on COX-2 enzyme using Glide XP docking mode. The structures that do not dock well were removed and the library was enumerated with filtered chemical reagents. In second alternative way, the single position docking stage was bypassed, and the entire library was enumerated using all chemical reagents by docking on the COX-2 enzyme. The entire library of approximately 15,629 compounds obtained from both ways after screening for drug like properties, were further screened for their binding affinity against COX-1 and 5-LOX enzymes using Virtual Screening Workflow. Finally, 142 hits were obtained and divided into two groups based on their binding affinity for COX-1/COX-2 and for both enzyme pathways (COX-1/COX-2 and 5-LOX). The ten molecules were selected, synthesized and evaluated for their COX-1, COX-2 and 5-LOX inhibiting activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Engineering tissue constructs to mimic native aortic and pulmonary valve leaflets' structures and mechanics

NASA Astrophysics Data System (ADS)

Masoumi, Nafiseh

There are several disadvantages correlated with current heart valve replacement, including anticoagulation therapy for patients with mechanical valves and the low durability of bioprosthetic valves. The non-viable nature of such devices is a critical drawback especially for pediatric cases due to the inability of the graft to grow in vivo with the patients. A tissue engineered heart valve (TEHV) with remodeling and growth ability, is conceptually appealing to use in the surgical repair and could serve as a permanent replacements when operating for pediatric valvular lesions. It is critical that scaffolds for functional heart valve tissue engineering, be capable of mimicking the native leaflet's structure and mechanical properties at the time of implantation. Meanwhile, the scaffolds should be able to support cellular proliferation and native-like tissue formation as the TEHV remodels toward a scaffold-free state. Our overall hypothesis is that an "ideal" engineered construct, designed based on native leaflet's structure and mechanics, will complement a native heart valve leaflet in providing benchmarks for use in the design of clinically-applicable TEHV. This hypothesis was addressed through several experiments conducted in the present study. To establish a functional biomimetic TEHV, we developed scaffolds capable of matching the anisotropic stiffness of native leaflet while promoting native-like cell and collagen content and supporting the ECM generation. Scaffolds with various polymer contents (e.g., poly (glycerol sebacate) (PGS) and poly (epsilon-caprolactone) (PCL)) and structural designs (e.g., microfabricated and microfibrous scaffolds), were fabricated based on native leaflet's structure and mechanics. It was found that the tri-layered scaffold, designed with assembly of microfabricated PGS and microfibrous PGS/PCL was a functional leaflet capable of promoting tissue formation. Furthermore, to investigate the effect of cyclic stress and flexure individually on the TEHV development, we designed a simple and novel stretch-flexure bioreactor in which samples were subjected to well-defined stimulations with a controlled strain-rate. The stretch and flexure was found to accelerate and increase tissue formation on the microfabricated PGS scaffolds cultivated in the bioreactors.

Structure-Activity Relationships for the Antifungal Activity of Selective Estrogen Receptor Antagonists Related to Tamoxifen

PubMed Central

Butts, Arielle; Martin, Jennifer A.; DiDone, Louis; Bradley, Erin K.; Mutz, Mitchell; Krysan, Damian J.

2015-01-01

Cryptococcosis is one of the most important invasive fungal infections and is a significant contributor to the mortality associated with HIV/AIDS. As part of our program to repurpose molecules related to the selective estrogen receptor modulator (SERM) tamoxifen as anti-cryptococcal agents, we have explored the structure-activity relationships of a set of structurally diverse SERMs and tamoxifen derivatives. Our data provide the first insights into the structural requirements for the antifungal activity of this scaffold. Three key molecular characteristics affecting anti-cryptococcal activity emerged from our studies: 1) the presence of an alkylamino group tethered to one of the aromatic rings of the triphenylethylene core; 2) an appropriately sized aliphatic substituent at the 2 position of the ethylene moiety; and 3) electronegative substituents on the aromatic rings modestly improved activity. Using a cell-based assay of calmodulin antagonism, we found that the anti-cryptococcal activity of the scaffold correlates with calmodulin inhibition. Finally, we developed a homology model of C. neoformans calmodulin and used it to rationalize the structural basis for the activity of these molecules. Taken together, these data and models provide a basis for the further optimization of this promising anti-cryptococcal scaffold. PMID:26016941

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

Exploring the Effect of Embedded Scaffolding within Curricular Tasks on Third-Grade Students' Model-Based Explanations about Hydrologic Cycling

ERIC Educational Resources Information Center

Zangori, Laura; Forbes, Cory T.; Schwarz, Christina V.

2015-01-01

Opportunities to generate model-based explanations are crucial for elementary students, yet are rarely foregrounded in elementary science learning environments despite evidence that early learners can reason from models when provided with scaffolding. We used a quasi-experimental research design to investigate the comparative impact of a scaffold…

The Impact of a Scaffolded Assessment Intervention on Students' Academic Achievement in Web-Based Peer Assessment Activities

ERIC Educational Resources Information Center

Lee, Chien-I; Yang, Ya-Fei; Mai, Shin-Yi

2016-01-01

Web-based peer assessment has been considered an important process for learning. However, students may not offer constructive feedback due to lack of expertise knowledge. Therefore, this study proposed a scaffolded assessment approach accordingly. To evaluate the effectiveness of the proposed approach, the quasi-experimental design was employed to…

Problem-Based Learning, Scaffolding, and Coaching: Improving Student Outcomes through Structured Group Time

ERIC Educational Resources Information Center

Murray, Lynn M.

2012-01-01

Live-client projects are increasingly used in marketing coursework. However, students, instructors, and clients are often disappointed by the results. This paper reports an approach drawn from the problem-based learning, scaffolding, and team formation and coaching literatures that uses favor of a series of workshops designed to guide students in…

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.

The discovery and preclinical evaluation of BMS-707035, a potent HIV-1 integrase strand transfer inhibitor.

PubMed

Naidu, B Narasimhulu; Walker, Michael A; Sorenson, Margaret E; Ueda, Yasutsugu; Matiskella, John D; Connolly, Timothy P; Dicker, Ira B; Lin, Zeyu; Bollini, Sagarika; Terry, Brian J; Higley, Helen; Zheng, Ming; Parker, Dawn D; Wu, Dedong; Adams, Stephen; Krystal, Mark R; Meanwell, Nicholas A

2018-07-01

BMS-707035 is an HIV-1 integrase strand transfer inhibitor (INSTI) discovered by systematic optimization of N-methylpyrimidinone carboxamides guided by structure-activity relationships (SARs) and the single crystal X-ray structure of compound 10. It was rationalized that the unexpectedly advantageous profiles of N-methylpyrimidinone carboxamides with a saturated C2-substitutent may be due, in part, to the geometric relationship between the C2-substituent and the pyrimidinone core. The single crystal X-ray structure of 10 provided support for this reasoning and guided the design of a spirocyclic series 12 which led to discovery of the morpholino-fused pyrimidinone series 13. Several carboxamides derived from this bicyclic scaffold displayed improved antiviral activity and pharmacokinetic profiles when compared with corresponding spirocyclic analogs. Based on the excellent antiviral activity, preclinical profiles and acceptable in vitro and in vivo toxicity profiles, 13a (BMS-707035) was selected for advancement into phase I clinical trials. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ultrafast Spreading Effect Induced Rapid Cell Trapping into Porous Scaffold with Superhydrophilic Surface.

PubMed

Wang, Chenmiao; Qiao, Chunyan; Song, Wenlong; Sun, Hongchen

2015-08-19

In this contribution, superhydrophilic chitosan-based scaffolds with ultrafast spreading property were fabricated and used to improve the trapped efficiency of cells. The ultrafast spreading property allowed cells to be trapped into the internal 3D porous structures of the prepared scaffolds more quickly and effectively. Cell adhesion, growth, and proliferation were also improved, which could be attributed to the combination of UV irradiation and ultrafast spreading property. The construction of ultrafast spreading property on the scaffold surface will offer a novel way to design more effective scaffold in tissue engineering that could largely shorten the therapeutic time for patients.

Recent advances in bone tissue engineering scaffolds

PubMed Central

Bose, Susmita; Roy, Mangal; Bandyopadhyay, Amit

2012-01-01

Bone disorders are of significant concern due to increase in the median age of our population. Traditionally, bone grafts have been used to restore damaged bone. Synthetic biomaterials are now being used as bone graft substitutes. These biomaterials were initially selected for structural restoration based on their biomechanical properties. Later scaffolds were engineered to be bioactive or bioresorbable to enhance tissue growth. Now scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous, biodegradable materials that harbor different growth factors, drugs, genes or stem cells. In this review, we highlight recent advances in bone scaffolds and discuss aspects that still need to be improved. PMID:22939815

Development of a General Aza-Cope Reaction Trigger Applied to Fluorescence Imaging of Formaldehyde in Living Cells.

PubMed

Bruemmer, Kevin J; Walvoord, Ryan R; Brewer, Thomas F; Burgos-Barragan, Guillermo; Wit, Niek; Pontel, Lucas B; Patel, Ketan J; Chang, Christopher J

2017-04-19

Formaldehyde (FA) is a reactive signaling molecule that is continuously produced through a number of central biological pathways spanning epigenetics to one-carbon metabolism. On the other hand, aberrant, elevated levels of FA are implicated in disease states ranging from asthma to neurodegenerative disorders. In this context, fluorescence-based probes for FA imaging are emerging as potentially powerful chemical tools to help disentangle the complexities of FA homeostasis and its physiological and pathological contributions. Currently available FA indicators require direct modification of the fluorophore backbone through complex synthetic considerations to enable FA detection, often limiting the generalization of designs to other fluorophore classes. To address this challenge, we now present the rational, iterative development of a general reaction-based trigger utilizing 2-aza-Cope reactivity for selective and sensitive detection of FA in living systems. Specifically, we developed a homoallylamine functionality that can undergo a subsequent self-immolative β-elimination, creating a FA-responsive trigger that is capable of masking a phenol on a fluorophore or any other potential chemical scaffold for related imaging and/or therapeutic applications. We demonstrate the utility of this trigger by creating a series of fluorescent probes for FA with excitation and emission wavelengths that span the UV to visible spectral regions through caging of a variety of dye units. In particular, Formaldehyde Probe 573 (FAP573), based on a resorufin scaffold, is the most red-shifted and FA sensitive in this series in terms of signal-to-noise responses and enables identification of alcohol dehydrogenase 5 (ADH5) as an enzyme that regulates FA metabolism in living cells. The results provide a starting point for the broader use of 2-aza-Cope reactivity for probing and manipulating FA biology.

Three-dimensional scaffolding to investigate neuronal derivatives of human embryonic stem cells.

PubMed

Soman, Pranav; Tobe, Brian T D; Lee, Jin Woo; Winquist, Alicia M; Singec, Ilyas; Vecchio, Kenneth S; Snyder, Evan Y; Chen, Shaochen

2012-10-01

Access to unlimited numbers of live human neurons derived from stem cells offers unique opportunities for in vitro modeling of neural development, disease-related cellular phenotypes, and drug testing and discovery. However, to develop informative cellular in vitro assays, it is important to consider the relevant in vivo environment of neural tissues. Biomimetic 3D scaffolds are tools to culture human neurons under defined mechanical and physico-chemical properties providing an interconnected porous structure that may potentially enable a higher or more complex organization than traditional two-dimensional monolayer conditions. It is known that even minor variations in the internal geometry and mechanical properties of 3D scaffolds can impact cell behavior including survival, growth, and cell fate choice. In this report, we describe the design and engineering of 3D synthetic polyethylene glycol (PEG)-based and biodegradable gelatin-based scaffolds generated by a free form fabrication technique with precise internal geometry and elastic stiffnesses. We show that human neurons, derived from human embryonic stem (hESC) cells, are able to adhere to these scaffolds and form organoid structures that extend in three dimensions as demonstrated by confocal and electron microscopy. Future refinements of scaffold structure, size and surface chemistries may facilitate long term experiments and designing clinically applicable bioassays.

Optimization of scaffold design for bone tissue engineering: A computational and experimental study.

PubMed

Dias, Marta R; Guedes, José M; Flanagan, Colleen L; Hollister, Scott J; Fernandes, Paulo R

2014-04-01

In bone tissue engineering, the scaffold has not only to allow the diffusion of cells, nutrients and oxygen but also provide adequate mechanical support. One way to ensure the scaffold has the right properties is to use computational tools to design such a scaffold coupled with additive manufacturing to build the scaffolds to the resulting optimized design specifications. In this study a topology optimization algorithm is proposed as a technique to design scaffolds that meet specific requirements for mass transport and mechanical load bearing. Several micro-structures obtained computationally are presented. Designed scaffolds were then built using selective laser sintering and the actual features of the fabricated scaffolds were measured and compared to the designed values. It was possible to obtain scaffolds with an internal geometry that reasonably matched the computational design (within 14% of porosity target, 40% for strut size and 55% for throat size in the building direction and 15% for strut size and 17% for throat size perpendicular to the building direction). These results support the use of these kind of computational algorithms to design optimized scaffolds with specific target properties and confirm the value of these techniques for bone tissue engineering. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

Porogen-based solid freeform fabrication of polycaprolactone-calcium phosphate scaffolds for tissue engineering.

PubMed

Mondrinos, Mark J; Dembzynski, Robert; Lu, Lin; Byrapogu, Venkata K C; Wootton, David M; Lelkes, Peter I; Zhou, Jack

2006-09-01

Drop on demand printing (DDP) is a solid freeform fabrication (SFF) technique capable of generating microscale physical features required for tissue engineering scaffolds. Here, we report results toward the development of a reproducible manufacturing process for tissue engineering scaffolds based on injectable porogens fabricated by DDP. Thermoplastic porogens were designed using Pro/Engineer and fabricated with a commercially available DDP machine. Scaffolds composed of either pure polycaprolactone (PCL) or homogeneous composites of PCL and calcium phosphate (CaP, 10% or 20% w/w) were subsequently fabricated by injection molding of molten polymer-ceramic composites, followed by porogen dissolution with ethanol. Scaffold pore sizes, as small as 200 microm, were attainable using the indirect (porogen-based) method. Scaffold structure and porosity were analyzed by scanning electron microscopy (SEM) and microcomputed tomography, respectively. We characterized the compressive strength of 90:10 and 80:20 PCL-CaP composite materials (19.5+/-1.4 and 24.8+/-1.3 Mpa, respectively) according to ASTM standards, as well as pure PCL scaffolds (2.77+/-0.26 MPa) fabricated using our process. Human embryonic palatal mesenchymal (HEPM) cells attached and proliferated on all scaffolds, as evidenced by fluorescent nuclear staining with Hoechst 33258 and the Alamar Blue assay, with increased proliferation observed on 80:20 PCL-CaP scaffolds. SEM revealed multilayer assembly of HEPM cells on 80:20 PCL-CaP composite, but not pure PCL, scaffolds. In summary, we have developed an SFF-based injection molding process for the fabrication of PCL and PCL-CaP scaffolds that display in vitro cytocompatibility and suitable mechanical properties for hard tissue repair.

Biocompatibility of hydrogel-based scaffolds for tissue engineering applications.

PubMed

Naahidi, Sheva; Jafari, Mousa; Logan, Megan; Wang, Yujie; Yuan, Yongfang; Bae, Hojae; Dixon, Brian; Chen, P

2017-09-01

Recently, understanding of the extracellular matrix (ECM) has expanded rapidly due to the accessibility of cellular and molecular techniques and the growing potential and value for hydrogels in tissue engineering. The fabrication of hydrogel-based cellular scaffolds for the generation of bioengineered tissues has been based on knowledge of the composition and structure of ECM. Attempts at recreating ECM have used either naturally-derived ECM components or synthetic polymers with structural integrity derived from hydrogels. Due to their increasing use, their biocompatibility has been questioned since the use of these biomaterials needs to be effective and safe. It is not surprising then that the evaluation of biocompatibility of these types of biomaterials for regenerative and tissue engineering applications has been expanded from being primarily investigated in a laboratory setting to being applied in the multi-billion dollar medicinal industry. This review will aid in the improvement of design of non-invasive, smart hydrogels that can be utilized for tissue engineering and other biomedical applications. In this review, the biocompatibility of hydrogels and design criteria for fabricating effective scaffolds are examined. Examples of natural and synthetic hydrogels, their biocompatibility and use in tissue engineering are discussed. The merits and clinical complications of hydrogel scaffold use are also reviewed. The article concludes with a future outlook of the field of biocompatibility within the context of hydrogel-based scaffolds. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Hydrophobicity as a design criterion for polymer scaffolds in bone tissue engineering.

PubMed

Jansen, Edwin J P; Sladek, Raymond E J; Bahar, Hila; Yaffe, Avinoam; Gijbels, Marion J; Kuijer, Roel; Bulstra, Sjoerd K; Guldemond, Nick A; Binderman, Itzhak; Koole, Leo H

2005-07-01

Porous polymeric scaffolds play a key role in most tissue-engineering strategies. A series of non-degrading porous scaffolds was prepared, based on bulk-copolymerisation of 1-vinyl-2-pyrrolidinone (NVP) and n-butyl methacrylate (BMA), followed by a particulate-leaching step to generate porosity. Biocompatibility of these scaffolds was evaluated in vitro and in vivo. Furthermore, the scaffold materials were studied using the so-called demineralised bone matrix (DBM) as an evaluation system in vivo. The DBM, which is essentially a part of a rat femoral bone after processing with mineral acid, provides a suitable environment for ectopic bone formation, provided that the cavity of the DBM is filled with bone marrow prior to subcutaneous implantation in the thoracic region of rats. Various scaffold materials, differing with respect to composition and, hence, hydrophilicity, were introduced into the centre of DBMs. The ends were closed with rat bone marrow, and ectopic bone formation was monitored after 4, 6, and 8 weeks, both through X-ray microradiography and histology. The 50:50 scaffold particles were found to readily accommodate formation of bone tissue within their pores, whereas this was much less the case for the more hydrophilic 70:30 counterpart scaffolds. New healthy bone tissue was encountered inside the pores of the 50:50 scaffold material, not only at the periphery of the constructs but also in the center. Active osteoblast cells were found at the bone-biomaterial interfaces. These data indicate that the hydrophobicity of the biomaterial is, most likely, an important design criterion for polymeric scaffolds which should promote the healing of bone defects. Furthermore, it is argued that stable, non-degrading porous biomaterials, like those used in this study, provide an important tool to expand our comprehension of the role of biomaterials in scaffold-based tissue engineering approaches.

Digital design of scaffold for mandibular defect repair based on tissue engineering*

PubMed Central

Liu, Yun-feng; Zhu, Fu-dong; Dong, Xing-tao; Peng, Wei

2011-01-01

Mandibular defect occurs more frequently in recent years, and clinical repair operations via bone transplantation are difficult to be further improved due to some intrinsic flaws. Tissue engineering, which is a hot research field of biomedical engineering, provides a new direction for mandibular defect repair. As the basis and key part of tissue engineering, scaffolds have been widely and deeply studied in regards to the basic theory, as well as the principle of biomaterial, structure, design, and fabrication method. However, little research is targeted at tissue regeneration for clinic repair operations. Since mandibular bone has a special structure, rather than uniform and regular structure in existing studies, a methodology based on tissue engineering is proposed for mandibular defect repair in this paper. Key steps regarding scaffold digital design, such as external shape design and internal microstructure design directly based on triangular meshes are discussed in detail. By analyzing the theoretical model and the measured data from the test parts fabricated by rapid prototyping, the feasibility and effectiveness of the proposed methodology are properly verified. More works about mechanical and biological improvements need to be done to promote its clinical application in future. PMID:21887853

Digital design of scaffold for mandibular defect repair based on tissue engineering.

PubMed

Liu, Yun-feng; Zhu, Fu-dong; Dong, Xing-tao; Peng, Wei

2011-09-01

Mandibular defect occurs more frequently in recent years, and clinical repair operations via bone transplantation are difficult to be further improved due to some intrinsic flaws. Tissue engineering, which is a hot research field of biomedical engineering, provides a new direction for mandibular defect repair. As the basis and key part of tissue engineering, scaffolds have been widely and deeply studied in regards to the basic theory, as well as the principle of biomaterial, structure, design, and fabrication method. However, little research is targeted at tissue regeneration for clinic repair operations. Since mandibular bone has a special structure, rather than uniform and regular structure in existing studies, a methodology based on tissue engineering is proposed for mandibular defect repair in this paper. Key steps regarding scaffold digital design, such as external shape design and internal microstructure design directly based on triangular meshes are discussed in detail. By analyzing the theoretical model and the measured data from the test parts fabricated by rapid prototyping, the feasibility and effectiveness of the proposed methodology are properly verified. More works about mechanical and biological improvements need to be done to promote its clinical application in future.

Development of a large peptoid-DOTA combinatorial library.

PubMed

Singh, Jaspal; Lopes, Daniel; Gomika Udugamasooriya, D

2016-09-01

Conventional one-bead one-compound (OBOC) library synthesis is typically used to identify molecules with therapeutic value. The design and synthesis of OBOC libraries that contain molecules with imaging or even potentially therapeutic and diagnostic capacities (e.g. theranostic agents) has been overlooked. The development of a therapeutically active molecule with a built-in imaging component for a certain target is a daunting task, and structure-based rational design might not be the best approach. We hypothesize to develop a combinatorial library with potentially therapeutic and imaging components fused together in each molecule. Such molecules in the library can be used to screen, identify, and validate as direct theranostic candidates against targets of interest. As the first step in achieving that aim, we developed an on-bead library of 153,600 Peptoid-DOTA compounds in which the peptoids are the target-recognizing and potentially therapeutic components and the DOTA is the imaging component. We attached the DOTA scaffold to TentaGel beads using one of the four arms of DOTA, and we built a diversified 6-mer peptoid library on the remaining three arms. We evaluated both the synthesis and the mass spectrometric sequencing capacities of the test compounds and of the final library. The compounds displayed unique ionization patterns including direct breakages of the DOTA scaffold into two units, allowing clear decoding of the sequences. Our approach provides a facile synthesis method for the complete on-bead development of large peptidomimetic-DOTA libraries for screening against biological targets for the identification of potential theranostic agents in the future. © 2016 The Authors. Biopolymers Published by Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 673-684, 2016. © 2016 The Authors. Biopolymers Published by Wiley Periodicals, Inc.

An Efficient, Recyclable, and Stable Immobilized Biocatalyst Based on Bioinspired Microcapsules-in-Hydrogel Scaffolds.

PubMed

Zhang, Shaohua; Jiang, Zhongyi; Shi, Jiafu; Wang, Xueyan; Han, Pingping; Qian, Weilun

2016-09-28

Design and preparation of high-performance immobilized biocatalysts with exquisite structures and elucidation of their profound structure-performance relationship are highly desired for green and sustainable biotransformation processes. Learning from nature has been recognized as a shortcut to achieve such an impressive goal. Loose connective tissue, which is composed of hierarchically organized cells by extracellular matrix (ECM) and is recognized as an efficient catalytic system to ensure the ordered proceeding of metabolism, may offer an ideal prototype for preparing immobilized biocatalysts with high catalytic activity, recyclability, and stability. Inspired by the hierarchical structure of loose connective tissue, we prepared an immobilized biocatalyst enabled by microcapsules-in-hydrogel (MCH) scaffolds via biomimetic mineralization in agarose hydrogel. In brief, the in situ synthesized hybrid microcapsules encapsulated with glucose oxidase (GOD) are hierarchically organized by the fibrous framework of agarose hydrogel, where the fibers are intercalated into the capsule wall. The as-prepared immobilized biocatalyst shows structure-dependent catalytic performance. The porous hydrogel permits free diffusion of glucose molecules (diffusion coefficient: ∼6 × 10(-6) cm(2) s(-1), close to that in water) and retains the enzyme activity as much as possible after immobilization (initial reaction rate: 1.5 × 10(-2) mM min(-1)). The monolithic macroscale of agarose hydrogel facilitates the easy recycling of the immobilized biocatalyst (only by using tweezers), which contributes to the nonactivity decline during the recycling test. The fiber-intercalating structure elevates the mechanical stability of the in situ synthesized hybrid microcapsules, which inhibits the leaching and enhances the stability of the encapsulated GOD, achieving immobilization efficiency of ∼95%. This study will, therefore, provide a generic method for the hierarchical organization of (bio)active materials and the rational design of novel (bio)catalysts.

Examining the Value of a Scaffolded Critique Framework to Promote Argumentative and Explanatory Writings within an Argument-Based Inquiry Approach

ERIC Educational Resources Information Center

Jang, Jeong-yoon; Hand, Brian

2017-01-01

This study investigated the value of using a scaffolded critique framework to promote two different types of writing--argumentative writing and explanatory writing--with different purposes within an argument-based inquiry approach known as the Science Writing Heuristic (SWH) approach. A quasi-experimental design with sixth and seventh grade…

Challenges in designing appropriate scaffolding to improve students' representational consistency: The case of a Gauss's law problem

NASA Astrophysics Data System (ADS)

Maries, Alexandru; Lin, Shih-Yin; Singh, Chandralekha

2017-12-01

Prior research suggests that introductory physics students have difficulty with graphing and interpreting graphs. Here, we discuss an investigation of student difficulties in translating between mathematical and graphical representations for a problem in electrostatics and the effect of increasing levels of scaffolding on students' representational consistency. Students in calculus-based introductory physics were given a typical problem that can be solved using Gauss's law involving a spherically symmetric charge distribution in which they were asked to write a mathematical expression for the electric field in various regions and then plot the electric field. In study 1, we found that students had great difficulty in plotting the electric field as a function of the distance from the center of the sphere consistent with the mathematical expressions in various regions, and interviews with students suggested possible reasons which may account for this difficulty. Therefore, in study 2, we designed two scaffolding interventions with levels of support which built on each other (i.e., the second scaffolding level built on the first) in order to help students plot their expressions consistently and compared the performance of students provided with scaffolding with a comparison group which was not given any scaffolding support. Analysis of student performance with different levels of scaffolding reveals that scaffolding from an expert perspective beyond a certain level may sometimes hinder student performance and students may not even discern the relevance of the additional support. We provide possible interpretations for these findings based on in-depth, think-aloud student interviews.

A mathematical model for the determination of forming tissue moduli in needled-nonwoven scaffolds.

PubMed

Soares, João S; Zhang, Will; Sacks, Michael S

2017-03-15

Formation of engineering tissues (ET) remains an important scientific area of investigation for both clinical translational and mechanobiological studies. Needled-nonwoven (NNW) scaffolds represent one of the most ubiquitous biomaterials based on their well-documented capacity to sustain tissue formation and the unique property of substantial construct stiffness amplification, the latter allowing for very sensitive determination of forming tissue modulus. Yet, their use in more fundamental studies is hampered by the lack of: (1) substantial understanding of the mechanics of the NNW scaffold itself under finite deformations and means to model the complex mechanical interactions between scaffold fibers, cells, and de novo tissue; and (2) rational models with reliable predictive capabilities describing their evolving mechanical properties and their response to mechanical stimulation. Our objective is to quantify the mechanical properties of the forming ET phase in constructs that utilize NNW scaffolds. We present herein a novel mathematical model to quantify their stiffness based on explicit considerations of the modulation of NNW scaffold fiber-fiber interactions and effective fiber stiffness by surrounding de novo ECM. Specifically, fibers in NNW scaffolds are effectively stiffer than if acting alone due to extensive fiber-fiber cross-over points that impart changes in fiber geometry, particularly crimp wavelength and amplitude. Fiber-fiber interactions in NNW scaffolds also play significant role in the bulk anisotropy of the material, mainly due to fiber buckling and large translational out-of-plane displacements occurring to fibers undergoing contraction. To calibrate the model parameters, we mechanically tested impregnated NNW scaffolds with polyacrylamide (PAM) gels with a wide range of moduli with values chosen to mimic the effects of surrounding tissues on the scaffold fiber network. Results indicated a high degree of model fidelity over a wide range of planar strains. Lastly, we illustrated the impact of our modeling approach quantifying the stiffness of engineered ECM after in vitro incubation and early stages of in vivo implantation obtained in a concurrent study of engineered tissue pulmonary valves in an ovine model. Regenerative medicine has the potential to fully restore diseased tissues or entire organs with engineered tissues. Needled-nonwoven scaffolds can be employed to serve as the support for their growth. However, there is a lack of understanding of the mechanics of these materials and their interactions with the forming tissues. We developed a mathematical model for these scaffold-tissue composites to quantify the mechanical properties of the forming tissues. Firstly, these measurements are pivotal to achieve functional requirements for tissue engineering implants; however, the theoretical development yielded critical insight into particular mechanisms and behaviors of these scaffolds that were not possible to conjecture without the insight given by modeling, let alone describe or foresee a priori. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Design and Characterization of Epitope-Scaffold Immunogens That Present the Motavizumab Epitope from Respiratory Syncytial Virus

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

McLellan, Jason S.; Correia, Bruno E.; Chen, Man

2012-06-28

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, but an effective vaccine has not yet been developed. An ideal vaccine would elicit protective antibodies while avoiding virus-specific T-cell responses, which have been implicated in vaccine-enhanced disease with previous RSV vaccines. We propose that heterologous proteins designed to present RSV-neutralizing antibody epitopes and to elicit cognate antibodies have the potential to fulfill these vaccine requirements, as they can be fashioned to be free of viral T-cell epitopes. Here we present the design and characterization of three epitope-scaffolds that present the epitope of motavizumab, a potentmore » neutralizing antibody that binds to a helix-loop-helix motif in the RSV fusion glycoprotein. Two of the epitope-scaffolds could be purified, and one epitope-scaffold based on a Staphylococcus aureus protein A domain bound motavizumab with kinetic and thermodynamic properties consistent with the free epitope-scaffold being stabilized in a conformation that closely resembled the motavizumab-bound state. This epitope-scaffold was well folded as assessed by circular dichroism and isothermal titration calorimetry, and its crystal structure (determined in complex with motavizumab to 1.9 {angstrom} resolution) was similar to the computationally designed model, with all hydrogen-bond interactions critical for binding to motavizumab preserved. Immunization of mice with this epitope-scaffold failed to elicit neutralizing antibodies but did elicit sera with F binding activity. The elicitation of F binding antibodies suggests that some of the design criteria for eliciting protective antibodies without virus-specific T-cell responses are being met, but additional optimization of these novel immunogens is required.« less

Design and characterization of epitope-scaffold immunogens that present the motavizumab epitope from respiratory syncytial virus.

PubMed

McLellan, Jason S; Correia, Bruno E; Chen, Man; Yang, Yongping; Graham, Barney S; Schief, William R; Kwong, Peter D

2011-06-24

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, but an effective vaccine has not yet been developed. An ideal vaccine would elicit protective antibodies while avoiding virus-specific T-cell responses, which have been implicated in vaccine-enhanced disease with previous RSV vaccines. We propose that heterologous proteins designed to present RSV-neutralizing antibody epitopes and to elicit cognate antibodies have the potential to fulfill these vaccine requirements, as they can be fashioned to be free of viral T-cell epitopes. Here we present the design and characterization of three epitope-scaffolds that present the epitope of motavizumab, a potent neutralizing antibody that binds to a helix-loop-helix motif in the RSV fusion glycoprotein. Two of the epitope-scaffolds could be purified, and one epitope-scaffold based on a Staphylococcus aureus protein A domain bound motavizumab with kinetic and thermodynamic properties consistent with the free epitope-scaffold being stabilized in a conformation that closely resembled the motavizumab-bound state. This epitope-scaffold was well folded as assessed by circular dichroism and isothermal titration calorimetry, and its crystal structure (determined in complex with motavizumab to 1.9 Å resolution) was similar to the computationally designed model, with all hydrogen-bond interactions critical for binding to motavizumab preserved. Immunization of mice with this epitope-scaffold failed to elicit neutralizing antibodies but did elicit sera with F binding activity. The elicitation of F binding antibodies suggests that some of the design criteria for eliciting protective antibodies without virus-specific T-cell responses are being met, but additional optimization of these novel immunogens is required. Published by Elsevier Ltd.

Enhancing the Hydrophilicity and Cell Attachment of 3D Printed PCL/Graphene Scaffolds for Bone Tissue Engineering

PubMed Central

Wang, Weiguang; Caetano, Guilherme; Ambler, William Stephen; Blaker, Jonny James; Frade, Marco Andrey; Mandal, Parthasarathi; Diver, Carl; Bártolo, Paulo

2016-01-01

Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly(ε-caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response. PMID:28774112

Enhancing the Hydrophilicity and Cell Attachment of 3D Printed PCL/Graphene Scaffolds for Bone Tissue Engineering.

PubMed

Wang, Weiguang; Caetano, Guilherme; Ambler, William Stephen; Blaker, Jonny James; Frade, Marco Andrey; Mandal, Parthasarathi; Diver, Carl; Bártolo, Paulo

2016-12-07

Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly( ε -caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response.

A Biosynthetic Scaffold that Facilitates Chondrocyte-Mediated Degradation and Promotes Articular Cartilage Extracellular Matrix Deposition.

PubMed

Sridhar, Balaji V; Dailing, Eric A; Brock, J Logan; Stansbury, Jeffrey W; Randolph, Mark A; Anseth, Kristi S

2015-12-01

Articular cartilage remains a significant clinical challenge to repair because of its limited self-healing capacity. Interest has grown in the delivery of autologous chondrocytes to cartilage defects, and combining cell-based therapies with scaffolds that capture aspects of native tissue and allow cell-mediated remodeling could improve outcomes. Currently, scaffold-based therapies with encapsulated chondrocytes permit matrix production; however, resorption of the scaffold often does not match the rate of matrix production by chondrocytes, which can limit functional tissue regeneration. Here, we designed a hybrid biosynthetic system consisting of poly (ethylene glycol) (PEG) endcapped with thiols and crosslinked by norbornene-functionalized gelatin via a thiol-ene photopolymerization. The protein crosslinker was selected to facilitate chondrocyte-mediated scaffold remodeling and matrix deposition. Gelatin was functionalized with norbornene to varying degrees (~4-17 norbornenes/gelatin), and the shear modulus of the resulting hydrogels was characterized (<0.1-0.5 kPa). Degradation of the crosslinked PEG-gelatin hydrogels by chondrocyte-secreted enzymes was confirmed by gel permeation chromatography. Finally, chondrocytes encapsulated in these biosynthetic scaffolds showed significantly increased glycosaminoglycan deposition over just 14 days of culture, while maintaining high levels of viability and producing a distributed matrix. These results indicate the potential of a hybrid PEG-gelatin hydrogel to permit chondrocyte-mediated remodeling and promote articular cartilage matrix production. Tunable scaffolds that can easily permit chondrocyte-mediated remodeling may be useful in designing treatment options for cartilage tissue engineering applications.

A Biosynthetic Scaffold that Facilitates Chondrocyte-Mediated Degradation and Promotes Articular Cartilage Extracellular Matrix Deposition

PubMed Central

Sridhar., Balaji V.; Dailing, Eric A.; Brock, J. Logan; Stansbury, Jeffrey W.; Randolph, Mark A.; Anseth, Kristi S.

2015-01-01

Articular cartilage remains a significant clinical challenge to repair because of its limited self-healing capacity. Interest has grown in the delivery of autologous chondrocytes to cartilage defects, and combining cell-based therapies with scaffolds that capture aspects of native tissue and allow cell-mediated remodeling could improve outcomes. Currently, scaffold-based therapies with encapsulated chondrocytes permit matrix production; however, resorption of the scaffold often does not match the rate of matrix production by chondrocytes, which can limit functional tissue regeneration. Here, we designed a hybrid biosynthetic system consisting of poly (ethylene glycol) (PEG) endcapped with thiols and crosslinked by norbornene-functionalized gelatin via a thiol-ene photopolymerization. The protein crosslinker was selected to facilitate chondrocyte-mediated scaffold remodeling and matrix deposition. Gelatin was functionalized with norbornene to varying degrees (~4–17 norbornenes/gelatin), and the shear modulus of the resulting hydrogels was characterized (<0.1–0.5 kPa). Degradation of the crosslinked PEG-gelatin hydrogels by chondrocyte-secreted enzymes was confirmed by gel permeation chromatography. Finally, chondrocytes encapsulated in these biosynthetic scaffolds showed significantly increased glycosaminoglycan deposition over just 14 days of culture, while maintaining high levels of viability and producing a distributed matrix. These results indicate the potential of a hybrid PEG-gelatin hydrogel to permit chondrocyte-mediated remodeling and promote articular cartilage matrix production. Tunable scaffolds that can easily permit chondrocyte-mediated remodeling may be useful in designing treatment options for cartilage tissue engineering applications. PMID:26900597

Design of Cell-Matrix Interactions in Hyaluronic Acid Hydrogel Scaffolds

PubMed Central

Segura, Tatiana

2013-01-01

The design of hyaluronic acid-based hydrogel scaffolds to elicit highly controlled and tunable cell response and behavior is a major field of interest in developing tissue engineering and regenerative medicine applications. This review will begin with an overview of the biological context of hyaluronic acid, knowledge needed to better understand how to engineer cell-matrix interactions in the scaffolds via the incorporation of different types of signals in order to direct and control cell behavior. Specifically, recent methods of incorporating various bioactive, mechanical, and spatial signals are reviewed, as well as novel hyaluronic acid modifications and crosslinking schemes with a focus on specificity. PMID:23899481

Finite element study of scaffold architecture design and culture conditions for tissue engineering.

PubMed

Olivares, Andy L; Marsal, Elia; Planell, Josep A; Lacroix, Damien

2009-10-01

Tissue engineering scaffolds provide temporary mechanical support for tissue regeneration and transfer global mechanical load to mechanical stimuli to cells through its architecture. In this study the interactions between scaffold pore morphology, mechanical stimuli developed at the cell microscopic level, and culture conditions applied at the macroscopic scale are studied on two regular scaffold structures. Gyroid and hexagonal scaffolds of 55% and 70% porosity were modeled in a finite element analysis and were submitted to an inlet fluid flow or compressive strain. A mechanoregulation theory based on scaffold shear strain and fluid shear stress was applied for determining the influence of each structures on the mechanical stimuli on initial conditions. Results indicate that the distribution of shear stress induced by fluid perfusion is very dependent on pore distribution within the scaffold. Gyroid architectures provide a better accessibility of the fluid than hexagonal structures. Based on the mechanoregulation theory, the differentiation process in these structures was more sensitive to inlet fluid flow than axial strain of the scaffold. This study provides a computational approach to determine the mechanical stimuli at the cellular level when cells are cultured in a bioreactor and to relate mechanical stimuli with cell differentiation.

Silk scaffolds in bone tissue engineering: An overview.

PubMed

Bhattacharjee, Promita; Kundu, Banani; Naskar, Deboki; Kim, Hae-Won; Maiti, Tapas K; Bhattacharya, Debasis; Kundu, Subhas C

2017-11-01

Bone tissue plays multiple roles in our day-to-day functionality. The frequency of accidental bone damage and disorder is increasing worldwide. Moreover, as the world population continues to grow, the percentage of the elderly population continues to grow, which results in an increased number of bone degenerative diseases. This increased elderly population pushes the need for artificial bone implants that specifically employ biocompatible materials. A vast body of literature is available on the use of silk in bone tissue engineering. The current work presents an overview of this literature from materials and fabrication perspective. As silk is an easy-to-process biopolymer; this allows silk-based biomaterials to be molded into diverse forms and architectures, which further affects the degradability. This makes silk-based scaffolds suitable for treating a variety of bone reconstruction and regeneration objectives. Silk surfaces offer active sites that aid the mineralization and/or bonding of bioactive molecules that facilitate bone regeneration. Silk has also been blended with a variety of polymers and minerals to enhance its advantageous properties or introduce new ones. Several successful works, both in vitro and in vivo, have been reported using silk-based scaffolds to regenerate bone tissues or other parts of the skeletal system such as cartilage and ligament. A growing trend is observed toward the use of mineralized and nanofibrous scaffolds along with the development of technology that allows to control scaffold architecture, its biodegradability and the sustained releasing property of scaffolds. Further development of silk-based scaffolds for bone tissue engineering, taking them up to and beyond the stage of human trials, is hoped to be achieved in the near future through a cross-disciplinary coalition of tissue engineers, material scientists and manufacturing engineers. The state-of-art of silk biomaterials in bone tissue engineering, covering their wide applications as cell scaffolding matrices to micro-nano carriers for delivering bone growth factors and therapeutic molecules to diseased or damaged sites to facilitate bone regeneration, is emphasized here. The review rationalizes that the choice of silk protein as a biomaterial is not only because of its natural polymeric nature, mechanical robustness, flexibility and wide range of cell compatibility but also because of its ability to template the growth of hydroxyapatite, the chief inorganic component of bone mineral matrix, resulting in improved osteointegration. The discussion extends to the role of inorganic ions such as Si and Ca as matrix components in combination with silk to influence bone regrowth. The effect of ions or growth factor-loaded vehicle incorporation into regenerative matrix, nanotopography is also considered. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Solid Free-form Fabrication Technology and Its Application to Bone Tissue Engineering

PubMed Central

Lee, Jin Woo; Kim, Jong Young; Cho, Dong-Woo

2010-01-01

The development of scaffolds for use in cell-based therapies to repair damaged bone tissue has become a critical component in the field of bone tissue engineering. However, design of scaffolds using conventional fabrication techniques has limited further advancement, due to a lack of the required precision and reproducibility. To overcome these constraints, bone tissue engineers have focused on solid free-form fabrication (SFF) techniques to generate porous, fully interconnected scaffolds for bone tissue engineering applications. This paper reviews the potential application of SFF fabrication technologies for bone tissue engineering with respect to scaffold fabrication. In the near future, bone scaffolds made using SFF apparatus should become effective therapies for bone defects. PMID:24855546

Computational design and experimental verification of a symmetric protein homodimer.

PubMed

Mou, Yun; Huang, Po-Ssu; Hsu, Fang-Ciao; Huang, Shing-Jong; Mayo, Stephen L

2015-08-25

Homodimers are the most common type of protein assembly in nature and have distinct features compared with heterodimers and higher order oligomers. Understanding homodimer interactions at the atomic level is critical both for elucidating their biological mechanisms of action and for accurate modeling of complexes of unknown structure. Computation-based design of novel protein-protein interfaces can serve as a bottom-up method to further our understanding of protein interactions. Previous studies have demonstrated that the de novo design of homodimers can be achieved to atomic-level accuracy by β-strand assembly or through metal-mediated interactions. Here, we report the design and experimental characterization of a α-helix-mediated homodimer with C2 symmetry based on a monomeric Drosophila engrailed homeodomain scaffold. A solution NMR structure shows that the homodimer exhibits parallel helical packing similar to the design model. Because the mutations leading to dimer formation resulted in poor thermostability of the system, design success was facilitated by the introduction of independent thermostabilizing mutations into the scaffold. This two-step design approach, function and stabilization, is likely to be generally applicable, especially if the desired scaffold is of low thermostability.

Design, Materials, and Mechanobiology of Biodegradable Scaffolds for Bone Tissue Engineering

PubMed Central

Velasco, Marco A.; Narváez-Tovar, Carlos A.; Garzón-Alvarado, Diego A.

2015-01-01

A review about design, manufacture, and mechanobiology of biodegradable scaffolds for bone tissue engineering is given. First, fundamental aspects about bone tissue engineering and considerations related to scaffold design are established. Second, issues related to scaffold biomaterials and manufacturing processes are discussed. Finally, mechanobiology of bone tissue and computational models developed for simulating how bone healing occurs inside a scaffold are described. PMID:25883972

Sulfonamide-Based Inhibitors of Aminoglycoside Acetyltransferase Eis Abolish Resistance to Kanamycin in Mycobacterium tuberculosis

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

Garzan, Atefeh; Willby, Melisa J.; Green, Keith D.

A two-drug combination therapy where one drug targets an offending cell and the other targets a resistance mechanism to the first drug is a time-tested, yet underexploited approach to combat or prevent drug resistance. By high-throughput screening, we identified a sulfonamide scaffold that served as a pharmacophore to generate inhibitors of Mycobacterium tuberculosis acetyltransferase Eis, whose upregulation causes resistance to the aminoglycoside (AG) antibiotic kanamycin A (KAN) in Mycobacterium tuberculosis. Rational systematic derivatization of this scaffold to maximize Eis inhibition and abolish the Eis-mediated KAN resistance of M. tuberculosis yielded several highly potent agents. A crystal structure of Eis inmore » complex with one of the most potent inhibitors revealed that the inhibitor bound Eis in the AG-binding pocket held by a conformationally malleable region of Eis (residues 28–37) bearing key hydrophobic residues. These Eis inhibitors are promising leads for preclinical development of innovative AG combination therapies against resistant TB.« less

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.

Three-dimensional dynamic fabrication of engineered cartilage based on chitosan/gelatin hybrid hydrogel scaffold in a spinner flask with a special designed steel frame.

PubMed

Song, Kedong; Li, Liying; Li, Wenfang; Zhu, Yanxia; Jiao, Zeren; Lim, Mayasari; Fang, Meiyun; Shi, Fangxin; Wang, Ling; Liu, Tianqing

2015-10-01

Cartilage transplantation using in vitro tissue engineered cartilage is considered a promising treatment for articular cartilage defects. In this study, we assessed the advantages of adipose derived stem cells (ADSCs) combined with chitosan/gelatin hybrid hydrogel scaffolds, which acted as a cartilage biomimetic scaffold, to fabricate a tissue engineered cartilage dynamically in vitro and compared this with traditional static culture. Physical properties of the hydrogel scaffolds were evaluated and ADSCs were inoculated into the hydrogel at a density of 1×10(7) cells/mL and cultured in a spinner flask with a special designed steel framework and feed with chondrogenic inductive media for two weeks. The results showed that the average pore size, porosity, swelling rate and elasticity modulus of hybrid scaffolds with good biocompatibility were 118.25±19.51 μm, 82.60±2.34%, 361.28±0.47% and 61.2±0.16 kPa, respectively. ADSCs grew well in chitosan/gelatin hybrid scaffold and successfully differentiated into chondrocytes, showing that the scaffolds were suitable for tissue engineering applications in cartilage regeneration. Induced cells cultivated in a dynamic spinner flask with a special designed steel frame expressed more proteoglycans and the cell distribution was much more uniform with the scaffold being filled mostly with extracellular matrix produced by cells. A spinner flask with framework promoted proliferation and chondrogenic differentiation of ADSCs within chitosan/gelatin hybrid scaffolds and accelerated dynamic fabrication of cell-hydrogel constructs, which could be a selective and good method to construct tissue engineered cartilage in vitro. Copyright © 2015 Elsevier B.V. All rights reserved.

An antibody based approach for multi-coloring osteogenic and chondrogenic proteins in tissue engineered constructs.

PubMed

Leferink, Anne M; Reis, Diogo Santos; van Blitterswijk, Clemens A; Moroni, Lorenzo

2018-04-11

When tissue engineering strategies rely on the combination of three-dimensional (3D) polymeric or ceramic scaffolds with cells to culture implantable tissue constructs in vitro, it is desirable to monitor tissue growth and cell fate to be able to more rationally predict the quality and success of the construct upon implantation. Such a 3D construct is often referred to as a 'black-box' since the properties of the scaffolds material limit the applicability of most imaging modalities to assess important construct parameters. These parameters include the number of cells, the amount and type of tissue formed and the distribution of cells and tissue throughout the construct. Immunolabeling enables the spatial and temporal identification of multiple tissue types within one scaffold without the need to sacrifice the construct. In this report, we concisely review the applicability of antibodies (Abs) and their conjugation chemistries in tissue engineered constructs. With some preliminary experiments, we show an efficient conjugation strategy to couple extracellular matrix Abs to fluorophores. The conjugated probes proved to be effective in determining the presence of collagen type I and type II on electrospun and additive manufactured 3D scaffolds seeded with adult human bone marrow derived mesenchymal stromal cells. The conjugation chemistry applied in our proof of concept study is expected to be applicable in the coupling of any other fluorophore or particle to the Abs. This could ultimately lead to a library of probes to permit high-contrast imaging by several imaging modalities.

Design of tissue engineering scaffolds based on hyperbolic surfaces: structural numerical evaluation.

PubMed

Almeida, Henrique A; Bártolo, Paulo J

2014-08-01

Tissue engineering represents a new field aiming at developing biological substitutes to restore, maintain, or improve tissue functions. In this approach, scaffolds provide a temporary mechanical and vascular support for tissue regeneration while tissue in-growth is being formed. These scaffolds must be biocompatible, biodegradable, with appropriate porosity, pore structure and distribution, and optimal vascularization with both surface and structural compatibility. The challenge is to establish a proper balance between porosity and mechanical performance of scaffolds. This work investigates the use of two different types of triple periodic minimal surfaces, Schwarz and Schoen, in order to design better biomimetic scaffolds with high surface-to-volume ratio, high porosity and good mechanical properties. The mechanical behaviour of these structures is assessed through the finite element method software Abaqus. The effect of two parametric parameters (thickness and surface radius) is also evaluated regarding its porosity and mechanical behaviour. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

Engineering the extracellular matrix for clinical applications: endoderm, mesoderm, and ectoderm.

PubMed

Williams, Miguel L; Bhatia, Sujata K

2014-03-01

Tissue engineering is rapidly progressing from a research-based discipline to clinical applications. Emerging technologies could be utilized to develop therapeutics for a wide range of diseases, but many are contingent on a cell scaffold that can produce proper tissue ultrastructure. The extracellular matrix, which a cell scaffold simulates, is not merely a foundation for tissue growth but a dynamic participant in cellular crosstalk and organ homeostasis. Cells change their growth rates, recruitment, and differentiation in response to the composition, modulus, and patterning of the substrate on which they reside. Cell scaffolds can regulate these factors through precision design, functionalization, and application. The ideal therapy would utilize highly specialized cell scaffolds to best mimic the tissue of interest. This paper discusses advantages and challenges of optimized cell scaffold design in the endoderm, mesoderm, and ectoderm for clinical applications in tracheal transplant, cardiac regeneration, and skin grafts, respectively. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anode Design Based on Microscale Porous Scaffolds for Advanced Lithium Ion Batteries

NASA Astrophysics Data System (ADS)

Park, Hyeji; Choi, Hyelim; Nam, Kyungju; Lee, Sukyung; Um, Ji Hyun; Kim, Kyungbae; Kim, Jae-Hun; Yoon, Won-Sub; Choe, Heeman

2017-06-01

Considering the increasing demands for advanced power sources, present-day lithium-ion batteries (LIBs) must provide a higher energy and power density and better cycling stability than conventional LIBs. This study suggests a promising electrode design solution to this problem using Cu, Co, and Ti scaffolds with a microscale porous structure synthesized via freeze-casting. Co3O4 and TiO2 layers are uniformly formed on the Co and Ti scaffolds, respectively, through a simple thermal heat-treatment process, and a SnO2 layer is formed on the Cu scaffold through electroless plating and thermal oxidation. This paper characterizes and evaluates the physical and electrochemical properties of the proposed electrodes using scanning electron microscopy, four-point probe and coin-cell tests to confirm the feasibility of their potential use in LIBs.

Three-dimensional plotter technology for fabricating polymeric scaffolds with micro-grooved surfaces.

PubMed

Son, JoonGon; Kim, GeunHyung

2009-01-01

Various mechanical techniques have been used to fabricate biomedical scaffolds, including rapid prototyping (RP) devices that operate from CAD files of the target feature information. The three-dimensional (3-D) bio-plotter is one RP system that can produce design-based scaffolds with good mechanical properties for mimicking cartilage and bones. However, the scaffolds fabricated by RP have very smooth surfaces, which tend to discourage initial cell attachment. Initial cell attachment, migration, differentiation and proliferation are strongly dependent on the chemical and physical characteristics of the scaffold surface. In this study, we propose a new 3-D plotting method supplemented with a piezoelectric system for fabricating surface-modified scaffolds. The effects of the physically-modified surface on the mechanical and hydrophilic properties were investigated, and the results of cell culturing of chondrocytes indicate that this technique is a feasible new method for fabricating high-quality 3-D polymeric scaffolds.

Dual-Purpose Bioreactors to Monitor Noninvasive Physical and Biochemical Markers of Kidney and Liver Scaffold Recellularization

PubMed Central

Uzarski, Joseph S.; Bijonowski, Brent M.; Wang, Bo; Ward, Heather H.; Wandinger-Ness, Angela

2015-01-01

Analysis of perfusion-based bioreactors for organ engineering and a detailed evaluation of physical and biochemical parameters that measure dynamic changes within maturing cell-laden scaffolds are critical components of ex vivo tissue development that remain understudied topics in the tissue and organ engineering literature. Intricately designed bioreactors that house developing tissue are critical to properly recapitulate the in vivo environment, deliver nutrients within perfused media, and monitor physiological parameters of tissue development. Herein, we provide an in-depth description and analysis of two dual-purpose perfusion bioreactors that improve upon current bioreactor designs and enable comparative analyses of ex vivo scaffold recellularization strategies and cell growth performance during long-term maintenance culture of engineered kidney or liver tissues. Both bioreactors are effective at maximizing cell seeding of small-animal organ scaffolds and maintaining cell survival in extended culture. We further demonstrate noninvasive monitoring capabilities for tracking dynamic changes within scaffolds as the native cellular component is removed during decellularization and model human cells are introduced into the scaffold during recellularization and proliferate in maintenance culture. We found that hydrodynamic pressure drop (ΔP) across the retained scaffold vasculature is a noninvasive measurement of scaffold integrity. We further show that ΔP, and thus resistance to fluid flow through the scaffold, decreases with cell loss during decellularization and correspondingly increases to near normal values for whole organs following recellularization of the kidney or liver scaffolds. Perfused media may be further sampled in real time to measure soluble biomarkers (e.g., resazurin, albumin, or kidney injury molecule-1) that indicate degree of cellular metabolic activity, synthetic function, or engraftment into the scaffold. Cell growth within bioreactors is validated for primary and immortalized cells, and the design of each bioreactor is scalable to accommodate any three-dimensional scaffold (e.g., synthetic or naturally derived matrix) that contains conduits for nutrient perfusion to deliver media to growing cells and monitor noninvasive parameters during scaffold repopulation, broadening the applicability of these bioreactor systems. PMID:25929317

Dual-Purpose Bioreactors to Monitor Noninvasive Physical and Biochemical Markers of Kidney and Liver Scaffold Recellularization.

PubMed

Uzarski, Joseph S; Bijonowski, Brent M; Wang, Bo; Ward, Heather H; Wandinger-Ness, Angela; Miller, William M; Wertheim, Jason A

2015-10-01

Analysis of perfusion-based bioreactors for organ engineering and a detailed evaluation of physical and biochemical parameters that measure dynamic changes within maturing cell-laden scaffolds are critical components of ex vivo tissue development that remain understudied topics in the tissue and organ engineering literature. Intricately designed bioreactors that house developing tissue are critical to properly recapitulate the in vivo environment, deliver nutrients within perfused media, and monitor physiological parameters of tissue development. Herein, we provide an in-depth description and analysis of two dual-purpose perfusion bioreactors that improve upon current bioreactor designs and enable comparative analyses of ex vivo scaffold recellularization strategies and cell growth performance during long-term maintenance culture of engineered kidney or liver tissues. Both bioreactors are effective at maximizing cell seeding of small-animal organ scaffolds and maintaining cell survival in extended culture. We further demonstrate noninvasive monitoring capabilities for tracking dynamic changes within scaffolds as the native cellular component is removed during decellularization and model human cells are introduced into the scaffold during recellularization and proliferate in maintenance culture. We found that hydrodynamic pressure drop (ΔP) across the retained scaffold vasculature is a noninvasive measurement of scaffold integrity. We further show that ΔP, and thus resistance to fluid flow through the scaffold, decreases with cell loss during decellularization and correspondingly increases to near normal values for whole organs following recellularization of the kidney or liver scaffolds. Perfused media may be further sampled in real time to measure soluble biomarkers (e.g., resazurin, albumin, or kidney injury molecule-1) that indicate degree of cellular metabolic activity, synthetic function, or engraftment into the scaffold. Cell growth within bioreactors is validated for primary and immortalized cells, and the design of each bioreactor is scalable to accommodate any three-dimensional scaffold (e.g., synthetic or naturally derived matrix) that contains conduits for nutrient perfusion to deliver media to growing cells and monitor noninvasive parameters during scaffold repopulation, broadening the applicability of these bioreactor systems.

Design, synthesis and biological evaluation of novel FGFR inhibitors bearing an indazole scaffold.

PubMed

Liu, Jian; Peng, Xia; Dai, Yang; Zhang, Wei; Ren, Sumei; Ai, Jing; Geng, Meiyu; Li, Yingxia

2015-07-28

Fibroblast growth factor receptor (FGFR) is a potential target for cancer therapy. Based on the structure of AZD4547 and NVPBGJ-398, we designed novel 1H-indazol-3-amine scaffold derivatives by utilizing scaffold hopping and molecular hybridization strategies. Consequently, twenty-eight new compounds were synthesized and evaluated for their inhibitory activity against FGFR1. Compound 7n bearing a 6-(3-methoxyphenyl)-1H-indazol-3-amine scaffold was first identified as a potent FGFR1 inhibitor, with good enzymatic inhibition (IC50 = 15.0 nM) and modest cellular inhibition (IC50 = 642.1 nM). The crystal structure of 7n bound to FGFR1 was obtained, which might provide a new basis for potent inhibitor design. Further structural optimization revealed that compound 7r stood out as the most potent FGFR1 inhibitor with the best enzyme inhibitory (IC50 = 2.9 nM) and cellular activity (IC50 = 40.5 nM).

Mechanoactive Scaffold Induces Tendon Remodeling and Expression of Fibrocartilage Markers

PubMed Central

Spalazzi, Jeffrey P.; Vyner, Moira C.; Jacobs, Matthew T.; Moffat, Kristen L.

2008-01-01

Biological fixation of soft tissue-based grafts for anterior cruciate ligament (ACL) reconstruction poses a major clinical challenge. The ACL integrates with subchondral bone through a fibrocartilage enthesis, which serves to minimize stress concentrations and enables load transfer between two distinct tissue types. Functional integration thus requires the reestablishment of this fibrocartilage interface on reconstructed ACL grafts. We designed and characterized a novel mechanoactive scaffold based on a composite of poly-α-hydroxyester nanofibers and sintered microspheres; we then used the scaffold to test the hypothesis that scaffold-induced compression of tendon grafts would result in matrix remodeling and the expression of fibrocartilage interface-related markers. Histology coupled with confocal microscopy and biochemical assays were used to evaluate the effects of scaffold-induced compression on tendon matrix collagen distribution, cellularity, proteoglycan content, and gene expression over a 2-week period. Scaffold contraction resulted in over 15% compression of the patellar tendon graft and upregulated the expression of fibrocartilage-related markers such as Type II collagen, aggrecan, and transforming growth factor-β3 (TGF-β3). Additionally, proteoglycan content was higher in the compressed tendon group after 1 day. The data suggest the potential of a mechanoactive scaffold to promote the formation of an anatomic fibrocartilage enthesis on tendon-based ACL reconstruction grafts. PMID:18512112

Mechanoactive scaffold induces tendon remodeling and expression of fibrocartilage markers.

PubMed

Spalazzi, Jeffrey P; Vyner, Moira C; Jacobs, Matthew T; Moffat, Kristen L; Lu, Helen H

2008-08-01

Biological fixation of soft tissue-based grafts for anterior cruciate ligament (ACL) reconstruction poses a major clinical challenge. The ACL integrates with subchondral bone through a fibrocartilage enthesis, which serves to minimize stress concentrations and enables load transfer between two distinct tissue types. Functional integration thus requires the reestablishment of this fibrocartilage interface on reconstructed ACL grafts. We designed and characterized a novel mechanoactive scaffold based on a composite of poly-alpha-hydroxyester nanofibers and sintered microspheres; we then used the scaffold to test the hypothesis that scaffold-induced compression of tendon grafts would result in matrix remodeling and the expression of fibrocartilage interface-related markers. Histology coupled with confocal microscopy and biochemical assays were used to evaluate the effects of scaffold-induced compression on tendon matrix collagen distribution, cellularity, proteoglycan content, and gene expression over a 2-week period. Scaffold contraction resulted in over 15% compression of the patellar tendon graft and upregulated the expression of fibrocartilage-related markers such as Type II collagen, aggrecan, and transforming growth factor-beta3 (TGF-beta3). Additionally, proteoglycan content was higher in the compressed tendon group after 1 day. The data suggest the potential of a mechanoactive scaffold to promote the formation of an anatomic fibrocartilage enthesis on tendon-based ACL reconstruction grafts.

Bionic Design, Materials and Performance of Bone Tissue Scaffolds

PubMed Central

Wu, Tong; Yu, Suihuai; Chen, Dengkai; Wang, Yanen

2017-01-01

Design, materials, and performance are important factors in the research of bone tissue scaffolds. This work briefly describes the bone scaffolds and their anatomic structure, as well as their biological and mechanical characteristics. Furthermore, we reviewed the characteristics of metal materials, inorganic materials, organic polymer materials, and composite materials. The importance of the bionic design in preoperative diagnosis models and customized bone scaffolds was also discussed, addressing both the bionic structure design (macro and micro structure) and the bionic performance design (mechanical performance and biological performance). Materials and performance are the two main problems in the development of customized bone scaffolds. Bionic design is an effective way to solve these problems, which could improve the clinical application of bone scaffolds, by creating a balance between mechanical performance and biological performance. PMID:29039749

Bionic Design, Materials and Performance of Bone Tissue Scaffolds.

PubMed

Wu, Tong; Yu, Suihuai; Chen, Dengkai; Wang, Yanen

2017-10-17

Design, materials, and performance are important factors in the research of bone tissue scaffolds. This work briefly describes the bone scaffolds and their anatomic structure, as well as their biological and mechanical characteristics. Furthermore, we reviewed the characteristics of metal materials, inorganic materials, organic polymer materials, and composite materials. The importance of the bionic design in preoperative diagnosis models and customized bone scaffolds was also discussed, addressing both the bionic structure design (macro and micro structure) and the bionic performance design (mechanical performance and biological performance). Materials and performance are the two main problems in the development of customized bone scaffolds. Bionic design is an effective way to solve these problems, which could improve the clinical application of bone scaffolds, by creating a balance between mechanical performance and biological performance.

Enantioselective Rhodium-Catalyzed [2+2+2] Cycloadditions of Terminal Alkynes and Alkenyl Isocyanates: Mechanistic Insights Lead to a Unified Model that Rationalizes Product Selectivity

PubMed Central

Dalton, Derek M.; Oberg, Kevin M.; Yu, Robert T.; Lee, Ernest E.; Perreault, Stéphane; Oinen, Mark Emil; Pease, Melissa L.; Malik, Guillaume; Rovis, Tomislav

2009-01-01

This manuscript describes the development and scope of the asymmetric rhodium-catalyzed [2+2+2] cycloaddition of terminal alkynes and alkenyl isocyanates leading to the formation of indolizidine and quinolizidine scaffolds. The use of phosphoramidite ligands proved crucial for avoiding competitive terminal alkyne dimerization. Both aliphatic and aromatic terminal alkynes participate well, with product selectivity a function of both the steric and electronic character of the alkyne. Manipulation of the phosphoramidite ligand leads to tuning of enantio- and product selectivity, with a complete turnover in product selectivity seen with aliphatic alkynes when moving from Taddol-based to biphenol-based phosphoramidites. Terminal and 1,1-disubstituted olefins are tolerated with nearly equal efficacy. Examination of a series of competition experiments in combination with analysis of reaction outcome shed considerable light on the operative catalytic cycle. Through a detailed study of a series of X-ray structures of rhodium(cod)chloride/phosphoramidite complexes, we have formulated a mechanistic hypothesis that rationalizes the observed product selectivity. PMID:19817441

Comprehensive computational design of ordered peptide macrocycles

PubMed Central

Hosseinzadeh, Parisa; Bhardwaj, Gaurav; Mulligan, Vikram Khipple; Shortridge, Matthew D.; Craven, Timothy W.; Pardo-Avila, Fátima; Rettie, Stephen A.; Kim, David E.; Silva, Daniel-Adriano; Ibrahim, Yehia M.; Webb, Ian K.; Cort, John R.; Adkins, Joshua N.; Varani, Gabriele; Baker, David

2018-01-01

Mixed-chirality peptide macrocycles such as cyclosporine are among the most potent therapeutics identified to date, but there is currently no way to systematically search the structural space spanned by such compounds. Natural proteins do not provide a useful guide: Peptide macrocycles lack regular secondary structures and hydrophobic cores, and can contain local structures not accessible with L-amino acids. Here, we enumerate the stable structures that can be adopted by macrocyclic peptides composed of L- and D-amino acids by near-exhaustive backbone sampling followed by sequence design and energy landscape calculations. We identify more than 200 designs predicted to fold into single stable structures, many times more than the number of currently available unbound peptide macrocycle structures. Nuclear magnetic resonance structures of 9 of 12 designed 7- to 10-residue macrocycles, and three 11- to 14-residue bicyclic designs, are close to the computational models. Our results provide a nearly complete coverage of the rich space of structures possible for short peptide macrocycles and vastly increase the available starting scaffolds for both rational drug design and library selection methods. PMID:29242347

Heterocyclic N-Oxides – An Emerging Class of Therapeutic Agents

PubMed Central

Mfuh, Adelphe M.; Larionov, Oleg V.

2016-01-01

Heterocyclic N-oxides have emerged as potent compounds with anticancer, antibacterial, antihypertensive, antiparasitic, anti-HIV, anti-inflammatory, herbicidal, neuroprotective, and procognitive activities. The N-oxide motif has been successfully employed in a number of recent drug development projects. This review surveys the emergence of this scaffold in the mainstream medicinal chemistry with a focus on the discovery of the heterocyclic N-oxide drugs, N-oxide-specific mechanisms of action, drug-receptor interactions and synthetic avenues to these compounds. As the first review on this subject that covers the developments since 1950s to date, it is expected that it will inspire wider implementation of the heterocyclic N-oxide motif in the rational design of new medicinal agents. PMID:26087764

Scaffold architecture and pharmacophoric properties of natural products and trade drugs: application in the design of natural product-based combinatorial libraries.

PubMed

Lee, M L; Schneider, G

2001-01-01

Natural products were analyzed to determine whether they contain appealing novel scaffold architectures for potential use in combinatorial chemistry. Ring systems were extracted and clustered on the basis of structural similarity. Several such potential scaffolds for combinatorial chemistry were identified that are not present in current trade drugs. For one of these scaffolds a virtual combinatorial library was generated. Pharmacophoric properties of natural products, trade drugs, and the virtual combinatorial library were assessed using a self-organizing map. Obviously, current trade drugs and natural products have several topological pharmacophore patterns in common. These features can be systematically explored with selected combinatorial libraries based on a combination of natural product-derived and synthetic molecular building blocks.

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.

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.

A polyhedron made of tRNAs.

PubMed

Severcan, Isil; Geary, Cody; Chworos, Arkadiusz; Voss, Neil; Jacovetty, Erica; Jaeger, Luc

2010-09-01

Supramolecular assembly is a powerful strategy used by nature to build nanoscale architectures with predefined sizes and shapes. With synthetic systems, however, numerous challenges remain to be solved before precise control over the synthesis, folding and assembly of rationally designed three-dimensional nano-objects made of RNA can be achieved. Here, using the transfer RNA molecule as a structural building block, we report the design, efficient synthesis and structural characterization of stable, modular three-dimensional particles adopting the polyhedral geometry of a non-uniform square antiprism. The spatial control within the final architecture allows the precise positioning and encapsulation of proteins. This work demonstrates that a remarkable degree of structural control can be achieved with RNA structural motifs for the construction of thermostable three-dimensional nano-architectures that do not rely on helix bundles or tensegrity. RNA three-dimensional particles could potentially be used as carriers or scaffolds in nanomedicine and synthetic biology.

A polyhedron made of tRNAs

PubMed Central

Severcan, Isil; Geary, Cody; Chworos, Arkadiusz; Voss, Neil; Jacovetty, Erica; Jaeger, Luc

2010-01-01

Supra-molecular assembly is a powerful strategy used by nature for building nano-scale architectures with predefined sizes and shapes. Numerous challenges remain however to be solved in order to demonstrate precise control over the synthesis, folding and assembly of rationally designed three-dimensional (3D) nano-objects made of RNA. Using the transfer RNA molecule as a structural building block, we report the design, efficient synthesis and structural characterization of stable, modular 3D particles adopting the polyhedral geometry of a non-uniform square antiprism. The spatial control within the final architecture allows precise positioning and encapsulation of proteins. This work demonstrates that a remarkable degree of structural control can be achieved with RNA structural motifs to build thermostable 3D nano-architectures that do not rely on helix bundles or tensegrity. RNA 3D particles can potentially be used as carriers or scaffolds in nano-medicine and synthetic biology. PMID:20729899

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…

Mechanical behavior of a cellulose-reinforced scaffold in vascular tissue engineering.

PubMed

Pooyan, Parisa; Tannenbaum, Rina; Garmestani, Hamid

2012-03-01

Scaffolds constitute an essential structural component in tissue engineering of a vascular substitute for small grafts by playing a significant role in integrating the overall tissue constructs. The microstructure and mechanical properties of such scaffolds are important parameters to promote further cellular activities and neo-tissue development. Cellulose nanowhiskers (CNWs), an abundant, biocompatible material, could potentially constitute an acceptable candidate in scaffolding of a tissue-engineered vessel. Inspired by the advantages of cellulose and its derivatives, we have designed a biomaterial comprising CNWs embedded in a matrix of cellulose acetate propionate to fabricate a fully bio-based scaffold. To ensure uniform distribution, CNWs were delicately extracted from a multi-stage process and dispersed in an acetone suspension prior to the composite fabrication. Comparable to carbon nanotubes or kevlar, CNWs impart significant strength and directional rigidity even at 0.2 wt% and almost double that at only 3.0 wt%. To ensure the accuracy of our experimental data and to predict the unusual reinforcing effect of CNWs in a cellulose-based composite, homogenization schemes such as the mean field approach and the percolation technique were also investigated. Based on these comparisons, the tendency of CNWs to interconnect with one another through strong hydrogen bonding confirmed the formation of a three-dimensional rigid percolating network, fact which imparted an excellent mechanical stability to the entire structure at such low filler contents. Hence, our fibrous porous microstructure with improved mechanical properties could introduce a potential scaffold to withstand the physiological pressure and to mimic the profile features of native extracellular matrix in a human vessel. We believe that our nanohybrid design not only could expand the biomedical applications of renewable cellulose-based materials but also could provide a potential scaffold candidate in tissue engineering of small diameter grafts. Copyright © 2011 Elsevier Ltd. All rights reserved.

Bioactive gyroid scaffolds formed by sacrificial templating of nanocellulose and nanochitin hydrogels as instructive platforms for biomimetic tissue engineering.

PubMed

Torres-Rendon, Jose Guillermo; Femmer, Tim; De Laporte, Laura; Tigges, Thomas; Rahimi, Khosrow; Gremse, Felix; Zafarnia, Sara; Lederle, Wiltrud; Ifuku, Shinsuke; Wessling, Matthias; Hardy, John G; Walther, Andreas

2015-05-20

A sacrificial templating process using lithographically printed minimal surface structures allows complex de novo geo-metries of delicate hydrogel materials. The hydrogel scaffolds based on cellulose and chitin nanofibrils show differences in terms of attachment of human mesenchymal stem cells, and allow their differentiation into osteogenic outcomes. The approach here serves as a first example toward designer hydrogel scaffolds viable for biomimetic tissue engineering. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crossing boundaries in interprofessional education: A call for instructional integration of two script concepts.

PubMed

Kiesewetter, Jan; Kollar, Ingo; Fernandez, Nicolas; Lubarsky, Stuart; Kiessling, Claudia; Fischer, Martin R; Charlin, Bernard

2016-09-01

Clinical work occurs in a context which is heavily influenced by social interactions. The absence of theoretical frameworks underpinning the design of collaborative learning has become a roadblock for interprofessional education (IPE). This article proposes a script-based framework for the design of IPE. This framework provides suggestions for designing learning environments intended to foster competences we feel are fundamental to successful interprofessional care. The current literature describes two script concepts: "illness scripts" and "internal/external collaboration scripts". Illness scripts are specific knowledge structures that link general disease categories and specific examples of diseases. "Internal collaboration scripts" refer to an individual's knowledge about how to interact with others in a social situation. "External collaboration scripts" are instructional scaffolds designed to help groups collaborate. Instructional research relating to illness scripts and internal collaboration scripts supports (a) putting learners in authentic situations in which they need to engage in clinical reasoning, and (b) scaffolding their interaction with others with "external collaboration scripts". Thus, well-established experiential instructional approaches should be combined with more fine-grained script-based scaffolding approaches. The resulting script-based framework offers instructional designers insights into how students can be supported to develop the necessary skills to master complex interprofessional clinical situations.

Proof of principle for epitope-focused vaccine design

PubMed Central

Correia, Bruno E.; Bates, John T.; Loomis, Rebecca J.; Baneyx, Gretchen; Carrico, Christopher; Jardine, Joseph G.; Rupert, Peter; Correnti, Colin; Kalyuzhniy, Oleksandr; Vittal, Vinayak; Connell, Mary J.; Stevens, Eric; Schroeter, Alexandria; Chen, Man; MacPherson, Skye; Serra, Andreia M.; Adachi, Yumiko; Holmes, Margaret A.; Li, Yuxing; Klevit, Rachel E.; Graham, Barney S.; Wyatt, Richard T.; Baker, David; Strong, Roland K.; Crowe, James E.; Johnson, Philip R.; Schief, William R.

2014-01-01

Summary Vaccines prevent infectious disease largely by inducing protective neutralizing antibodies against vulnerable epitopes. Multiple major pathogens have resisted traditional vaccine development, although vulnerable epitopes targeted by neutralizing antibodies have been identified for several such cases. Hence, new vaccine design methods to induce epitope-specific neutralizing antibodies are needed. Here we show, with a neutralization epitope from respiratory syncytial virus (RSV), that computational protein design can generate small, thermally and conformationally stable protein scaffolds that accurately mimic the viral epitope structure and induce potent neutralizing antibodies. These scaffolds represent promising leads for research and development of a human RSV vaccine needed to protect infants, young children and the elderly. More generally, the results provide proof of principle for epitope-focused and scaffold-based vaccine design, and encourage the evaluation and further development of these strategies for a variety of other vaccine targets including antigenically highly variable pathogens such as HIV and influenza. PMID:24499818

Proof of principle for epitope-focused vaccine design

NASA Astrophysics Data System (ADS)

Correia, Bruno E.; Bates, John T.; Loomis, Rebecca J.; Baneyx, Gretchen; Carrico, Chris; Jardine, Joseph G.; Rupert, Peter; Correnti, Colin; Kalyuzhniy, Oleksandr; Vittal, Vinayak; Connell, Mary J.; Stevens, Eric; Schroeter, Alexandria; Chen, Man; MacPherson, Skye; Serra, Andreia M.; Adachi, Yumiko; Holmes, Margaret A.; Li, Yuxing; Klevit, Rachel E.; Graham, Barney S.; Wyatt, Richard T.; Baker, David; Strong, Roland K.; Crowe, James E.; Johnson, Philip R.; Schief, William R.

2014-03-01

Vaccines prevent infectious disease largely by inducing protective neutralizing antibodies against vulnerable epitopes. Several major pathogens have resisted traditional vaccine development, although vulnerable epitopes targeted by neutralizing antibodies have been identified for several such cases. Hence, new vaccine design methods to induce epitope-specific neutralizing antibodies are needed. Here we show, with a neutralization epitope from respiratory syncytial virus, that computational protein design can generate small, thermally and conformationally stable protein scaffolds that accurately mimic the viral epitope structure and induce potent neutralizing antibodies. These scaffolds represent promising leads for the research and development of a human respiratory syncytial virus vaccine needed to protect infants, young children and the elderly. More generally, the results provide proof of principle for epitope-focused and scaffold-based vaccine design, and encourage the evaluation and further development of these strategies for a variety of other vaccine targets, including antigenically highly variable pathogens such as human immunodeficiency virus and influenza.

De novo design, synthesis, and in vitro activity of LFA-1 antagonists based on a bicyclic[5.5]hydantoin scaffold.

PubMed

Potin, Dominique; Launay, Michele; Nicolai, Eric; Fabreguette, Maud; Malabre, Patrice; Caussade, François; Besse, Dominique; Skala, Stacey; Stetsko, Dawn K; Todderud, Gordon; Beno, Brett R; Cheney, Daniel L; Chang, Chiehying J; Sheriff, Steven; Hollenbaugh, Diane L; Barrish, Joel C; Iwanowicz, Edwin J; Suchard, Suzanne J; Dhar, T G Murali

2005-02-15

LFA-1 (leukocyte function-associated antigen-1), is a member of the beta(2)-integrin family and is expressed on all leukocytes. The LFA-1/ICAM interaction promotes tight adhesion between activated leukocytes and the endothelium, as well as between T cells and antigen-presenting cells. Evidence from both animal models and clinical trials provides support for LFA-1 as a target in several different inflammatory diseases. This paper describes the de novo design, synthesis and in vitro activity of LFA-1 antagonists based on a bicyclic[5.5]hydantoin scaffold.

Macro- and micro-designed chitosan-alginate scaffold architecture by three-dimensional printing and directional freezing.

PubMed

Reed, Stephanie; Lau, Grace; Delattre, Benjamin; Lopez, David Don; Tomsia, Antoni P; Wu, Benjamin M

2016-01-07

While many tissue-engineered constructs aim to treat cartilage defects, most involve chondrocyte or stem cell seeding on scaffolds. The clinical application of cell-based techniques is limited due to the cost of maintaining cellular constructs on the shelf, potential immune response to allogeneic cell lines, and autologous chondrocyte sources requiring biopsy from already diseased or injured, scarce tissue. An acellular scaffold that can induce endogenous influx and homogeneous distribution of native stem cells from bone marrow holds great promise for cartilage regeneration. This study aims to develop such an acellular scaffold using designed, channeled architecture that simultaneously models the native zones of articular cartilage and subchondral bone. Highly porous, hydrophilic chitosan-alginate (Ch-Al) scaffolds were fabricated in three-dimensionally printed (3DP) molds designed to create millimeter scale macro-channels. Different polymer preform casting techniques were employed to produce scaffolds from both negative and positive 3DP molds. Macro-channeled scaffolds improved cell suspension distribution and uptake overly randomly porous scaffolds, with a wicking volumetric flow rate of 445.6 ± 30.3 mm(3) s(-1) for aqueous solutions and 177 ± 16 mm(3) s(-1) for blood. Additionally, directional freezing was applied to Ch-Al scaffolds, resulting in lamellar pores measuring 300 μm and 50 μm on the long and short axes, thus creating micrometer scale micro-channels. After directionally freezing Ch-Al solution cast in 3DP molds, the combined macro- and micro-channeled scaffold architecture enhanced cell suspension uptake beyond either macro- or micro-channels alone, reaching a volumetric flow rate of 1782.1 ± 48 mm(3) s(-1) for aqueous solutions and 440.9 ± 0.5 mm(3) s(-1) for blood. By combining 3DP and directional freezing, we can control the micro- and macro-architecture of Ch-Al to drastically improve cell influx into and distribution within the scaffold, while achieving porous zones that mimic articular cartilage zonal architecture. In future applications, precisely controlled micro- and macro-channels have the potential to assist immediate endogenous bone marrow uptake, stimulate chondrogenesis, and encourage vascularization of bone in an osteochondral scaffold.

Metallic powder-bed based 3D printing of cellular scaffolds for orthopaedic implants: A state-of-the-art review on manufacturing, topological design, mechanical properties and biocompatibility.

PubMed

Tan, X P; Tan, Y J; Chow, C S L; Tor, S B; Yeong, W Y

2017-07-01

Metallic cellular scaffold is one of the best choices for orthopaedic implants as a replacement of human body parts, which could improve life quality and increase longevity for the people needed. Unlike conventional methods of making cellular scaffolds, three-dimensional (3D) printing or additive manufacturing opens up new possibilities to fabricate those customisable intricate designs with highly interconnected pores. In the past decade, metallic powder-bed based 3D printing methods emerged and the techniques are becoming increasingly mature recently, where selective laser melting (SLM) and selective electron beam melting (SEBM) are the two representatives. Due to the advantages of good dimensional accuracy, high build resolution, clean build environment, saving materials, high customisability, etc., SLM and SEBM show huge potential in direct customisable manufacturing of metallic cellular scaffolds for orthopaedic implants. Ti-6Al-4V to date is still considered to be the optimal materials for producing orthopaedic implants due to its best combination of biocompatibility, corrosion resistance and mechanical properties. This paper presents a state-of-the-art overview mainly on manufacturing, topological design, mechanical properties and biocompatibility of cellular Ti-6Al-4V scaffolds via SLM and SEBM methods. Current manufacturing limitations, topological shortcomings, uncertainty of biocompatible test were sufficiently discussed herein. Future perspectives and recommendations were given at the end. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanical control of tissue-engineered bone.

PubMed

Hung, Ben P; Hutton, Daphne L; Grayson, Warren L

2013-01-31

Bone is a load-bearing tissue and physical forces play key roles in the development and maintenance of its structure. Mechanical cues can stimulate the expression of an osteogenic phenotype, enhance matrix and mineral deposition, and influence tissue organization to improve the functional outcome of engineered bone grafts. In recent years, a number of studies have investigated the effects of biophysical forces on the bone formation properties of osteoprogenitor cells. The application of physiologically relevant stimuli to tissue-engineered bone may be determined through observation and understanding of forces to which osteoblasts, osteoclasts, and osteocytes are exposed in native bone. Subsequently, these cues may be parameterized and their effects studied in well-defined in vitro systems. The osteo-inductive effects of three specific mechanical cues - shear stress, substrate rigidity, and nanotopography - on cells cultured in monolayer or in three-dimensional biomaterial scaffolds in vitro are reviewed. Additionally, we address the time-dependent effects of mechanical cues on vascular infiltration and de novo bone formation in acellular scaffolds implanted into load-bearing sites in vivo. Recent studies employing cutting-edge advances in biomaterial fabrication and bioreactor design have provided key insights into the role of mechanical cues on cellular fate and tissue properties of engineered bone grafts. By providing mechanistic understanding, future studies may go beyond empirical approaches to rational design of engineering systems to control tissue development.

Systematic search for benzimidazole compounds and derivatives with antileishmanial effects.

PubMed

Sánchez-Salgado, Juan Carlos; Bilbao-Ramos, Pablo; Dea-Ayuela, María Auxiliadora; Hernández-Luis, Francisco; Bolás-Fernández, Francisco; Medina-Franco, José L; Rojas-Aguirre, Yareli

2018-05-10

Leishmaniasis is a neglected tropical disease that currently affects 12 million people, and over 1 billion people are at risk of infection. Current chemotherapeutic approaches used to treat this disease are unsatisfactory, and the limitations of these drugs highlight the necessity to develop treatments with improved efficacy and safety. To inform the rational design and development of more efficient therapies, the present study reports a chemoinformatic approach using the ChEMBL database to retrieve benzimidazole as a target scaffold. Our analysis revealed that a limited number of studies had investigated the antileishmanial effects of benzimidazoles. Among this limited number, L. major was the species most commonly used to evaluate the antileishmanial effects of these compounds, whereas L. amazonensis and L. braziliensis were used least often in the reported studies. The antileishmanial activities of benzimidazole derivatives were notably variable, a fact that may depend on the substitution pattern of the scaffold. In addition, we investigated the effects of a benzimidazole derivative on promastigotes and amastigotes of L. infantum and L. amazonensis using a novel fluorometric method. Significant antileishmanial effects were observed on both species, with L. amazonensis being the most sensitive. To the best of our knowledge, this chemoinformatic analysis represents the first attempt to determine the relevance of benzimidazole scaffolds for antileishmanial drug discovery using the ChEMBL database. The present findings will provide relevant information for future structure-activity relationship studies and for the investigation of benzimidazole-derived drugs as potential treatments for leishmaniasis.

Network reconstruction and systems analysis of plant cell wall deconstruction by Neurospora crassa.

PubMed

Samal, Areejit; Craig, James P; Coradetti, Samuel T; Benz, J Philipp; Eddy, James A; Price, Nathan D; Glass, N Louise

2017-01-01

Plant biomass degradation by fungal-derived enzymes is rapidly expanding in economic importance as a clean and efficient source for biofuels. The ability to rationally engineer filamentous fungi would facilitate biotechnological applications for degradation of plant cell wall polysaccharides. However, incomplete knowledge of biomolecular networks responsible for plant cell wall deconstruction impedes experimental efforts in this direction. To expand this knowledge base, a detailed network of reactions important for deconstruction of plant cell wall polysaccharides into simple sugars was constructed for the filamentous fungus Neurospora crassa . To reconstruct this network, information was integrated from five heterogeneous data types: functional genomics, transcriptomics, proteomics, genetics, and biochemical characterizations. The combined information was encapsulated into a feature matrix and the evidence weighted to assign annotation confidence scores for each gene within the network. Comparative analyses of RNA-seq and ChIP-seq data shed light on the regulation of the plant cell wall degradation network, leading to a novel hypothesis for degradation of the hemicellulose mannan. The transcription factor CLR-2 was subsequently experimentally shown to play a key role in the mannan degradation pathway of N. crassa . Here we built a network that serves as a scaffold for integration of diverse experimental datasets. This approach led to the elucidation of regulatory design principles for plant cell wall deconstruction by filamentous fungi and a novel function for the transcription factor CLR-2. This expanding network will aid in efforts to rationally engineer industrially relevant hyper-production strains.

Conformationally constrained opioid ligands: the Dmt-Aba and Dmt-Aia versus Dmt-Tic scaffold.

PubMed

Ballet, Steven; Feytens, Debby; Wachter, Rien De; Vlaeminck, Magali De; Marczak, Ewa D; Salvadori, Severo; Graaf, Chris de; Rognan, Didier; Negri, Lucia; Lattanzi, Roberta; Lazarus, Lawrence H; Tourwé, Dirk; Balboni, Gianfranco

2009-01-15

Replacement of the constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) in the opioid Dmt-Tic-Gly-NH-Bn scaffold by the 4-amino-1,2,4,5-tetrahydro-indolo[2,3-c]azepin-3-one (Aia) and 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) scaffolds has led to the discovery of novel potent mu-selective agonists (Structures 5 and 12) as well as potent and selective delta-opioid receptor antagonists (Structures 9 and 15). Both stereochemistry and N-terminal N,N-dimethylation proved to be crucial factors for opioid receptor selectivity and functional bioactivity in the investigated small peptidomimetic templates. In addition to the in vitro pharmacological evaluation, automated docking models of Dmt-Tic and Dmt-Aba analogues were constructed in order to rationalize the observed structure-activity data.

Conformationally constrained opioid ligands: The Dmt-Aba and Dmt-Aia vs. Dmt-Tic scaffold

PubMed Central

Ballet, Steven; Feytens, Debby; De Wachter, Rien; De Vlaeminck, Magali; Marczak, Ewa D.; Salvadori, Severo; de Graaf, Chris; Rognan, Didier; Negri, Lucia; Lattanzi, Roberta; Lazarus, Lawrence H.; Tourwé, Dirk; Balboni, Gianfranco

2009-01-01

Replacement of the constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) in the opioid Dmt-Tic-Gly-NH-Bn scaffold by the 4-amino-1,2,4,5-tetrahydro-indolo[2,3-c]azepin-3-one (Aia) and 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) scaffolds has led to the discovery of novel potent μ-selective agonists (Structures 5 and 12) as well as potent and selective δ-opioid receptor antagonists (Structures 9 and 15). Both stereochemistry and N-terminal N,N-dimethylation proved to be crucial factors for opioid receptor selectivity and functional bioactivity in the investigated small peptidomimetic templates. In addition to the in vitro pharmacological evaluation, automated docking models of Dmt-Tic and Dmt-Aba analogues were constructed in order to rationalize the observed structure-activity data. PMID:19062273

Assessing the morphology of selective laser melted NiTi-scaffolds for a three-dimensional quantification of the one-way shape memory effect

NASA Astrophysics Data System (ADS)

Bormann, Therese; de Wild, Michael; Beckmann, Felix; Müller, Bert

2013-04-01

NiTi is promising for the use as bone scaffold, because the pseudoelasticity or the one- and two-way shape memory effect in the physiological window can mechanically stimulate the adherent cells. Such stimuli can enhance osseointegration and might reduce stress shielding associated with load bearing implants. The present study is based on the additive manufacturing technique of selective laser melting (SLM) to fabricate three-dimensional NiTi scaffolds. We demonstrate that the morphology of the scaffolds can be quantified using synchrotron radiation-based micro computed tomography (SRμCT) and sophisticated registration software. Comparing the CAD file with the SLM scaffolds, quality factors are derived. With respect to the CAD file, the overlap corresponds to (92.5 +/- 0.6) %. (7.4 +/- 0.42) % of material was missing and (48.9 +/- 2.3) % of excess material found. This means that the actual scaffold is less porous than expected, a fact that has to be considered for the scaffold design. In order to quantify the shape memory effect during the shape recovery process, we acquired radiographs rotating an initially deformed scaffold in angular steps of 0.2 degree during controlled heating. The continuously acquired radiographs were combined to tomography data, showing that the quality factors evolved with temperature as the scaffold height, measured by conventional thermo-mechanical analysis. Furthermore, the data comprise the presence of compressive and tensile local strains in the three-dimensional scaffolds to be compared with the physiological situation.

Validation of scaffold design optimization in bone tissue engineering: finite element modeling versus designed experiments.

PubMed

Uth, Nicholas; Mueller, Jens; Smucker, Byran; Yousefi, Azizeh-Mitra

2017-02-21

This study reports the development of biological/synthetic scaffolds for bone tissue engineering (TE) via 3D bioplotting. These scaffolds were composed of poly(L-lactic-co-glycolic acid) (PLGA), type I collagen, and nano-hydroxyapatite (nHA) in an attempt to mimic the extracellular matrix of bone. The solvent used for processing the scaffolds was 1,1,1,3,3,3-hexafluoro-2-propanol. The produced scaffolds were characterized by scanning electron microscopy, microcomputed tomography, thermogravimetric analysis, and unconfined compression test. This study also sought to validate the use of finite-element optimization in COMSOL Multiphysics for scaffold design. Scaffold topology was simplified to three factors: nHA content, strand diameter, and strand spacing. These factors affect the ability of the scaffold to bear mechanical loads and how porous the structure can be. Twenty four scaffolds were constructed according to an I-optimal, split-plot designed experiment (DE) in order to generate experimental models of the factor-response relationships. Within the design region, the DE and COMSOL models agreed in their recommended optimal nHA (30%) and strand diameter (460 μm). However, the two methods disagreed by more than 30% in strand spacing (908 μm for DE; 601 μm for COMSOL). Seven scaffolds were 3D-bioplotted to validate the predictions of DE and COMSOL models (4.5-9.9 MPa measured moduli). The predictions for these scaffolds showed relative agreement for scaffold porosity (mean absolute percentage error of 4% for DE and 13% for COMSOL), but were substantially poorer for scaffold modulus (51% for DE; 21% for COMSOL), partly due to some simplifying assumptions made by the models. Expanding the design region in future experiments (e.g., higher nHA content and strand diameter), developing an efficient solvent evaporation method, and exerting a greater control over layer overlap could allow developing PLGA-nHA-collagen scaffolds to meet the mechanical requirements for bone TE.

In vitro characterization of design and compressive properties of 3D-biofabricated/decellularized hybrid grafts for tracheal tissue engineering.

PubMed

Johnson, Christopher; Sheshadri, Priyanka; Ketchum, Jessica M; Narayanan, Lokesh K; Weinberger, Paul M; Shirwaiker, Rohan A

2016-06-01

Infection or damage to the trachea, a thin walled and cartilage reinforced conduit that connects the pharynx and larynx to the lungs, leads to serious respiratory medical conditions which can often prove fatal. Current clinical strategies for complex tracheal reconstruction are of limited availability and efficacy, but tissue engineering and regenerative medicine approaches may provide viable alternatives. In this study, we have developed a new "hybrid graft" approach that utilizes decellularized tracheal tissue along with a resorbable polymer scaffold, and holds promise for potential clinical applications. First, we evaluated the effect of our decellularization process on the compression properties of porcine tracheal segments, and noted approximately 63% decrease in resistance to compression following decellularization. Next we developed four C-shape scaffold designs by varying the base geometry and thickness, and fabricated polycaprolactone scaffolds using a combination of 3D-Bioplotting and thermally-assisted forming. All scaffolds designs were evaluated in vitro under three different environmental testing conditions to determine the design that offered the best resistance to compression. These were further studied to determine the effect of gamma radiation sterilization and cyclic compression loading. Finally, hybrid grafts were developed by securing these optimal design scaffolds to decellularized tracheal segments and evaluated in vitro under physiological testing conditions. Results show that the resistance to compression offered by the hybrid grafts created using gamma radiation sterilized scaffolds was comparable to that of fresh tracheal segments. Given that current clinical attempts at tracheal transplantation using decellularized tissue have been fraught with luminal collapse and complications, our data support the possibility that future embodiments using a hybrid graft approach may reduce the need for intraluminal stenting in tracheal transplant recipients. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cell–scaffold interaction within engineered tissue

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

Chen, Haiping; Liu, Yuanyuan, E-mail: Yuanyuan_liu@shu.edu.cn; Jiang, Zhenglong

The structure of a tissue engineering scaffold plays an important role in modulating tissue growth. A novel gelatin–chitosan (Gel–Cs) scaffold with a unique structure produced by three-dimensional printing (3DP) technology combining with vacuum freeze-drying has been developed for tissue-engineering applications. The scaffold composed of overall construction, micro-pore, surface morphology, and effective mechanical property. Such a structure meets the essential design criteria of an ideal engineered scaffold. The favorable cell–matrix interaction supports the active biocompatibility of the structure. The structure is capable of supporting cell attachment and proliferation. Cells seeded into this structure tend to maintain phenotypic shape and secreted largemore » amounts of extracellular matrix (ECM) and the cell growth decreased the mechanical properties of scaffold. This novel biodegradable scaffold has potential applications for tissue engineering based upon its unique structure, which acts to support cell growth. - Highlights: • The scaffold is not only for providing a surface for cell residence but also for determining cell phenotype and retaining structural integrity. • The mechanical property of scaffold can be affected by activities of cell. • The scaffold provides a microenvironment for cell attachment, growth, and migration.« less

[Fabrication and in vivo implantation of ligament-bone composite scaffolds based on three-dimensional printing technique].

PubMed

Zhang, Wenyou; He, Jiankang; Li, Xiang; Liu, Yaxiong; Bian, Weiguo; Li, Dichen; Jin, Zhongmin

2014-03-01

To solve the fixation problem between ligament grafts and host bones in ligament reconstruction surgery by using ligament-bone composite scaffolds to repair the ligaments, to explore the fabrication method for ligament-bone composite scaffolds based on three-dimensional (3-D) printing technique, and to investigate their mechanical and biological properties in animal experiments. The model of bone scaffolds was designed using CAD software, and the corresponding negative mould was created by boolean operation. 3-D printing techinique was employed to fabricate resin mold. Ceramic bone scaffolds were obtained by casting the ceramic slurry in the resin mould and sintering the dried ceramics-resin composites. Ligament scaffolds were obtained by weaving degummed silk fibers, and then assembled with bone scaffolds and bone anchors. The resultant ligament-bone composite scaffolds were implanted into 10 porcine left anterior cruciate ligament rupture models at the age of 4 months. Mechanical testing and histological examination were performed at 3 months postoperatively, and natural anterior cruciate ligaments of the right sides served as control. Biomechanical testing showed that the natural anterior cruciate ligament of control group can withstand maximum tensile force of (1 384 +/- 181) N and dynamic creep of (0.74 +/- 0.21) mm, while the regenerated ligament-bone scaffolds of experimental group can withstand maximum tensile force of (370 +/- 103) N and dynamic creep of (1.48 +/- 0.49) mm, showing significant differences (t = 11.617, P = 0.000; t = 2.991, P = 0.020). In experimental group, histological examination showed that new bone formed in bone scaffolds. A hierarchical transition structure regenerated between ligament-bone scaffolds and the host bones, which was similar to the structural organizations of natural ligament-bone interface. Ligament-bone composite scaffolds based on 3-D printing technique facilitates the regeneration of biomimetic ligament-bone interface. It is expected to achieve physical fixation between ligament grafts and host bone.

Synthetic (polymer) biology (membrane): functionalization of polymer scaffolds for membrane proteins.

PubMed

Hu, Zhaolong; Ho, James C S; Nallani, Madhavan

2017-08-01

A plethora of polymer-based scaffolds have been designed to facilitate biochemical and biophysical investigation of membrane proteins, with a common goal to stabilize and present them in a functional format. In this review, an up-to-date account of such polymer-based supports and incorporation methodologies are presented. Furthermore, conceptual and imminent technological advances, with associated technical challenges are proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Unveiling the molecular mechanism of brassinosteroids: Insights from structure-based molecular modeling studies.

PubMed

Lei, Beilei; Liu, Jiyuan; Yao, Xiaojun

2015-12-01

Brassinosteroid (BR) phytohormones play indispensable roles in plant growth and development. Brassinolide (BL) and 24-epibrassinolide (24-epiBL) are the most active ones among the BRs reported thus far. Unfortunately, the extremely low natural content and intricate synthesis process limit their popularization in agricultural production. Earlier reports to discover alternative compounds have resulted in molecules with nearly same scaffold structure and without diversity in chemical space. In the present study, receptors structure based BRs regulation mechanism was analyzed. First, we examined the detailed binding interactions and their dynamic stability between BL and its receptor BRI1 and co-receptor BAK1. Then, the binding modes and binding free energies for 24-epiBL and a series of representative BRs binding with BRI1 and BRI1-BAK1 were carried out by molecular docking, energy minimization and MM-PBSA free energy calculation. The obtained binding structures and energetic results provided vital insights into the structural factors affecting the activity from both receptors and BRs aspects. Subsequently, the obtained knowledge will serve as valuable guidance to build pharmacophore models for rational screening of new scaffold alternative BRs. Copyright © 2015 Elsevier Inc. All rights reserved.

The Role of Scaffolding in CSCL in General and in Specific Environments

ERIC Educational Resources Information Center

Verdú, N.; Sanuy, J.

2014-01-01

This paper aims to analyse if virtual forums set up in an environment specifically designed to improve collaborative learning can effectively influence students' discourse quality and learning when compared with those forums set up in a general environment. Following a coding schema based upon the set of scaffolds offered in the Knowledge…

Integrating Elements of Inquiry into the Flow of Middle Level Teaching.

ERIC Educational Resources Information Center

Flick, Lawrence B.

This paper is a part of a research program whose purpose it is to design instruction for scaffolding classroom inquiry in middle school classrooms. Scaffolding is a dynamic process, reflecting teacher adjustments based on student responses. Even though a computer, textbook, or laboratory materials may serve as proxy for a "teacher", arguably the…

The design of 3D scaffold for tissue engineering using automated scaffold design algorithm.

PubMed

Mahmoud, Shahenda; Eldeib, Ayman; Samy, Sherif

2015-06-01

Several progresses have been introduced in the field of bone regenerative medicine. A new term tissue engineering (TE) was created. In TE, a highly porous artificial extracellular matrix or scaffold is required to accommodate cells and guide their growth in three dimensions. The design of scaffolds with desirable internal and external structure represents a challenge for TE. In this paper, we introduce a new method known as automated scaffold design (ASD) for designing a 3D scaffold with a minimum mismatches for its geometrical parameters. The method makes use of k-means clustering algorithm to separate the different tissues and hence decodes the defected bone portions. The segmented portions of different slices are registered to construct the 3D volume for the data. It also uses an isosurface rendering technique for 3D visualization of the scaffold and bones. It provides the ability to visualize the transplanted as well as the normal bone portions. The proposed system proves good performance in both the segmentation results and visualizations aspects.

A biomimetic three-dimensional woven composite scaffold for functional tissue engineering of cartilage

NASA Astrophysics Data System (ADS)

Moutos, Franklin T.; Freed, Lisa E.; Guilak, Farshid

2007-02-01

Tissue engineering seeks to repair or regenerate tissues through combinations of implanted cells, biomaterial scaffolds and biologically active molecules. The rapid restoration of tissue biomechanical function remains an important challenge, emphasizing the need to replicate structural and mechanical properties using novel scaffold designs. Here we present a microscale 3D weaving technique to generate anisotropic 3D woven structures as the basis for novel composite scaffolds that are consolidated with a chondrocyte-hydrogel mixture into cartilage tissue constructs. Composite scaffolds show mechanical properties of the same order of magnitude as values for native articular cartilage, as measured by compressive, tensile and shear testing. Moreover, our findings showed that porous composite scaffolds could be engineered with initial properties that reproduce the anisotropy, viscoelasticity and tension-compression nonlinearity of native articular cartilage. Such scaffolds uniquely combine the potential for load-bearing immediately after implantation in vivo with biological support for cell-based tissue regeneration without requiring cultivation in vitro.

Strategic Design and Fabrication of Engineered Scaffolds for Articular Cartilage Repair

PubMed Central

Izadifar, Zohreh; Chen, Xiongbiao; Kulyk, William

2012-01-01

Damage to articular cartilage can eventually lead to osteoarthritis (OA), a debilitating, degenerative joint disease that affects millions of people around the world. The limited natural healing ability of cartilage and the limitations of currently available therapies make treatment of cartilage defects a challenging clinical issue. Hopes have been raised for the repair of articular cartilage with the help of supportive structures, called scaffolds, created through tissue engineering (TE). Over the past two decades, different designs and fabrication techniques have been investigated for developing TE scaffolds suitable for the construction of transplantable artificial cartilage tissue substitutes. Advances in fabrication technologies now enable the strategic design of scaffolds with complex, biomimetic structures and properties. In particular, scaffolds with hybrid and/or biomimetic zonal designs have recently been developed for cartilage tissue engineering applications. This paper reviews critical aspects of the design of engineered scaffolds for articular cartilage repair as well as the available advanced fabrication techniques. In addition, recent studies on the design of hybrid and zonal scaffolds for use in cartilage tissue repair are highlighted. PMID:24955748

Fabrication, characterization, and in vitro evaluation of poly(lactic acid glycolic acid)/nano-hydroxyapatite composite microsphere-based scaffolds for bone tissue engineering in rotating bioreactors.

PubMed

Lv, Qing; Nair, Lakshmi; Laurencin, Cato T

2009-12-01

Dynamic flow culture bioreactor systems have been shown to enhance in vitro bone tissue formation by facilitating mass transfer and providing mechanical stimulation. Our laboratory has developed a biodegradable poly (lactic acid glycolic acid) (PLAGA) mixed scaffold consisting of lighter-than-water (LTW) and heavier-than-water (HTW) microspheres as potential matrices for engineering tissue using a high aspect ratio vessel (HARV) rotating bioreactor system. We have demonstrated enhanced osteoblast differentiation and mineralization on PLAGA scaffolds in the HARV rotating bioreactor system when compared with static culture. The objective of the present study is to improve the mechanical properties and bioactivity of polymeric scaffolds by designing LTW polymer/ceramic composite scaffolds suitable for dynamic culture using a HARV bioreactor. We employed a microsphere sintering method to fabricate three-dimensional PLAGA/nano-hydroxyapatite (n-HA) mixed scaffolds composed of LTW and HTW composite microspheres. The mechanical properties, pore size and porosity of the composite scaffolds were controlled by varying parameters, such as sintering temperature, sintering time, and PLAGA/n-HA ratio. The PLAGA/n-HA (4:1) scaffold sintered at 90 degrees C for 3 h demonstrated the highest mechanical properties and an appropriate pore structure for bone tissue engineering applications. Furthermore, evaluation human mesenchymal stem cells (HMSCs) response to PLAGA/n-HA scaffolds was performed. HMSCs on PLAGA/n-HA scaffolds demonstrated enhanced proliferation, differentiation, and mineralization when compared with those on PLAGA scaffolds. Therefore, PLAGA/n-HA mixed scaffolds are promising candidates for HARV bioreactor-based bone tissue engineering applications. Copyright 2008 Wiley Periodicals, Inc.

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.

Sericin removal from raw Bombyx mori silk scaffolds of high hierarchical order.

PubMed

Teuschl, Andreas Herbert; van Griensven, Martijn; Redl, Heinz

2014-05-01

Silk fibroin has previously been described as a promising candidate for ligament tissue engineering (TE) approaches. For biocompatibility reasons, silkworm silk requires removal of sericin, which can elicit adverse immune responses in the human body. One disadvantage of the required degumming process is the alteration of the silk fiber structural properties, which can hinder textile engineering of high order hierarchical structures. Therefore, the aim of this study was to find a way to remove sericin from a compact and highly ordered raw silk fiber matrix. The wire rope design of the test model scaffold comprises several levels of geometric hierarchy. Commonly used degumming solutions fail in removing sericin in this wire rope design. Weight loss measurements, picric acid and carmine staining as well as scanning electron microscopy demonstrated that the removal of sericin from the model scaffold of a wire rope design can be achieved through a borate buffer-based system. Furthermore, the borate buffer degummed silks were shown to be nontoxic and did not alter cell proliferation behavior. The possibility to remove sericin after the textile engineering process has taken place eases the production of highly ordered scaffold structures and may expand the use of silk as scaffold material in further TE and regenerative medicine applications.

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.

Biomedical applications of nanodiamond (Review)

NASA Astrophysics Data System (ADS)

Turcheniuk, K.; Mochalin, Vadym N.

2017-06-01

The interest in nanodiamond applications in biology and medicine is on the rise over recent years. This is due to the unique combination of properties that nanodiamond provides. Small size (∼5 nm), low cost, scalable production, negligible toxicity, chemical inertness of diamond core and rich chemistry of nanodiamond surface, as well as bright and robust fluorescence resistant to photobleaching are the distinct parameters that render nanodiamond superior to any other nanomaterial when it comes to biomedical applications. The most exciting recent results have been related to the use of nanodiamonds for drug delivery and diagnostics—two components of a quickly growing area of biomedical research dubbed theranostics. However, nanodiamond offers much more in addition: it can be used to produce biodegradable bone surgery devices, tissue engineering scaffolds, kill drug resistant microbes, help us to fight viruses, and deliver genetic material into cell nucleus. All these exciting opportunities require an in-depth understanding of nanodiamond. This review covers the recent progress as well as general trends in biomedical applications of nanodiamond, and underlines the importance of purification, characterization, and rational modification of this nanomaterial when designing nanodiamond based theranostic platforms.

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

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.

Designing Online Scaffolds for Interactive Computer Simulation

ERIC Educational Resources Information Center

Chen, Ching-Huei; Wu, I-Chia; Jen, Fen-Lan

2013-01-01

The purpose of this study was to examine the effectiveness of online scaffolds in computer simulation to facilitate students' science learning. We first introduced online scaffolds to assist and model students' science learning and to demonstrate how a system embedded with online scaffolds can be designed and implemented to help high school…

3D printing for the design and fabrication of polymer-based gradient scaffolds.

PubMed

Bracaglia, Laura G; Smith, Brandon T; Watson, Emma; Arumugasaamy, Navein; Mikos, Antonios G; Fisher, John P

2017-07-01

To accurately mimic the native tissue environment, tissue engineered scaffolds often need to have a highly controlled and varied display of three-dimensional (3D) architecture and geometrical cues. Additive manufacturing in tissue engineering has made possible the development of complex scaffolds that mimic the native tissue architectures. As such, architectural details that were previously unattainable or irreproducible can now be incorporated in an ordered and organized approach, further advancing the structural and chemical cues delivered to cells interacting with the scaffold. This control over the environment has given engineers the ability to unlock cellular machinery that is highly dependent upon the intricate heterogeneous environment of native tissue. Recent research into the incorporation of physical and chemical gradients within scaffolds indicates that integrating these features improves the function of a tissue engineered construct. This review covers recent advances on techniques to incorporate gradients into polymer scaffolds through additive manufacturing and evaluate the success of these techniques. As covered here, to best replicate different tissue types, one must be cognizant of the vastly different types of manufacturing techniques available to create these gradient scaffolds. We review the various types of additive manufacturing techniques that can be leveraged to fabricate scaffolds with heterogeneous properties and discuss methods to successfully characterize them. Additive manufacturing techniques have given tissue engineers the ability to precisely recapitulate the native architecture present within tissue. In addition, these techniques can be leveraged to create scaffolds with both physical and chemical gradients. This work offers insight into several techniques that can be used to generate graded scaffolds, depending on the desired gradient. Furthermore, it outlines methods to determine if the designed gradient was achieved. This review will help to condense the abundance of information that has been published on the creation and characterization of gradient scaffolds and to provide a single review discussing both methods for manufacturing gradient scaffolds and evaluating the establishment of a gradient. Copyright © 2017. Published by Elsevier Ltd.

Diamond and diamond-like carbon MEMS

NASA Astrophysics Data System (ADS)

Luo, J. K.; Fu, Y. Q.; Le, H. R.; Williams, J. A.; Spearing, S. M.; Milne, W. I.

2007-07-01

To generate complex cartilage/bone tissues, scaffolds must possess several structural features that are difficult to create using conventional scaffold design/fabrication technologies. Successful cartilage/bone regeneration depends on the ability to assemble chondrocytes/osteoblasts into three-dimensional (3D) scaffolds. Therefore, we developed a 3D scaffold fabrication system that applies the axiomatic approach to our microstereolithography system. The new system offers a reduced machine size by minimizing the optical components, and shows that the design matrix is decoupled. This analysis identified the key factors affecting microstructure fabrication and an improved scaffold fabrication system was constructed. The results demonstrate that precise, predesigned 3D structures can be fabricated. Using this 3D scaffold, cell adhesion behavior was observed. The use of 3D scaffolds might help determine key factors in the study of cell behavior in complex environments and could eventually lead to the optimal design of scaffolds for the regeneration of various tissues, such as cartilage and bone.

Design and Fabrication of 3D printed Scaffolds with a Mechanical Strength Comparable to Cortical Bone to Repair Large Bone Defects

PubMed Central

Roohani-Esfahani, Seyed-Iman; Newman, Peter; Zreiqat, Hala

2016-01-01

A challenge in regenerating large bone defects under load is to create scaffolds with large and interconnected pores while providing a compressive strength comparable to cortical bone (100–150 MPa). Here we design a novel hexagonal architecture for a glass-ceramic scaffold to fabricate an anisotropic, highly porous three dimensional scaffolds with a compressive strength of 110 MPa. Scaffolds with hexagonal design demonstrated a high fatigue resistance (1,000,000 cycles at 1–10 MPa compressive cyclic load), failure reliability and flexural strength (30 MPa) compared with those for conventional architecture. The obtained strength is 150 times greater than values reported for polymeric and composite scaffolds and 5 times greater than reported values for ceramic and glass scaffolds at similar porosity. These scaffolds open avenues for treatment of load bearing bone defects in orthopaedic, dental and maxillofacial applications. PMID:26782020

Design and Fabrication of 3D printed Scaffolds with a Mechanical Strength Comparable to Cortical Bone to Repair Large Bone Defects

NASA Astrophysics Data System (ADS)

Roohani-Esfahani, Seyed-Iman; Newman, Peter; Zreiqat, Hala

2016-01-01

A challenge in regenerating large bone defects under load is to create scaffolds with large and interconnected pores while providing a compressive strength comparable to cortical bone (100-150 MPa). Here we design a novel hexagonal architecture for a glass-ceramic scaffold to fabricate an anisotropic, highly porous three dimensional scaffolds with a compressive strength of 110 MPa. Scaffolds with hexagonal design demonstrated a high fatigue resistance (1,000,000 cycles at 1-10 MPa compressive cyclic load), failure reliability and flexural strength (30 MPa) compared with those for conventional architecture. The obtained strength is 150 times greater than values reported for polymeric and composite scaffolds and 5 times greater than reported values for ceramic and glass scaffolds at similar porosity. These scaffolds open avenues for treatment of load bearing bone defects in orthopaedic, dental and maxillofacial applications.

Design variables for mechanical properties of bone tissue scaffolds.

PubMed

Howk, Daniel; Chu, Tien-Min G

2006-01-01

The reconstruction of segmental defect in long bone is a clinical challenge. Multiple surgeries are typically required to restore the structure and function of the affected defect site. In order to overcome this defect a biodegradable bone tissue engineering scaffold is used. This scaffold acts as a carrier of proteins and growth factors, while also supporting the load that the bone would normally sustain, until the natural bone can regenerate in its place. Work was done to optimize an existing solid free-form scaffold design. The goal of the optimization was to increase the porosity of the scaffold while maintaining the strength of a previously-tested prototype design. With this in mind, eight new designs were created. These designs were drawn using CAD software and then through the use of finite element analysis the theoretical ultimate compressive strength of each design was obtained. Each scaffold design was constructed by casting a thermal-curable poly(propylene fumarate)/tricalcium phosphate (PPF/TCP) suspension into wax molds fabricated on inkjet printing rapid prototyping machine. The constructs were then experimentally tested by applying a uniaxial compressive load. The theoretical and experimental values of ultimate compressive strength and specific strength of each design were compared. Theoretically, the best scaffold design produced from this work improved upon the current design by increasing the porosity by 46% and also increasing the ultimate compressive strength by 27%. The experimental data was found to match the theoretical strength in four designs, but deviate from the theoretical strength in five designs. The reasons for the deviations and their relation to the rapid prototyping manufacturing technique were discussed. The results of this work show that it is possible to increase the porosity and strength of a bone tissue engineering scaffold through simple iterations in architectural design.

Targeting Mantle Cell Lymphoma with Anti-SYK Nanoparticles

PubMed Central

Cely, Ingrid; Yiv, Seang; Yin, Qian; Shahidzadeh, Anoush; Tang, Li; Cheng, Jianjun; Uckun, Fatih M.

2013-01-01

The pentapeptide mimic 1,4-bis(9-O-dihydroquinidinyl)phthalazine / hydroquinidine 1,4-phathalazinediyl diether (“compound 61”) (C-61) is the first reported inhibitor targeting the P-site of SYK. Here we report a nanotechnology platform to target C-61 to mantle cell lymphoma (MCL) cells. Liposomal nanoparticles (NP) loaded with C-61 were prepared using the standard thin film evaporation method. The entrapment of C-61 was obtained using the pH gradient procedure with lactobionic acid (LBA) being used as a low pH buffer inside the NP. Formulation F6A was selected as a lead candidate for further biological testing. The average diameter, zeta potential and C-61 content of the F6A NP was 40 nm, 0.1 mV, and 12.6 mg/ml, respectively. F6A induces apoptosis in SYK+ but not SYK− leukemia/lymphoma cells. We also evaluated the cytotoxic activity of F6A in the context of an in vitro artificial bone marrow assay platform based on a 3D scaffold with inverted colloidal crystal geometry mimicking the structural topology of actual bone marrow matrix. The ability of C-61 to induce apoptosis in ALL-1 cells was not adversely affected by the scaffolds. F6A, but not the drug-free NP formulation F6B, caused apoptosis of MCL cell lines MAVER-1 and MINO within 24h. Further development of rationally designed SYK inhibitors and their nanoscale formulations may provide the foundation for therapeutic innovation against a broad spectrum of lymphoid malignancies, including MCL. PMID:23730399

A multiple multicomponent approach to chimeric peptide-peptoid podands.

PubMed

Rivera, Daniel G; León, Fredy; Concepción, Odette; Morales, Fidel E; Wessjohann, Ludger A

2013-05-10

The success of multi-armed, peptide-based receptors in supramolecular chemistry traditionally is not only based on the sequence but equally on an appropriate positioning of various peptidic chains to create a multivalent array of binding elements. As a faster, more versatile and alternative access toward (pseudo)peptidic receptors, a new approach based on multiple Ugi four-component reactions (Ugi-4CR) is proposed as a means of simultaneously incorporating several binding and catalytic elements into organizing scaffolds. By employing α-amino acids either as the amino or acid components of the Ugi-4CRs, this multiple multicomponent process allows for the one-pot assembly of podands bearing chimeric peptide-peptoid chains as appended arms. Tripodal, bowl-shaped, and concave polyfunctional skeletons are employed as topologically varied platforms for positioning the multiple peptidic chains formed by Ugi-4CRs. In a similar approach, steroidal building blocks with several axially-oriented isocyano groups are synthesized and utilized to align the chimeric chains with conformational constrains, thus providing an alternative to the classical peptido-steroidal receptors. The branched and hybrid peptide-peptoid appendages allow new possibilities for both rational design and combinatorial production of synthetic receptors. The concept is also expandable to other multicomponent reactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Story-Based Pedagogical Agents: A Scaffolding Design Approach for the Process of Historical Inquiry in a Web-Based Self-Learning Environment

ERIC Educational Resources Information Center

Fujimoto, Toru

2010-01-01

The purpose of this research was to design and evaluate a web-based self-learning environment for historical inquiry embedded with different types of instructional support featuring story-based pedagogical agents. This research focused on designing a learning environment by integrating story-based instruction and pedagogical agents as a means to…

Tissue-engineering-based Strategies for Regenerative Endodontics

PubMed Central

Albuquerque, M.T.P.; Valera, M.C.; Nakashima, M.; Nör, J.E.; Bottino, M.C.

2014-01-01

Stemming from in vitro and in vivo pre-clinical and human models, tissue-engineering-based strategies continue to demonstrate great potential for the regeneration of the pulp-dentin complex, particularly in necrotic, immature permanent teeth. Nanofibrous scaffolds, which closely resemble the native extracellular matrix, have been successfully synthesized by various techniques, including but not limited to electrospinning. A common goal in scaffold synthesis has been the notion of promoting cell guidance through the careful design and use of a collection of biochemical and physical cues capable of governing and stimulating specific events at the cellular and tissue levels. The latest advances in processing technologies allow for the fabrication of scaffolds where selected bioactive molecules can be delivered locally, thus increasing the possibilities for clinical success. Though electrospun scaffolds have not yet been tested in vivo in either human or animal pulpless models in immature permanent teeth, recent studies have highlighted their regenerative potential both from an in vitro and in vivo (i.e., subcutaneous model) standpoint. Possible applications for these bioactive scaffolds continue to evolve, with significant prospects related to the regeneration of both dentin and pulp tissue and, more recently, to root canal disinfection. Nonetheless, no single implantable scaffold can consistently guide the coordinated growth and development of the multiple tissue types involved in the functional regeneration of the pulp-dentin complex. The purpose of this review is to provide a comprehensive perspective on the latest discoveries related to the use of scaffolds and/or stem cells in regenerative endodontics. The authors focused this review on bioactive nanofibrous scaffolds, injectable scaffolds and stem cells, and pre-clinical findings using stem-cell-based strategies. These topics are discussed in detail in an attempt to provide future direction and to shed light on their potential translation to clinical settings. PMID:25201917

In-situ birth of MSCs multicellular spheroids in poly(L-glutamic acid)/chitosan scaffold for hyaline-like cartilage regeneration.

PubMed

Zhang, Kunxi; Yan, Shifeng; Li, Guifei; Cui, Lei; Yin, Jingbo

2015-12-01

The success of mesenchymal stem cells (MSCs) based articular cartilage tissue engineering is limited by the presence of fibrous tissue in generated cartilage, which is associated with the current scaffold strategy that promotes cellular adhesion and spreading. Here we design a non-fouling scaffold based on amide bonded poly(l-glutamic acid) (PLGA) and chitosan (CS) to drive adipose stem cells (ASCs) to aggregate to form multicellular spheroids with diameter of 80-110 μm in-situ. To illustrate the advantage of the present scaffolds, a cellular adhesive scaffold based on the same amide bonded PLGA and CS was created through a combination of air-drying and freeze-drying to limit the hydration effect while also achieving porous structure. Compared to ASCs spreading along the surface of pores within scaffold, the dense mass of aggregated ASCs in PLGA/CS scaffold exhibited enhanced chondrogenic differentiation capacity, as determined by up-regulated GAGs and COL II expression, and greatly decreased COL I deposition during in vitro chondrogenesis. Furthermore, after 12 weeks of implantation, neo-cartilages generated by ASCs adhered on scaffold significantly presented fibrous matrix which was characterized by high levels of COL I deposition. However, neo-cartilage at 12 weeks post-implantation generated by PLGA/CS scaffold carrying ASC spheroids possessed similar high level of GAGs and COL II and low level of COL I as that in normal cartilage. The in vitro and in vivo results indicated the present strategy could not only promote chondrogenesis of ASCs, but also facilitate hyaline-like cartilage regeneration with reduced fibrous tissue formation which may attenuate cartilage degradation in future long-term follow-up. Copyright © 2015 Elsevier Ltd. All rights reserved.

Improving Sample Distribution Homogeneity in Three-Dimensional Microfluidic Paper-Based Analytical Devices by Rational Device Design.

PubMed

Morbioli, Giorgio Gianini; Mazzu-Nascimento, Thiago; Milan, Luis Aparecido; Stockton, Amanda M; Carrilho, Emanuel

2017-05-02

Paper-based devices are a portable, user-friendly, and affordable technology that is one of the best analytical tools for inexpensive diagnostic devices. Three-dimensional microfluidic paper-based analytical devices (3D-μPADs) are an evolution of single layer devices and they permit effective sample dispersion, individual layer treatment, and multiplex analytical assays. Here, we present the rational design of a wax-printed 3D-μPAD that enables more homogeneous permeation of fluids along the cellulose matrix than other existing designs in the literature. Moreover, we show the importance of the rational design of channels on these devices using glucose oxidase, peroxidase, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) reactions. We present an alternative method for layer stacking using a magnetic apparatus, which facilitates fluidic dispersion and improves the reproducibility of tests performed on 3D-μPADs. We also provide the optimized designs for printing, facilitating further studies using 3D-μPADs.

A three dimensional scaffold with precise micro-architecture and surface micro-textures

PubMed Central

Mata, Alvaro; Kim, Eun Jung; Boehm, Cynthia A.; Fleischman, Aaron J.; Muschler, George F.; Roy, Shuvo

2013-01-01

A three-dimensional (3D) structure comprising precisely defined microarchitecture and surface micro-textures, designed to present specific physical cues to cells and tissues, may provide an efficient scaffold in a variety of tissue engineering and regenerative medicine applications. We report a fabrication technique based on microfabrication and soft lithography that permits for the development of 3D scaffolds with both precisely engineered architecture and tailored surface topography. The scaffold fabrication technique consists of three key steps starting with microfabrication of a mold using an epoxy-based photoresist (SU-8), followed by dual-sided molding of a single layer of polydimethylsiloxane (PDMS) using a mechanical jig for precise motion control; and finally, alignment, stacking, and adhesion of multiple PDMS layers to achieve a 3D structure. This technique was used to produce 3D Texture and 3D Smooth PDMS scaffolds, where the surface topography comprised 10 μm-diameter/height posts and smooth surfaces, respectively. The potential utility of the 3D microfabricated scaffolds, and the role of surface topography, were subsequently investigated in vitro with a combined heterogeneous population of adult human stem cells and their resultant progenitor cells, collectively termed connective tissue progenitors (CTPs), under conditions promoting the osteoblastic phenotype. Examination of bone-marrow derived CTPs cultured on the 3D Texture scaffold for 9 days revealed cell growth in three dimensions and increased cell numbers compared to those on the 3D Smooth scaffold. Furthermore, expression of alkaline phosphatase mRNA was higher on the 3D Texture scaffold, while osteocalcin mRNA expression was comparable for both types of scaffolds. PMID:19524292

Predicting Monoamine Oxidase Inhibitory Activity through Ligand-Based Models

PubMed Central

Vilar, Santiago; Ferino, Giulio; Quezada, Elias; Santana, Lourdes; Friedman, Carol

2013-01-01

The evolution of bio- and cheminformatics associated with the development of specialized software and increasing computer power has produced a great interest in theoretical in silico methods applied in drug rational design. These techniques apply the concept that “similar molecules have similar biological properties” that has been exploited in Medicinal Chemistry for years to design new molecules with desirable pharmacological profiles. Ligand-based methods are not dependent on receptor structural data and take into account two and three-dimensional molecular properties to assess similarity of new compounds in regards to the set of molecules with the biological property under study. Depending on the complexity of the calculation, there are different types of ligand-based methods, such as QSAR (Quantitative Structure-Activity Relationship) with 2D and 3D descriptors, CoMFA (Comparative Molecular Field Analysis) or pharmacophoric approaches. This work provides a description of a series of ligand-based models applied in the prediction of the inhibitory activity of monoamine oxidase (MAO) enzymes. The controlled regulation of the enzymes’ function through the use of MAO inhibitors is used as a treatment in many psychiatric and neurological disorders, such as depression, anxiety, Alzheimer’s and Parkinson’s disease. For this reason, multiple scaffolds, such as substituted coumarins, indolylmethylamine or pyridazine derivatives were synthesized and assayed toward MAO-A and MAO-B inhibition. Our intention is to focus on the description of ligand-based models to provide new insights in the relationship between the MAO inhibitory activity and the molecular structure of the different inhibitors, and further study enzyme selectivity and possible mechanisms of action. PMID:23231398

Tailoring vessel morphology in vivo

NASA Astrophysics Data System (ADS)

Gould, Daniel Joseph

Tissue engineering is a rapidly growing field which seeks to provide alternatives to organ transplantation in order to address the increasing need for transplantable tissues. One huge hurdle in this effort is the provision of thick tissues; this hurdle exists because currently there is no way to provide prevascularized or rapidly vascularizable scaffolds. To design thick, vascularized tissues, scaffolds are needed that can induce vessels which are similar to the microvasculature found in normal tissues. Angiogenic biomaterials are being developed to provide useful scaffolds to address this problem. In this thesis angiogenic and cell signaling and adhesion factors were incorporated into a biomimetic poly(ethylene glycol) (PEG) hydrogel system. The composition of these hydrogels was precisely tuned to induce the formation of differing vessel morphology. To sensitively measure induced microvascular morphology and to compare it to native microvessels in several tissues, this thesis developed an image-based tool for quantification of scale invariant and classical measures of vessel morphology. The tool displayed great utility in the comparison of native vessels and remodeling vessels in normal tissues. To utilize this tool to tune the vessel response in vivo, Flk1::myr-mCherry fluorescently labeled mice were implanted with Platelet Derived Growth Factor-BB (PDGF-BB) and basic Fibroblast Growth Factor (FGF-2) containing PEG-based hydrogels in a modified mouse corneal angiogenesis assay. Resulting vessels were imaged with confocal microscopy, analyzed with the image based tool created in this thesis to compare morphological differences between treatment groups, and used to create a linear relationship between space filling parameters and dose of growth factor release. Morphological parameters of native mouse tissue vessels were then compared to the linear fit to calculate the dose of growth factors needed to induce vessels similar in morphology to native vessels. Resulting induced vessels did match in morphology to the target vessels. Several other covalently bound signals were then analyzed in the assay and resulting morphology of vessels was compared in several studies which further highlighted the utility of the micropocket assay in conjunction with the image based tool for vessel morphological quantification. Finally, an alternative method to provide rapid vasculature to the constructs, which relied on pre-seeded hydrogels encapsulated endothelial cells was also developed and shown to allow anastamosis between induced host vessels and the implanted construct within 48 hours. These results indicate great promise in the rational design of synthetic, bioactive hydrogels, which can be used as a platform to study microvascular induction for regenerative medicine and angiogenesis research. Future applications of this research may help to develop therapeutic strategies to ameliorate human disease by replacing organs or correcting vessel morphology in the case of ischemic diseases and cancer.

Rational design of new electrolyte materials for electrochemical double layer capacitors

NASA Astrophysics Data System (ADS)

Schütter, Christoph; Husch, Tamara; Viswanathan, Venkatasubramanian; Passerini, Stefano; Balducci, Andrea; Korth, Martin

2016-09-01

The development of new electrolytes is a centerpiece of many strategies to improve electrochemical double layer capacitor (EDLC) devices. We present here a computational screening-based rational design approach to find new electrolyte materials. As an example application, the known chemical space of almost 70 million compounds is investigated in search of electrochemically more stable solvents. Cyano esters are identified as especially promising new compound class. Theoretical predictions are validated with subsequent experimental studies on a selected case. These studies show that based on theoretical predictions only, a previously untested, but very well performing compound class was identified. We thus find that our rational design strategy is indeed able to successfully identify completely new materials with substantially improved properties.

Controlled local drug delivery strategies from chitosan hydrogels for wound healing.

PubMed

Elviri, Lisa; Bianchera, Annalisa; Bergonzi, Carlo; Bettini, Ruggero

2017-07-01

The main target of tissue engineering is the preparation and application of adequate materials for the design and production of scaffolds, that possess properties promoting cell adhesion, proliferation and differentiation. The use of natural polysaccharides, such as chitosan, to prepare hydrogels for wound healing and controlled drug delivery is a research topic of wide and increasing interest. Areas covered: This review presents the latest results and challenges in the preparation of chitosan and chitosan-based scaffold/hydrogel for wound healing applications. A detailed overview of their behavior in terms of controlled drug delivery, divided by drug categories, and efficacy was provided and critically discussed. Expert opinion: The need to establish and exploit the advantages of natural biomaterials in combination with active compounds is playing a pivotal role in the regenerative medicine fields. The challenges posed by the many variables affecting tissue repair and regeneration need to be standardized and adhere to recognized guidelines to improve the quality of evidence in the wound healing process. Currently, different methodologies are followed to prepare innovative scaffold formulations and structures. Innovative technologies such as 3D printing or bio-electrospray are promising to create chitosan-based scaffolds with finely controlled structures with customizable shape porosity and thickness. Chitosan scaffolds could be designed in combination with a variety of polysaccharides or active compounds with selected and reproducible spacial distribution, providing active wound dressing with highly tunable controlled drug delivery.

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.

Bioreactor-based bone tissue engineering: The influence of dynamic flow on osteoblast phenotypic expression and matrix mineralization

PubMed Central

Yu, Xiaojun; Botchwey, Edward A.; Levine, Elliot M.; Pollack, Solomon R.; Laurencin, Cato T.

2004-01-01

An important issue in tissue engineering concerns the possibility of limited tissue ingrowth in tissue-engineered constructs because of insufficient nutrient transport. We report a dynamic flow culture system using high-aspect-ratio vessel rotating bioreactors and 3D scaffolds for culturing rat calvarial osteoblast cells. 3D scaffolds were designed by mixing lighter-than-water (density, <1g/ml) and heavier-than-water (density, >1g/ml) microspheres of 85:15 poly(lactide-co-glycolide). We quantified the rate of 3D flow through the scaffolds by using a particle-tracking system, and the results suggest that motion trajectories and, therefore, the flow velocity around and through scaffolds in rotating bioreactors can be manipulated by varying the ratio of heavier-than-water to lighter-than-water microspheres. When rat primary calvarial cells were cultured on the scaffolds in bioreactors for 7 days, the 3D dynamic flow environment affected bone cell distribution and enhanced cell phenotypic expression and mineralized matrix synthesis within tissue-engineered constructs compared with static conditions. These studies provide a foundation for exploring the effects of dynamic flow on osteoblast function and provide important insight into the design and optimization of 3D scaffolds suitable in bioreactors for in vitro tissue engineering of bone. PMID:15277663

Scaffold Seeking: A Reverse Design of Scaffolding in Computer-Supported Word Problem Solving

ERIC Educational Resources Information Center

Cheng, Hercy N. H.; Yang, Euphony F. Y.; Liao, Calvin C. Y.; Chang, Ben; Huang, Yana C. Y.; Chan, Tak-Wai

2015-01-01

Although well-designed scaffolding may assist students to accomplish learning tasks, its insufficient capability to dynamically assess students' abilities and to adaptively support them may result in the problem of overscaffolding. Our previous project has also shown that students using scaffolds to solve mathematical word problems for a long time…

Pyrrole-indolinone SU11652 targets the nucleoside diphosphate kinase from Leishmania parasites.

PubMed

Vieira, Plínio Salmazo; Souza, Tatiana de Arruda Campos Brasil; Honorato, Rodrigo Vargas; Zanphorlin, Letícia Maria; Severiano, Kelven Ulisses; Rocco, Silvana Aparecida; de Oliveira, Arthur Henrique Cavalcante; Cordeiro, Artur Torres; Oliveira, Paulo Sérgio Lopes; de Giuseppe, Priscila Oliveira; Murakami, Mário Tyago

2017-07-01

Nucleoside diphosphate kinases (NDKs) are key enzymes in the purine-salvage pathway of trypanosomatids and have been associated with the maintenance of host-cell integrity for the benefit of the parasite, being potential targets for rational drug discovery and design. The NDK from Leishmania major (LmNDK) and mutants were expressed and purified to homogeneity. Thermal shift assays were employed to identify potential inhibitors for LmNDK. Calorimetric experiments, site-directed mutagenesis and molecular docking analysis were performed to validate the interaction and to evaluate the structural basis of ligand recognition. Furthermore, the anti-leishmanial activity of the newly identified and validated compound was tested in vitro against different Leishmania species. The molecule SU11652, a Sunitinib analog, was identified as a potential inhibitor for LmNDK and structural studies indicated that this molecule binds to the active site of LmNDK in a similar conformation to nucleotides, mimicking natural substrates. Isothermal titration calorimetry experiments combined with site-directed mutagenesis revealed that the residues H50 and H117, considered essential for catalysis, play an important role in ligand binding. In vitro cell studies showed that SU11652 had similar efficacy to Amphotericin b against some Leishmania species. Together, our results indicate the pyrrole-indolinone SU11652 as a promising scaffold for the rational design of new drugs targeting the enzyme NDK from Leishmania parasites. Copyright © 2017 Elsevier Inc. All rights reserved.

[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.

Enzyme sensitive smart inulin-dehydropeptide conjugate self-assembles into nanostructures useful for targeted delivery of ornidazole.

PubMed

Shivhare, Kriti; Garg, Charu; Priyam, Ayushi; Gupta, Alka; Sharma, Ashwani Kumar; Kumar, Pradeep

2018-01-01

Molecular self-assembly of biodegradable amphiphilic polymers allows rational design of biocompatible nanomaterials for drug delivery. Use of substituted polysaccharides for such applications offers the ease of design and synthesis, and provides higher biofunctionality and biocompatibility to nanomaterials. The present work focuses on the synthesis, characterization and potential biomedical applications of self-assembled polysaccharide-based materials. We demonstrated that the synthesized amphiphilic inulin self-assembled in aqueous medium into nanostructures with average size in the range of 146-486nm and encapsulated hydrophobic therapeutic molecule, ornidazole. Hydrophophic dehydropeptide was conjugated with inulin via a biocompatible ester linkage. Dehydrophenylalanine, an unusual amino acid, was incorporated in the peptide to make it stable at a broader range of pH as well as against proteases. The resulting core-shell type of nanostructures could encapsulate ornidazole in the hydrophobic core and released it in a controlled fashion. By taking the advantage of inulin, which gets degraded in the colon by colonic bacteria, the effect of enzyme, inulinase, present in the microflora of the large intestine, on inulin-peptide degradation followed by drug release has been studied. Altogether, small peptide conjugated to inulin offers novel scaffold for the future design of nanostructures with potential applications in the field of targeted drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

Current trends in the design of scaffolds for computer-aided tissue engineering.

PubMed

Giannitelli, S M; Accoto, D; Trombetta, M; Rainer, A

2014-02-01

Advances introduced by additive manufacturing have significantly improved the ability to tailor scaffold architecture, enhancing the control over microstructural features. This has led to a growing interest in the development of innovative scaffold designs, as testified by the increasing amount of research activities devoted to the understanding of the correlation between topological features of scaffolds and their resulting properties, in order to find architectures capable of optimal trade-off between often conflicting requirements (such as biological and mechanical ones). The main aim of this paper is to provide a review and propose a classification of existing methodologies for scaffold design and optimization in order to address key issues and help in deciphering the complex link between design criteria and resulting scaffold properties. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Non-viral gene activated matrices for mesenchymal stem cells based tissue engineering of bone and cartilage.

PubMed

Raisin, Sophie; Belamie, Emmanuel; Morille, Marie

2016-10-01

Recent regenerative medicine and tissue engineering strategies for bone and cartilage repair have led to fascinating progress of translation from basic research to clinical applications. In this context, the use of gene therapy is increasingly being considered as an important therapeutic modality and regenerative technique. Indeed, in the last 20 years, nucleic acids (plasmid DNA, interferent RNA) have emerged as credible alternative or complement to proteins, which exhibited major issues including short half-life, loss of bioactivity in pathologic environment leading to high dose requirement and therefore high production costs. The relevance of gene therapy strategies in combination with a scaffold, following a so-called "Gene-Activated Matrix (GAM)" approach, is to achieve a direct, local and sustained delivery of nucleic acids from a scaffold to ensure efficient and durable cell transfection. Among interesting cells sources, Mesenchymal Stem Cells (MSC) are promising for a rational use in gene/cell therapy with more than 1700 clinical trials approved during the last decade. The aim of the present review article is to provide a comprehensive overview of recent and ongoing work in non-viral genetic engineering of MSC combined with scaffolds. More specifically, we will show how this inductive strategy can be applied to orient stem cells fate for bone and cartilage repair. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Multi-Step Usage of in Vivo Models During Rational Drug Design and Discovery

PubMed Central

Williams, Charles H.; Hong, Charles C.

2011-01-01

In this article we propose a systematic development method for rational drug design while reviewing paradigms in industry, emerging techniques and technologies in the field. Although the process of drug development today has been accelerated by emergence of computational methodologies, it is a herculean challenge requiring exorbitant resources; and often fails to yield clinically viable results. The current paradigm of target based drug design is often misguided and tends to yield compounds that have poor absorption, distribution, metabolism, and excretion, toxicology (ADMET) properties. Therefore, an in vivo organism based approach allowing for a multidisciplinary inquiry into potent and selective molecules is an excellent place to begin rational drug design. We will review how organisms like the zebrafish and Caenorhabditis elegans can not only be starting points, but can be used at various steps of the drug development process from target identification to pre-clinical trial models. This systems biology based approach paired with the power of computational biology; genetics and developmental biology provide a methodological framework to avoid the pitfalls of traditional target based drug design. PMID:21731440

Identification of novel B-RafV600E inhibitors employing FBDD strategy.

PubMed

Wang, Peng-Fei; Qiu, Han-Yue; Wang, Ze-Feng; Zhang, Yong-Jiao; Wang, Zhong-Chang; Li, Dong-Dong; Zhu, Hai-Liang

2017-05-15

B-Raf kinase is the key point in a main branch of mitogen-activated protein kinase pathways and some of its mutations, such as the V600E mutation, lead to the persistent activation of ERK signaling and the trigger of severe diseases, including melanoma and other somatic cancers. Several potent drugs have been approved to treat B-Raf-related tumors, however, cases of resistance and relapse have been reported universally. Hence, differential scaffolds are in need to alleviate the scarcity of drugs and benefit the therapy of B-Raf-mutant cancers. Herein we report our recent work on the construction of novel B-Raf V600E inhibitors employing fragment-based drug design strategy. In this research, we decomposed known inhibitors to fragments and rebuilt new candidates using these blocks according to the evaluation of their potential. Lead compounds were synthesized after selection by means of virtual screening and molecular dynamics validation. Afterwards, we tested the pharmacological efficiency of these entities both in vitro and in vivo utilizing A375 xenograft model. The results favored our rational design intention and hinted this new kind of inhibitors might be helpful in the further explorations of potent agents. Copyright © 2017 Elsevier Inc. All rights reserved.

Additive Manufacturing of Patient-Customizable Scaffolds for Tubular Tissues Using the Melt-Drawing Method.

PubMed

Tan, Yu Jun; Tan, Xipeng; Yeong, Wai Yee; Tor, Shu Beng

2016-11-03

Polymeric fibrous scaffolds for guiding cell growth are designed to be potentially used for the tissue engineering (TE) of tubular organs including esophagi, blood vessels, tracheas, etc. Tubular scaffolds were fabricated via melt-drawing of highly elastic poly(l-lactide-co-ε-caprolactone) (PLC) fibers layer-by-layer on a cylindrical mandrel. The diameter and length of the scaffolds are customizable via 3D printing of the mandrel. Thickness of the scaffolds was varied by changing the number of layers of the melt-drawing process. The morphology and tensile properties of the PLC fibers were investigated. The fibers were highly aligned with a uniform diameter. Their diameters and tensile properties were tunable by varying the melt-drawing speeds. These tailorable topographies and tensile properties show that the additive-based scaffold fabrication technique is customizable at the micro- and macro-scale for different tubular tissues. The merits of these scaffolds in TE were further shown by the finding that myoblast and fibroblast cells seeded onto the scaffolds in vitro showed appropriate cell proliferation and distribution. Human mesenchymal stem cells (hMSCs) differentiated to smooth muscle lineage on the microfibrous scaffolds in the absence of soluble induction factors, showing cellular shape modulation and scaffold elasticity may encourage the myogenic differentiation of stem cells.

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.

Fabrication of polyurethane and polyurethane based composite fibres by the electrospinning technique for soft tissue engineering of cardiovascular system.

PubMed

Kucinska-Lipka, J; Gubanska, I; Janik, H; Sienkiewicz, M

2015-01-01

Electrospinning is a unique technique, which provides forming of polymeric scaffolds for soft tissue engineering, which include tissue scaffolds for soft tissues of the cardiovascular system. Such artificial soft tissues of the cardiovascular system may possess mechanical properties comparable to native vascular tissues. Electrospinning technique gives the opportunity to form fibres with nm- to μm-scale in diameter. The arrangement of obtained fibres and their surface determine the biocompatibility of the scaffolds. Polyurethanes (PUs) are being commonly used as a prosthesis of cardiovascular soft tissues due to their excellent biocompatibility, non-toxicity, elasticity and mechanical properties. PUs also possess fine spinning properties. The combination of a variety of PU properties with an electrospinning technique, conducted at the well tailored conditions, gives unlimited possibilities of forming novel polyurethane materials suitable for soft tissue scaffolds applied in cardiovascular tissue engineering. This paper can help researches to gain more widespread and deeper understanding of designing electrospinable PU materials, which may be used as cardiovascular soft tissue scaffolds. In this paper we focus on reagents used in PU synthesis designed to increase PU biocompatibility (polyols) and biodegradability (isocyanates). We also describe suggested surface modifications of electrospun PUs, and the direct influence of surface wettability on providing enhanced biocompatibility of scaffolds. We indicate a great influence of electrospinning parameters (voltage, flow rate, working distance) and used solvents (mostly DMF, THF and HFIP) on fibre alignment and diameter - what impacts the biocompatibility and hemocompatibility of such electrospun PU scaffolds. Moreover, we present PU modifications with natural polymers with novel approach applied in electrospinning of PU scaffolds. This work may contribute with further developing of novel electrospun PUs, which may be applied as soft tissue scaffolds of the cardiovascular system. Copyright © 2014. Published by Elsevier B.V.

Synthetic biodegradable functional polymers for tissue engineering: a brief review.

PubMed

BaoLin, Guo; Ma, Peter X

2014-04-01

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

Water-based polyurethane 3D printed scaffolds with controlled release function for customized cartilage tissue engineering.

PubMed

Hung, Kun-Che; Tseng, Ching-Shiow; Dai, Lien-Guo; Hsu, Shan-hui

2016-03-01

Conventional 3D printing may not readily incorporate bioactive ingredients for controlled release because the process often involves the use of heat, organic solvent, or crosslinkers that reduce the bioactivity of the ingredients. Water-based 3D printing materials with controlled bioactivity for customized cartilage tissue engineering is developed in this study. The printing ink contains the water dispersion of synthetic biodegradable polyurethane (PU) elastic nanoparticles, hyaluronan, and bioactive ingredients TGFβ3 or a small molecule drug Y27632 to replace TGFβ3. Compliant scaffolds are printed from the ink at low temperature. These scaffolds promote the self-aggregation of mesenchymal stem cells (MSCs) and, with timely release of the bioactive ingredients, induce the chondrogenic differentiation of MSCs and produce matrix for cartilage repair. Moreover, the growth factor-free controlled release design may prevent cartilage hypertrophy. Rabbit knee implantation supports the potential of the novel 3D printing scaffolds in cartilage regeneration. We consider that the 3D printing composite scaffolds with controlled release bioactivity may have potential in customized tissue engineering. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Four Scaffolding Modules for Collaborative Problem-Based Learning through the Computer Network on Moodle LMS for the Computer Programming Course

ERIC Educational Resources Information Center

Tiantong, Monchai; Teemuangsai, Sanit

2013-01-01

Scaffolding is a learning approach designed to promote a deeper understanding, it is the support given during the learning process which is tailored to the needs of the student with the intention of helping the student achieve the learning goals, including resources, a compelling task, templates and guides, and guidance on the development of…

Peptide Probe for Crystalline Hydroxyapatite: In Situ Detection of Biomineralization

NASA Astrophysics Data System (ADS)

Cicerone, Marcus; Becker, Matthew; Simon, Carl; Chatterjee, Kaushik

2009-03-01

While cells template mineralization in vitro and in vivo, specific detection strategies that impart chemical and structural information on this process have proven elusive. Recently we have developed an in situ based peptide probe via phage display methods that is specific to crystalline hydroxyapatite (HA). We are using this in fluorescence based assays to characterize mineralization. One application being explored is the screening of tissue engineering scaffolds for their ability to support osteogenesis. Specifically, osteoblasts are being cultured in hydrogel scaffolds possessing property gradients to provide a test bed for the HA peptide probe. Hydrogel properties that support osteogenesis and HA deposition will be identified using the probe to demonstrate its utility in optimizing design of tissue scaffolds.

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.

Inter-level Scaffolding and Sequences of Representational Activities in Teaching a Chemical System with Graphical Simulations

NASA Astrophysics Data System (ADS)

Li, Na; Black, John B.

2016-10-01

Chemistry knowledge can be represented at macro-, micro- and symbolic levels, and learning a chemistry topic requires students to engage in multiple representational activities. This study focused on scaffolding for inter-level connection-making in learning chemistry knowledge with graphical simulations. We also tested whether different sequences of representational activities produced different student learning outcomes in learning a chemistry topic. A sample of 129 seventh graders participated in this study. In a simulation-based environment, participants completed three representational activities to learn several ideal gas law concepts. We conducted a 2 × 3 factorial design experiment. We compared two scaffolding conditions: (1) the inter- level scaffolding condition in which participants received inter-level questions and experienced the dynamic link function in the simulation-based environment and (2) the intra- level scaffolding condition in which participants received intra-level questions and did not experience the dynamic link function. We also compared three different sequences of representational activities: macro-symbolic-micro, micro-symbolic-macro and symbolic-micro-macro. For the scaffolding variable, we found that the inter- level scaffolding condition produced significantly better performance in both knowledge comprehension and application, compared to the intra- level scaffolding condition. For the sequence variable, we found that the macro-symbolic-micro sequence produced significantly better knowledge comprehension performance than the other two sequences; however, it did not benefit knowledge application performance. There was a trend that the treatment group who experienced inter- level scaffolding and the micro-symbolic-macro sequence achieved the best knowledge application performance.

Artificial enzymes with protein scaffolds: structural design and modification.

PubMed

Matsuo, Takashi; Hirota, Shun

2014-10-15

Recent development in biochemical experiment techniques and bioinformatics has enabled us to create a variety of artificial biocatalysts with protein scaffolds (namely 'artificial enzymes'). The construction methods of these catalysts include genetic mutation, chemical modification using synthetic molecules and/or a combination of these methods. Designed evolution strategy based on the structural information of host proteins has become more and more popular as an effective approach to construct artificial protein-based biocatalysts with desired reactivities. From the viewpoint of application of artificial enzymes for organic synthesis, recently constructed artificial enzymes mediating oxidation, reduction and C-C bond formation/cleavage are introduced in this review article. Copyright © 2014 Elsevier Ltd. All rights reserved.

Post Processing and Biological Evaluation of the Titanium Scaffolds for Bone Tissue Engineering.

PubMed

Wysocki, Bartłomiej; Idaszek, Joanna; Szlązak, Karol; Strzelczyk, Karolina; Brynk, Tomasz; Kurzydłowski, Krzysztof J; Święszkowski, Wojciech

2016-03-15

Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate the effect of the chemical polishing with various acid baths on novel scaffolds' morphology, porosity and mechanical properties. In the first stage, Magics software (Materialise NV, Leuven, Belgium) was used to design a porous scaffolds with pore size equal to (A) 200 µm, (B) 500 µm and (C) 200 + 500 µm, and diamond cell structure. The scaffolds were fabricated from commercially pure titanium powder (CP Ti) using a SLM50 3D printing machine (Realizer GmbH, Borchen, Germany). The selective laser melting (SLM) process was optimized and the laser beam energy density in range of 91-151 J/mm³ was applied to receive 3D structures with fully dense struts. To remove not fully melted titanium particles the scaffolds were chemically polished using various HF and HF-HNO₃ acid solutions. Based on scaffolds mass loss and scanning electron (SEM) observations, baths which provided most uniform surface cleaning were proposed for each porosity. The pore and strut size after chemical treatments was calculated based on the micro-computed tomography (µ-CT) and SEM images. The mechanical tests showed that the treated scaffolds had Young's modulus close to that of compact bone. Additionally, the effect of pore size of chemically polished scaffolds on cell retention, proliferation and differentiation was studied using human mesenchymal stem cells. Small pores yielded higher cell retention within the scaffolds, which then affected their growth. This shows that in vitro cell performance can be controlled to certain extent by varying pore sizes.

Geometry Design Optimization of Functionally Graded Scaffolds for Bone Tissue Engineering: A Mechanobiological Approach.

PubMed

Boccaccio, Antonio; Uva, Antonio Emmanuele; Fiorentino, Michele; Mori, Giorgio; Monno, Giuseppe

2016-01-01

Functionally Graded Scaffolds (FGSs) are porous biomaterials where porosity changes in space with a specific gradient. In spite of their wide use in bone tissue engineering, possible models that relate the scaffold gradient to the mechanical and biological requirements for the regeneration of the bony tissue are currently missing. In this study we attempt to bridge the gap by developing a mechanobiology-based optimization algorithm aimed to determine the optimal graded porosity distribution in FGSs. The algorithm combines the parametric finite element model of a FGS, a computational mechano-regulation model and a numerical optimization routine. For assigned boundary and loading conditions, the algorithm builds iteratively different scaffold geometry configurations with different porosity distributions until the best microstructure geometry is reached, i.e. the geometry that allows the amount of bone formation to be maximized. We tested different porosity distribution laws, loading conditions and scaffold Young's modulus values. For each combination of these variables, the explicit equation of the porosity distribution law-i.e the law that describes the pore dimensions in function of the spatial coordinates-was determined that allows the highest amounts of bone to be generated. The results show that the loading conditions affect significantly the optimal porosity distribution. For a pure compression loading, it was found that the pore dimensions are almost constant throughout the entire scaffold and using a FGS allows the formation of amounts of bone slightly larger than those obtainable with a homogeneous porosity scaffold. For a pure shear loading, instead, FGSs allow to significantly increase the bone formation compared to a homogeneous porosity scaffolds. Although experimental data is still necessary to properly relate the mechanical/biological environment to the scaffold microstructure, this model represents an important step towards optimizing geometry of functionally graded scaffolds based on mechanobiological criteria.

Low-temperature deposition manufacturing: A novel and promising rapid prototyping technology for the fabrication of tissue-engineered scaffold.

PubMed

Liu, Wei; Wang, Daming; Huang, Jianghong; Wei, You; Xiong, Jianyi; Zhu, Weimin; Duan, Li; Chen, Jielin; Sun, Rong; Wang, Daping

2017-01-01

Developed in recent years, low-temperature deposition manufacturing (LDM) represents one of the most promising rapid prototyping technologies. It is not only based on rapid deposition manufacturing process but also combined with phase separation process. Besides the controlled macropore size, tissue-engineered scaffold fabricated by LDM has inter-connected micropores in the deposited lines. More importantly, it is a green manufacturing process that involves non-heating liquefying of materials. It has been employed to fabricate tissue-engineered scaffolds for bone, cartilage, blood vessel and nerve tissue regenerations. It is a promising technology in the fabrication of tissue-engineered scaffold similar to ideal scaffold and the design of complex organs. In the current paper, this novel LDM technology is introduced, and its control parameters, biomedical applications and challenges are included and discussed as well. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Designing Uniquely Addressable Bio-orthogonal Synthetic Scaffolds for DNA and RNA Origami.

PubMed

Kozyra, Jerzy; Ceccarelli, Alessandro; Torelli, Emanuela; Lopiccolo, Annunziata; Gu, Jing-Ying; Fellermann, Harold; Stimming, Ulrich; Krasnogor, Natalio

2017-07-21

Nanotechnology and synthetic biology are rapidly converging, with DNA origami being one of the leading bridging technologies. DNA origami was shown to work well in a wide array of biotic environments. However, the large majority of extant DNA origami scaffolds utilize bacteriophages or plasmid sequences thus severely limiting its future applicability as a bio-orthogonal nanotechnology platform. In this paper we present the design of biologically inert (i.e., "bio-orthogonal") origami scaffolds. The synthetic scaffolds have the additional advantage of being uniquely addressable (unlike biologically derived ones) and hence are better optimized for high-yield folding. We demonstrate our fully synthetic scaffold design with both DNA and RNA origamis and describe a protocol to produce these bio-orthogonal and uniquely addressable origami scaffolds.

Construction of bionic tissue engineering cartilage scaffold based on three-dimensional printing and oriented frozen technology.

PubMed

Xu, Yuanyuan; Guo, Xiao; Yang, Shuaitao; Li, Long; Zhang, Peng; Sun, Wei; Liu, Changyong; Mi, Shengli

2018-06-01

Articular cartilage (AC) has gradient features in both mechanics and histology as well as a poor regeneration ability. The repair of AC poses difficulties in both research and the clinic. In this paper, a gradient scaffold based on poly(lactic-co-glycolic acid) (PLGA)-extracellular matrix was proposed. Cartilage scaffolds with a three-layer gradient structure were fabricated by PLGA through three-dimensional printing, and the microstructure orientation and pore fabrication were made by decellularized extracellular matrix injection and directional freezing. The manufactured scaffold has a mechanical strength close to that of real cartilage. A quantitative optimization of the Young's modulus and shear modulus was achieved by material mechanics formulas, which achieved a more accurate mechanical bionic and a more stable interface performance because of the one-time molding process. At the same time, the scaffolds have a bionic and gradient microstructure orientation and pore size, and the stratification ratio can be quantitatively optimized by design of the freeze box and temperature simulation. In general, this paper provides a method to optimize AC scaffolds by both mechanics and histology as well as a bionic multimaterial scaffold. This paper is of significance for cell culture and clinical transplantation experiments. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1664-1676, 2018. © 2018 Wiley Periodicals, Inc.

Microfluidic-based screening of resveratrol and drug-loading PLA/Gelatine nano-scaffold for the repair of cartilage defect.

PubMed

Ming, Li; Zhipeng, Yuan; Fei, Yu; Feng, Rao; Jian, Weng; Baoguo, Jiang; Yongqiang, Wen; Peixun, Zhang

2018-03-26

Cartilage defect is common in clinical but notoriously difficult to treat for low regenerative and migratory capacity of chondrocytes. Biodegradable tissue engineering nano-scaffold with a lot of advantages has been the direction of material to repair cartilage defect in recent years. The objective of our study is to establish a biodegradable drug-loading synthetic polymer (PLA) and biopolymer (Gelatine) composite 3D nano-scaffold to support the treatment of cartilage defect. We designed a microfluidic chip-based drug-screening device to select the optimum concentration of resveratrol, which has strong protective capability for chondrocyte. Then biodegradable resveratrol-loading PLA/Gelatine 3D nano-scaffolds were fabricated and used to repair the cartilage defects. As a result, we successfully cultured primary chondrocytes and screened the appropriate concentrations of resveratrol by the microfluidic device. We also smoothly obtained superior biodegradable resveratrol-loading PLA/Gelatine 3D nano-scaffolds and compared the properties and therapeutic effects of cartilage defect in rats. In summary, our microfluidic device is a simple but efficient platform for drug screening and resveratrol-loading PLA/Gelatine 3D nano-scaffolds could greatly promote the cartilage formation. It would be possible for materials and medical researchers to explore individualized pharmacotherapy and drug-loading synthetic polymer and biopolymer composite tissue engineering scaffolds for the repair of cartilage defect in future.

Rational Design of an Ultrasensitive Quorum-Sensing Switch.

PubMed

Zeng, Weiqian; Du, Pei; Lou, Qiuli; Wu, Lili; Zhang, Haoqian M; Lou, Chunbo; Wang, Hongli; Ouyang, Qi

2017-08-18

One of the purposes of synthetic biology is to develop rational methods that accelerate the design of genetic circuits, saving time and effort spent on experiments and providing reliably predictable circuit performance. We applied a reverse engineering approach to design an ultrasensitive transcriptional quorum-sensing switch. We want to explore how systems biology can guide synthetic biology in the choice of specific DNA sequences and their regulatory relations to achieve a targeted function. The workflow comprises network enumeration that achieves the target function robustly, experimental restriction of the obtained candidate networks, global parameter optimization via mathematical analysis, selection and engineering of parts based on these calculations, and finally, circuit construction based on the principles of standardization and modularization. The performance of realized quorum-sensing switches was in good qualitative agreement with the computational predictions. This study provides practical principles for the rational design of genetic circuits with targeted functions.

Selected approaches for rational drug design and high throughput screening to identify anti-cancer molecules.

PubMed

Hedvat, Michael; Emdad, Luni; Das, Swadesh K; Kim, Keetae; Dasgupta, Santanu; Thomas, Shibu; Hu, Bin; Zhu, Shan; Dash, Rupesh; Quinn, Bridget A; Oyesanya, Regina A; Kegelman, Timothy P; Sokhi, Upneet K; Sarkar, Siddik; Erdogan, Eda; Menezes, Mitchell E; Bhoopathi, Praveen; Wang, Xiang-Yang; Pomper, Martin G; Wei, Jun; Wu, Bainan; Stebbins, John L; Diaz, Paul W; Reed, John C; Pellecchia, Maurizio; Sarkar, Devanand; Fisher, Paul B

2012-11-01

Structure-based modeling combined with rational drug design, and high throughput screening approaches offer significant potential for identifying and developing lead compounds with therapeutic potential. The present review focuses on these two approaches using explicit examples based on specific derivatives of Gossypol generated through rational design and applications of a cancer-specificpromoter derived from Progression Elevated Gene-3. The Gossypol derivative Sabutoclax (BI-97C1) displays potent anti-tumor activity against a diverse spectrum of human tumors. The model of the docked structure of Gossypol bound to Bcl-XL provided a virtual structure-activity-relationship where appropriate modifications were predicted on a rational basis. These structure-based studies led to the isolation of Sabutoclax, an optically pure isomer of Apogossypol displaying superior efficacy and reduced toxicity. These studies illustrate the power of combining structure-based modeling with rational design to predict appropriate derivatives of lead compounds to be empirically tested and evaluated for bioactivity. Another approach to cancer drug discovery utilizes a cancer-specific promoter as readouts of the transformed state. The promoter region of Progression Elevated Gene-3 is such a promoter with cancer-specific activity. The specificity of this promoter has been exploited as a means of constructing cancer terminator viruses that selectively kill cancer cells and as a systemic imaging modality that specifically visualizes in vivo cancer growth with no background from normal tissues. Screening of small molecule inhibitors that suppress the Progression Elevated Gene-3-promoter may provide relevant lead compounds for cancer therapy that can be combined with further structure-based approaches leading to the development of novel compounds for cancer therapy.

Synthetic beta-solenoid proteins with the fragment-free computational design of a beta-hairpin extension

PubMed Central

MacDonald, James T.; Kabasakal, Burak V.; Godding, David; Kraatz, Sebastian; Henderson, Louie; Barber, James; Freemont, Paul S.; Murray, James W.

2016-01-01

The ability to design and construct structures with atomic level precision is one of the key goals of nanotechnology. Proteins offer an attractive target for atomic design because they can be synthesized chemically or biologically and can self-assemble. However, the generalized protein folding and design problem is unsolved. One approach to simplifying the problem is to use a repetitive protein as a scaffold. Repeat proteins are intrinsically modular, and their folding and structures are better understood than large globular domains. Here, we have developed a class of synthetic repeat proteins based on the pentapeptide repeat family of beta-solenoid proteins. We have constructed length variants of the basic scaffold and computationally designed de novo loops projecting from the scaffold core. The experimentally solved 3.56-Å resolution crystal structure of one designed loop matches closely the designed hairpin structure, showing the computational design of a backbone extension onto a synthetic protein core without the use of backbone fragments from known structures. Two other loop designs were not clearly resolved in the crystal structures, and one loop appeared to be in an incorrect conformation. We have also shown that the repeat unit can accommodate whole-domain insertions by inserting a domain into one of the designed loops. PMID:27573845

The Effectiveness of Scaffolding Design in Training Writing Skills Physics Teaching Materials

ERIC Educational Resources Information Center

Sinaga, Parlindungan; Suhandi, Andi; Liliasari

2015-01-01

Result of field studies showed low writing skill of teachers in teaching material. The root of the problem lies in their inability on translating description of teaching material into writing. This research focused on the effectiveness of scaffolding design. The scaffolding design was tested in the selected topics of physics courses for…

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.

Shaping the micromechanical behavior of multi-phase composites for bone tissue engineering.

PubMed

Ranganathan, Shivakumar I; Yoon, Diana M; Henslee, Allan M; Nair, Manitha B; Smid, Christine; Kasper, F Kurtis; Tasciotti, Ennio; Mikos, Antonios G; Decuzzi, Paolo; Ferrari, Mauro

2010-09-01

Mechanical stiffness is a fundamental parameter in the rational design of composites for bone tissue engineering in that it affects both the mechanical stability and the osteo-regeneration process at the fracture site. A mathematical model is presented for predicting the effective Young's modulus (E) and shear modulus (G) of a multi-phase biocomposite as a function of the geometry, material properties and volume concentration of each individual phase. It is demonstrated that the shape of the reinforcing particles may dramatically affect the mechanical stiffness: E and G can be maximized by employing particles with large geometrical anisotropy, such as thin platelet-like or long fibrillar-like particles. For a porous poly(propylene fumarate) (60% porosity) scaffold reinforced with silicon particles (10% volume concentration) the Young's (shear) modulus could be increased by more than 10 times by just using thin platelet-like as opposed to classical spherical particles, achieving an effective modulus E approximately 8 GPa (G approximately 3.5 GPa). The mathematical model proposed provides results in good agreement with several experimental test cases and could help in identifying the proper formulation of bone scaffolds, reducing the development time and guiding the experimental testing. 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Development of collagen peptide-based biomaterials for tissue engineering applications

NASA Astrophysics Data System (ADS)

Hernandez Gordillo, Victor

The transition from in vitro to in vivo use of stem cells in regenerative medicine requires biomaterial scaffolds that can maintain stem cell viability and at the same time allow cell differentiation. We have previously reported the design of a collagen mimetic peptide (CMP) that assembles into a mesh-like three-dimensional (3D) structure upon the addition of metal ions and its potential for the culture of human cells. The addition of a chelating solution, such as EDTA, results in disassembly of the 3D structure, demonstrating the flexibility in the assembly/disassembly process. In the second chapter of this dissertation, we report the design of CMPs that can be functionalized with His-tagged cargoes within the 3D scaffold, via metal coordination. We show that the addition of GFP-His8 and human epidermal growth factor (hEGF-His6) has minimal effect in the assembly process. Additionally, we show that the bound hEGF-His6 can be released gradually in vitro for 5 days and induces cell proliferation in an EGF-dependent cell line. Furthermore, we functionalized the CMPs with the cell adhesion sequence (RGDS) to promote cell differentiation of two human non-tumorigenic cells lines, MCF10A and 3522-S1. In the third chapter, we evaluated the possibility of using the collagen mimetic-peptide-based (CMP) scaffolds for cell encapsulation and differentiation of human mesenchymal stem cells (hMSC). We show that hMSC encapsulated within the CMP scaffold are viable for up to 24 days post encapsulation. Moreover, hMSC at days 1, 4 and 8 days after encapsulation can be recovered from the scaffold and retain their stemness properties when analyzed for in vitro differentiation. We also demonstrate by real time PCR (RT-PCR) that genes important for osteogenic and chondrogenic differentiation are over-expressed in the absence of stimulating factors when the cells are encapsulated in the 3D scaffold at 8 and 24 days post encapsulation. Lastly, the incorporation of the cell adhesion sequence (RGDS) was shown to influence the scaffold-cell interaction. hMSCs within these RGDS-modified scaffold adopted spindle shape morphology and a complex cell organization at the outermost layer of the scaffold. In contrast, in the scaffold lacking the RGDS sequence hSMCs formed cell aggregates.

Biological properties of solid free form designed ceramic scaffolds with BMP-2: in vitro and in vivo evaluation.

PubMed

Abarrategi, Ander; Moreno-Vicente, Carolina; Martínez-Vázquez, Francisco Javier; Civantos, Ana; Ramos, Viviana; Sanz-Casado, José Vicente; Martínez-Corriá, Ramón; Perera, Fidel Hugo; Mulero, Francisca; Miranda, Pedro; López-Lacomba, José Luís

2012-01-01

Porous ceramic scaffolds are widely studied in the tissue engineering field due to their potential in medical applications as bone substitutes or as bone-filling materials. Solid free form (SFF) fabrication methods allow fabrication of ceramic scaffolds with fully controlled pore architecture, which opens new perspectives in bone tissue regeneration materials. However, little experimentation has been performed about real biological properties and possible applications of SFF designed 3D ceramic scaffolds. Thus, here the biological properties of a specific SFF scaffold are evaluated first, both in vitro and in vivo, and later scaffolds are also implanted in pig maxillary defect, which is a model for a possible application in maxillofacial surgery. In vitro results show good biocompatibility of the scaffolds, promoting cell ingrowth. In vivo results indicate that material on its own conducts surrounding tissue and allow cell ingrowth, thanks to the designed pore size. Additional osteoinductive properties were obtained with BMP-2, which was loaded on scaffolds, and optimal bone formation was observed in pig implantation model. Collectively, data show that SFF scaffolds have real application possibilities for bone tissue engineering purposes, with the main advantage of being fully customizable 3D structures.

Biological Properties of Solid Free Form Designed Ceramic Scaffolds with BMP-2: In Vitro and In Vivo Evaluation

PubMed Central

Abarrategi, Ander; Moreno-Vicente, Carolina; Martínez-Vázquez, Francisco Javier; Civantos, Ana; Ramos, Viviana; Sanz-Casado, José Vicente; Martínez-Corriá, Ramón; Perera, Fidel Hugo; Mulero, Francisca; Miranda, Pedro; López-Lacomba, José Luís

2012-01-01

Porous ceramic scaffolds are widely studied in the tissue engineering field due to their potential in medical applications as bone substitutes or as bone-filling materials. Solid free form (SFF) fabrication methods allow fabrication of ceramic scaffolds with fully controlled pore architecture, which opens new perspectives in bone tissue regeneration materials. However, little experimentation has been performed about real biological properties and possible applications of SFF designed 3D ceramic scaffolds. Thus, here the biological properties of a specific SFF scaffold are evaluated first, both in vitro and in vivo, and later scaffolds are also implanted in pig maxillary defect, which is a model for a possible application in maxillofacial surgery. In vitro results show good biocompatibility of the scaffolds, promoting cell ingrowth. In vivo results indicate that material on its own conducts surrounding tissue and allow cell ingrowth, thanks to the designed pore size. Additional osteoinductive properties were obtained with BMP-2, which was loaded on scaffolds, and optimal bone formation was observed in pig implantation model. Collectively, data show that SFF scaffolds have real application possibilities for bone tissue engineering purposes, with the main advantage of being fully customizable 3D structures. PMID:22470527

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

DOE PAGES

Stewart, Jaimie Marie; Subramanian, Hari K. K.; Franco, Elisa

2017-02-16

Rational design of nucleic acidmolecules yields selfassembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. We demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 m in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowlymore » annealed, and a one-pot transcription and anneal procedure. We then identify the tile nick position as a structural requirement for lattice formation. These results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components.« less

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

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

Stewart, Jaimie Marie; Subramanian, Hari K. K.; Franco, Elisa

Rational design of nucleic acidmolecules yields selfassembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. We demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 m in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowlymore » annealed, and a one-pot transcription and anneal procedure. We then identify the tile nick position as a structural requirement for lattice formation. These results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components.« less

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

PubMed Central

Stewart, Jaimie Marie; Subramanian, Hari K. K.

2017-01-01

Abstract Rational design of nucleic acid molecules yields self-assembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. Here we demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 μm in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowly annealed, and a one-pot transcription and anneal procedure. We identify the tile nick position as a structural requirement for lattice formation. Our results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components. PMID:28204562

Structural insights into FRS2α PTB domain recognition by neurotrophin receptor TrkB.

PubMed

Zeng, Lei; Kuti, Miklos; Mujtaba, Shiraz; Zhou, Ming-Ming

2014-07-01

The fibroblast growth factor receptor (FGFR) substrate 2 (FRS2) family proteins function as scaffolding adapters for receptor tyrosine kinases (RTKs). The FRS2α proteins interact with RTKs through the phosphotyrosine-binding (PTB) domain and transfer signals from the activated receptors to downstream effector proteins. Here, we report the nuclear magnetic resonance structure of the FRS2α PTB domain bound to phosphorylated TrkB. The structure reveals that the FRS2α-PTB domain is comprised of two distinct but adjacent pockets for its mutually exclusive interaction with either nonphosphorylated juxtamembrane region of the FGFR, or tyrosine phosphorylated peptides TrkA and TrkB. The new structural insights suggest rational design of selective small molecules through targeting of the two conjunct pockets in the FRS2α PTB domain. © 2014 Wiley Periodicals, Inc.

How to Crack the Sugar Code.

PubMed

Gabius, H-J

2017-01-01

The known ubiquitous presence of glycans fulfils an essential prerequisite for fundamental roles in cell sociology. Since carbohydrates are chemically predestined to form biochemical messages of a maximum of structural diversity in a minimum of space, coding of biological information by sugars is the reason for the broad occurrence of cellular glycoconjugates. Their glycans originate from sophisticated enzymatic assembly and dynamically adaptable remodelling. These signals are read and translated into effects by receptors (lectins). The functional pairing between lectins and their counterreceptor(s) is highly specific, often orchestrated by intimate co-regulation of the receptor, the cognate glycan and the bioactive scaffold (e.g., an integrin). Bottom-up approaches, teaming up synthetic and supramolecular chemistry to prepare fully programmable nanoparticles as binding partners with systematic network analysis of lectins and rational design of variants, enable us to delineate the rules of the sugar code.

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.

Rationally designed mineralization for selective recovery of the rare earth elements

NASA Astrophysics Data System (ADS)

Hatanaka, Takaaki; Matsugami, Akimasa; Nonaka, Takamasa; Takagi, Hideki; Hayashi, Fumiaki; Tani, Takao; Ishida, Nobuhiro

2017-05-01

The increasing demand for rare earth (RE) elements in advanced materials for permanent magnets, rechargeable batteries, catalysts and lamp phosphors necessitates environmentally friendly approaches for their recovery and separation. Here, we propose a mineralization concept for direct extraction of RE ions with Lamp (lanthanide ion mineralization peptide). In aqueous solution containing various metal ions, Lamp promotes the generation of RE hydroxide species with which it binds to form hydrophobic complexes that accumulate spontaneously as insoluble precipitates, even under physiological conditions (pH ~6.0). This concept for stabilization of an insoluble lanthanide hydroxide complex with an artificial peptide also works in combination with stable scaffolds like synthetic macromolecules and proteins. Our strategy opens the possibility for selective separation of target metal elements from seawater and industrial wastewater under mild conditions without additional energy input.

Rationally designed mineralization for selective recovery of the rare earth elements

PubMed Central

Hatanaka, Takaaki; Matsugami, Akimasa; Nonaka, Takamasa; Takagi, Hideki; Hayashi, Fumiaki; Tani, Takao; Ishida, Nobuhiro

2017-01-01

The increasing demand for rare earth (RE) elements in advanced materials for permanent magnets, rechargeable batteries, catalysts and lamp phosphors necessitates environmentally friendly approaches for their recovery and separation. Here, we propose a mineralization concept for direct extraction of RE ions with Lamp (lanthanide ion mineralization peptide). In aqueous solution containing various metal ions, Lamp promotes the generation of RE hydroxide species with which it binds to form hydrophobic complexes that accumulate spontaneously as insoluble precipitates, even under physiological conditions (pH ∼6.0). This concept for stabilization of an insoluble lanthanide hydroxide complex with an artificial peptide also works in combination with stable scaffolds like synthetic macromolecules and proteins. Our strategy opens the possibility for selective separation of target metal elements from seawater and industrial wastewater under mild conditions without additional energy input. PMID:28548098

Rationally designed mineralization for selective recovery of the rare earth elements.

PubMed

Hatanaka, Takaaki; Matsugami, Akimasa; Nonaka, Takamasa; Takagi, Hideki; Hayashi, Fumiaki; Tani, Takao; Ishida, Nobuhiro

2017-05-26

The increasing demand for rare earth (RE) elements in advanced materials for permanent magnets, rechargeable batteries, catalysts and lamp phosphors necessitates environmentally friendly approaches for their recovery and separation. Here, we propose a mineralization concept for direct extraction of RE ions with Lamp (lanthanide ion mineralization peptide). In aqueous solution containing various metal ions, Lamp promotes the generation of RE hydroxide species with which it binds to form hydrophobic complexes that accumulate spontaneously as insoluble precipitates, even under physiological conditions (pH ∼6.0). This concept for stabilization of an insoluble lanthanide hydroxide complex with an artificial peptide also works in combination with stable scaffolds like synthetic macromolecules and proteins. Our strategy opens the possibility for selective separation of target metal elements from seawater and industrial wastewater under mild conditions without additional energy input.

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…

Direct Bio-printing with Heterogeneous Topology Design.

PubMed

Ahsan, Amm Nazmul; Xie, Ruinan; Khoda, Bashir

2017-01-01

Bio-additive manufacturing is a promising tool to fabricate porous scaffold structures for expediting the tissue regeneration processes. Unlike the most traditional bulk material objects, the microstructures of tissue and organs are mostly highly anisotropic, heterogeneous, and porous in nature. However, modelling the internal heterogeneity of tissues/organs structures in the traditional CAD environment is difficult and oftentimes inaccurate. Besides, the de facto STL conversion of bio-models introduces loss of information and piles up more errors in each subsequent step (build orientation, slicing, tool-path planning) of the bio-printing process plan. We are proposing a topology based scaffold design methodology to accurately represent the heterogeneous internal architecture of tissues/organs. An image analysis technique is used that digitizes the topology information contained in medical images of tissues/organs. A weighted topology reconstruction algorithm is implemented to represent the heterogeneity with parametric functions. The parametric functions are then used to map the spatial material distribution. The generated information is directly transferred to the 3D bio-printer and heterogeneous porous tissue scaffold structure is manufactured without STL file. The proposed methodology is implemented to verify the effectiveness of the approach and the designed example structure is bio-fabricated with a deposition based bio-additive manufacturing system.

Unique catalytic activities and scaffolding of p21 activated kinase-1 in cardiovascular signaling.

PubMed

Ke, Yunbo; Lei, Ming; Wang, Xin; Solaro, R John

2013-09-27

P21 activated kinase-1 (Pak1) has diverse functions in mammalian cells. Although a large number of phosphoproteins have been designated as Pak1 substrates from in vitro studies, emerging evidence has indicated that Pak1 may function as a signaling molecule through a unique molecular mechanism - scaffolding. By scaffolding, Pak1 delivers signals through an auto-phosphorylation-induced conformational change without transfer of a phosphate group to its immediate downstream effector(s). Here we review evidence for this regulatory mechanism based on structural and functional studies of Pak1 in different cell types and research models as well as in vitro biochemical assays. We also discuss the implications of Pak1 scaffolding in disease-related signaling processes and the potential in cardiovascular drug development.

A Longitudinal Examination of Middle School Science Learners' Use of Scaffolding In and Around a Dynamic Modeling Tool

NASA Astrophysics Data System (ADS)

Fretz, Eric Bruce

Scaffolding is a term rooted in multiple research communities over decades of development. Customized, contingent support can be provided to learners to enable performances beyond what they can do alone. This dissertation seeks to examine how effectively scaffolds designed to promote articulation (written expressions of learner understanding) actually work, and if this effectiveness and/or the quality of the resulting models changes over time. It longitudinally examines the use of scaffolds designed into a dynamic modeling tool, as it is used by middle school science learners to create, test, and revise models of complex science phenomena like stream ecosystems. This dissertation also reviews the origins of the scaffolding construct, and summarizes conceptions of scaffolding from various lines of research. Scaffolding can be provided by both human and non-human agents, such as computers, which require specialized interface design to ensure maximum effectiveness. In the study, learners created models in four curriculum units over the seventh and eighth grade school years. Additionally, this dissertation examines the nature of the discussion learners have while using these scaffolds and the frequency and types of interpersonal scaffolds employed during the creation of models. Model quality is also examined using a rubric developed through review of prior research on assessing models and concept maps. Learner pairs' model creation sessions on a computer are captured with screen video and learner audio, and then distilled to transcripts for subsequent coding and analysis, supported by qualitative analysis software. Articulation scaffolds were found to succeed in promoting articulations and the quality of those articulations improved over time. Learner dialog associated with these written articulations is of reasonable quality but did not improve over time. Quality of model artifacts did improve over time. The overall use of scaffolding by each learner pair was contrasted with that pairs model quality, but no relationship was found. Software design and classroom implementation implications of these findings are discussed. The frequency of interpersonal scaffolding provided by teachers highlights the need to consider scaffolding holistically and synergistically, with design decisions for software tools made in light of careful analysis as to what human and non-human agents can and should each provide.

Feasibility of autologous bone marrow mesenchymal stem cell-derived extracellular matrix scaffold for cartilage tissue engineering.

PubMed

Tang, Cheng; Xu, Yan; Jin, Chengzhe; Min, Byoung-Hyun; Li, Zhiyong; Pei, Xuan; Wang, Liming

2013-12-01

Extracellular matrix (ECM) materials are widely used in cartilage tissue engineering. However, the current ECM materials are unsatisfactory for clinical practice as most of them are derived from allogenous or xenogenous tissue. This study was designed to develop a novel autologous ECM scaffold for cartilage tissue engineering. The autologous bone marrow mesenchymal stem cell-derived ECM (aBMSC-dECM) membrane was collected and fabricated into a three-dimensional porous scaffold via cross-linking and freeze-drying techniques. Articular chondrocytes were seeded into the aBMSC-dECM scaffold and atelocollagen scaffold, respectively. An in vitro culture and an in vivo implantation in nude mice model were performed to evaluate the influence on engineered cartilage. The current results showed that the aBMSC-dECM scaffold had a good microstructure and biocompatibility. After 4 weeks in vitro culture, the engineered cartilage in the aBMSC-dECM scaffold group formed thicker cartilage tissue with more homogeneous structure and higher expressions of cartilaginous gene and protein compared with the atelocollagen scaffold group. Furthermore, the engineered cartilage based on the aBMSC-dECM scaffold showed better cartilage formation in terms of volume and homogeneity, cartilage matrix content, and compressive modulus after 3 weeks in vivo implantation. These results indicated that the aBMSC-dECM scaffold could be a successful novel candidate scaffold for cartilage tissue engineering. © 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.

Scaffolding the design of accessible eLearning content: a user-centered approach and cognitive perspective.

PubMed

Catarci, Tiziana; De Giovanni, Loredana; Gabrielli, Silvia; Kimani, Stephen; Mirabella, Valeria

2008-08-01

There exist various guidelines for facilitating the design, preparation, and deployment of accessible eLearning applications and contents. However, such guidelines prevalently address accessibility in a rather technical sense, without giving sufficient consideration to the cognitive aspects and issues related to the use of eLearning materials by learners with disabilities. In this paper we describe how a user-centered design process was applied to develop a method and set of guidelines for didactical experts to scaffold their creation of accessible eLearning content, based on a more sound approach to accessibility. The paper also discusses possible design solutions for tools supporting eLearning content authors in the adoption and application of the proposed approach.

Near-infrared fluorescence probes for enzymes based on binding affinity modulation of squarylium dye scaffold.

PubMed

Oushiki, Daihi; Kojima, Hirotatsu; Takahashi, Yuki; Komatsu, Toru; Terai, Takuya; Hanaoka, Kenjiro; Nishikawa, Makiya; Takakura, Yoshinobu; Nagano, Tetsuo

2012-05-15

We present a novel design strategy for near-infrared (NIR) fluorescence probes utilizing dye-protein interaction as a trigger for fluorescence enhancement. The design principle involves modification of a polymethine dye with cleavable functional groups that reduce the dye's protein-binding affinity. When these functional groups are removed by specific interaction with the target enzymes, the dye's protein affinity is restored, protein binding occurs, and the dye's fluorescence is strongly enhanced. To validate this strategy, we first designed and synthesized an alkaline phosphatase (ALP) sensor by introducing phosphate into the squarylium dye scaffold; this sensor was able to detect ALP-labeled secondary antibodies in Western blotting analysis. Second, we synthesized a probe for β-galactosidase (widely used as a reporter of gene expression) by means of β-galactosyl substitution of the squarylium scaffold; this sensor was able to visualize β-galactosidase activity both in vitro and in vivo. Our strategy should be applicable to obtain NIR fluorescence probes for a wide range of target enzymes.

Quickening: Translational design of resorbable synthetic vascular grafts.

PubMed

Stowell, Chelsea E T; Wang, Yadong

2018-08-01

Traditional tissue-engineered vascular grafts have yet to gain wide clinical use. The difficulty of scaling production of these cell- or biologic-based products has hindered commercialization. In situ tissue engineering bypasses such logistical challenges by using acellular resorbable scaffolds. Upon implant, the scaffolds become remodeled by host cells. This review describes the scientific and translational advantages of acellular, synthetic vascular grafts. It surveys in vivo results obtained with acellular synthetics over their fifty years of technological development. Finally, it discusses emerging principles, highlights strategic considerations for designers, and identifies questions needing additional research. Copyright © 2018 Elsevier Ltd. All rights reserved.

A review of rapid prototyping techniques for tissue engineering purposes.

PubMed

Peltola, Sanna M; Melchels, Ferry P W; Grijpma, Dirk W; Kellomäki, Minna

2008-01-01

Rapid prototyping (RP) is a common name for several techniques, which read in data from computer-aided design (CAD) drawings and manufacture automatically three-dimensional objects layer-by-layer according to the virtual design. The utilization of RP in tissue engineering enables the production of three-dimensional scaffolds with complex geometries and very fine structures. Adding micro- and nanometer details into the scaffolds improves the mechanical properties of the scaffold and ensures better cell adhesion to the scaffold surface. Thus, tissue engineering constructs can be customized according to the data acquired from the medical scans to match the each patient's individual needs. In addition RP enables the control of the scaffold porosity making it possible to fabricate applications with desired structural integrity. Unfortunately, every RP process has its own unique disadvantages in building tissue engineering scaffolds. Hence, the future research should be focused on the development of RP machines designed specifically for fabrication of tissue engineering scaffolds, although RP methods already can serve as a link between tissue and engineering.

Recent Advances in Bioink Design for 3D Bioprinting of Tissues and Organs.

PubMed

Ji, Shen; Guvendiren, Murat

2017-01-01

There is a growing demand for alternative fabrication approaches to develop tissues and organs as conventional techniques are not capable of fabricating constructs with required structural, mechanical, and biological complexity. 3D bioprinting offers great potential to fabricate highly complex constructs with precise control of structure, mechanics, and biological matter [i.e., cells and extracellular matrix (ECM) components]. 3D bioprinting is an additive manufacturing approach that utilizes a "bioink" to fabricate devices and scaffolds in a layer-by-layer manner. 3D bioprinting allows printing of a cell suspension into a tissue construct with or without a scaffold support. The most common bioinks are cell-laden hydrogels, decellulerized ECM-based solutions, and cell suspensions. In this mini review, a brief description and comparison of the bioprinting methods, including extrusion-based, droplet-based, and laser-based bioprinting, with particular focus on bioink design requirements are presented. We also present the current state of the art in bioink design including the challenges and future directions.

Recent Advances in Bioink Design for 3D Bioprinting of Tissues and Organs

PubMed Central

Ji, Shen; Guvendiren, Murat

2017-01-01

There is a growing demand for alternative fabrication approaches to develop tissues and organs as conventional techniques are not capable of fabricating constructs with required structural, mechanical, and biological complexity. 3D bioprinting offers great potential to fabricate highly complex constructs with precise control of structure, mechanics, and biological matter [i.e., cells and extracellular matrix (ECM) components]. 3D bioprinting is an additive manufacturing approach that utilizes a “bioink” to fabricate devices and scaffolds in a layer-by-layer manner. 3D bioprinting allows printing of a cell suspension into a tissue construct with or without a scaffold support. The most common bioinks are cell-laden hydrogels, decellulerized ECM-based solutions, and cell suspensions. In this mini review, a brief description and comparison of the bioprinting methods, including extrusion-based, droplet-based, and laser-based bioprinting, with particular focus on bioink design requirements are presented. We also present the current state of the art in bioink design including the challenges and future directions. PMID:28424770

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.)

In vivo response to starch-based scaffolds designed for bone tissue engineering applications.

PubMed

Salgado, A J; Coutinho, O P; Reis, R L; Davies, J E

2007-03-15

Our purpose was to evaluate the in vivo endosseous response to three starch-based scaffolds implanted in rats (n = 54). We implanted the three scaffold groups; a 50/50 (wt %) blend of corn starch and ethylene-vinyl alcohol (SEVA-C), the same composition coated with a biomimetic calcium phosphate (Ca-P) layer (SEVA-C/CaP), and a 50/50 (wt %) blend of corn starch and cellulose acetate (SCA), all produced by extrusion with blowing agents, into distal femurs proximal to the epiphyseal plate, for 1, 3, or 6 weeks. Our results showed that at 1 week considerable reparative bone formed around all scaffold groups, although the bone was separated from the scaffold by an intervening soft tissue interfacial zone that comprised two distinct compartments: the surface of the scaffold was occupied by multinucleate giant cells and the compartment between these cells and the surrounding bone was occupied by a streaming fibrous-like tissue. The extracellular matrix of the latter was continuous with the extracellular bone matrix itself, labeled positively for osteocalcin and appeared mineralized by back-scattered electron imaging. All three scaffolds showed a similar tissue response, with the soft tissue interface diminishing with time. No bone contact was observed with SEVA-C at any time point, only transitory bone contact was observed with SEVA-C/CaP at 3 weeks, but SCA exhibited direct bone contact at 6 weeks where 56.23 +/- 6.46% of the scaffold surface was occupied by bone. We conclude that all materials exhibited a favorable bony response and that the rapidly forming initial "connective tissue" seen around all scaffolds was a very early form of bone formation.

Post Processing and Biological Evaluation of the Titanium Scaffolds for Bone Tissue Engineering

PubMed Central

Wysocki, Bartłomiej; Idaszek, Joanna; Szlązak, Karol; Strzelczyk, Karolina; Brynk, Tomasz; Kurzydłowski, Krzysztof J.; Święszkowski, Wojciech

2016-01-01

Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate the effect of the chemical polishing with various acid baths on novel scaffolds’ morphology, porosity and mechanical properties. In the first stage, Magics software (Materialise NV, Leuven, Belgium) was used to design a porous scaffolds with pore size equal to (A) 200 µm, (B) 500 µm and (C) 200 + 500 µm, and diamond cell structure. The scaffolds were fabricated from commercially pure titanium powder (CP Ti) using a SLM50 3D printing machine (Realizer GmbH, Borchen, Germany). The selective laser melting (SLM) process was optimized and the laser beam energy density in range of 91–151 J/mm3 was applied to receive 3D structures with fully dense struts. To remove not fully melted titanium particles the scaffolds were chemically polished using various HF and HF-HNO3 acid solutions. Based on scaffolds mass loss and scanning electron (SEM) observations, baths which provided most uniform surface cleaning were proposed for each porosity. The pore and strut size after chemical treatments was calculated based on the micro-computed tomography (µ-CT) and SEM images. The mechanical tests showed that the treated scaffolds had Young’s modulus close to that of compact bone. Additionally, the effect of pore size of chemically polished scaffolds on cell retention, proliferation and differentiation was studied using human mesenchymal stem cells. Small pores yielded higher cell retention within the scaffolds, which then affected their growth. This shows that in vitro cell performance can be controlled to certain extent by varying pore sizes. PMID:28773323

Antigenicity and Immunogenicity in HIV-1 Antibody-Based Vaccine Design

PubMed Central

Kong, Leopold; Sattentau, Quentin J

2012-01-01

Neutralizing antibodies can protect from infection by immunodeficiency viruses. However, the induction by active vaccination of antibodies that can potently neutralize a broad range of circulating virus strains is a goal not yet achieved, despite more than 2 decades of research. Here we review progress made in the field, from early empirical studies to today’s rational structure-based vaccine antigen design. We discuss the existence of broadly neutralizing antibodies, their implications for epitope discovery and recent progress made in antigen design. Finally, we consider the relationship between antigenicity and immunogenicity for B cell recognition and antibody production, a major hurdle for rational vaccine design to overcome. PMID:23227445

Rational design of a high-strength bone scaffold platform based on in situ hybridization of bacterial cellulose/nano-hydroxyapatite framework and silk fibroin reinforcing phase.

PubMed

Jiang, Pei; Ran, Jiabing; Yan, Pan; Zheng, Lingyue; Shen, Xinyu; Tong, Hua

2018-02-01

Bacterial cellulose/hydroxyapatite (BC/HAp) composite had favourable bioaffinity but its poor mechanical strength limited its widespread applications in bone tissue engineering (BTE). Silk fibroin, which possesses special crystalline structure, has been widely used as organic reinforcing material, and different SFs have different amino acid sequences, which exhibit different bioaffinity and mechanical properties. In this regard, bacterial cellulose-Antheraea yamamai silk fibroin/hydroxyapatite (BC-AYSF/HAp), bacterial cellulose-Bombyx mori silk fibroin/hydroxyapatite (BC-BMSF/HAp), and BC/HAp nano-composites were synthesized via a novel in situ hybridization method. Compared with BC/HAp and BC-BMSF/HAp, the BC-AYSF/HAp exhibited better interpenetration, which may benefit for the transportation of nutrients and wastes, the adhesion of cells as well. Additionally, the BC-AYSF/HAp also presented superior thermal stability than the other two composites revealed by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Compression testing indicated that the mechanical strength of BC-BMSF/HAp was greatly reinforced compared with BC/HAp and was even a little higher than that of BC-AYSF/HAp. Tensile testing showed that BC-AYSF/HAp possesses extraordinary mechanical properties with a higher elastic modulus at low strain and higher fracture strength simultaneously than the other two composites. In vitro cell culture exhibited that MC3T3-E1 cells on the BC-AYSF/HAp membrane took on higher proliferative potential than those on the BC-BMSF/HAp membrane. These results suggested that compared with BC-BMSF/HAp, the BC-AYSF/HAp composite was more appropriate as an ideal bone scaffold platform or biomedical membrane to be used in BTE.

Differential associations between maternal scaffolding and toddler emotion regulation in toddlers born preterm and full term

PubMed Central

Erickson, Sarah J.; Duvall, Susanne W.; Fuller, Janell; Schrader, Ron; MacLean, Peggy; Lowe, Jean

2013-01-01

Background Parental “scaffolding” behavior has been associated with developmental outcomes in at-risk children. Aims Because there are limited empirical data regarding how scaffolding is associated with emotion-based developmental skills, the purpose of this study was to compare associations between maternal verbal scaffolding and toddler emotion regulation, including fewer displays of negative affect and increased contentment and enjoyment during play, in toddlers born preterm and full term. Study Design This study was a cross-sectional cohort design. Maternal and toddler behavior was assessed during 5 minutes of videotaped free play with standardized toys. Subjects 131 toddlers (18-22 months) and their mothers were included (77 born preterm; 54 born full term). Outcome Measures Toddler emotion regulation, negative affect, and dyadic mutual enjoyment were coded from videotaped play. Results The association between maternal scaffolding and emotion regulation was different for dyads with a toddler born preterm versus full term, wherein the association was positive for toddlers born preterm and non-significant for toddlers born full term. Similarly, the association between maternal scaffolding and negative affect was different for the two groups: negative for toddlers born preterm and non-significant for toddlers born full term. Finally, the association between maternal scaffolding and mutual enjoyment was positive for toddlers born preterm and non-significant for toddlers born full term. Conclusions Our findings highlight early differences in mother-child interactive style correlates of children born preterm compared to those born full term. Maternal scaffolding behavior may be uniquely associated with emotion regulation and a positive dyadic encounter for toddlers born preterm. PMID:23773306

Scaffold design of trivalent chelator heads dictates high-affinity and stable His-tagged protein labeling in vitro and in cellulo.

PubMed

Gatterdam, Karl; Joest, Eike F; Gatterdam, Volker; Tampé, Robert

2018-05-29

Small chemical/biological interaction pairs are at the forefront in tracing proteins' function and interaction at high signal-to-background ratio in cellular pathways. Pharma ventures have eager plans to develop trisNTA probes for in vitro and in vivo screening of His-tagged protein targets. However, the optimal design of scaffold, linker, and chelator head yet deserves systematic investigations to achieve highest affinity and kinetic stability for in vitro and especially cell applications. In this study, we report on a library of N-nitrilotriacetic acid (NTA) based multivalent chelator heads (MCHs) built up on linear, cyclic, and dendritic scaffolds and contrast these with regard to their binding affinity and stability for labeling of cellular His-tagged proteins. Furthermore, we assign a new approach for tracing cellular target proteins at picomolar probe concentrations in cells. Finally, we describe fundamental differences between the MCH scaffold and define a cyclic trisNTA chelator, which displays the highest affinity and kinetic stability of all reversible, low-molecular weight interaction pairs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fused-ring structure of decahydroisoquinolin as a novel scaffold for SARS 3CL protease inhibitors.

PubMed

Shimamoto, Yasuhiro; Hattori, Yasunao; Kobayashi, Kazuya; Teruya, Kenta; Sanjoh, Akira; Nakagawa, Atsushi; Yamashita, Eiki; Akaji, Kenichi

2015-02-15

The design and evaluation of a novel decahydroisoquinolin scaffold as an inhibitor for severe acute respiratory syndrome (SARS) chymotrypsin-like protease (3CL(pro)) are described. Focusing on hydrophobic interactions at the S2 site, the decahydroisoquinolin scaffold was designed by connecting the P2 site cyclohexyl group of the substrate-based inhibitor to the main-chain at the α-nitrogen atom of the P2 position via a methylene linker. Starting from a cyclohexene enantiomer obtained by salt resolution, trans-decahydroisoquinolin derivatives were synthesized. All decahydroisoquinolin inhibitors synthesized showed moderate but clear inhibitory activities for SARS 3CL(pro), which confirmed the fused ring structure of the decahydroisoquinolin functions as a novel scaffold for SARS 3CL(pro) inhibitor. X-ray crystallographic analyses of the SARS 3CL(pro) in a complex with the decahydroisoquinolin inhibitor revealed the expected interactions at the S1 and S2 sites, as well as additional interactions at the N-substituent of the inhibitor. Copyright © 2014 Elsevier Ltd. All rights reserved.

Design, synthesis, and biological activities of novel hexahydropyrazino[1,2-a]indole derivatives as potent inhibitors of apoptosis (IAP) proteins antagonists with improved membrane permeability across MDR1 expressing cells.

PubMed

Shiokawa, Zenyu; Hashimoto, Kentaro; Saito, Bunnai; Oguro, Yuya; Sumi, Hiroyuki; Yabuki, Masato; Yoshimatsu, Mie; Kosugi, Yohei; Debori, Yasuyuki; Morishita, Nao; Dougan, Douglas R; Snell, Gyorgy P; Yoshida, Sei; Ishikawa, Tomoyasu

2013-12-15

We previously reported octahydropyrrolo[1,2-a]pyrazine derivative 2 (T-3256336) as a potent antagonist for inhibitors of apoptosis (IAP) proteins. Because compound 2 was susceptible to MDR1 mediated efflux, we developed another scaffold, hexahydropyrazino[1,2-a]indole, using structure-based drug design. The fused benzene ring of this scaffold was aimed at increasing the lipophilicity and decreasing the basicity of the scaffold to improve the membrane permeability across MDR1 expressing cells. We established a chiral pool synthetic route to yield the desired tricyclic chiral isomers. Chemical modification of the core scaffold led to a representative compound 50, which showed strong inhibition of IAP binding (X chromosome-linked IAP [XIAP]: IC50 23 nM and cellular IAP [cIAP]: IC50 1.1 nM) and cell growth inhibition (MDA-MB-231 cells: GI50 2.8 nM) with high permeability and low potential of MDR1 substrate. Copyright © 2013 Elsevier Ltd. All rights reserved.

Three-Dimensional Cell Behavior in Microgels

NASA Astrophysics Data System (ADS)

Bhattacharjee, Tapomoy; Palmer, Glyn; Ghivizzani, Steven; Keselowsky, Benjamin; Sawyer, W. Gregory; Angelini, Thomas

The number of dimensions in which particles can freely move strongly influences the collective behavior that emerges from their individual fluctuations. Thus, in 2D systems of cells in petri-dishes, our growing understanding of collective migration may be insufficient to explain cell behavior in 3D tissues. To study cell behavior in 3D, polymer scaffolds are used. Contemporary designs of 3D cell growth scaffolds enable cell migration and proliferative expansion by incorporating of degradable motifs. Matrix degradation creates space for cells to move and proliferate. However, different cell types and experimental conditions require the design of different scaffolds to optimize degradation with specific cell behaviors. By contrast, liquid like solids made from packed microgels can yield under cell generated stresses, allowing for cell motion without the need for scaffold degradation. Moreover, the use of microgels as 3D culture media allows arranging cells in arbitrary structures, harvesting cells, and delivering drugs and nutrients. Preliminary data describing cell behavior in 3D microgel culture will be presented. This material is based on work supported by the National Science Foundation under Grant No. DMR-1352043.

HYDROGEL-BASED NANOCOMPOSITES OF THERAPEUTIC PROTEINS FOR TISSUE REPAIR

PubMed Central

Zhu, Suwei; Segura, Tatiana

2014-01-01

The ability to design artificial extracellular matrices as cell instructive scaffolds has opened the door to technologies capable of studying cell fates in vitro and to guide tissue repair in vivo. One main component of the design of artificial extracellular matrices is the incorporation of protein-based biochemical cues to guide cell phenotypes and multicellular organizations. However, promoting the long-term bioactivity, controlling the bioavailability and understanding how the physical presentations of these proteins impacts cellular fates are among the challenges of the field. Nanotechnolgy has advanced to meet the challenges of protein therapeutics. For example, the approaches to incorporating proteins into tissue repairing scaffolds have ranged from bulk encapsulations to smart nanodepots that protect proteins from degradations and allow opportunities for controlled release. PMID:24778979

HYDROGEL-BASED NANOCOMPOSITES OF THERAPEUTIC PROTEINS FOR TISSUE REPAIR.

PubMed

Zhu, Suwei; Segura, Tatiana

2014-05-01

The ability to design artificial extracellular matrices as cell instructive scaffolds has opened the door to technologies capable of studying cell fates in vitro and to guide tissue repair in vivo . One main component of the design of artificial extracellular matrices is the incorporation of protein-based biochemical cues to guide cell phenotypes and multicellular organizations. However, promoting the long-term bioactivity, controlling the bioavailability and understanding how the physical presentations of these proteins impacts cellular fates are among the challenges of the field. Nanotechnolgy has advanced to meet the challenges of protein therapeutics. For example, the approaches to incorporating proteins into tissue repairing scaffolds have ranged from bulk encapsulations to smart nanodepots that protect proteins from degradations and allow opportunities for controlled release.

Effects of Toy Crane Design-Based Learning on Simple Machines

ERIC Educational Resources Information Center

Korur, Fikret; Efe, Gülfem; Erdogan, Fisun; Tunç, Berna

2017-01-01

The aim of this 2-group study was to investigate the following question: Are there significant differences between scaffolded design-based learning controlled using 7 forms and teacher-directed instruction methods for the toy crane project on grade 7 students' posttest scores on the simple machines achievement test, attitude toward simple…

Reliability-based evaluation of bridge components for consistent safety margins.

DOT National Transportation Integrated Search

2010-10-01

The Load and Resistant Factor Design (LRFD) approach is based on the concept of structural reliability. The approach is more : rational than the former design approaches such as Load Factor Design or Allowable Stress Design. The LRFD Specification fo...

Hybrid PCL/CaCO3 scaffolds with capabilities of carrying biologically active molecules: Synthesis, loading and in vivo applications.

PubMed

Saveleva, M S; Ivanov, A N; Kurtukova, M O; Atkin, V S; Ivanova, A G; Lyubun, G P; Martyukova, A V; Cherevko, E I; Sargsyan, A K; Fedonnikov, A S; Norkin, I A; Skirtach, A G; Gorin, D A; Parakhonskiy, B V

2018-04-01

Designing advanced biomaterials for tissue regeneration with drug delivery and release functionalities remains a challenge in regenerative medicine. In this research, we have developed novel composite scaffolds based on polymeric polycaprolactone fibers coated with porous calcium carbonate structures (PCL/CaCO 3 ) for tissue engineering and have shown their drug delivery and release in rats. In vivo biocompatibility tests of PCL/CaCO 3 scaffolds were complemented with in vivo drug release study, where tannic acid (TA) was used as a model drug. Release of TA from the scaffolds was realized by recrystallization of the porous vaterite phase of calcium carbonate into the crystalline calcite. Cell colonization and tissue vascularization as well as transplantability of developed PCL/CaCO 3 +TA scaffolds were observed. Detailed study of scaffold transformations during 21-day implantation period was followed by scanning electron microscopy and X-ray diffraction studies before and after in vivo implantation. The presented results demonstrate that PCL/CaCO 3 scaffolds are attractive candidates for implants in bone regeneration and tissue engineering with a possibility of loading biologically active molecules and controlled release. Copyright © 2017 Elsevier B.V. All rights reserved.

Teachers as Designers: Multimodal Immersion and Strategic Reading on the Internet

ERIC Educational Resources Information Center

Dalton, Bridget; Smith, Blaine E.

2012-01-01

This study examined teachers' literacy and technology integration in their design of Internet-based lessons for Grade 1-6 students using a tool that scaffolds the design process to focus on Internet resources and reading strategies. Twenty-six teachers' lessons on a public database were analyzed for design orientation, goals, curricular…

Multilayer scaffolds in orthopaedic tissue engineering.

PubMed

Atesok, Kivanc; Doral, M Nedim; Karlsson, Jon; Egol, Kenneth A; Jazrawi, Laith M; Coelho, Paulo G; Martinez, Amaury; Matsumoto, Tomoyuki; Owens, Brett D; Ochi, Mitsuo; Hurwitz, Shepard R; Atala, Anthony; Fu, Freddie H; Lu, Helen H; Rodeo, Scott A

2016-07-01

The purpose of this study was to summarize the recent developments in the field of tissue engineering as they relate to multilayer scaffold designs in musculoskeletal regeneration. Clinical and basic research studies that highlight the current knowledge and potential future applications of the multilayer scaffolds in orthopaedic tissue engineering were evaluated and the best evidence collected. Studies were divided into three main categories based on tissue types and interfaces for which multilayer scaffolds were used to regenerate: bone, osteochondral junction and tendon-to-bone interfaces. In vitro and in vivo studies indicate that the use of stratified scaffolds composed of multiple layers with distinct compositions for regeneration of distinct tissue types within the same scaffold and anatomic location is feasible. This emerging tissue engineering approach has potential applications in regeneration of bone defects, osteochondral lesions and tendon-to-bone interfaces with successful basic research findings that encourage clinical applications. Present data supporting the advantages of the use of multilayer scaffolds as an emerging strategy in musculoskeletal tissue engineering are promising, however, still limited. Positive impacts of the use of next generation scaffolds in orthopaedic tissue engineering can be expected in terms of decreasing the invasiveness of current grafting techniques used for reconstruction of bone and osteochondral defects, and tendon-to-bone interfaces in near future.

Microstereolithography-Based Fabrication of Anatomically Shaped Beta-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering

PubMed Central

Du, Dajiang; Asaoka, Teruo; Shinohara, Makoto; Kageyama, Tomonori; Ushida, Takashi; Furukawa, Katsuko Sakai

2015-01-01

Porous ceramic scaffolds with shapes matching the bone defects may result in more efficient grafting and healing than the ones with simple geometries. Using computer-assisted microstereolithography (MSTL), we have developed a novel gelcasting indirect MSTL technology and successfully fabricated two scaffolds according to CT images of rabbit femur. Negative resin molds with outer 3D dimensions conforming to the femur and an internal structure consisting of stacked meshes with uniform interconnecting struts, 0.5 mm in diameter, were fabricated by MSTL. The second mold type was designed for cortical bone formation. A ceramic slurry of beta-tricalcium phosphate (β-TCP) with room temperature vulcanization (RTV) silicone as binder was cast into the molds. After the RTV silicone was completely cured, the composite was sintered at 1500°C for 5 h. Both gross anatomical shape and the interpenetrating internal network were preserved after sintering. Even cortical structure could be introduced into the customized scaffolds, which resulted in enhanced strength. Biocompatibility was confirmed by vital staining of rabbit bone marrow mesenchymal stromal cells cultured on the customized scaffolds for 5 days. This fabrication method could be useful for constructing bone substitutes specifically designed according to local anatomical defects. PMID:26504839

Method for making a bio-compatible scaffold

DOEpatents

Cesarano, III, Joseph; Stuecker, John N [Albuquerque, NM; Dellinger, Jennifer G [Champaigne, IL; Jamison, Russell D [Urbana, IL

2006-01-31

A method for forming a three-dimensional, biocompatible, porous scaffold structure using a solid freeform fabrication technique (referred to herein as robocasting) that can be used as a medical implant into a living organism, such as a human or other mammal. Imaging technology and analysis is first used to determine the three-dimensional design required for the medical implant, such as a bone implant or graft, fashioned as a three-dimensional, biocompatible scaffold structure. The robocasting technique is used to either directly produce the three-dimensional, porous scaffold structure or to produce an over-sized three-dimensional, porous scaffold lattice which can be machined to produce the designed three-dimensional, porous scaffold structure for implantation.

Structural and cytotoxic studies of cationic thiosemicarbazones

NASA Astrophysics Data System (ADS)

Sinniah, Saravana Kumar; Sim, Kae Shin; Ng, Seik Weng; Tan, Kong Wai

2017-06-01

Schiff bases from the thiosemicarbazones family with variable N4 substituents are known to show enhanced growth inhibitory properties. In view of these facts and as a part of our continuous interest in cationic Schiff bases, we have developed several Schiff base ligands from (3-formyl-4-hydroxyphenyl)methyltriphenylphosphonium (T) in present study. The compounds were characterized by various spectroscopic methods (infrared spectra, 1H NMR, 13C NMR, HRESIMS and X-ray crystallography). Three of the N4 substituents, namely P(tsc)T, FP(tsc)T and EP(tsc)T exerted strong growth inhibitory properties by inhibiting the highly metastasis prostate cancer growth (PC-3). The thiosemicarbazone with ethylphenyl (EP) moiety displayed most potent activity against all cell lines tested. The MTT data obtained from analysis establishes that phenyl substituent enhances the growth inhibitory properties of the compound. The result affirms that EP(tsc)T would serve as a lead scaffold for rational anticancer agent development.

Optimal design of piezoelectric transformers: a rational approach based on an analytical model and a deterministic global optimization.

PubMed

Pigache, Francois; Messine, Frédéric; Nogarede, Bertrand

2007-07-01

This paper deals with a deterministic and rational way to design piezoelectric transformers in radial mode. The proposed approach is based on the study of the inverse problem of design and on its reformulation as a mixed constrained global optimization problem. The methodology relies on the association of the analytical models for describing the corresponding optimization problem and on an exact global optimization software, named IBBA and developed by the second author to solve it. Numerical experiments are presented and compared in order to validate the proposed approach.

A new design for electrospinner collecting device facilitates the removal of small diameter tubular scaffolds and paves the way for tissue engineering of capillaries.

PubMed

Sohrabi, Abbas; Naderi, Mahmood; Gorjipour, Fazel; Ghamgosar, Abolfazl; Ahmadbeigi, Naser

2016-09-10

Electrospinning is a technique widely used for tissue engineering. Despite hurdles, electrospun vascular tissue scaffolds has shown great promise in in vitro studies. One problem is the removal of tubular scaffolds from a electrospinning collection device with no unwanted crumpling or tearing, especially for small diameter scaffolds. To tackle this problem we designed a collection device for simple removal of the scaffold from the collector while no chemical pretreatment was required. The scaffolds fabricated on this collecting device maintained their tubular structure and showed favorable surface properties, mechanical strength and biocompatibility. The device offers a new opportunity for tissue engineering researchers to fabricate tubular scaffolds from materials which have not been possible to date and help them improve the quality of synthesized scaffolds. Copyright © 2016 Elsevier Inc. All rights reserved.

Osteochondral tissue engineering: scaffolds, stem cells and applications

PubMed Central

Nooeaid, Patcharakamon; Salih, Vehid; Beier, Justus P; Boccaccini, Aldo R

2012-01-01

Osteochondral tissue engineering has shown an increasing development to provide suitable strategies for the regeneration of damaged cartilage and underlying subchondral bone tissue. For reasons of the limitation in the capacity of articular cartilage to self-repair, it is essential to develop approaches based on suitable scaffolds made of appropriate engineered biomaterials. The combination of biodegradable polymers and bioactive ceramics in a variety of composite structures is promising in this area, whereby the fabrication methods, associated cells and signalling factors determine the success of the strategies. The objective of this review is to present and discuss approaches being proposed in osteochondral tissue engineering, which are focused on the application of various materials forming bilayered composite scaffolds, including polymers and ceramics, discussing the variety of scaffold designs and fabrication methods being developed. Additionally, cell sources and biological protein incorporation methods are discussed, addressing their interaction with scaffolds and highlighting the potential for creating a new generation of bilayered composite scaffolds that can mimic the native interfacial tissue properties, and are able to adapt to the biological environment. PMID:22452848

Design and fabrication of porous biodegradable scaffolds: a strategy for tissue engineering.

PubMed

Raeisdasteh Hokmabad, Vahideh; Davaran, Soodabeh; Ramazani, Ali; Salehi, Roya

2017-11-01

Current strategies of tissue engineering are focused on the reconstruction and regeneration of damaged or deformed tissues by grafting of cells with scaffolds and biomolecules. Recently, much interest is given to scaffolds which are based on mimic the extracellular matrix that have induced the formation of new tissues. To return functionality of the organ, the presence of a scaffold is essential as a matrix for cell colonization, migration, growth, differentiation and extracellular matrix deposition, until the tissues are totally restored or regenerated. A wide variety of approaches has been developed either in scaffold materials and production procedures or cell sources and cultivation techniques to regenerate the tissues/organs in tissue engineering applications. This study has been conducted to present an overview of the different scaffold fabrication techniques such as solvent casting and particulate leaching, electrospinning, emulsion freeze-drying, thermally induced phase separation, melt molding and rapid prototyping with their properties, limitations, theoretical principles and their prospective in tailoring appropriate micro-nanostructures for tissue regeneration applications. This review also includes discussion on recent works done in the field of tissue engineering.

Triplet-Triplet Annihilation Photon Upconversion in Polymer Thin Film: Sensitizer Design.

PubMed

Jiang, Xinpeng; Guo, Xinyan; Peng, Jiang; Zhao, Dahui; Ma, Yuguo

2016-05-11

Efficient visible-to-UV photon upconversion via triplet-triplet annihilation (TTA) is accomplished in polyurethane (PU) films by developing new, powerful photosensitizers fully functional in the solid-state matrix. These rationally designed triplet sensitizers feature a bichromophoric scaffold comprising a tris-cyclometalated iridium(III) complex covalently tethered to a suitable organic small molecule. The very rapid intramolecular triplet energy transfer from the former to the latter is pivotal for achieving the potent sensitizing ability, because this process out-competes the radiative and nonradiative decays inherent to the metal complex and produces long-lived triplet excitons localized with the acceptor moiety readily available for intermolecular transfer and TTA. Nonetheless, compared to the solution state, the molecular diffusion is greatly limited in solid matrices, which even creates difficulty for the Dexter-type intramolecular energy transfer. This is proven by the experimental results showing that the sensitizing performance of the bichromophoric molecules strongly depends on the spatial distance separating the donor (D) and acceptor (A) units and that incorporating a longer linker between the D and A evidently curbs the TTA upconversion efficiency in PU films. Using a rationally optimized sensitizer structure in combination with 2,7-di-tert-butylpyrene as the annihilator/emitter, the doped polyurethane (PU) films demonstrate effective visible-to-UV upconverted emission signal under noncoherent-light irradiation, attaining an upconversion quantum yield of 2.6%. Such quantum efficiency is the highest value so far reported for the visible-to-UV TTA systems in solid matrices.

A Rationally Designed Agonist Defines Subfamily IIIA Abscisic Acid Receptors As Critical Targets for Manipulating Transpiration.

PubMed

Vaidya, Aditya S; Peterson, Francis C; Yarmolinsky, Dmitry; Merilo, Ebe; Verstraeten, Inge; Park, Sang-Youl; Elzinga, Dezi; Kaundal, Amita; Helander, Jonathan; Lozano-Juste, Jorge; Otani, Masato; Wu, Kevin; Jensen, Davin R; Kollist, Hannes; Volkman, Brian F; Cutler, Sean R

2017-11-17

Increasing drought and diminishing freshwater supplies have stimulated interest in developing small molecules that can be used to control transpiration. Receptors for the plant hormone abscisic acid (ABA) have emerged as key targets for this application, because ABA controls the apertures of stomata, which in turn regulate transpiration. Here, we describe the rational design of cyanabactin, an ABA receptor agonist that preferentially activates Pyrabactin Resistance 1 (PYR1) with low nanomolar potency. A 1.63 Å X-ray crystallographic structure of cyanabactin in complex with PYR1 illustrates that cyanabactin's arylnitrile mimics ABA's cyclohexenone oxygen and engages the tryptophan lock, a key component required to stabilize activated receptors. Further, its sulfonamide and 4-methylbenzyl substructures mimic ABA's carboxylate and C6 methyl groups, respectively. Isothermal titration calorimetry measurements show that cyanabactin's compact structure provides ready access to high ligand efficiency on a relatively simple scaffold. Cyanabactin treatments reduce Arabidopsis whole-plant stomatal conductance and activate multiple ABA responses, demonstrating that its in vitro potency translates to ABA-like activity in vivo. Genetic analyses show that the effects of cyanabactin, and the previously identified agonist quinabactin, can be abolished by the genetic removal of PYR1 and PYL1, which form subclade A within the dimeric subfamily III receptors. Thus, cyanabactin is a potent and selective agonist with a wide spectrum of ABA-like activities that defines subfamily IIIA receptors as key target sites for manipulating transpiration.

Scaffolds with a standardized macro-architecture fabricated from several calcium phosphate ceramics using an indirect rapid prototyping technique

PubMed Central

Wilson, C. E.; van Blitterswijk, C. A.; Verbout, A. J.; de Bruijn, J. D.

2010-01-01

Calcium phosphate ceramics, commonly applied as bone graft substitutes, are a natural choice of scaffolding material for bone tissue engineering. Evidence shows that the chemical composition, macroporosity and microporosity of these ceramics influences their behavior as bone graft substitutes and bone tissue engineering scaffolds but little has been done to optimize these parameters. One method of optimization is to place focus on a particular parameter by normalizing the influence, as much as possible, of confounding parameters. This is difficult to accomplish with traditional fabrication techniques. In this study we describe a design based rapid prototyping method of manufacturing scaffolds with virtually identical macroporous architectures from different calcium phosphate ceramic compositions. Beta-tricalcium phosphate, hydroxyapatite (at two sintering temperatures) and biphasic calcium phosphate scaffolds were manufactured. The macro- and micro-architectures of the scaffolds were characterized as well as the influence of the manufacturing method on the chemistries of the calcium phosphate compositions. The structural characteristics of the resulting scaffolds were remarkably similar. The manufacturing process had little influence on the composition of the materials except for the consistent but small addition of, or increase in, a beta-tricalcium phosphate phase. Among other applications, scaffolds produced by the method described provide a means of examining the influence of different calcium phosphate compositions while confidently excluding the influence of the macroporous structure of the scaffolds. PMID:21069558

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.

RNA design rules from a massive open laboratory

PubMed Central

Lee, Jeehyung; Kladwang, Wipapat; Lee, Minjae; Cantu, Daniel; Azizyan, Martin; Kim, Hanjoo; Limpaecher, Alex; Gaikwad, Snehal; Yoon, Sungroh; Treuille, Adrien; Das, Rhiju

2014-01-01

Self-assembling RNA molecules present compelling substrates for the rational interrogation and control of living systems. However, imperfect in silico models—even at the secondary structure level—hinder the design of new RNAs that function properly when synthesized. Here, we present a unique and potentially general approach to such empirical problems: the Massive Open Laboratory. The EteRNA project connects 37,000 enthusiasts to RNA design puzzles through an online interface. Uniquely, EteRNA participants not only manipulate simulated molecules but also control a remote experimental pipeline for high-throughput RNA synthesis and structure mapping. We show herein that the EteRNA community leveraged dozens of cycles of continuous wet laboratory feedback to learn strategies for solving in vitro RNA design problems on which automated methods fail. The top strategies—including several previously unrecognized negative design rules—were distilled by machine learning into an algorithm, EteRNABot. Over a rigorous 1-y testing phase, both the EteRNA community and EteRNABot significantly outperformed prior algorithms in a dozen RNA secondary structure design tests, including the creation of dendrimer-like structures and scaffolds for small molecule sensors. These results show that an online community can carry out large-scale experiments, hypothesis generation, and algorithm design to create practical advances in empirical science. PMID:24469816

Integrating Advance Organizers and Multidimensional Information Display in Electronic Performance Support Systems

ERIC Educational Resources Information Center

Hung, Wei-Chen; Chao, Chia-An

2007-01-01

This study has reviewed major design approaches for electronic performance support systems and identified two common problems: users' inability to comprehend screen-based material and poorly designed instructional scaffolds. This paper presents a design approach, called the "Matrix-Aided Performance System" ("MAPS"), which enables these problems…

An Investigation of Software Scaffolds Supporting Modeling Practices

NASA Astrophysics Data System (ADS)

Fretz, Eric B.; Wu, Hsin-Kai; Zhang, Baohui; Davis, Elizabeth A.; Krajcik, Joseph S.; Soloway, Elliot

2002-08-01

Modeling of complex systems and phenomena is of value in science learning and is increasingly emphasised as an important component of science teaching and learning. Modeling engages learners in desired pedagogical activities. These activities include practices such as planning, building, testing, analysing, and critiquing. Designing realistic models is a difficult task. Computer environments allow the creation of dynamic and even more complex models. One way of bringing the design of models within reach is through the use of scaffolds. Scaffolds are intentional assistance provided to learners from a variety of sources, allowing them to complete tasks that would otherwise be out of reach. Currently, our understanding of how scaffolds in software tools assist learners is incomplete. In this paper the scaffolds designed into a dynamic modeling software tool called Model-It are assessed in terms of their ability to support learners' use of modeling practices. Four pairs of middle school students were video-taped as they used the modeling software for three hours, spread over a two week time frame. Detailed analysis of coded videotape transcripts provided evidence of the importance of scaffolds in supporting the use of modeling practices. Learners used a variety of modeling practices, the majority of which occurred in conjunction with scaffolds. The use of three tool scaffolds was assessed as directly as possible, and these scaffolds were seen to support a variety of modeling practices. An argument is made for the continued empirical validation of types and instances of tool scaffolds, and further investigation of the important role of teacher and peer scaffolding in the use of scaffolded tools.

Walking and talking the tree of life: Why and how to teach about biodiversity.

PubMed

Ballen, Cissy J; Greene, Harry W

2017-03-01

Taxonomic details of diversity are an essential scaffolding for biology education, yet outdated methods for teaching the tree of life (TOL), as implied by textbook content and usage, are still commonly employed. Here, we show that the traditional approach only vaguely represents evolutionary relationships, fails to denote major events in the history of life, and relies heavily on memorizing near-meaningless taxonomic ranks. Conversely, a clade-based strategy-focused on common ancestry, monophyletic groups, and derived functional traits-is explicitly based on Darwin's "descent with modification," provides students with a rational system for organizing the details of biodiversity, and readily lends itself to active learning techniques. We advocate for a phylogenetic classification that mirrors the TOL, a pedagogical format of increasingly complex but always hierarchical presentations, and the adoption of active learning technologies and tactics.

Design of a hybrid biomaterial for tissue engineering: Biopolymer-scaffold integrated with an autologous hydrogel carrying mesenchymal stem-cells.

PubMed

Weinstein-Oppenheimer, Caroline R; Brown, Donald I; Coloma, Rodrigo; Morales, Patricio; Reyna-Jeldes, Mauricio; Díaz, María J; Sánchez, Elizabeth; Acevedo, Cristian A

2017-10-01

Biologically active biomaterials as biopolymers and hydrogels have been used in medical applications providing favorable results in tissue engineering. In this research, a wound dressing device was designed by integration of an autologous clot hydrogel carrying mesenchymal stem-cells onto a biopolymeric scaffold. This hybrid biomaterial was tested in-vitro and in-vivo, and used in a human clinical case. The biopolymeric scaffold was made with gelatin, chitosan and hyaluronic acid, using a freeze-drying method. The scaffold was a porous material which was designed evaluating both physical properties (glass transition, melting temperature and pore size) and biological properties (cell viability and fibronectin expression). Two types of chitosan (120 and 300kDa) were used to manufacture the scaffold, being the high molecular weight the most biologically active and stable after sterilization with gamma irradiation (25kGy). A clot hydrogel was formulated with autologous plasma and calcium chloride, using an approach based on design of experiments. The optimum hydrogel was used to incorporate cells onto the porous scaffold, forming a wound dressing biomaterial. The wound dressing device was firstly tested in-vitro using human cells, and then, its biosecurity was evaluated in-vivo using a rabbit model. The in-vitro results showed high cell viability after one week (99.5%), high mitotic index (19.8%) and high fibronectin expression. The in-vivo application to rabbits showed adequate biodegradability capacity (between 1 and 2weeks), and the histological evaluation confirmed absence of rejection signs and reepithelization on the wound zone. Finally, the wound dressing biomaterial was used in a single human case to implant autologous cells on a skin surgery. The medical examination indicated high biocompatibility, partial biodegradation at one week, early regeneration capacity at 4weeks and absence of rejection signs. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanofiber Scaffold-Based Tissue-Engineered Retinal Pigment Epithelium to Treat Degenerative Eye Diseases

PubMed Central

Khristov, Vladimir; Wan, Qin; Sharma, Ruchi; Jha, Balendu Shekhar; Lotfi, Mostafa; Maminishkis, Arvydas; Simon, Carl G.

2016-01-01

Abstract Clinical-grade manufacturing of a functional retinal pigment epithelium (RPE) monolayer requires reproducing, as closely as possible, the natural environment in which RPE grows. In vitro, this can be achieved by a tissue engineering approach, in which the RPE is grown on a nanofibrous biological or synthetic scaffold. Recent research has shown that nanofiber scaffolds perform better for cell growth and transplantability compared with their membrane counterparts and that the success of the scaffold in promoting cell growth/function is not heavily material dependent. With these strides, the field has advanced enough to begin to consider implementation of one, or a combination, of the tissue engineering strategies discussed herein. In this study, we review the current state of tissue engineering research for in vitro culture of RPE/scaffolds and the parameters for optimal scaffold design that have been uncovered during this research. Next, we discuss production methods and manufacturers that are capable of producing the nanofiber scaffolds in such a way that would be biologically, regulatory, clinically, and commercially viable. Then, a discussion of how the scaffolds could be characterized, both morphologically and mechanically, to develop a testing process that is viable for regulatory screening is performed. Finally, an example of a tissue-engineered RPE/scaffold construct is given to provide the reader a framework for understanding how these pieces could fit together to develop a tissue-engineered RPE/scaffold construct that could pass regulatory scrutiny and can be commercially successful. PMID:27110730

The influence of stereolithographic scaffold architecture and composition on osteogenic signal expression with rat bone marrow stromal cells

PubMed Central

Kim, Kyobum; Dean, David; Wallace, Jonathan; Breithaupt, Rob; Mikos, Antonios G.; Fisher, John P.

2011-01-01

Scaffold design parameters, especially physical construction factors such as mechanical stiffness of substrate materials, pore size of 3D porous scaffolds, and channel geometry, are known to influence the osteogenic signal expression and subsequent differentiation of a transplanted cell population. In this study of photocrosslinked poly(propylene fumarate) (PPF) and diethyl fumarate (DEF) scaffolds, the effect of DEF incorporation ratio and pore size on the osteogenic signal expression of rat bone marrow stromal cells (BMSCs) was investigated. Results demonstrated that DEF concentrations and pore sizes that led to increased scaffold mechanical stiffness also upregulated osteogenic signal expression, including bone morphogenic protein-2 (BMP-2), fibroblast growth factors-2 (FGF-2), transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), and Runx2 transcriptional factor. Similar scaffold fabrication parameters supported rapid BMSC osteoblastic differentiation, as demonstrated by increased alkaline phosphatase (ALP) and osteocalcin expression. When scaffolds with random architecture, fabricated by porogen leaching, were compared to those with controlled architecture, fabricated by stereolithography (SLA), results showed that SLA scaffolds with the highly permeable and porous channels also have significantly higher expression of FGF-2, TGF-β1, and VEGF. Subsequent ALP expression and osteopontin secretion were also significantly increased in SLA scaffolds. Based upon these results, we conclude that scaffold properties provided by additive manufacturing techniques such as SLA fabrication, particularly increased mechanical stiffness and high permeability, may stimulate dramatic BMSC responses that promote rapid bone tissue regeneration. PMID:21396709

Inhibition of NAADP signalling on reperfusion protects the heart by preventing lethal calcium oscillations via two-pore channel 1 and opening of the mitochondrial permeability transition pore.

PubMed

Davidson, Sean M; Foote, Kirsty; Kunuthur, Suma; Gosain, Raj; Tan, Noah; Tyser, Richard; Zhao, Yong Juan; Graeff, Richard; Ganesan, A; Duchen, Michael R; Patel, Sandip; Yellon, Derek M

2015-12-01

In the heart, a period of ischaemia followed by reperfusion evokes powerful cytosolic Ca(2+) oscillations that can cause lethal cell injury. These signals represent attractive cardioprotective targets, but the underlying mechanisms of genesis are ill-defined. Here, we investigated the role of the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP), which is known in several cell types to induce Ca(2+) oscillations that initiate from acidic stores such as lysosomes, likely via two-pore channels (TPCs, TPC1 and 2). An NAADP antagonist called Ned-K was developed by rational design based on a previously existing scaffold. Ned-K suppressed Ca(2+) oscillations and dramatically protected cardiomyocytes from cell death in vitro after ischaemia and reoxygenation, preventing opening of the mitochondrial permeability transition pore. Ned-K profoundly decreased infarct size in mice in vivo. Transgenic mice lacking the endo-lysosomal TPC1 were also protected from injury. NAADP signalling plays a major role in reperfusion-induced cell death and represents a potent pathway for protection against reperfusion injury. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Cardiology.

Inhibition of NAADP signalling on reperfusion protects the heart by preventing lethal calcium oscillations via two-pore channel 1 and opening of the mitochondrial permeability transition pore

PubMed Central

Davidson, Sean M.; Foote, Kirsty; Kunuthur, Suma; Gosain, Raj; Tan, Noah; Tyser, Richard; Zhao, Yong Juan; Graeff, Richard; Ganesan, A.; Duchen, Michael R.; Patel, Sandip; Yellon, Derek M.

2015-01-01

Aims In the heart, a period of ischaemia followed by reperfusion evokes powerful cytosolic Ca2+ oscillations that can cause lethal cell injury. These signals represent attractive cardioprotective targets, but the underlying mechanisms of genesis are ill-defined. Here, we investigated the role of the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP), which is known in several cell types to induce Ca2+ oscillations that initiate from acidic stores such as lysosomes, likely via two-pore channels (TPCs, TPC1 and 2). Methods and results An NAADP antagonist called Ned-K was developed by rational design based on a previously existing scaffold. Ned-K suppressed Ca2+ oscillations and dramatically protected cardiomyocytes from cell death in vitro after ischaemia and reoxygenation, preventing opening of the mitochondrial permeability transition pore. Ned-K profoundly decreased infarct size in mice in vivo. Transgenic mice lacking the endo-lysosomal TPC1 were also protected from injury. Conclusion NAADP signalling plays a major role in reperfusion-induced cell death and represents a potent pathway for protection against reperfusion injury. PMID:26395965

Discovery of Novel New Delhi Metallo-β-Lactamases-1 Inhibitors by Multistep Virtual Screening

PubMed Central

Wang, Xuequan; Lu, Meiling; Shi, Yang; Ou, Yu; Cheng, Xiaodong

2015-01-01

The emergence of NDM-1 containing multi-antibiotic resistant "Superbugs" necessitates the needs of developing of novel NDM-1inhibitors. In this study, we report the discovery of novel NDM-1 inhibitors by multi-step virtual screening. From a 2,800,000 virtual drug-like compound library selected from the ZINC database, we generated a focused NDM-1 inhibitor library containing 298 compounds of which 44 chemical compounds were purchased and evaluated experimentally for their ability to inhibit NDM-1 in vitro. Three novel NDM-1 inhibitors with micromolar IC50 values were validated. The most potent inhibitor, VNI-41, inhibited NDM-1 with an IC50 of 29.6 ± 1.3 μM. Molecular dynamic simulation revealed that VNI-41 interacted extensively with the active site. In particular, the sulfonamide group of VNI-41 interacts directly with the metal ion Zn1 that is critical for the catalysis. These results demonstrate the feasibility of applying virtual screening methodologies in identifying novel inhibitors for NDM-1, a metallo-β-lactamase with a malleable active site and provide a mechanism base for rational design of NDM-1 inhibitors using sulfonamide as a functional scaffold. PMID:25734558

Rational design and synthesis of an orally bioavailable peptide guided by NMR amide temperature coefficients

PubMed Central

Wang, Conan K.; Northfield, Susan E.; Colless, Barbara; Chaousis, Stephanie; Hamernig, Ingrid; Lohman, Rink-Jan; Nielsen, Daniel S.; Schroeder, Christina I.; Liras, Spiros; Price, David A.; Fairlie, David P.; Craik, David J.

2014-01-01

Enhancing the oral bioavailability of peptide drug leads is a major challenge in drug design. As such, methods to address this challenge are highly sought after by the pharmaceutical industry. Here, we propose a strategy to identify appropriate amides for N-methylation using temperature coefficients measured by NMR to identify exposed amides in cyclic peptides. N-methylation effectively caps these amides, modifying the overall solvation properties of the peptides and making them more membrane permeable. The approach for identifying sites for N-methylation is a rapid alternative to the elucidation of 3D structures of peptide drug leads, which has been a commonly used structure-guided approach in the past. Five leucine-rich peptide scaffolds are reported with selectively designed N-methylated derivatives. In vitro membrane permeability was assessed by parallel artificial membrane permeability assay and Caco-2 assay. The most promising N-methylated peptide was then tested in vivo. Here we report a novel peptide (15), which displayed an oral bioavailability of 33% in a rat model, thus validating the design approach. We show that this approach can also be used to explain the notable increase in oral bioavailability of a somatostatin analog. PMID:25416591

Rational design and synthesis of an orally bioavailable peptide guided by NMR amide temperature coefficients.

PubMed

Wang, Conan K; Northfield, Susan E; Colless, Barbara; Chaousis, Stephanie; Hamernig, Ingrid; Lohman, Rink-Jan; Nielsen, Daniel S; Schroeder, Christina I; Liras, Spiros; Price, David A; Fairlie, David P; Craik, David J

2014-12-09

Enhancing the oral bioavailability of peptide drug leads is a major challenge in drug design. As such, methods to address this challenge are highly sought after by the pharmaceutical industry. Here, we propose a strategy to identify appropriate amides for N-methylation using temperature coefficients measured by NMR to identify exposed amides in cyclic peptides. N-methylation effectively caps these amides, modifying the overall solvation properties of the peptides and making them more membrane permeable. The approach for identifying sites for N-methylation is a rapid alternative to the elucidation of 3D structures of peptide drug leads, which has been a commonly used structure-guided approach in the past. Five leucine-rich peptide scaffolds are reported with selectively designed N-methylated derivatives. In vitro membrane permeability was assessed by parallel artificial membrane permeability assay and Caco-2 assay. The most promising N-methylated peptide was then tested in vivo. Here we report a novel peptide (15), which displayed an oral bioavailability of 33% in a rat model, thus validating the design approach. We show that this approach can also be used to explain the notable increase in oral bioavailability of a somatostatin analog.

Clustering of disulfide-rich peptides provides scaffolds for hit discovery by phage display: application to interleukin-23.

PubMed

Barkan, David T; Cheng, Xiao-Li; Celino, Herodion; Tran, Tran T; Bhandari, Ashok; Craik, Charles S; Sali, Andrej; Smythe, Mark L

2016-11-23

Disulfide-rich peptides (DRPs) are found throughout nature. They are suitable scaffolds for drug development due to their small cores, whose disulfide bonds impart extraordinary chemical and biological stability. A challenge in developing a DRP therapeutic is to engineer binding to a specific target. This challenge can be overcome by (i) sampling the large sequence space of a given scaffold through a phage display library and by (ii) panning multiple libraries encoding structurally distinct scaffolds. Here, we implement a protocol for defining these diverse scaffolds, based on clustering structurally defined DRPs according to their conformational similarity. We developed and applied a hierarchical clustering protocol based on DRP structural similarity, followed by two post-processing steps, to classify 806 unique DRP structures into 81 clusters. The 20 most populated clusters comprised 85% of all DRPs. Representative scaffolds were selected from each of these clusters; the representatives were structurally distinct from one another, but similar to other DRPs in their respective clusters. To demonstrate the utility of the clusters, phage libraries were constructed for three of the representative scaffolds and panned against interleukin-23. One library produced a peptide that bound to this target with an IC 50 of 3.3 μM. Most DRP clusters contained members that were diverse in sequence, host organism, and interacting proteins, indicating that cluster members were functionally diverse despite having similar structure. Only 20 peptide scaffolds accounted for most of the natural DRP structural diversity, providing suitable starting points for seeding phage display experiments. Through selection of the scaffold surface to vary in phage display, libraries can be designed that present sequence diversity in architecturally distinct, biologically relevant combinations of secondary structures. We supported this hypothesis with a proof-of-concept experiment in which three phage libraries were constructed and panned against the IL-23 target, resulting in a single-digit μM hit and suggesting that a collection of libraries based on the full set of 20 scaffolds increases the potential to identify efficiently peptide binders to a protein target in a drug discovery program.

The simulation study of protein-protein interfaces based on the 4-helix bundle structure

NASA Astrophysics Data System (ADS)

Fukuda, Masaki; Komatsu, Yu; Morikawa, Ryota; Miyakawa, Takeshi; Takasu, Masako; Akanuma, Satoshi; Yamagishi, Akihiko

2013-02-01

Docking of two protein molecules is induced by intermolecular interactions. Our purposes in this study are: designing binding interfaces on the two proteins, which specifically interact to each other; and inducing intermolecular interactions between the two proteins by mixing them. A 4-helix bundle structure was chosen as a scaffold on which binding interfaces were created. Based on this scaffold, we designed binding interfaces involving charged and nonpolar amino acid residues. We performed molecular dynamics (MD) simulation to identify suitable amino acid residues for the interfaces. We chose YciF protein as the scaffold for the protein-protein docking simulation. We observed the structure of two YciF protein molecules (I and II), and we calculated the distance between centroids (center of gravity) of the interfaces' surface planes of the molecules I and II. We found that the docking of the two protein molecules can be controlled by the number of hydrophobic and charged amino acid residues involved in the interfaces. Existence of six hydrophobic and five charged amino acid residues within an interface were most suitable for the protein-protein docking.

Nanofibrous scaffolds for the guidance of stem cell-derived neurons for auditory nerve regeneration.

PubMed

Hackelberg, Sandra; Tuck, Samuel J; He, Long; Rastogi, Arjun; White, Christina; Liu, Liqian; Prieskorn, Diane M; Miller, Ryan J; Chan, Che; Loomis, Benjamin R; Corey, Joseph M; Miller, Josef M; Duncan, R Keith

2017-01-01

Impairment of spiral ganglion neurons (SGNs) of the auditory nerve is a major cause for hearing loss occurring independently or in addition to sensory hair cell damage. Unfortunately, mammalian SGNs lack the potential for autonomous regeneration. Stem cell based therapy is a promising approach for auditory nerve regeneration, but proper integration of exogenous cells into the auditory circuit remains a fundamental challenge. Here, we present novel nanofibrous scaffolds designed to guide the integration of human stem cell-derived neurons in the internal auditory meatus (IAM), the foramen allowing passage of the spiral ganglion to the auditory brainstem. Human embryonic stem cells (hESC) were differentiated into neural precursor cells (NPCs) and seeded onto aligned nanofiber mats. The NPCs terminally differentiated into glutamatergic neurons with high efficiency, and neurite projections aligned with nanofibers in vitro. Scaffolds were assembled by seeding GFP-labeled NPCs on nanofibers integrated in a polymer sheath. Biocompatibility and functionality of the NPC-seeded scaffolds were evaluated in vivo in deafened guinea pigs (Cavia porcellus). To this end, we established an ouabain-based deafening procedure that depleted an average 72% of SGNs from apex to base of the cochleae and caused profound hearing loss. Further, we developed a surgical procedure to implant seeded scaffolds directly into the guinea pig IAM. No evidence of an inflammatory response was observed, but post-surgery tissue repair appeared to be facilitated by infiltrating Schwann cells. While NPC survival was found to be poor, both subjects implanted with NPC-seeded and cell-free control scaffolds showed partial recovery of electrically-evoked auditory brainstem thresholds. Thus, while future studies must address cell survival, nanofibrous scaffolds pose a promising strategy for auditory nerve regeneration.

Design and characterization of a biodegradable double-layer scaffold aimed at periodontal tissue-engineering applications.

PubMed

Requicha, João F; Viegas, Carlos A; Hede, Shantesh; Leonor, Isabel B; Reis, Rui L; Gomes, Manuela E

2016-05-01

The inefficacy of the currently used therapies in achieving the regeneration ad integrum of the periodontium stimulates the search for alternative approaches, such as tissue-engineering strategies. Therefore, the core objective of this study was to develop a biodegradable double-layer scaffold for periodontal tissue engineering. The design philosophy was based on a double-layered construct obtained from a blend of starch and poly-ε-caprolactone (30:70 wt%; SPCL). A SPCL fibre mesh functionalized with silanol groups to promote osteogenesis was combined with a SPCL solvent casting membrane aiming at acting as a barrier against the migration of gingival epithelium into the periodontal defect. Each layer of the double-layer scaffolds was characterized in terms of morphology, surface chemical composition, degradation behaviour and mechanical properties. Moreover, the behaviour of seeded/cultured canine adipose-derived stem cells (cASCs) was assessed. In general, the developed double-layered scaffolds demonstrated adequate degradation and mechanical behaviour for the target application. Furthermore, the biological assays revealed that both layers of the scaffold allow adhesion and proliferation of the seeded undifferentiated cASCs, and the incorporation of silanol groups into the fibre-mesh layer enhance the expression of a typical osteogenic marker. This study allowed an innovative construct to be developed, combining a three-dimensional (3D) scaffold with osteoconductive properties and with potential to assist periodontal regeneration, carrying new possible solutions to current clinical needs. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd.

Biomimetic fiber mesh scaffolds based on gelatin and hydroxyapatite nano-rods: Designing intrinsic skills to attain bone reparation abilities.

PubMed

Sartuqui, Javier; Gravina, A Noel; Rial, Ramón; Benedini, Luciano A; Yahia, L'Hocine; Ruso, Juan M; Messina, Paula V

2016-09-01

Intrinsic material skills have a deep effect on the mechanical and biological performance of bone substitutes, as well as on its associated biodegradation properties. In this work we have manipulated the preparation of collagenous derived fiber mesh frameworks to display a specific composition, morphology, open macroporosity, surface roughness and permeability characteristics. Next, the effect of the induced physicochemical attributes on the scaffold's mechanical behavior, bone bonding potential and biodegradability were evaluated. It was found that the scaffold microstructure, their inherent surface roughness, and the compression strength of the gelatin scaffolds can be modulated by the effect of the cross-linking agent and, essentially, by mimicking the nano-scale size of hydroxyapatite in natural bone. A clear effect of bioactive hydroxyapatite nano-rods on the scaffolds skills can be appreciated and it is greater than the effect of the cross-linking agent, offering a huge perspective for the upcoming progress of bone implant technology. Copyright © 2016 Elsevier B.V. All rights reserved.

Design and characterization of fibrin-based acoustically responsive scaffolds for tissue engineering applications

PubMed Central

Moncion, Alexander; Arlotta, Keith J.; Kripfgans, Oliver D.; Fowlkes, J. Brian; Carson, Paul L.; Putnam, Andrew J.; Franceschi, Renny T.; Fabiilli, Mario L.

2015-01-01

Hydrogel scaffolds are used in tissue engineering as a delivery vehicle for regenerative growth factors (GFs). Spatiotemporal patterns of GF signaling are critical for tissue regeneration, yet most scaffolds afford limited control of GF release, especially after implantation. We previously demonstrated that acoustic droplet vaporization (ADV) can control GF release from a fibrin scaffold doped with a perfluorocarbon emulsion. This study investigates properties of the acoustically responsive scaffold (ARS) critical for further translation. At 2.5 MHz, ADV and inertial cavitation thresholds ranged from 1.5 – 3.0 MPa and 2.0 – 7.0 MPa peak rarefactional pressure, respectively, for ARSs of varying compositions. Viability of C3H10T1/2 cells, encapsulated in the ARS, did not decrease significantly for pressures below 4 MPa. ARSs with perfluorohexane emulsions displayed higher stability versus perfluoropentane emulsions, while surrogate payload release was minimal without ultrasound. These results enable the selection of ARS compositions and acoustic parameters needed for optimized spatiotemporal control. PMID:26526782

Regenerating Articular Tissue by Converging Technologies

PubMed Central

Paoluzzi, Luca; Pieper, Jeroen; de Wijn, Joost R.; van Blitterswijk, Clemens A.

2008-01-01

Scaffolds for osteochondral tissue engineering should provide mechanical stability, while offering specific signals for chondral and bone regeneration with a completely interconnected porous network for cell migration, attachment, and proliferation. Composites of polymers and ceramics are often considered to satisfy these requirements. As such methods largely rely on interfacial bonding between the ceramic and polymer phase, they may often compromise the use of the interface as an instrument to direct cell fate. Alternatively, here, we have designed hybrid 3D scaffolds using a novel concept based on biomaterial assembly, thereby omitting the drawbacks of interfacial bonding. Rapid prototyped ceramic particles were integrated into the pores of polymeric 3D fiber-deposited (3DF) matrices and infused with demineralized bone matrix (DBM) to obtain constructs that display the mechanical robustness of ceramics and the flexibility of polymers, mimicking bone tissue properties. Ostechondral scaffolds were then fabricated by directly depositing a 3DF structure optimized for cartilage regeneration adjacent to the bone scaffold. Stem cell seeded scaffolds regenerated both cartilage and bone in vivo. PMID:18716660

Magnesium Oxide Nanoparticles Reinforced Electrospun Alginate-Based Nanofibrous Scaffolds with Improved Physical Properties

PubMed Central

Mantilaka, M. M. M. G. P. G.; Goh, K. L.; Ratnayake, S. P.; Amaratunga, G. A. J.; de Silva, K. M. Nalin

2017-01-01

Mechanically robust alginate-based nanofibrous scaffolds were successfully fabricated by electrospinning method to mimic the natural extracellular matrix structure which benefits development and regeneration of tissues. Alginate-based nanofibres were electrospun from an alginate/poly(vinyl alcohol) (PVA) polyelectrolyte complex. SEM images revealed the spinnability of the complex composite nanofibrous scaffolds, showing randomly oriented, ultrafine, and virtually defects-free alginate-based/MgO nanofibrous scaffolds. Here, it is shown that an alginate/PVA complex scaffold, blended with near-spherical MgO nanoparticles (⌀ 45 nm) at a predetermined concentration (10% (w/w)), is electrospinnable to produce a complex composite nanofibrous scaffold with enhanced mechanical stability. For the comparison purpose, chemically cross-linked electrospun alginate-based scaffolds were also fabricated. Tensile test to rupture revealed the significant differences in the tensile strength and elastic modulus among the alginate scaffolds, alginate/MgO scaffolds, and cross-linked alginate scaffolds (P < 0.05). In contrast to cross-linked alginate scaffolds, alginate/MgO scaffolds yielded the highest tensile strength and elastic modulus while preserving the interfibre porosity of the scaffolds. According to the thermogravimetric analysis, MgO reinforced alginate nanofibrous scaffolds exhibited improved thermal stability. These novel alginate-based/MgO scaffolds are economical and versatile and may be further optimised for use as extracellular matrix substitutes for repair and regeneration of tissues. PMID:28694826

The Synthesis Approach to Analysing Educational Design Dataset: Application of Three Scaffolds to a Learning by Design Task for Postgraduate Education Students

ERIC Educational Resources Information Center

Thompson, Kate; Carvalho, Lucila; Aditomo, Anindito; Dimitriadis, Yannis; Dyke, Gregory; Evans, Michael A.; Khosronejad, Maryam; Martinez-Maldonado, Roberto; Reimann, Peter; Wardak, Dewa

2015-01-01

The aims of the Synthesis and Scaffolding Project were to understand: the role of specific scaffolds in relation to the activity of learners, and the activity of learners during a collaborative design task from multiple perspectives, through the collection and analysis of multiple streams of data and the adoption of a synthesis approach to the…

Shape optimization using a NURBS-based interface-enriched generalized FEM

DOE PAGES

Najafi, Ahmad R.; Safdari, Masoud; Tortorelli, Daniel A.; ...

2016-11-26

This study presents a gradient-based shape optimization over a fixed mesh using a non-uniform rational B-splines-based interface-enriched generalized finite element method, applicable to multi-material structures. In the proposed method, non-uniform rational B-splines are used to parameterize the design geometry precisely and compactly by a small number of design variables. An analytical shape sensitivity analysis is developed to compute derivatives of the objective and constraint functions with respect to the design variables. Subtle but important new terms involve the sensitivity of shape functions and their spatial derivatives. As a result, verification and illustrative problems are solved to demonstrate the precision andmore » capability of the method.« less

Strategies on process engineering of chondrocyte culture for cartilage tissue regeneration.

PubMed

Mallick, Sarada Prasanna; Rastogi, Amit; Tripathi, Satyavrat; Srivastava, Pradeep

2017-04-01

The current work is an attempt to study the strategies for cartilage tissue regeneration using porous scaffold in wavy walled airlift bioreactor (ALBR). Novel chitosan, poly (L-lactide) and hyaluronic acid based composite scaffold were prepared. The scaffolds were cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, N-hydroxysuccinimide and chondroitin sulfate to obtain interconnected 3D microstructure showing excellent biocompatibility, higher cellular differentiation and increased stability. The surface morphology and porosity of the scaffolds were analyzed using scanning electron microscopy (SEM) and mercury intrusion porosimeter and optimized for chondrocyte regeneration. The study shows that the scaffolds were highly porous with pore size ranging from 48 to 180 µm and the porosities in the range 80-92%. Swelling and in vitro degradation studies were performed for the composite scaffolds; by increasing the chitosan: HA ratio in the composite scaffolds, the swelling property increases and stabilizes after 24 h. There was controlled degradation of composite scaffolds for 4 weeks. The uniform chondrocyte distribution in the scaffold using various growth modes in the shake flask and ALBR was studied by glycosaminoglycans (GAG) quantification, MTT assay and mixing time evaluation. The cell culture studies demonstrated that efficient designing of ALBR increases the cartilage regeneration as compared to using a shake flask. The free chondrocyte microscopy and cell attachment were performed by inverted microscope and SEM, and from the study it was confirmed that the cells uniformly attached to the scaffold. This study focuses on optimizing strategies for the culture of chondrocyte using suitable scaffold for improved cartilage tissue regeneration.

In silico simulation and in vitro evaluation of an elastomeric scaffold using ultrasonic shear wave imaging

NASA Astrophysics Data System (ADS)

Yu, Jiao; Nie, Erwei; Zhu, Yanying; Hong, Yi

2018-03-01

Biodegradable elastomeric scaffolds for soft tissue repair represent a growing area of biomaterials research. Mechanical strength is one of the key factors to consider in the evaluation of candidate materials and the designs for tissue scaffolds. It is desirable to develop non-invasive evaluation methods of the mechanical property of scaffolds which would provide options for monitoring temporal mechanical property changes in situ. In this paper, we conduct in silico simulation and in vitro evaluation of an elastomeric scaffold using a novel ultrasonic shear wave imaging (USWI). The scaffold is fabricated from a biodegradable elastomer, poly(carbonate urethane) urea using salt leaching method. A numerical simulation is performed to test the robustness of the developed inversion algorithm for the elasticity map reconstruction which will be implemented in the phantom experiment. The generation and propagation of shear waves in a homogeneous tissue-mimicking medium with a circular scaffold inclusion is simulated and the elasticity map is well reconstructed. A PVA phantom experiment is performed to test the ability of USWI combined with the inversion algorithm to non-invasively characterize the mechanical property of a porous, biodegradable elastomeric scaffold. The elastic properties of the tested scaffold can be easily differentiated from the surrounding medium in the reconstructed image. The ability of the developed method to identify the edge of the scaffold and characterize the elasticity distribution is demonstrated. Preliminary results in this pilot study support the idea of applying the USWI based method for non-invasive elasticity characterization of tissue scaffolds.

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.

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.

A Perspective on the Clinical Translation of Scaffolds for Tissue Engineering

PubMed Central

Webber, Matthew J.; Khan, Omar F.; Sydlik, Stefanie A.; Tang, Benjamin C.; Langer, Robert

2016-01-01

Scaffolds have been broadly applied within tissue engineering and regenerative medicine to regenerate, replace, or augment diseased or damaged tissue. For a scaffold to perform optimally, several design considerations must be addressed, with an eye toward the eventual form, function, and tissue site. The chemical and mechanical properties of the scaffold must be tuned to optimize the interaction with cells and surrounding tissues. For complex tissue engineering, mass transport limitations, vascularization, and host tissue integration are important considerations. As the tissue architecture to be replaced becomes more complex and hierarchical, scaffold design must also match this complexity to recapitulate a functioning tissue. We outline these design constraints and highlight creative and emerging strategies to overcome limitations and modulate scaffold properties for optimal regeneration. We also highlight some of the most advanced strategies that have seen clinical application and discuss the hurdles that must be overcome for clinical use and commercialization of tissue engineering technologies. Finally, we provide a perspective on the future of scaffolds as a functional contributor to advancing tissue engineering and regenerative medicine. PMID:25201605

A perspective on the clinical translation of scaffolds for tissue engineering.

PubMed

Webber, Matthew J; Khan, Omar F; Sydlik, Stefanie A; Tang, Benjamin C; Langer, Robert

2015-03-01

Scaffolds have been broadly applied within tissue engineering and regenerative medicine to regenerate, replace, or augment diseased or damaged tissue. For a scaffold to perform optimally, several design considerations must be addressed, with an eye toward the eventual form, function, and tissue site. The chemical and mechanical properties of the scaffold must be tuned to optimize the interaction with cells and surrounding tissues. For complex tissue engineering, mass transport limitations, vascularization, and host tissue integration are important considerations. As the tissue architecture to be replaced becomes more complex and hierarchical, scaffold design must also match this complexity to recapitulate a functioning tissue. We outline these design constraints and highlight creative and emerging strategies to overcome limitations and modulate scaffold properties for optimal regeneration. We also highlight some of the most advanced strategies that have seen clinical application and discuss the hurdles that must be overcome for clinical use and commercialization of tissue engineering technologies. Finally, we provide a perspective on the future of scaffolds as a functional contributor to advancing tissue engineering and regenerative medicine.

Geometry Design Optimization of Functionally Graded Scaffolds for Bone Tissue Engineering: A Mechanobiological Approach

PubMed Central

Boccaccio, Antonio; Uva, Antonio Emmanuele; Fiorentino, Michele; Mori, Giorgio; Monno, Giuseppe

2016-01-01

Functionally Graded Scaffolds (FGSs) are porous biomaterials where porosity changes in space with a specific gradient. In spite of their wide use in bone tissue engineering, possible models that relate the scaffold gradient to the mechanical and biological requirements for the regeneration of the bony tissue are currently missing. In this study we attempt to bridge the gap by developing a mechanobiology-based optimization algorithm aimed to determine the optimal graded porosity distribution in FGSs. The algorithm combines the parametric finite element model of a FGS, a computational mechano-regulation model and a numerical optimization routine. For assigned boundary and loading conditions, the algorithm builds iteratively different scaffold geometry configurations with different porosity distributions until the best microstructure geometry is reached, i.e. the geometry that allows the amount of bone formation to be maximized. We tested different porosity distribution laws, loading conditions and scaffold Young’s modulus values. For each combination of these variables, the explicit equation of the porosity distribution law–i.e the law that describes the pore dimensions in function of the spatial coordinates–was determined that allows the highest amounts of bone to be generated. The results show that the loading conditions affect significantly the optimal porosity distribution. For a pure compression loading, it was found that the pore dimensions are almost constant throughout the entire scaffold and using a FGS allows the formation of amounts of bone slightly larger than those obtainable with a homogeneous porosity scaffold. For a pure shear loading, instead, FGSs allow to significantly increase the bone formation compared to a homogeneous porosity scaffolds. Although experimental data is still necessary to properly relate the mechanical/biological environment to the scaffold microstructure, this model represents an important step towards optimizing geometry of functionally graded scaffolds based on mechanobiological criteria. PMID:26771746

Controlling the extrudate swell in melt extrusion additive manufacturing of 3D scaffolds: a designed experiment.

PubMed

Yousefi, Azizeh-Mitra; Smucker, Byran; Naber, Alex; Wyrick, Cara; Shaw, Charles; Bennett, Katelyn; Szekely, Sarah; Focke, Carlie; Wood, Katherine A

2018-02-01

Tissue engineering using three-dimensional porous scaffolds has shown promise for the restoration of normal function in injured and diseased tissues and organs. Rigorous control over scaffold architecture in melt extrusion additive manufacturing is highly restricted mainly due to pronounced variations in the deposited strand diameter upon any variations in process conditions and polymer viscoelasticity. We have designed an I-optimal, split-plot experiment to study the extrudate swell in melt extrusion additive manufacturing and to control the scaffold architecture. The designed experiment was used to generate data to relate three responses (swell, density, and modulus) to a set of controllable factors (plotting needle diameter, temperature, pressure, and the dispensing speed). The fitted regression relationships were used to optimize the three responses simultaneously. The swell response was constrained to be close to 1 while maximizing the modulus and minimizing the density. Constraining the extrudate swell to 1 generates design-driven scaffolds, with strand diameters equal to the plotting needle diameter, and allows a greater control over scaffold pore size. Hence, the modulus of the scaffolds can be fully controlled by adjusting the in-plane distance between the deposited strands. To the extent of the model's validity, we can eliminate the effect of extrudate swell in designing these scaffolds, while targeting a range of porosity and modulus appropriate for bone tissue engineering. The result of this optimization was a predicted modulus of 14 MPa and a predicted density of 0.29 g/cm 3 (porosity ≈ 75%) using polycaprolactone as scaffold material. These predicted responses corresponded to factor levels of 0.6 μm for the plotting needle diameter, plotting pressure of 2.5 bar, melt temperature of 113.5 °C, and dispensing speed of 2 mm/s. The validation scaffold enabled us to quantify the percentage difference for the predictions, which was 9.5% for the extrudate swell, 19% for the density, and 29% for the modulus.

A Systems Approach to Scaffold Communication Skills Development

PubMed Central

Er, Nelson L.

2008-01-01

Objectives To implement a communication skills development (CSD) system and evaluate its effectiveness in a clinical communications course. Design Students conducted baseline interviews and wrote SOAP notes, and based on faculty, patient, self- and peer assessments, set goals for improvement of their communication skills. Students participated in various activities to scaffold their learning, several of which took place in a web-based environment to enhance access and function for both students and faculty members. Quantitative and qualitative analyses were performed. Assessment Students' communication skills improved as evidenced by assessment scores. Student and faculty comments offered additional evidence of the effectiveness of standardized patient interviews, learning strategies, and assessment methods. Conclusion The CSD system effectively integrated various types of learning activities and feedback processes. The use of scaffolding strategies appeared to enhance the development of students' communication skills. PMID:18483601

Pharmacological and Nutritional Effects of Natural Coumarins and Their Structure-Activity Relationships.

PubMed

Zhu, Jing-Jing; Jiang, Jian-Guo

2018-05-11

Coumarins are fused benzene and pyrone ring systems with a wide spectrum of bioactivities including anti-tumor, anti-inflammation, antiviral and antibacterial effects. In this paper, the current development of coumarins-based drugs is introduced, and their structure-activity relationship is discussed by reviewing the relevant literatures published in the past twenty years. Coumarin molecules can be customized by the target site to prevent systemic side effects by virtue of structural modification. The ortho-phenolic hydroxyl on the benzene ring had remarkable antioxidant and anti-tumor activities. Coumarins with aryl groups at the C-4 position have good activities in anti-HIV, anti-tumor, anti-inflammation and analgesia. C-3 phenylcoumarins have strong anti-HIV and antioxidant effects. Tetracycline pyranocoumarins can significantly inhibit the HIV, osthol structural analogues have antimicrobial activity. Praeruptorin C and its derivatives play an important role in lowering blood pressure and dilating coronary arteries, and khellactone derivatives have significant inhibitory effects on AIDS, cancer and cardiovascular diseases. It is concluded that the specific site on the core structure of coumarin exhibits one or more activities due to the electronic or steric effects of the substituents. This review is designed to be conducive to rational design and development of more active and less toxic agents with a coumarin scaffold. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Supporting Teachers in Designing CSCL Activities: A Case Study of Principle-Based Pedagogical Patterns in Networked Second Language Classrooms

ERIC Educational Resources Information Center

Wen, Yun; Looi, Chee-Kit; Chen, Wenli

2012-01-01

This paper proposes the identification and use of principle-based pedagogical patterns to help teachers to translate design principles into actionable teaching activities, and to scaffold student learning with sufficient flexibility and creativity. A set of pedagogical patterns for networked Second language (L2) learning, categorized and…

Using Narrative-Based Design Scaffolds within a Mobile Learning Environment to Support Learning Outdoors with Young Children

ERIC Educational Resources Information Center

Seely, Brian J.

2015-01-01

This study aims to advance learning outdoors with mobile devices. As part of the ongoing Tree Investigators design-based research study, this research investigated a mobile application to support observation, identification, and explanation of the tree life cycle within an authentic, outdoor setting. Recognizing the scientific and conceptual…

Examining the Characteristics of Student Postings That Are Liked and Linked in a CSCL Environment

ERIC Educational Resources Information Center

Makos, Alexandra; Lee, Kyungmee; Zingaro, Daniel

2015-01-01

This case study is the first iteration of a large-scale design-based research project to improve Pepper, an interactive discussion-based learning environment. In this phase, we designed and implemented two social features to scaffold positive learner interactivity behaviors: a "Like" button and linking tool. A mixed-methods approach was…

Database Design Learning: A Project-Based Approach Organized through a Course Management System

ERIC Educational Resources Information Center

Dominguez, Cesar; Jaime, Arturo

2010-01-01

This paper describes an active method for database design learning through practical tasks development by student teams in a face-to-face course. This method integrates project-based learning, and project management techniques and tools. Some scaffolding is provided at the beginning that forms a skeleton that adapts to a great variety of…

Sexual harassment in healthcare: classification of harassers and rationalizations of sex-based harassment behavior.

PubMed

Madison, J; Minichiello, V

2001-11-01

This study identified how 16 Australian registered nurses classified sex-based harassers and explained their own behavior and the behavior of the harasser. A qualitative research design, relying on in-depth interviews, was used to collect the data. The study found that harassment is linked to gender roles and that the harassed are reluctant to blame the harasser--the harassed had "sound" rationalizations for harassment. Awareness of the interactional dynamics of self-blame and these rationalizations will help nurse executives ensure a harassment-free workplace.

Hybrid Carbon-Based Scaffolds for Applications in Soft Tissue Reconstruction

PubMed Central

Lafdi, Khalid; Joseph, Robert M.; Tsonis, Panagiotis A.

2012-01-01

Current biomedical scaffolds utilized in surgery to repair soft tissues commonly fail to meet the optimal combination of biomechanical and tissue regenerative properties. Carbon is a scaffold alternative that potentially optimizes the balance between mechanical strength, durability, and function as a cell and biologics delivery vehicle that is necessary to restore tissue function while promoting tissue repair. The goals of this study were to investigate the feasibility of fabricating hybrid fibrous carbon scaffolds modified with biopolymer, polycaprolactone and to analyze their mechanical properties and ability to support cell growth and proliferation. Environmental scanning electron microscopy, micro-computed tomography, and cell adhesion and cell proliferation studies were utilized to test scaffold suitability as a cell delivery vehicle. Mechanical properties were tested to examine load failure and elastic modulus. Results were compared to an acellular dermal matrix scaffold control (GraftJacket® [GJ] Matrix), selected for its common use in surgery for the repair of soft tissues. Results indicated that carbon scaffolds exhibited similar mechanical maximums and capacity to support fibroblast adhesion and proliferation in comparison with GJ. Fibroblast adhesion and proliferation was collinear with carbon fiber orientation in regions of sparsely distributed fibers and occurred in clusters in regions of higher fiber density and low porosity. Overall, fibroblast adhesion and proliferation was greatest in lower porosity carbon scaffolds with highly aligned fibers. Stepwise multivariate regression showed that the variability in maximum load of carbon scaffolds and controls were dependent on unique and separate sets of parameters. These finding suggested that there were significant differences in the functional implications of scaffold design and material properties between carbon and dermis derived scaffolds that affect scaffold utility as a tissue replacement construct. PMID:22092333

Rational Design of a Water-Storable Hierarchical Architecture Decorated with Amorphous Barium Oxide and Nickel Nanoparticles as a Solid Oxide Fuel Cell Anode with Excellent Sulfur Tolerance.

PubMed

Song, Yufei; Wang, Wei; Ge, Lei; Xu, Xiaomin; Zhang, Zhenbao; Julião, Paulo Sérgio Barros; Zhou, Wei; Shao, Zongping

2017-11-01

Solid oxide fuel cells (SOFCs), which can directly convert chemical energy stored in fuels into electric power, represent a useful technology for a more sustainable future. They are particularly attractive given that they can be easily integrated into the currently available fossil fuel infrastructure to realize an ideal clean energy system. However, the widespread use of the SOFC technology is hindered by sulfur poisoning at the anode caused by the sulfur impurities in fossil fuels. Therefore, improving the sulfur tolerance of the anode is critical for developing SOFCs for use with fossil fuels. Herein, a novel, highly active, sulfur-tolerant anode for intermediate-temperature SOFCs is prepared via a facile impregnation and limited reaction protocol. During synthesis, Ni nanoparticles, water-storable BaZr 0.4 Ce 0.4 Y 0.2 O 3- δ (BZCY) perovskite, and amorphous BaO are formed in situ and deposited on the surface of a Sm 0.2 Ce 0.8 O 1.9 (SDC) scaffold. More specifically, a porous SDC scaffold is impregnated with a well-designed proton-conducting perovskite oxide liquid precursor with the nominal composition of Ba(Zr 0.4 Ce 0.4 Y 0.2 ) 0.8 Ni 0.2 O 3- δ (BZCYN), calcined and reduced in hydrogen. The as-synthesized hierarchical architecture exhibits high H 2 electro-oxidation activity, excellent operational stability, superior sulfur tolerance, and good thermal cyclability. This work demonstrates the potential of combining nanocatalysts and water-storable materials in advanced electrocatalysts for SOFCs.

Computer-based teaching module design: principles derived from learning theories.

PubMed

Lau, K H Vincent

2014-03-01

The computer-based teaching module (CBTM), which has recently gained prominence in medical education, is a teaching format in which a multimedia program serves as a single source for knowledge acquisition rather than playing an adjunctive role as it does in computer-assisted learning (CAL). Despite empirical validation in the past decade, there is limited research into the optimisation of CBTM design. This review aims to summarise research in classic and modern multimedia-specific learning theories applied to computer learning, and to collapse the findings into a set of design principles to guide the development of CBTMs. Scopus was searched for: (i) studies of classic cognitivism, constructivism and behaviourism theories (search terms: 'cognitive theory' OR 'constructivism theory' OR 'behaviourism theory' AND 'e-learning' OR 'web-based learning') and their sub-theories applied to computer learning, and (ii) recent studies of modern learning theories applied to computer learning (search terms: 'learning theory' AND 'e-learning' OR 'web-based learning') for articles published between 1990 and 2012. The first search identified 29 studies, dominated in topic by the cognitive load, elaboration and scaffolding theories. The second search identified 139 studies, with diverse topics in connectivism, discovery and technical scaffolding. Based on their relative representation in the literature, the applications of these theories were collapsed into a list of CBTM design principles. Ten principles were identified and categorised into three levels of design: the global level (managing objectives, framing, minimising technical load); the rhetoric level (optimising modality, making modality explicit, scaffolding, elaboration, spaced repeating), and the detail level (managing text, managing devices). This review examined the literature in the application of learning theories to CAL to develop a set of principles that guide CBTM design. Further research will enable educators to take advantage of this unique teaching format as it gains increasing importance in medical education. © 2014 John Wiley & Sons Ltd.

Diffusion chamber system for testing of collagen-based cell migration barriers for separation of ligament enthesis zones in tissue-engineered ACL constructs.

PubMed

Hahner, J; Hoyer, M; Hillig, S; Schulze-Tanzil, G; Meyer, M; Schröpfer, M; Lohan, A; Garbe, L-A; Heinrich, G; Breier, A

2015-01-01

A temporary barrier separating scaffold zones seeded with different cell types prevents faster growing cells from overgrowing co-cultured cells within the same construct. This barrier should allow sufficient nutrient diffusion through the scaffold. The aim of this study was to test the effect of two variants of collagen-based barriers on macromolecule diffusion, viability, and the spreading efficiency of primary ligament cells on embroidered scaffolds. Two collagen barriers, a thread consisting of a twisted film tape and a sponge, were integrated into embroidered poly(lactic-co-caprolactone) and polypropylene scaffolds, which had the dimension of lapine anterior cruciate ligaments (ACL). A diffusion chamber system was designed and established to monitor nutrient diffusion using fluorescein isothiocyanate-labeled dextran of different molecular weights (20, 40, 150, 500 kDa). Vitality of primary lapine ACL cells was tested at days 7 and 14 after seeding using fluorescein diacetate and ethidium bromide staining. Cell spreading on the scaffold surface was measured using histomorphometry. Nuclei staining of the cross-sectioned scaffolds revealed the penetration of ligament cells through both barrier types. The diffusion chamber was suitable to characterize the diffusivity of dextran molecules through embroidered scaffolds with or without integrated collagen barriers. The diffusion coefficients were generally significantly lower in scaffolds with barriers compared to those without barriers. No significant differences between diffusion coefficients of both barrier types were detected. Both barriers were cyto-compatible and prevented most of the ACL cells from crossing the barrier, whereby the collagen thread was easier to handle and allowed a higher rate of cell spreading.

Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique.

PubMed

Ryan, Garrett E; Pandit, Abhay S; Apatsidis, Dimitrios P

2008-09-01

One of the main issues in orthopaedic implant design is the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. This research reports on a multi-stage rapid prototyping technique that was successfully developed to produce porous titanium scaffolds with fully interconnected pore networks and reproducible porosity and pore size. The scaffolds' porous characteristics were governed by a sacrificial wax template, fabricated using a commercial 3D-printer. Powder metallurgy processes were employed to generate the titanium scaffolds by filling around the wax template with titanium slurry. In the attempt to optimise the powder metallurgy technique, variations in slurry concentration, compaction pressure and sintering temperature were investigated. By altering the wax design template, pore sizes ranging from 200 to 400 microm were achieved. Scaffolds with porosities of 66.8 +/- 3.6% revealed compression strengths of 104.4+/-22.5 MPa in the axial direction and 23.5 +/- 9.6 MPa in the transverse direction demonstrating their anisotropic nature. Scaffold topography was characterised using scanning electron microscopy and microcomputed tomography. Three-dimensional reconstruction enabled the main architectural parameters such as pore size, interconnecting porosity, level of anisotropy and level of structural disorder to be determined. The titanium scaffolds were compared to their intended designs, as governed by their sacrificial wax templates. Although discrepancies in architectural parameters existed between the intended and the actual scaffolds, overall the results indicate that the porous titanium scaffolds have the properties to be potentially employed in orthopaedic applications.

Force-controlled automatic microassembly of tissue engineering scaffolds

NASA Astrophysics Data System (ADS)

Zhao, Guoyong; Teo, Chee Leong; Hutmacher, Dietmar Werner; Burdet, Etienne

2010-03-01

This paper presents an automated system for 3D assembly of tissue engineering (TE) scaffolds made from biocompatible microscopic building blocks with relatively large fabrication error. It focuses on the pin-into-hole force control developed for this demanding microassembly task. A beam-like gripper with integrated force sensing at a 3 mN resolution with a 500 mN measuring range is designed, and is used to implement an admittance force-controlled insertion using commercial precision stages. Visual-based alignment followed by an insertion is complemented by a haptic exploration strategy using force and position information. The system demonstrates fully automated construction of TE scaffolds with 50 microparts whose dimension error is larger than 5%.

Perfusion properties of scaffolds: A new approach to tissue engineering designs for bone regeneration

NASA Astrophysics Data System (ADS)

Larionov, P. M.; Maslov, N. A.; Papaeva, E. O.; Yunoshev, A. S.; Filipenko, M. L.; Bogachev, S. S.; Proskurina, A. S.; Samokhin, A. G.; Kudrov, G. A.; Tereshchenko, V. P.; Pavlov, V. V.; Mihailovsky, M. V.; Prohorenko, V. M.; Titov, A. T.; Mamonova, E. V.; Sadovoy, M. A.

2017-09-01

The main approach to tissue engineering involves the use of scaffolds seeded with cells, followed by culturing in a bioreactor. However, the effective use of a bioreactor requires adaptation of the scaffold at the stage of its design. In our opinion, this means assessment of the perfusion properties of the scaffold. Transverse and longitudinal perfusion under hydrostatic pressure of 5, 10, and 15 mmHg, as well as the significance of electrospinning parameters for fabrication of a scaffold sheet and the composition of composite material—11% w/v polycaprolactone with gelatinization of 0.5%, 2%, and 4%, were demonstrated.

Scaffold metamaterial and its application as strain sensor

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

Wu, Wei; Ren, Mengxin, E-mail: ren-mengxin@nankai.edu.cn; Pi, Biao

2015-08-31

In this paper, strain sensors based on planar scaffold metamaterial design are demonstrated. The optical properties of such metamaterials are studied, which are proved to be highly dependent on the deformation of the structure. Fabricating such metamaterial on compliant polymeric substrate, the geometric parameters could be tuned with external strain and hence are found to control the reflection resonance condition of the metamaterial. Such mechanical tunability provides the opportunity to realize efficient strain sensors and about 27 nm resonance wavelength shift is observed by applying as much as 37% tensile strain. Furthermore, distinct from most of the previous works, our structuresmore » are based on “intaglio” design, which could be manufactured directly by one step fabrication using focused ion beam cutting, hence makes the fabrication process much simpler.« less

Effect of Layer Thickness and Printing Orientation on Mechanical Properties and Dimensional Accuracy of 3D Printed Porous Samples for Bone Tissue Engineering

PubMed Central

Farzadi, Arghavan; Solati-Hashjin, Mehran; Asadi-Eydivand, Mitra; Abu Osman, Noor Azuan

2014-01-01

Powder-based inkjet 3D printing method is one of the most attractive solid free form techniques. It involves a sequential layering process through which 3D porous scaffolds can be directly produced from computer-generated models. 3D printed products' quality are controlled by the optimal build parameters. In this study, Calcium Sulfate based powders were used for porous scaffolds fabrication. The printed scaffolds of 0.8 mm pore size, with different layer thickness and printing orientation, were subjected to the depowdering step. The effects of four layer thicknesses and printing orientations, (parallel to X, Y and Z), on the physical and mechanical properties of printed scaffolds were investigated. It was observed that the compressive strength, toughness and Young's modulus of samples with 0.1125 and 0.125 mm layer thickness were more than others. Furthermore, the results of SEM and μCT analyses showed that samples with 0.1125 mm layer thickness printed in X direction have more dimensional accuracy and significantly close to CAD software based designs with predefined pore size, porosity and pore interconnectivity. PMID:25233468

Cyclic Triimidazole Derivatives: Intriguing Examples of Multiple Emissions and Ultralong Phosphorescence at Room Temperature.

PubMed

Lucenti, Elena; Forni, Alessandra; Botta, Chiara; Carlucci, Lucia; Giannini, Clelia; Marinotto, Daniele; Pavanello, Alessandro; Previtali, Andrea; Righetto, Stefania; Cariati, Elena

2017-12-18

The performance of solid luminogens depends on both their inherent electronic properties and their packing status. Intermolecular interactions have been exploited to achieve persistent room-temperature phosphorescence (RTP) from organic molecules. However, the design of organic materials with bright RTP and the rationalization of the role of interchromophoric electronic coupling remain challenging tasks. Cyclic triimidazole has been shown to be a promising scaffold for such purposes owing to its crystallization-induced room-temperature ultralong phosphorescence (RTUP), which has been associated with H-aggregation. Herein, we report three triimidazole derivatives as significant examples of multifaceted emission. In particular, dual fluorescence, RTUP, and phosphorescence from the molecular and supramolecular units were observed. H-aggregation is responsible for the red RTUP, and Br substituents favor yellow molecular phosphorescence while halogen-bonded Br⋅⋅⋅Br tetrameric units are involved in the blue-green phosphorescence. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Some Benzofuran Derivatives Containing Pyrimidine Moiety as Potent Antimicrobial Agents.

PubMed

Venkatesh, Talavara; Bodke, Yadav Dasharathrao; Joy, Muthipeedika Nibin; Dhananjaya, Bhadrapura Lakkappa; Venkataraman, Sivaramakrishnan

2018-01-01

In this investigation, the synthesis of 2-substituted pyrimidines by the reaction of benzofuran chalcones (3a-d) with urea, thiourea and guanidine hydrochloride was reported. The structures of title compounds (4a-d), (5a-d) and (6a-d) were established on the basis of analytical and spectral data. The synthesized compounds were screened for antimicrobial activity and molecular docking studies. Some of the compounds displayed excellent antimicrobial activity. The molecular docking analysis revealed that compounds 5a and 5c with the lowest binding energy in comparison to others suggesting its potential as best inhibitor of GluN-6-P. Consequently, it is confirmed from the above analysis that the compounds 5a and 5c might serve as a useful backbone scaffold for rational design, adaptation and investigation of more active analogs as potential broad spectrum antimicrobial agents.

Pharmacokinetic and pharmacodynamic considerations for the next generation protein therapeutics.

PubMed

Shah, Dhaval K

2015-10-01

Increasingly sophisticated protein engineering efforts have been undertaken lately to generate protein therapeutics with desired properties. This has resulted in the discovery of the next generation of protein therapeutics, which include: engineered antibodies, immunoconjugates, bi/multi-specific proteins, antibody mimetic novel scaffolds, and engineered ligands/receptors. These novel protein therapeutics possess unique physicochemical properties and act via a unique mechanism-of-action, which collectively makes their pharmacokinetics (PK) and pharmacodynamics (PD) different than other established biological molecules. Consequently, in order to support the discovery and development of these next generation molecules, it becomes important to understand the determinants controlling their PK/PD. This review discusses the determinants that a PK/PD scientist should consider during the design and development of next generation protein therapeutics. In addition, the role of systems PK/PD models in enabling rational development of the next generation protein therapeutics is emphasized.

Pharmacokinetic and pharmacodynamic considerations for the next generation protein therapeutics

PubMed Central

Shah, Dhaval K.

2015-01-01

Increasingly sophisticated protein engineering efforts have been undertaken lately to generate protein therapeutics with desired properties. This has resulted in the discovery of the next generation of protein therapeutics, which include: engineered antibodies, immunoconjugates, bi/multi-specific proteins, antibody mimetic novel scaffolds, and engineered ligands/receptors. These novel protein therapeutics possess unique physicochemical properties and act via a unique mechanism-of-action, which collectively makes their pharmacokinetics (PK) and pharmacodynamics (PD) different than other established biological molecules. Consequently, in order to support the discovery and development of these next generation molecules, it becomes important to understand the determinants controlling their PK/PD. This review discusses the determinants that a PK/PD scientist should consider during the design and development of next generation protein therapeutics. In addition, the role of systems PK/PD models in enabling rational development of the next generation protein therapeutics is emphasized. PMID:26373957

Vascular Mechanobiology: Towards Control of In Situ Regeneration

PubMed Central

van Haaften, Eline E.; Bouten, Carlijn V. C.; Kurniawan, Nicholas A.

2017-01-01

The paradigm of regenerative medicine has recently shifted from in vitro to in situ tissue engineering: implanting a cell-free, biodegradable, off-the-shelf available scaffold and inducing the development of functional tissue by utilizing the regenerative potential of the body itself. This approach offers a prospect of not only alleviating the clinical demand for autologous vessels but also circumventing the current challenges with synthetic grafts. In order to move towards a hypothesis-driven engineering approach, we review three crucial aspects that need to be taken into account when regenerating vessels: (1) the structure-function relation for attaining mechanical homeostasis of vascular tissues; (2) the environmental cues governing cell function; and (3) the available experimental platforms to test instructive scaffolds for in situ tissue engineering. The understanding of cellular responses to environmental cues leads to the development of computational models to predict tissue formation and maturation, which are validated using experimental platforms recapitulating the (patho)physiological micro-environment. With the current advances, a progressive shift is anticipated towards a rational and effective approach of building instructive scaffolds for in situ vascular tissue regeneration. PMID:28671618

Vascular Mechanobiology: Towards Control of In Situ Regeneration.

PubMed

van Haaften, Eline E; Bouten, Carlijn V C; Kurniawan, Nicholas A

2017-07-03

The paradigm of regenerative medicine has recently shifted from in vitro to in situ tissue engineering: implanting a cell-free, biodegradable, off-the-shelf available scaffold and inducing the development of functional tissue by utilizing the regenerative potential of the body itself. This approach offers a prospect of not only alleviating the clinical demand for autologous vessels but also circumventing the current challenges with synthetic grafts. In order to move towards a hypothesis-driven engineering approach, we review three crucial aspects that need to be taken into account when regenerating vessels: (1) the structure-function relation for attaining mechanical homeostasis of vascular tissues, (2) the environmental cues governing cell function, and (3) the available experimental platforms to test instructive scaffolds for in situ tissue engineering. The understanding of cellular responses to environmental cues leads to the development of computational models to predict tissue formation and maturation, which are validated using experimental platforms recapitulating the (patho)physiological micro-environment. With the current advances, a progressive shift is anticipated towards a rational and effective approach of building instructive scaffolds for in situ vascular tissue regeneration.

Braided and Stacked Electrospun Nanofibrous Scaffolds for Tendon and Ligament Tissue Engineering.

PubMed

Rothrauff, Benjamin B; Lauro, Brian B; Yang, Guang; Debski, Richard E; Musahl, Volker; Tuan, Rocky S

2017-05-01

Tendon and ligament injuries are a persistent orthopedic challenge given their poor innate healing capacity. Nonwoven electrospun nanofibrous scaffolds composed of polyesters have been used to mimic the mechanics and topographical cues of native tendons and ligaments. However, nonwoven nanofibers have several limitations that prevent broader clinical application, including poor cell infiltration, as well as tensile and suture-retention strengths that are inferior to native tissues. In this study, multilayered scaffolds of aligned electrospun nanofibers of two designs-stacked or braided-were fabricated. Mechanical properties, including structural and mechanical properties and suture-retention strength, were determined using acellular scaffolds. Human bone marrow-derived mesenchymal stem cells (MSCs) were seeded on scaffolds for up to 28 days, and assays for tenogenic differentiation, histology, and biochemical composition were performed. Braided scaffolds exhibited improved tensile and suture-retention strengths, but reduced moduli. Both scaffold designs supported expression of tenogenic markers, although the effect was greater on braided scaffolds. Conversely, cell infiltration was superior in stacked constructs, resulting in enhanced cell number, total collagen content, and total sulfated glycosaminoglycan content. However, when normalized against cell number, both designs modulated extracellular matrix protein deposition to a similar degree. Taken together, this study demonstrates that multilayered scaffolds of aligned electrospun nanofibers supported tenogenic differentiation of seeded MSCs, but the macroarchitecture is an important consideration for applications of tendon and ligament tissue engineering.

A Meta-Analysis Method to Advance Design of Technology-Based Learning Tool: Combining Qualitative and Quantitative Research to Understand Learning in Relation to Different Technology Features

ERIC Educational Resources Information Center

Zhang, Lin

2014-01-01

Educators design and create various technology tools to scaffold students' learning. As more and more technology designs are incorporated into learning, growing attention has been paid to the study of technology-based learning tool. This paper discusses the emerging issues, such as how can learning effectiveness be understood in relation to…

Biomaterials Transforming growth factor-beta 1 delivery from microporous scaffolds decreases inflammation post-implant and enhances function of transplanted islets

PubMed Central

Liu, JMH; Zhang, J; Zhang, X; Hlavaty, KA; Ricci, CF; Leonard, JN; Shea, LD; Gower, RM

2015-01-01

Biomaterial scaffolds are central to many regenerative strategies as they create a space for infiltration of host tissue and provide a platform to deliver growth factors and progenitor cells. However, biomaterial implantation results in an unavoidable inflammatory response, which can impair tissue regeneration and promote loss or dysfunction of transplanted cells. We investigated localized TGF-β1 delivery to modulate this immunological environment around scaffolds and transplanted cells. TGF-β1 was delivered from layered scaffolds, with protein entrapped within an inner layer and outer layers designed for cell seeding and host tissue integration. Scaffolds were implanted into the epididymal fat pad, a site frequently used for cell transplantation. Expression of cytokines TNF-a, IL-12, and MCP-1 were decreased by at least 40% for scaffolds releasing TGF-β1 relative to control scaffolds. This decrease in inflammatory cytokine production corresponded to a 60% decrease in leukocyte infiltration. Transplantation of islets into diabetic mice on TGF-β1 scaffolds significantly improved the ability of syngeneic islets to control blood glucose levels within the first week of transplant and delayed rejection of allogeneic islets. Together, these studies emphasize the ability of localized TGF-β1 delivery to modulate the immune response to biomaterial implants and enhance cell function in cell-based therapies. PMID:26701143

Nanostructured fumarate copolymer-chitosan crosslinked scaffold: An in vitro osteochondrogenesis regeneration study.

PubMed

Lastra, María Laura; Molinuevo, María Silvina; Blaszczyk-Lezak, Iwona; Mijangos, Carmen; Cortizo, María Susana

2018-02-01

In the tissue engineering field, the design of the scaffold inspired on the natural occurring tissue is of vital importance. Ideally, the scaffold surface must promote cell growth and differentiation, while promote angiogenesis in the in vivo implant of the scaffold. On the other hand, the material selection must be biocompatible and the degradation times should meet tissue reparation times. In the present work, we developed a nanofibrous scaffold based on chitosan crosslinked with diisopropylfumarate-vinyl acetate copolymer using anodized aluminum oxide (AAO) templates. We have previously demonstrated its biocompatibility properties with low cytotoxicity and proper degradation times. Now, we extended our studies to demonstrate that it can be successfully nanostructured using the AAO templates methodology, obtaining a nanorod-like scaffold with a diameter comparable to those of collagen fibers of the bone matrix (170 and 300 nm). The nanorods obtained presented a very homogeneous pattern in diameter and length, and supports cell attachment and growth. We also found that both osteoblastic and chondroblastic matrix production were promoted on bone marrow progenitor cells and primary condrocytes growing on the scaffolds, respectively. In addition, the nanostructured scaffold presented no cytotoxicity as it was evaluated using a model of macrophages on culture. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 570-579, 2018. © 2017 Wiley Periodicals, Inc.

Scaffold Translation: Barriers Between Concept and Clinic

PubMed Central

Murphy, William L.

2011-01-01

Translation of scaffold-based bone tissue engineering (BTE) therapies to clinical use remains, bluntly, a failure. This dearth of translated tissue engineering therapies (including scaffolds) remains despite 25 years of research, research funding totaling hundreds of millions of dollars, over 12,000 papers on BTE and over 2000 papers on BTE scaffolds alone in the past 10 years (PubMed search). Enabling scaffold translation requires first an understanding of the challenges, and second, addressing the complete range of these challenges. There are the obvious technical challenges of designing, manufacturing, and functionalizing scaffolds to fill the Form, Fixation, Function, and Formation needs of bone defect repair. However, these technical solutions should be targeted to specific clinical indications (e.g., mandibular defects, spine fusion, long bone defects, etc.). Further, technical solutions should also address business challenges, including the need to obtain regulatory approval, meet specific market needs, and obtain private investment to develop products, again for specific clinical indications. Finally, these business and technical challenges present a much different model than the typical research paradigm, presenting the field with philosophical challenges in terms of publishing and funding priorities that should be addressed as well. In this article, we review in detail the technical, business, and philosophical barriers of translating scaffolds from Concept to Clinic. We argue that envisioning and engineering scaffolds as modular systems with a sliding scale of complexity offers the best path to addressing these translational challenges. PMID:21902613

Hydroxyapatite/polylactide biphasic combination scaffold loaded with dexamethasone for bone regeneration.

PubMed

Son, Jun-Sik; Kim, Su-Gwan; Oh, Ji-Su; Appleford, Mark; Oh, Sunho; Ong, Joo L; Lee, Kyu-Bok

2011-12-15

This study presents a novel design of a ceramic/polymer biphasic combination scaffold that mimics natural bone structures and is used as a bone graft substitute. To mimic the natural bone structures, the outside cortical-like shells were composed of porous hydroxyapatite (HA) with a hollow interior using a polymeric template-coating technique; the inner trabecular-like core consisted of porous poly(D,L-lactic acid) (PLA) that was loaded with dexamethasone (DEX) and was directly produced using a particle leaching/gas forming technique to create the inner diameter of the HA scaffold. It was observed that the HA and PLA parts of the fabricated HA/PLA biphasic scaffold contained open and interconnected pore structures, and the boundary between both parts was tightly connected without any gaps. It was found that the structure of the combination scaffold was analogous to that of natural bone based on micro-computed tomography analysis. Additionally, the dense, uniform apatite layer was formed on the surface of the HA/PLA biphasic scaffold through a biomimetic process, and DEX was successfully released from the PLA of the biphasic scaffold over a 1-month period. This release caused human embryonic palatal mesenchyme cells to proliferate, differentiate, produce ECM, and form tissue in vitro. Therefore, it was concluded that this functionally graded scaffold is similar to natural bone and represents a potential bone-substitute material. Copyright © 2011 Wiley Periodicals, Inc.

A simple and effective method for making multipotent/multilineage scaffolds with hydrophilic nature without any postmodification/treatment.

PubMed

Vaikkath, Dhanesh; Anitha, Rakhi; Sumathy, Babitha; Nair, Prabha D

2016-05-01

A number of biodegradable and bioresorbable materials, as well as scaffold designs, have been experimentally and/or clinically studied for tissue engineering of diverse tissue types. Cell-material responses are strongly dependent on the properties of the scaffold material. In this study, scaffolds based on polycaprolactone (PCL) and PCL blended with a triblock copolymer, Polycaprolactone-polytetrahydrofuran-polycaprolactone (PCL-PTHF-PCL) at different ratios were fabricated by electrospinning. Blending and electrospinning of the triblock copolymer with PCL generated a super hydrophilic scaffold, the mechanical and biological properties of which varied with the concentration of the triblock copolymer. The hydrophilicity of the electrospun scaffolds was determined by measurement of water-air contact angle. Cellular response to the electrospun scaffolds was studied by seeding two types of cells, L929 fibroblast cell line and rat mesenchymal stem cells (RMSC). We observed that the super hydrophilicity of the material did not prevent cell adhesion, while the cell proliferation was low or negligible for scaffolds containing higher amount of PCL-PTHF-PCL. Chondrogenic differentiation of RMSC was found to be better on the PCL blend containing 10% (w/v) of PCL-PTHF-PCL than the bare PCL. Our studies indicate that the cellular response is dependent on the biomaterial composition and highlight the importance of tailoring the scaffold properties for applications in tissue engineering and regenerative medicine. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of strontium addition and chitosan concentration variation on cytotoxicity of chitosan-alginate-carbonate apatite based bone scaffold

NASA Astrophysics Data System (ADS)

Perkasa, Rilis Eka; Umniati, B. Sri; Sunendar, Bambang

2017-09-01

Bone scaffold is one of the most important component in bone tissue engineering. Basically, bone scaffold is a biocompatible structure designed to replace broken bone tissue temporarily. Unlike conventional bone replacements, an advanced bone scaffold should be bioactive (e.g: supporting bone growth) and biodegradable as new bone tissue grow, while retain its mechanical properties similarity with bone. It is also possible to add more bioactive substrates to bone scaffold to further support its performance. One of the substrate is strontium, an element that could improve the ability of the bone to repair itself. However, it must be noted that excessive consumption of strontium could lead to toxicity and diseases, such as osteomalacia and hypocalcemia. This research aimed to investigate the effect of strontium addition to the cytotoxic property of chitosan-alginate-carbonate apatite bone scaffold. The amount of strontium added to the bone scaffold was 5% molar of the carbonate apatite content. As a control, bone scaffold without stronsium (0% molar) were also made. The effect of chitosan concentration variation on the cytotoxicity were also observed, where the concentration varies on 1% and 3% w/v of chitosan solution. The results showed an optimum result on bone scaffold sample with 5% molar of strontium and 3% chitosan, where 87.67% cells in the performed MTS-Assay cytotoxicity testing survived. This showed that the use of up to 5% molar addition of strontium and 3% chitosan could enhance the survivability of the cell.

The enhancement of students' mathematical problem solving ability through teaching with metacognitive scaffolding approach

NASA Astrophysics Data System (ADS)

Prabawanto, Sufyani

2017-05-01

This research aims to investigate the enhancement of students' mathematical problem solving through teaching with metacognitive scaffolding approach. This research used a quasi-experimental design with pretest-posttest control. The subjects were pre-service elementary school teachers in a state university in Bandung. In this study, there were two groups: experimental and control groups. The experimental group consists of 60 studentswho acquire teaching mathematicsunder metacognitive scaffolding approach, while the control group consists of 58 studentswho acquire teaching mathematicsunder direct approach. Students were classified into three categories based on the mathematical prior ability, namely high, middle, and low. Data collection instruments consist of mathematical problem solving test instruments. By usingmean difference test, two conclusions of the research:(1) there is a significant difference in the enhancement of mathematical problem solving between the students who attended the course under metacognitive scaffolding approach and students who attended the course under direct approach, and(2) thereis no significant interaction effect of teaching approaches and ability level based on the mathematical prior ability toward enhancement of students' mathematical problem solving.

Molecularly Imprinted Intelligent Scaffolds for Tissue Engineering Applications.

PubMed

Neves, Mariana I; Wechsler, Marissa E; Gomes, Manuela E; Reis, Rui L; Granja, Pedro L; Peppas, Nicholas A

2017-02-01

The development of molecularly imprinted polymers (MIPs) using biocompatible production methods enables the possibility to further exploit this technology for biomedical applications. Tissue engineering (TE) approaches use the knowledge of the wound healing process to design scaffolds capable of modulating cell behavior and promote tissue regeneration. Biomacromolecules bear great interest for TE, together with the established recognition of the extracellular matrix, as an important source of signals to cells, both promoting cell-cell and cell-matrix interactions during the healing process. This review focuses on exploring the potential of protein molecular imprinting to create bioactive scaffolds with molecular recognition for TE applications based on the most recent approaches in the field of molecular imprinting of macromolecules. Considerations regarding essential components of molecular imprinting technology will be addressed for TE purposes. Molecular imprinting of biocompatible hydrogels, namely based on natural polymers, is also reviewed here. Hydrogel scaffolds with molecular memory show great promise for regenerative therapies. The first molecular imprinting studies analyzing cell adhesion report promising results with potential applications for cell culture systems, or biomaterials for implantation with the capability for cell recruitment by selectively adsorbing desired molecules.

Refolding of proteins from inclusion bodies: rational design and recipes.

PubMed

Basu, Anindya; Li, Xiang; Leong, Susanna Su Jan

2011-10-01

The need to develop protein biomanufacturing platforms that can deliver proteins quickly and cost-effectively is ever more pressing. The rapid rate at which genomes can now be sequenced demands efficient protein production platforms for gene function identification. There is a continued need for the biotech industry to deliver new and more effective protein-based drugs to address new diseases. Bacterial production platforms have the advantage of high expression yields, but insoluble expression of many proteins necessitates the development of diverse and optimised refolding-based processes. Strategies employed to eliminate insoluble expression are reviewed, where it is concluded that inclusion bodies are difficult to eliminate for various reasons. Rational design of refolding systems and recipes are therefore needed to expedite production of recombinant proteins. This review article discusses efforts towards rational design of refolding systems and recipes, which can be guided by the development of refolding screening platforms that yield both qualitative and quantitative information on the progression of a given refolding process. The new opportunities presented by light scattering technologies for developing rational protein refolding buffer systems which in turn can be used to develop new process designs armed with better monitoring and controlling functionalities are discussed. The coupling of dynamic and static light scattering methodologies for incorporation into future bioprocess designs to ensure delivery of high-quality refolded proteins at faster rates is also discussed.

Looking into the Future: Toward Advanced 3D Biomaterials for Stem-Cell-Based Regenerative Medicine.

PubMed

Liu, Zhongmin; Tang, Mingliang; Zhao, Jinping; Chai, Renjie; Kang, Jiuhong

2018-04-01

Stem-cell-based therapies have the potential to provide novel solutions for the treatment of a variety of diseases, but the main obstacles to such therapies lie in the uncontrolled differentiation and functional engraftment of implanted tissues. The physicochemical microenvironment controls the self-renewal and differentiation of stem cells, and the key step in mimicking the stem cell microenvironment is to construct a more physiologically relevant 3D culture system. Material-based 3D assemblies of stem cells facilitate the cellular interactions that promote morphogenesis and tissue organization in a similar manner to that which occurs during embryogenesis. Both natural and artificial materials can be used to create 3D scaffolds, and synthetic organic and inorganic porous materials are the two main kinds of artificial materials. Nanotechnology provides new opportunities to design novel advanced materials with special physicochemical properties for 3D stem cell culture and transplantation. Herein, the advances and advantages of 3D scaffold materials, especially with respect to stem-cell-based therapies, are first outlined. Second, the stem cell biology in 3D scaffold materials is reviewed. Third, the progress and basic principles of developing 3D scaffold materials for clinical applications in tissue engineering and regenerative medicine are reviewed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Controlled Cooling in Bimodal Scaffold Fabrication Using Polymers with Different Melting Temperatures.

PubMed

Lara-Padilla, Hernan; Mendoza-Buenrostro, Christian; Cardenas, Diego; Rodriguez-Garcia, Aida; Rodriguez, Ciro A

2017-06-11

The combination of different materials and capabilities to manufacture at several scales open new possibilities in scaffold design for bone regeneration. This work is focused on bimodal scaffolds that combine polylactic acid (PLA) melt extruded strands with polycaprolactone (PCL) electrospun fibers. This type of bimodal scaffold offers better mechanical properties, compared to the use of PCL for the extruded strands, and provides potential a means for controlled drug and/or growth factor delivery through the electrospun fibers. The technologies of fused deposition modeling (FDM) and electrospinning were combined to create 3D bimodal constructs. The system uses a controlled cooling system allowing the combination of polymers with different melting temperatures to generate integrated scaffold architecture. The thermoplastic polymers used in the FDM process enhance the mechanical properties of the bimodal scaffold and control the pore structure. Integrated layers of electrospun microfibers induce an increase of the surface area for cell culture purposes, as well as potential in situ controlled drug and/or growth factor delivery. The proposed bimodal scaffolds (PLA extruded strands and PCL electrospun fibers) show appropriate morphology and better mechanical properties when compared to the use of PCL extruded strands. On average, bimodal scaffolds with overall dimensions of 30 × 30 × 2.4 mm³ (strand diameter of 0.5 mm, strand stepover of 2.5 mm, pore size of 2 mm, and layer height of 0.3 mm) showed scaffold stiffness of 23.73 MPa and compression strength of 3.85 MPa. A cytotoxicity assay based human fibroblasts showed viability of the scaffold materials.

Influence of Controlled Cooling in Bimodal Scaffold Fabrication Using Polymers with Different Melting Temperatures

PubMed Central

Lara-Padilla, Hernan; Mendoza-Buenrostro, Christian; Cardenas, Diego; Rodriguez-Garcia, Aida; Rodriguez, Ciro A.

2017-01-01

The combination of different materials and capabilities to manufacture at several scales open new possibilities in scaffold design for bone regeneration. This work is focused on bimodal scaffolds that combine polylactic acid (PLA) melt extruded strands with polycaprolactone (PCL) electrospun fibers. This type of bimodal scaffold offers better mechanical properties, compared to the use of PCL for the extruded strands, and provides potential a means for controlled drug and/or growth factor delivery through the electrospun fibers. The technologies of fused deposition modeling (FDM) and electrospinning were combined to create 3D bimodal constructs. The system uses a controlled cooling system allowing the combination of polymers with different melting temperatures to generate integrated scaffold architecture. The thermoplastic polymers used in the FDM process enhance the mechanical properties of the bimodal scaffold and control the pore structure. Integrated layers of electrospun microfibers induce an increase of the surface area for cell culture purposes, as well as potential in situ controlled drug and/or growth factor delivery. The proposed bimodal scaffolds (PLA extruded strands and PCL electrospun fibers) show appropriate morphology and better mechanical properties when compared to the use of PCL extruded strands. On average, bimodal scaffolds with overall dimensions of 30 × 30 × 2.4 mm3 (strand diameter of 0.5 mm, strand stepover of 2.5 mm, pore size of 2 mm, and layer height of 0.3 mm) showed scaffold stiffness of 23.73 MPa and compression strength of 3.85 MPa. A cytotoxicity assay based human fibroblasts showed viability of the scaffold materials. PMID:28773000

Selection of specific interactors from phage display library based on sea lamprey variable lymphocyte receptor sequences.

PubMed

Wezner-Ptasinska, Magdalena; Otlewski, Jacek

2015-12-01

Variable lymphocyte receptors (VLRs) are non-immunoglobulin components of adaptive immunity in jawless vertebrates. These proteins composed of leucine-rich repeat modules offer some advantages over antibodies in target binding and therefore are attractive candidates for biotechnological applications. In this paper we report the design and characterization of a phage display library based on a previously proposed dVLR scaffold containing six LRR modules [Wezner-Ptasinska et al., 2011]. Our library was designed based on a consensus approach in which the randomization scheme reflects the frequencies of amino acids naturally occurring in respective positions responsible for antigen recognition. We demonstrate general applicability of the scaffold by selecting dVLRs specific for lysozyme and S100A7 protein with KD values in the micromolar range. The dVLR library could be used as a convenient alternative to antibodies for effective isolation of high affinity binders.

Rational and Modular Design of Potent Ligands Targeting the RNA that Causes Myotonic Dystrophy 2

PubMed Central

Lee, Melissa M.; Pushechnikov, Alexei; Disney, Matthew D.

2009-01-01

Most ligands targeting RNA are identified through screening a therapeutic target for binding members of a ligand library. A potential alternative way to construct RNA binders is through rational design using information about the RNA motifs ligands prefer to bind. Herein, we describe such an approach to design modularly assembled ligands targeting the RNA that causes myotonic dystrophy type 2 (DM2), a currently untreatable disease. A previous study identified that 6′-N-5-hexynoate kanamycin A (1) prefers to bind 2×2 nucleotide, pyrimidine-rich RNA internal loops. Multiple copies of such loops were found in the RNA hairpin that causes DM2. The 1 ligand was then modularly displayed on a peptoid scaffold with varied number and spacing to target several internal loops simultaneously. Modularly assembled ligands were tested for binding to a series of RNAs and for inhibiting the formation of the toxic DM2 RNA-muscleblind protein (MBNL-1) interaction. The most potent ligand displays three 1 modules, each separated by four spacing submonomers, and inhibits the formation of the RNA-protein complex with an IC50 of 25 nM. This ligand is higher affinity and more specific for binding DM2 RNA than MBNL-1. It binds the DM2 RNA at least 20-times more tightly than related RNAs and 15-fold more tightly than MBNL-1. A related control peptoid displaying 6′-N-5-hexynoate neamine (2) is >100-fold less potent at inhibiting the RNA-protein interaction and binds to DM2 RNA >125-fold more weakly. Uptake studies into a mouse myoblast cell line also show that the most potent ligand is cell permeable. PMID:19348464

Formative feedback and scaffolding for developing complex problem solving and modelling outcomes

NASA Astrophysics Data System (ADS)

Frank, Brian; Simper, Natalie; Kaupp, James

2018-07-01

This paper discusses the use and impact of formative feedback and scaffolding to develop outcomes for complex problem solving in a required first-year course in engineering design and practice at a medium-sized research-intensive Canadian university. In 2010, the course began to use team-based, complex, open-ended contextualised problems to develop problem solving, communications, teamwork, modelling, and professional skills. Since then, formative feedback has been incorporated into: task and process-level feedback on scaffolded tasks in-class, formative assignments, and post-assignment review. Development in complex problem solving and modelling has been assessed through analysis of responses from student surveys, direct criterion-referenced assessment of course outcomes from 2013 to 2015, and an external longitudinal study. The findings suggest that students are improving in outcomes related to complex problem solving over the duration of the course. Most notably, the addition of new feedback and scaffolding coincided with improved student performance.

Mechanical properties of ceramic structures based on Triply Periodic Minimal Surface (TPMS) processed by 3D printing

NASA Astrophysics Data System (ADS)

Restrepo, S.; Ocampo, S.; Ramírez, J. A.; Paucar, C.; García, C.

2017-12-01

Repairing tissues and organs has been the main goal of surgical procedures. Since the 1990s, the main goal of tissue engineering has been reparation, using porous scaffolds that serve as a three-dimensional template for the initial fixation of cells and subsequent tissue formation both in vitro and in vivo. A scaffold must have specific characteristics of porosity, interconnectivity, surface area, pore volume, surface tortuosity, permeability and mechanical properties, which makes its design, manufacturing and characterization a complex process. Inspired by nature, triply periodic minimal surfaces (TPMS) have emerged as an alternative for the manufacture of porous pieces with design requirements, such as scaffolds for tissue repair. In the present work, we used the technique of 3D printing to obtain ceramic structures with Gyroid, Schwarz Primitive and Schwarz Diamond Surfaces shapes, three TPMS that fulfil the geometric requirements of a bone tissue scaffold. The main objective of this work is to compare the mechanical properties of ceramic pieces of three different forms of TPMS printed in 3D using a commercial ceramic paste. In this way it will be possible to clarify which is the TPMS with appropriate characteristics to construct scaffolds of ceramic materials for bone repair. A dependence of the mechanical properties with the geometry was found being the Primitive Surface which shows the highest mechanical properties.

Insight into the Structural Determinants of Imidazole Scaffold-Based Derivatives as TNF-α Release Inhibitors by in Silico Explorations

PubMed Central

Wang, Yuan; Wu, Mingwei; Ai, Chunzhi; Wang, Yonghua

2015-01-01

Presently, 151 widely-diverse pyridinylimidazole-based compounds that show inhibitory activities at the TNF-α release were investigated. By using the distance comparison technique (DISCOtech), comparative molecular field analysis (CoMFA), and comparative molecular similarity index analysis (CoMSIA) methods, the pharmacophore models and the three-dimensional quantitative structure-activity relationships (3D-QSAR) of the compounds were explored. The proposed pharmacophore model, including two hydrophobic sites, two aromatic centers, two H-bond donor atoms, two H-bond acceptor atoms, and two H-bond donor sites characterizes the necessary structural features of TNF-α release inhibitors. Both the resultant CoMFA and CoMSIA models exhibited satisfactory predictability (with Q2 (cross-validated correlation coefficient) = 0.557, R2ncv (non-cross-validated correlation coefficient) = 0.740, R2pre (predicted correlation coefficient) = 0.749 and Q2 = 0.598, R2ncv = 0.767, R2pre = 0.860, respectively). Good consistency was observed between the 3D-QSAR models and the pharmacophore model that the hydrophobic interaction and hydrogen bonds play crucial roles in the mechanism of actions. The corresponding contour maps generated by these models provide more diverse information about the key intermolecular interactions of inhibitors with the surrounding environment. All these models have extended the understanding of imidazole-based compounds in the structure-activity relationship, and are useful for rational design and screening of novel 2-thioimidazole-based TNF-α release inhibitors. PMID:26307982

Insight into the Structural Determinants of Imidazole Scaffold-Based Derivatives as TNF-α Release Inhibitors by in Silico Explorations.

PubMed

Wang, Yuan; Wu, Mingwei; Ai, Chunzhi; Wang, Yonghua

2015-08-25

Presently, 151 widely-diverse pyridinylimidazole-based compounds that show inhibitory activities at the TNF-α release were investigated. By using the distance comparison technique (DISCOtech), comparative molecular field analysis (CoMFA), and comparative molecular similarity index analysis (CoMSIA) methods, the pharmacophore models and the three-dimensional quantitative structure-activity relationships (3D-QSAR) of the compounds were explored. The proposed pharmacophore model, including two hydrophobic sites, two aromatic centers, two H-bond donor atoms, two H-bond acceptor atoms, and two H-bond donor sites characterizes the necessary structural features of TNF-α release inhibitors. Both the resultant CoMFA and CoMSIA models exhibited satisfactory predictability (with Q(2) (cross-validated correlation coefficient) = 0.557, R(2)ncv (non-cross-validated correlation coefficient) = 0.740, R(2)pre (predicted correlation coefficient) = 0.749 and Q(2) = 0.598, R(2)ncv = 0.767, R(2)pre = 0.860, respectively). Good consistency was observed between the 3D-QSAR models and the pharmacophore model that the hydrophobic interaction and hydrogen bonds play crucial roles in the mechanism of actions. The corresponding contour maps generated by these models provide more diverse information about the key intermolecular interactions of inhibitors with the surrounding environment. All these models have extended the understanding of imidazole-based compounds in the structure-activity relationship, and are useful for rational design and screening of novel 2-thioimidazole-based TNF-α release inhibitors.

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.

Designing the method for optical in vitro monitoring of the cell-mediated scaffold technology for bone regeneration based on laser-induced fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Larionov, P. M.; Maslov, N. A.; Papaeva, E. O.; Tereshchenko, V. P.; Khlestkin, V. K.; Bogachev, S. S.; Proskurina, A. S.; Titov, A. T.; Filipenko, M. L.; Pavlov, V. V.; Kudrov, G. A.; Orishich, A. M.

2016-08-01

One of the main unsolved problems in traumatology and orthopedics is reconstruction of critical-sized segmental bone defects. We believe that implementation of noninvasive monitoring of the bioengineering stages for cell-mediated bone scaffold by laser-induced fluorescence (LIF) can become a positive aspect in mastering this technique. An electrospun scaffold model (parameters: 10 wt. % polycaprolactone; 5% wt type A gelatin; mean fiber diameter 877.1 ± 169.1, and contact angle 45.3°) seeded with BHK IR cell culture (182 ± 38 cells/mm2) was used to show the principal possibility of differentiating between the scaffold seeded and unseeded with cells. First of all, the fluorescence spectra of the cell-seeded scaffold contain a peak at 305 nm for the excitation range of 230-290 nm, which can be used to differentiate between the samples. An increase in fluorescence intensity of the cell-seeded scaffold in the range of 400- 580 nm upon excitation at 230-340 nm is also noticeable. The wavelength of 250 nm is characterized by high signal intensity and is most suitable for differentiation between the samples.

3D bioprinting of structural proteins.

PubMed

Włodarczyk-Biegun, Małgorzata K; Del Campo, Aránzazu

2017-07-01

3D bioprinting is a booming method to obtain scaffolds of different materials with predesigned and customized morphologies and geometries. In this review we focus on the experimental strategies and recent achievements in the bioprinting of major structural proteins (collagen, silk, fibrin), as a particularly interesting technology to reconstruct the biochemical and biophysical composition and hierarchical morphology of natural scaffolds. The flexibility in molecular design offered by structural proteins, combined with the flexibility in mixing, deposition, and mechanical processing inherent to bioprinting technologies, enables the fabrication of highly functional scaffolds and tissue mimics with a degree of complexity and organization which has only just started to be explored. Here we describe the printing parameters and physical (mechanical) properties of bioinks based on structural proteins, including the biological function of the printed scaffolds. We describe applied printing techniques and cross-linking methods, highlighting the modifications implemented to improve scaffold properties. The used cell types, cell viability, and possible construct applications are also reported. We envision that the application of printing technologies to structural proteins will enable unprecedented control over their supramolecular organization, conferring printed scaffolds biological properties and functions close to natural systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Advances in the Application of Designed Ankyrin Repeat Proteins (DARPins) as Research Tools and Protein Therapeutics.

PubMed

Boersma, Ykelien L

2018-01-01

Nonimmunoglobulin scaffolds have been developed to overcome the limitations of monoclonal antibodies with regard to stability and size. Of these scaffolds, the class of designed ankyrin repeat proteins (DARPins) has advanced the most in biochemical and biomedical applications. This review focuses on the recent progress in DARPin technology, highlighting the scaffold's potential and possibilities.

Porous ceramic scaffolds with complex architectures

NASA Astrophysics Data System (ADS)

Munch, E.; Franco, J.; Deville, S.; Hunger, P.; Saiz, E.; Tomsia, A. P.

2008-06-01

This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.

An accomplished teacher's use of scaffolding during a second-grade unit on designing games.

PubMed

Chen, Weiyun; Rovegno, Inez; Cone, Stephen L; Cone, Theresa P

2012-06-01

The purpose of this study was to describe how an accomplished teacher taught second-grade students to design games that integrated movement and mathematics content. The participants were one physical education teacher; a classroom teacher, and an intact class of 20 second-grade students. Qualitative data were gathered through videotaping of all lessons, descriptions of 20 children's responses to all lesson segments, and interviews with all participants. In keeping with constructivist principles, the teacher used a progression of tasks and multiple instructional techniques to scaffold the design process allowing children to design games that were meaningful to them. Contrary to descriptions of scaffolding fading across a unit, in this study the scaffolding was a function of the interaction between learners' needs and task content.

Finite element analysis on the biomechanical stability of open porous titanium scaffolds for large segmental bone defects under physiological load conditions.

PubMed

Wieding, Jan; Souffrant, Robert; Mittelmeier, Wolfram; Bader, Rainer

2013-04-01

Repairing large segmental defects in long bones caused by fracture, tumour or infection is still a challenging problem in orthopaedic surgery. Artificial materials, i.e. titanium and its alloys performed well in clinical applications, are plenary available, and can be manufactured in a wide range of scaffold designs. Although the mechanical properties are determined, studies about the biomechanical behaviour under physiological loading conditions are rare. The goal of our numerical study was to determine the suitability of open-porous titanium scaffolds to act as bone scaffolds. Hence, the mechanical stability of fourteen different scaffold designs was characterized under both axial compression and biomechanical loading within a large segmental distal femoral defect of 30mm. This defect was stabilized with an osteosynthesis plate and physiological hip reaction forces as well as additional muscle forces were implemented to the femoral bone. Material properties of titanium scaffolds were evaluated from experimental testing. Scaffold porosity was varied between 64 and 80%. Furthermore, the amount of material was reduced up to 50%. Uniaxial compression testing revealed a structural modulus for the scaffolds between 3.5GPa and 19.1GPa depending on porosity and material consumption. The biomechanical testing showed defect gap alterations between 0.03mm and 0.22mm for the applied scaffolds and 0.09mm for the intact bone. Our results revealed that minimizing the amount of material of the inner core has a smaller influence than increasing the porosity when the scaffolds are loaded under biomechanical loading. Furthermore, an advanced scaffold design was found acting similar as the intact bone. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

Prediction and Estimation of Scaffold Strength with different pore size

NASA Astrophysics Data System (ADS)

Muthu, P.; Mishra, Shubhanvit; Sri Sai Shilpa, R.; Veerendranath, B.; Latha, S.

2018-04-01

This paper emphasizes the significance of prediction and estimation of the mechanical strength of 3D functional scaffolds before the manufacturing process. Prior evaluation of the mechanical strength and structural properties of the scaffold will reduce the cost fabrication and in fact ease up the designing process. Detailed analysis and investigation of various mechanical properties including shear stress equivalence have helped to estimate the effect of porosity and pore size on the functionality of the scaffold. The influence of variation in porosity was examined by computational approach via finite element analysis (FEA) and ANSYS application software. The results designate the adequate perspective of the evolutionary method for the regulation and optimization of the intricate engineering design process.

Stimulating Scientific Reasoning with Drawing-Based Modeling

NASA Astrophysics Data System (ADS)

Heijnes, Dewi; van Joolingen, Wouter; Leenaars, Frank

2018-02-01

We investigate the way students' reasoning about evolution can be supported by drawing-based modeling. We modified the drawing-based modeling tool SimSketch to allow for modeling evolutionary processes. In three iterations of development and testing, students in lower secondary education worked on creating an evolutionary model. After each iteration, the user interface and instructions were adjusted based on students' remarks and the teacher's observations. Students' conversations were analyzed on reasoning complexity as a measurement of efficacy of the modeling tool and the instructions. These findings were also used to compose a set of recommendations for teachers and curriculum designers for using and constructing models in the classroom. Our findings suggest that to stimulate scientific reasoning in students working with a drawing-based modeling, tool instruction about the tool and the domain should be integrated. In creating models, a sufficient level of scaffolding is necessary. Without appropriate scaffolds, students are not able to create the model. With scaffolding that is too high, students may show reasoning that incorrectly assigns external causes to behavior in the model.

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.

Formation of Nanofibrous Matrices, Three-Dimensional Scaffolds, and Microspheres: From Theory to Practice

PubMed Central

Ma, Chi

2017-01-01

Nanofibrous architecture presents unique biophysical cues to facilitate cellular responses and is considered an indispensable feature of a biomimetic three-dimensional (3D) scaffold and cell carrier. While electrospinning is a widely used method to prepare natural extracellular matrix-like nanofibers, it faces significant challenges to incorporate nanofibrous architecture into well-defined macroporous 3D scaffolds or injectable microspheres. Here we report a nonelectrospinning approach that is effective at generating nanofibers from a variety of synthetic and natural biodegradable polymers and integrating these nanofibers into (1) 3D scaffolds with constructive geometry and designed internal macropore structures; and (2) injectable microspheres. Our approach to generating polymer nanofibers is based on the control of polymer–solvent interaction parameter χp-s. We obtained the χp-s and solvent composition phase diagrams of different temperatures according to the Flory–Huggins classic lattice model and the Hildebrand-Scott solubility parameter equation. A critical polymer–solvent interaction parameter χcrit was introduced as a criterion to predict phase separation and nanofiber formation. To test the effectiveness of our approach, a total of 15 widely used biodegradable polymers were selected and successfully fabricated into nanofibrous matrices. Furthermore, macroporous nanofibrous 3D scaffolds with complex architecture and nanofibrous injectable microspheres were generated from those biodegradable polymers by combining our method with other processes. Our approach is universally effective to fabricate nanofibrous matrices from any polymeric materials. This work, therefore, greatly expands our ability to design appropriate biomimetic 3D scaffolds and injectable cell carriers for advanced regenerative therapies. PMID:27923327

Repair of osteochondral defects with hyaluronan- and polyester-based scaffolds.

PubMed

Solchaga, Luis A; Temenoff, Johnna S; Gao, Jizong; Mikos, Antonios G; Caplan, Arnold I; Goldberg, Victor M

2005-04-01

The natural repair of osteochondral defects can be enhanced with biocompatible, biodegradable materials that support the repair process. It is our hypothesis that hyaluronan-based scaffolds are superior to synthetic scaffolds because they provide biological cues. We tested this thesis by comparing two hyaluronan-based scaffolds [auto cross-linked polysaccharide polymer (ACP) and HYAFF-11] to polyester-based scaffolds [poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA)] with similar pore size, porosity and degradation times. Fifty-four rabbits received bilateral osteochondral defects. One defect received a hyaluronan-based scaffold and the contralateral defect received the corresponding polyester-based scaffold. Rabbits were euthanized 4, 12 and 20 weeks after surgery and the condyles dissected and processed for histology. Only ACP-treated defects presented bone at the base of the defect at 4 weeks. At 12 weeks, only defects treated with rapidly dissolving implants (ACP and PLGA) presented bone reconstitution consistently, while bone was present in only one third of those treated with slowly dissolving scaffolds (HYAFF-11 and PLLA). After 20 weeks, the articular surface of PLGA-treated defects presented fibrillation more frequently than in ACP-treated defects. The surface of defects treated with slowly dissolving scaffolds presented more cracks and fissures. The degradation rate of the scaffolds is critical for the repair process. Slowly dissolving scaffolds sustain thicker cartilage at the surface but, it frequently presents cracks and discontinuities. These scaffolds also delay bone formation at the base of the defects. Hyaluronan-based scaffolds appear to allow faster cell infiltration leading to faster tissue formation. The degradation of ACP leads to rapid bone formation while the slow degradation of HYAFF-11 prolongs the presence of cartilage and delays endochondral bone formation.

A Rational Reconstruction of the Kinetic Molecular Theory of Gases Based on History and Philosophy of Science and Its Implications for Chemistry Textbooks.

ERIC Educational Resources Information Center

Niaz, Mansoor

2000-01-01

Describes a study that was designed to develop a framework for examining the way in which chemistry textbooks describe the kinetic theory and related issues. The framework was developed by a rational reconstruction of the kinetic molecular theory of gases based on historians and philosophers of science. (Contains 102 references.)(Author/LRW)

Production of amino acids - Genetic and metabolic engineering approaches.

PubMed

Lee, Jin-Ho; Wendisch, Volker F

2017-12-01

The biotechnological production of amino acids occurs at the million-ton scale and annually about 6milliontons of l-glutamate and l-lysine are produced by Escherichia coli and Corynebacterium glutamicum strains. l-glutamate and l-lysine production from starch hydrolysates and molasses is very efficient and access to alternative carbon sources and new products has been enabled by metabolic engineering. This review focusses on genetic and metabolic engineering of amino acid producing strains. In particular, rational approaches involving modulation of transcriptional regulators, regulons, and attenuators will be discussed. To address current limitations of metabolic engineering, this article gives insights on recent systems metabolic engineering approaches based on functional tools and method such as genome reduction, amino acid sensors based on transcriptional regulators and riboswitches, CRISPR interference, small regulatory RNAs, DNA scaffolding, and optogenetic control, and discusses future prospects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Walking and talking the tree of life: Why and how to teach about biodiversity

PubMed Central

Ballen, Cissy J.; Greene, Harry W.

2017-01-01

Taxonomic details of diversity are an essential scaffolding for biology education, yet outdated methods for teaching the tree of life (TOL), as implied by textbook content and usage, are still commonly employed. Here, we show that the traditional approach only vaguely represents evolutionary relationships, fails to denote major events in the history of life, and relies heavily on memorizing near-meaningless taxonomic ranks. Conversely, a clade-based strategy—focused on common ancestry, monophyletic groups, and derived functional traits—is explicitly based on Darwin’s “descent with modification,” provides students with a rational system for organizing the details of biodiversity, and readily lends itself to active learning techniques. We advocate for a phylogenetic classification that mirrors the TOL, a pedagogical format of increasingly complex but always hierarchical presentations, and the adoption of active learning technologies and tactics. PMID:28319149

3D plotting of growth factor loaded calcium phosphate cement scaffolds.

PubMed

Akkineni, Ashwini Rahul; Luo, Yongxiang; Schumacher, Matthias; Nies, Berthold; Lode, Anja; Gelinsky, Michael

2015-11-01

Additive manufacturing allows to widely control the geometrical features of implants. Recently, we described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of a storable CPC paste based on water-immiscible carrier liquid. Plotting and hardening is conducted under mild conditions allowing the (precise and local) integration of biological components. In this study, we have developed a procedure for efficient loading of growth factors in the CPC scaffolds during plotting and demonstrated the feasibility of this approach. Bovine serum albumin (BSA) or vascular endothelial growth factor (VEGF), used as model proteins, were encapsulated in chitosan/dextran sulphate microparticles which could be easily mixed into the CPC paste in freeze-dried state. In order to prevent leaching of the proteins during cement setting, usually carried out by immersion in aqueous solutions, the plotted scaffolds were aged in water-saturated atmosphere (humidity). Setting in humidity avoided early loss of loaded proteins but provided sufficient amount of water to allow cement setting, as indicated by XRD analysis and mechanical testing in comparison to scaffolds set in water. Moreover, humidity-set scaffolds were characterised by altered, even improved properties: no swelling or crack formation was observed and accordingly, surface topography, total porosity and compressive modulus of the humidity-set scaffolds differed from those of the water-set counterparts. Direct cultivation of mesenchymal stem cells on the humidity-set scaffolds over 21days revealed their cytocompatibility. Maintenance of the bioactivity of VEGF during the fabrication procedure was proven in indirect and direct culture experiments with endothelial cells. Additive manufacturing techniques allow the fabrication of implants with defined architecture (inner pore structure and outer shape). Especially printing technologies conducted under mild conditions allow additionally the (spatially controlled) integration of biological components such as drugs or growth factors. That enables the generation of individualized implants which can better meet the requirements of a patient and of tissue engineering constructs. To our knowledge, simultaneous printing of biological components was up to now only described for hydrogel/biopolymer-based materials which suffer from poor mechanical properties. In contrast, we have developed a procedure (based on 3D plotting of a calcium phosphate cement paste) for the fabrication of designed and growth factor loaded calcium-phosphate-based scaffolds applicable for bone regeneration. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Tunable emission in lanthanide coordination polymer gels based on a rationally designed blue emissive gelator.

PubMed

Sutar, Papri; Suresh, Venkata M; Maji, Tapas Kumar

2015-06-18

Rational design and synthesis of a new low molecular weight gelator (LMWG) having 9,10-diphenylanthracene core and terminal terpyridine is reported. Tb(III) and Eu(III) ion coordination to a LMWG results in green and pink emissive coordination polymer gels, respectively, with coiled nanofiber morphology. Further, control over stoichiometry of LMWG:Tb(III):Eu(III) leads to yellow and white light emitting bimetallic gels.

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…

Rational Design of Small Molecules Targeting Oncogenic Noncoding RNAs from Sequence.

PubMed

Disney, Matthew D; Angelbello, Alicia J

2016-12-20

The discovery of RNA catalysis in the 1980s and the dissemination of the human genome sequence at the start of this century inspired investigations of the regulatory roles of noncoding RNAs in biology. In fact, the Encyclopedia of DNA Elements (ENCODE) project has shown that only 1-2% of the human genome encodes protein, yet 75% is transcribed into RNA. Functional studies both preceding and following the ENCODE project have shown that these noncoding RNAs have important roles in regulating gene expression, developmental timing, and other critical functions. RNA's diverse roles are often a consequence of the various folds that it adopts. The single-stranded nature of the biopolymer enables it to adopt intramolecular folds with noncanonical pairings to lower its free energy. These folds can be scaffolds to bind proteins or to form frameworks to interact with other RNAs. Not surprisingly, dysregulation of certain noncoding RNAs has been shown to be causative of disease. Given this as the background, it is easy to see why it would be useful to develop methods that target RNA and manipulate its biology in rational and predictable ways. The antisense approach has afforded strategies to target RNAs via Watson-Crick base pairing and has typically focused on targeting partially unstructured regions of RNA. Small molecule strategies to target RNA would be desirable not only because compounds could be lead optimized via medicinal chemistry but also because structured regions within an RNA of interest could be targeted to directly interfere with RNA folds that contribute to disease. Additionally, small molecules have historically been the most successful drug candidates. Until recently, the ability to design small molecules that target non-ribosomal RNAs has been elusive, creating the perception that they are "undruggable". In this Account, approaches to demystify targeting RNA with small molecules are described. Rather than bulk screening for compounds that bind to singular targets, which is the purview of the pharmaceutical industry and academic institutions with high throughput screening facilities, we focus on methods that allow for the rational design of small molecules toward biological RNAs. One enabling and foundational technology that has been developed is two-dimensional combinatorial screening (2DCS), a library-versus-library selection approach that allows the identification of the RNA motif binding preferences of small molecules from millions of combinations. A landscape map of the 2DCS-defined and annotated RNA motif-small molecule interactions is then placed into Inforna, a computational tool that allows one to mine these interactions against an RNA of interest or an entire transcriptome. Indeed, this approach has been enabled by tools to annotate RNA structure from sequence, an invaluable asset to the RNA community and this work, and has allowed for the rational identification of "druggable" RNAs in a target agnostic fashion.

49 CFR 214.109 - Scaffolding.

Code of Federal Regulations, 2010 CFR

2010-10-01

... guardrail system and the walking/working level. (b) Scaffolds shall not be altered or moved while they are occupied. This paragraph does not apply to vertical movements of mobile scaffolds that are designed to move...

Cyclic deformation-induced solute transport in tissue scaffolds with computer designed, interconnected, pore networks: experiments and simulations.

PubMed

Den Buijs, Jorn Op; Dragomir-Daescu, Dan; Ritman, Erik L

2009-08-01

Nutrient supply and waste removal in porous tissue engineering scaffolds decrease from the periphery to the center, leading to limited depth of ingrowth of new tissue into the scaffold. However, as many tissues experience cyclic physiological strains, this may provide a mechanism to enhance solute transport in vivo before vascularization of the scaffold. The hypothesis of this study was that pore cross-sectional geometry and interconnectivity are of major importance for the effectiveness of cyclic deformation-induced solute transport. Transparent elastic polyurethane scaffolds, with computer-programmed design of pore networks in the form of interconnected channels, were fabricated using a 3D printing and injection molding technique. The scaffold pores were loaded with a colored tracer for optical contrast, cyclically compressed with deformations of 10 and 15% of the original undeformed height at 1.0 Hz. Digital imaging was used to quantify the spatial distribution of the tracer concentration within the pores. Numerical simulations of a fluid-structure interaction model of deformation-induced solute transport were compared to the experimental data. The results of experiments and modeling agreed well and showed that pore interconnectivity heavily influences deformation-induced solute transport. Pore cross-sectional geometry appears to be of less relative importance in interconnected pore networks. Validated computer models of solute transport can be used to design optimal scaffold pore geometries that will enhance the convective transport of nutrients inside the scaffold and the removal of waste, thus improving the cell survivability deep inside the scaffold.

Scaffolding Preservice Teachers' WebQuest Design: A Qualitative Study

ERIC Educational Resources Information Center

Wang, Feng; Hannafin, Michael J.

2009-01-01

This study examined how participating preservice teachers reported their perceptions and use of different scaffolds provided to support their WebQuest design. Sixteen preservice teachers participated in a succession of course activities designed to guide WebQuest design and development. Results indicated that while participants followed, adapted,…

3D fiber deposited polymeric scaffolds for external auditory canal wall.

PubMed

Mota, Carlos; Milazzo, Mario; Panetta, Daniele; Trombi, Luisa; Gramigna, Vera; Salvadori, Piero A; Giannotti, Stefano; Bruschini, Luca; Stefanini, Cesare; Moroni, Lorenzo; Berrettini, Stefano; Danti, Serena

2018-05-07

The external auditory canal (EAC) is an osseocartilaginous structure extending from the auricle to the eardrum, which can be affected by congenital, inflammatory, and neoplastic diseases, thus reconstructive materials are needed. Current biomaterial-based approaches for the surgical reconstruction of EAC posterior wall still suffer from resorption (biological) and extrusion (synthetic). In this study, 3D fiber deposited scaffolds based on poly(ethylene oxide terephthalate)/poly(butylene terephthalate) were designed and fabricated to replace the EAC wall. Fiber diameter and scaffold porosity were optimized, leading to 200 ± 33 µm and 55% ± 5%, respectively. The mechanical properties were evaluated, resulting in a Young's modulus of 25.1 ± 7.0 MPa. Finally, the EAC scaffolds were tested in vitro with osteo-differentiated human mesenchymal stromal cells (hMSCs) with different seeding methods to produce homogeneously colonized replacements of interest for otologic surgery. This study demonstrated the fabrication feasibility of EAC wall scaffolds aimed to match several important requirements for biomaterial application to the ear under the Tissue Engineering paradigm, including shape, porosity, surface area, mechanical properties and favorable in vitro interaction with osteoinduced hMSCs. This study demonstrated the fabrication feasibility of outer ear canal wall scaffolds via additive manufacturing. Aimed to match several important requirements for biomaterial application to ear replacements under the Tissue Engineering paradigm, including shape, porosity and pore size, surface area, mechanical properties and favorable in vitro interaction with osteo-differentiated mesenchymal stromal cells.

The Development of CK2 Inhibitors: From Traditional Pharmacology to in Silico Rational Drug Design

PubMed Central

Cozza, Giorgio

2017-01-01

Casein kinase II (CK2) is an ubiquitous and pleiotropic serine/threonine protein kinase able to phosphorylate hundreds of substrates. Being implicated in several human diseases, from neurodegeneration to cancer, the biological roles of CK2 have been intensively studied. Upregulation of CK2 has been shown to be critical to tumor progression, making this kinase an attractive target for cancer therapy. Several CK2 inhibitors have been developed so far, the first being discovered by “trial and error testing”. In the last decade, the development of in silico rational drug design has prompted the discovery, de novo design and optimization of several CK2 inhibitors, active in the low nanomolar range. The screening of big chemical libraries and the optimization of hit compounds by Structure Based Drug Design (SBDD) provide telling examples of a fruitful application of rational drug design to the development of CK2 inhibitors. Ligand Based Drug Design (LBDD) models have been also applied to CK2 drug discovery, however they were mainly focused on methodology improvements rather than being critical for de novo design and optimization. This manuscript provides detailed description of in silico methodologies whose applications to the design and development of CK2 inhibitors proved successful and promising. PMID:28230762

A Framework for Designing Scaffolds that Improve Motivation and Cognition

ERIC Educational Resources Information Center

Belland, Brian R.; Kim, ChanMin; Hannafin, Michael J.

2013-01-01

A problematic, yet common, assumption among educational researchers is that when teachers provide authentic, problem-based experiences, students will automatically be engaged. Evidence indicates that this is often not the case. In this article, we discuss (a) problems with ignoring motivation in the design of learning environments, (b)…

Identification of small-molecule antagonists of the Pseudomonas aeruginosa transcriptional regulator PqsR: biophysically guided hit discovery and optimization.

PubMed

Klein, Tobias; Henn, Claudia; de Jong, Johannes C; Zimmer, Christina; Kirsch, Benjamin; Maurer, Christine K; Pistorius, Dominik; Müller, Rolf; Steinbach, Anke; Hartmann, Rolf W

2012-09-21

The Gram-negative pathogen Pseudomonas aeruginosa produces an intercellular alkyl quinolone signaling molecule, the Pseudomonas quinolone signal. The pqs quorum sensing communication system that is characteristic for P. aeruginosa regulates the production of virulence factors. Therefore, we consider the pqs system a novel target to limit P. aeruginosa pathogenicity. Here, we present small molecules targeting a key player of the pqs system, PqsR. A rational design strategy in combination with surface plasmon resonance biosensor analysis led to the identification of PqsR binders. Determination of thermodynamic binding signatures and functional characterization in E. coli guided the hit optimization, resulting in the potent hydroxamic acid derived PqsR antagonist 11 (IC(50) = 12.5 μM). Remarkably it displayed a comparable potency in P. aeruginosa (IC(50) = 23.6 μM) and reduced the production of the virulence factor pyocyanin. Beyond this, site-directed mutagenesis together with thermodynamic analysis provided insights into the energetic characteristics of protein-ligand interactions. Thus the identified PqsR antagonists are promising scaffolds for further drug design efforts against this important pathogen.

[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.

A three-dimensional hierarchical collagen scaffold fabricated by a combined solid freeform fabrication (SFF) and electrospinning process to enhance mesenchymal stem cell (MSC) proliferation

NASA Astrophysics Data System (ADS)

Ahn, SeungHyun; Koh, Young Ho; Kim, GeunHyung

2010-06-01

Collagen has the advantage of being very similar to macromolecular substances that can be recognized and metabolized in the biological environment. Although the natural material has superior property for this purpose, its use to fabricate reproducible and pore-structure-controlled 3D structures, which are designed to allow the entry of sufficient cells and the easy diffusion of nutrients, has been limited due to its low processability. Here, we propose a hybrid technology that combines a cryogenic plotting system with an electrospinning process. Using this technique, an easily pore-size-controllable hierarchical 3D scaffold consisting of micro-sized highly porous collagen strands and micro/nano-sized collagen fibers was fabricated. The pore structure of the collagen scaffold was controlled by the collagen micro/nanofibers, which were layered in the scaffold. The hierarchical scaffolds were characterized with respect to initial cell attachment and proliferation of bone marrow-derived mesenchymal stem cells within the scaffolds. The hierarchical scaffold exhibited incredibly enhanced initial cell attachment and cell compactness between pores of the plotted scaffold relative to the normally designed 3D collagen scaffold.

Binary phase solid-state photopolymerization of acrylates: design, characterization and biomineralization of 3D scaffolds for tissue engineering

NASA Astrophysics Data System (ADS)

Maitlo, Inamullah; Ali, Safdar; Akram, Muhammad Yasir; Shehzad, Farooq Khurum; Nie, Jun

2017-12-01

Porous polymer scaffolds designed by the cryogel method are attractive materials for a range of tissue engineering applications. However, the use of toxic crosslinker for retaining the pore structure limits their clinical applications. In this research, acrylates (HEA/PEGDA, HEMA/PEGDA and PEGDA) were used in the low-temperature solid-state photopolymerization to produce porous scaffolds with good structural retention. The morphology, pore diameter, mineral deposition and water absorption of the scaffold were characterized by SEM and water absorption test respectively. Elemental analysis and cytotoxicity of the biomineralized scaffold were revealed by using XRD and MTT assay test. The PEGDA-derived scaffold showed good water absorption ability and a higher degree of porosity with larger pore size compared to others. XRD patterns and IR results confirmed the formation of hydroxyapatite crystals from an alternative socking process. The overall cell proliferation was excellent, where PEGDA-derived scaffold had the highest and the most uniform cell growth, while HEMA/PEGDA scaffold showed the least. These results suggest that the cell proliferation and adhesion are directly proportional to the pore size, the shape and the porosity of scaffolds.

Student Use of Scaffolding Software: Relationships with Motivation and Conceptual Understanding

ERIC Educational Resources Information Center

Butler, Kyle A.; Lumpe, Andrew

2008-01-01

This study was designed to theoretically articulate and empirically assess the role of computer scaffolds. In this project, several examples of educational software were developed to scaffold the learning of students performing high level cognitive activities. The software used in this study, Artemis, focused on scaffolding the learning of…

Osteogenic differentiation of mesenchymal progenitor cells in computer designed fibrin-polymer-ceramic scaffolds manufactured by fused deposition modeling.

PubMed

Schantz, Jan-Thorsten; Brandwood, Arthur; Hutmacher, Dietmar Werner; Khor, Hwei Ling; Bittner, Katharina

2005-09-01

Biomimetic scaffolds offer great potentials in the development of bone analogs for tissue engineering. The studies presented in this paper focus specifically on the osteogenic potential of the novel PCL/CaP matrices and its degradation behavior. Biodegradable Polymer-ceramic Scaffolds were fabricated using the solid free form fabrication technology: Fused Deposition Modeling (FDM). The scaffold architecture was characterized by a honeycomb-like design and a complete interconnectivity of the pores. Human mesenchymal stem cells (MSCs) were seeded together with fibrin glue into PCL/CaP scaffolds and cultured in vitro for periods of up to eight weeks. Cellular adhesion, proliferation and osteogenic differentiation were assessed in these constructs using a range of histological and microscopic techniques. In additional experiments, degradation was assessed by measuring mass loss, diameter change, molecular weight change and by scanning electron micrographs. MSCs were able to adhere, migrate, and differentiate along the osteogenic lineage with in these scaffolds. The PCL/CaP scaffolds showed up to 27 fold increased degradation of compared to PCL scaffolds.

A protein/antibiotic releasing poly(lactic-co-glycolic acid)/lecithin scaffold for bone repair applications.

PubMed

Shi, Xuetao; Wang, Yingjun; Ren, Li; Huang, Wei; Wang, Dong-An

2009-05-21

Novel poly(lactic-co-glycolic acid) (PLGA)-hybridizing-lecithin scaffolds loaded with drug or protein were prepared with water/oil/water techniques and sintering microspheres technique. In such fabricated composite scaffolds (abbreviated "PLGA/Lec-SMS"), the introduction of lecithin component has been proven capable of largely enhancing Gentamicin (GS) and protein (Bovine Serum Albumin) encapsulation efficiency. The in vitro GS and BSA releasing profiles of PLGA/Lec-SMS system were plotted basing over 60 days' and 18 days' data collection, respectively. It indicates a sustained releasing tendency despite a burst at the very beginning. The antibacterial properties of GS-laden scaffolds were determined in vitro, and the antibacterial activity of scaffolds was enhanced by incorporating lecithin into PLGA bulks. Additionally, mesenchymal stem cells (MSCs) were seeded onto PLGA-SMS and PLGA/Lec-SMS in vitro. The outcome confirmed PLGA/Lec(5%)-SMS functions to improve MSC proliferation and also to enhance general ALP production and calcium secretion which is the vital markers for osteogenesis. In conclusion, this newly designed antibiotic releasing PLGA/Lec-SMS is promising for bone-repairing therapeutics.

3D Printed Structures Filled with Carbon Fibers and Functionalized with Mesenchymal Stem Cell Conditioned Media as In Vitro Cell Niches for Promoting Chondrogenesis.

PubMed

García-Ruíz, Josefa Predestinación; Díaz Lantada, Andrés

2017-12-24

In this study, we present a novel approach towards the straightforward, rapid, and low-cost development of biomimetic composite scaffolds for tissue engineering strategies. The system is based on the additive manufacture of a computer-designed lattice structure or framework, into which carbon fibers are subsequently knitted or incorporated. The 3D-printed lattice structure acts as support and the knitted carbon fibers perform as driving elements for promoting cell colonization of the three-dimensional construct. A human mesenchymal stem cell (h-MSC) conditioned medium (CM) is also used for improving the scaffold's response and promoting cell adhesion, proliferation, and viability. Cell culture results-in which scaffolds become buried in collagen type II-provide relevant information regarding the viability of the composite scaffolds used and the prospective applications of the proposed approach. In fact, the advanced composite scaffold developed, together with the conditioned medium functionalization, constitutes a biomimetic stem cell niche with clear potential, not just for tendon and ligament repair, but also for cartilage and endochondral bone formation and regeneration strategies.

Sustained Local Delivery of siRNA from an Injectable Scaffold

PubMed Central

Nelson, Christopher E.; Gupta, Mukesh K.; Adolph, Elizabeth J.; Shannon, Joshua M.; Guelcher, Scott A.; Duvall, Craig L.

2011-01-01

Controlled gene silencing technologies have significant, unrealized potential for use in tissue regeneration applications. The design described herein provides a means to package and protect siRNA within pH-responsive, endosomolytic micellar nanoparticles (si-NPs) that can be incorporated into nontoxic, biodegradable, and injectable polyurethane (PUR) tissue scaffolds. The si-NPs were homogeneously incorporated throughout the porous PUR scaffolds, and they were shown to be released via a diffusion-based mechanism for over three weeks. The siRNA-loaded micelles were larger but retained nano particulate morphology of approximately 100 nm diameter following incorporation into and release from the scaffolds. PUR scaffold releasate collected in vitro in PBS at 37°C for 1–4 days was able to achieve dose-dependent siRNA-mediated silencing with approximately 50% silencing achieved of the model gene GAPDH in NIH3T3 mouse fibroblasts. This promising platform technology provides both a research tool capable of probing the effects of local gene silencing and a potentially high-impact therapeutic approach for sustained, local silencing of deleterious genes within tissue defects. PMID:22061489

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.

A new class of HIV-1 protease inhibitor: the crystallographic structure, inhibition and chemical synthesis of an aminimide peptide isostere.

PubMed

Rutenber, E E; McPhee, F; Kaplan, A P; Gallion, S L; Hogan, J C; Craik, C S; Stroud, R M

1996-09-01

The essential role of HIV-1 protease (HIV-1 PR) in the viral life cycle makes it an attractive target for the development of substrate-based inhibitors that may find efficacy as anti-AIDS drugs. However, resistance has arisen to potent peptidomimetic drugs necessitating the further development of novel chemical backbones for diversity based chemistry focused on probing the active site for inhibitor interactions and binding modes that evade protease resistance. AQ148 is a potent inhibitor of HIV-1 PR and represents a new class of transition state analogues incorporating an aminimide peptide isostere. A 3-D crystallographic structure of AQ148, a tetrapeptide isostere, has been determined in complex with its target HIV-1 PR to a resolution of 2.5 A and used to evaluate the specific structural determinants of AQ148 potency and to correlate structure-activity relationships within the class of related compounds. AQ148 is a competitive inhibitor of HIV-1 PR with a Ki value of 137 nM. Twenty-nine derivatives have been synthesized and chemical modifications have been made at the P1, P2, P1', and P2' sites. The atomic resolution structure of AQ148 bound to HIV-1 PR reveals both an inhibitor binding mode that closely resembles that of other peptidomimetic inhibitors and specific protein/inhibitor interactions that correlate with structure-activity relationships. The structure provides the basis for the design, synthesis and evaluation of the next generation of hydroxyethyl aminimide inhibitors. The aminimide peptide isostere is a scaffold with favorable biological properties well suited to both the combinatorial methods of peptidomimesis and the rational design of potent and specific substrate-based analogues.

Calibration of the live load factor in LRFD design guidelines.

DOT National Transportation Integrated Search

2010-09-01

The Load and Resistant Factor Design (LRFD) approach is based on the concept of structural reliability. The approach is : more rational than the former design approaches such as Load Factor Design or Allowable Stress Design. The LRFD : Specification ...

Calibration of the live load factor in LRFD design guidelines : [revised].

DOT National Transportation Integrated Search

2011-07-01

The Load and Resistant Factor Design (LRFD) approach is based on the concept of structural reliability. The approach is : more rational than the former design approaches such as Load Factor Design or Allowable Stress Design. The LRFD : Specification ...

The use of collagen-based scaffolds to simulate prostate cancer bone metastases with potential for evaluating delivery of nanoparticulate gene therapeutics.

PubMed

Fitzgerald, Kathleen A; Guo, Jianfeng; Tierney, Erica G; Curtin, Caroline M; Malhotra, Meenakshi; Darcy, Raphael; O'Brien, Fergal J; O'Driscoll, Caitriona M

2015-10-01

Prostate cancer bone metastases are a leading cause of cancer-related death in men with current treatments offering only marginally improved rates of survival. Advances in the understanding of the genetic basis of prostate cancer provide the opportunity to develop gene-based medicines capable of treating metastatic disease. The aim of this work was to establish a 3D cell culture model of prostate cancer bone metastasis using collagen-based scaffolds, to characterise this model, and to assess the potential of the model to evaluate delivery of gene therapeutics designed to target bone metastases. Two prostate cancer cell lines (PC3 and LNCaP) were cultured in 2D standard culture and compared to 3D cell growth on three different collagen-based scaffolds (collagen and composites of collagen containing either glycosaminoglycan or nanohydroxyapatite). The 3D model was characterised for cell proliferation, viability and for matrix metalloproteinase (MMP) enzyme and Prostate Specific Antigen (PSA) secretion. Chemosensitivity to docetaxel treatment was assessed in 2D in comparison to 3D. Nanoparticles (NPs) containing siRNA formulated using a modified cyclodextrin were delivered to the cells on the scaffolds and gene silencing was quantified. Both prostate cancer cell lines actively infiltrated and proliferated on the scaffolds. Cell culture in 3D resulted in reduced levels of MMP1 and MMP9 secretion in PC3 cells. In contrast, LNCaP cells grown in 3D secreted elevated levels of PSA, particularly on the scaffold composed of collagen and glycosaminoglycans. Both cell lines grown in 3D displayed increased resistance to docetaxel treatment. The cyclodextrin.siRNA nanoparticles achieved cellular uptake and knocked down the endogenous GAPDH gene in the 3D model. In conclusion, development of a novel 3D cell culture model of prostate cancer bone metastasis has been initiated resulting, for the first time, in the successful delivery of gene therapeutics in a 3D in vitro model. Further enhancement of this model will help elucidate the pathogenesis of prostate cancer and also accelerate the design of effective therapies which can penetrate into the bone microenvironment for prostate cancer therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Structure and assembly of the essential RNA ring component of a viral DNA packaging motor

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

Ding, Fang; Lu, Changrui; Zhao, Wei

2011-07-25

Prohead RNA (pRNA) is an essential component in the assembly and operation of the powerful bacteriophage {psi}29 DNA packaging motor. The pRNA forms a multimeric ring via intermolecular base-pairing interactions between protomers that serves to guide the assembly of the ring ATPase that drives DNA packaging. Here we report the quaternary structure of this rare multimeric RNA at 3.5 {angstrom} resolution, crystallized as tetrameric rings. Strong quaternary interactions and the inherent flexibility helped rationalize how free pRNA is able to adopt multiple oligomerization states in solution. These characteristics also allowed excellent fitting of the crystallographic pRNA protomers into previous prohead/pRNAmore » cryo-EM reconstructions, supporting the presence of a pentameric, but not hexameric, pRNA ring in the context of the DNA packaging motor. The pentameric pRNA ring anchors itself directly to the phage prohead by interacting specifically with the fivefold symmetric capsid structures that surround the head-tail connector portal. From these contacts, five RNA superhelices project from the pRNA ring, where they serve as scaffolds for binding and assembly of the ring ATPase, and possibly mediate communication between motor components. Construction of structure-based designer pRNAs with little sequence similarity to the wild-type pRNA were shown to fully support the packaging of {psi}29 DNA.« less

Micromechanical finite element modeling and experimental characterization of the compressive mechanical properties of polycaprolactone:hydroxyapatite composite scaffolds prepared by selective laser sintering for bone tissue engineering

PubMed Central

Eshraghi, Shaun; Das, Suman

2012-01-01

Bioresorbable scaffolds with mechanical properties suitable for bone tissue engineering were fabricated from polycaprolactone (PCL) and hydroxyapatite (HA) by selective laser sintering (SLS) and modeled by finite element analysis (FEA). Both solid gage parts and scaffolds having 1-D, 2-D and 3-D orthogonal, periodic porous architectures were made with 0, 10, 20 and 30% HA by volume. PCL:HA scaffolds manufactured by SLS had nearly full density (99%) in the designed solid regions and had excellent geometric and dimensional control. Through optimization of the SLS process, the compressive moduli for our solid gage parts and scaffolds are the highest reported in the literature for additive manufacturing. The compressive moduli of solid gage parts were 299.3, 311.2, 415.5 and 498.3 MPa for PCL:HA loading at 100:0, 90:10, 80:20 and 70:30 respectively. The compressive effective stiffness tended to increase as the loading of HA was increased and the designed porosity was lowered. In the case of the most 3-D porous scaffold, the compressive modulus more than doubled from 14.9 MPa to 36.2 MPa when changing the material from 100:0 to 70:30 PCL:HA. A micromechanical finite element analysis (FEA) model was developed to investigate the reinforcement effect of HA loading on the compressive modulus of the bulk material. Using a first-principles based approach, the random distribution of HA particles in a solidified PCL matrix was modeled for any loading of HA to predict the bulk mechanical properties of the composites. The bulk mechanical properties were also used for FEA of the scaffold geometries. Results of the FEA were found to be in good agreement with experimental mechanical testing. The development of patient and site-specific composite tissue engineering constructs with tailored properties can be seen as a direct extension of this work on computational design, a priori modeling of mechanical properties and direct digital manufacturing. PMID:22522129

Micromechanical finite-element modeling and experimental characterization of the compressive mechanical properties of polycaprolactone-hydroxyapatite composite scaffolds prepared by selective laser sintering for bone tissue engineering.

PubMed

Eshraghi, Shaun; Das, Suman

2012-08-01

Bioresorbable scaffolds with mechanical properties suitable for bone tissue engineering were fabricated from polycaprolactone (PCL) and hydroxyapatite (HA) by selective laser sintering (SLS) and modeled by finite-element analysis (FEA). Both solid gage parts and scaffolds having 1-D, 2-D and 3-D orthogonal, periodic porous architectures were made with 0, 10, 20 and 30 vol.% HA. PCL:HA scaffolds manufactured by SLS had nearly full density (99%) in the designed solid regions and had excellent geometric and dimensional control. Through optimization of the SLS process, the compressive moduli for our solid gage parts and scaffolds are the highest reported in the literature for additive manufacturing. The compressive moduli of solid gage parts were 299.3, 311.2, 415.5 and 498.3 MPa for PCL:HA loading at 100:0, 90:10, 80:20 and 70:30, respectively. The compressive effective stiffness tended to increase as the loading of HA was increased and the designed porosity was lowered. In the case of the most 3-D porous scaffold, the compressive modulus more than doubled from 14.9 to 36.2 MPa when changing the material from 100:0 to 70:30 PCL:HA. A micromechanical FEA model was developed to investigate the reinforcement effect of HA loading on the compressive modulus of the bulk material. Using a first-principles based approach, the random distribution of HA particles in a solidified PCL matrix was modeled for any HA loading to predict the bulk mechanical properties of the composites. The bulk mechanical properties were also used for FEA of the scaffold geometries. The results of the FEA were found to be in good agreement with experimental mechanical testing. The development of patient- and site-specific composite tissue-engineering constructs with tailored properties can be seen as a direct extension of this work on computational design, a priori modeling of mechanical properties and direct digital manufacturing. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Alginate/nanohydroxyapatite scaffolds with designed core/shell structures fabricated by 3D plotting and in situ mineralization for bone tissue engineering.

PubMed

Luo, Yongxiang; Lode, Anja; Wu, Chengtie; Chang, Jiang; Gelinsky, Michael

2015-04-01

Composite scaffolds, especially polymer/hydroxyapatite (HAP) composite scaffolds with predesigned structures, are promising materials for bone tissue engineering. Various methods including direct mixing of HAP powder with polymers or incubating polymer scaffolds in simulated body fluid for preparing polymer/HAP composite scaffolds are either uncontrolled or require long times of incubation. In this work, alginate/nano-HAP composite scaffolds with designed pore parameters and core/shell structures were fabricated using 3D plotting technique and in situ mineralization under mild conditions (at room temperature and without the use of any organic solvents). Light microscopy, scanning electron microscopy, microcomputer tomography, X-ray diffraction, and Fourier transform infrared spectroscopy were applied to characterize the fabricated scaffolds. Mechanical properties and protein delivery of the scaffolds were evaluated, as well as the cell response to the scaffolds by culturing human bone-marrow-derived mesenchymal stem cells (hBMSC). The obtained data indicate that this method is suitable to fabricate alginate/nano-HAP composite scaffolds with a layer of nano-HAP, coating the surface of the alginate strands homogeneously and completely. The surface mineralization enhanced the mechanical properties and improved the cell attachment and spreading, as well as supported sustaining protein release, compared to pure alginate scaffolds without nano-HAP shell layer. The results demonstrated that the method provides an interesting option for bone tissue engineering application.

DD-ligases as a potential target for antibiotics: past, present and future.

PubMed

Tytgat, I; Colacino, E; Tulkens, P M; Poupaert, J H; Prévost, M; Van Bambeke, F

2009-01-01

DD-ligases catalyze the synthesis of the D-Ala-D-Ala and D-Ala-D-Ser dipeptides or the D Ala-D-Lac depsipeptide in an early step of peptidoglycan synthesis. Their function is essential for bacterial growth and specific to bacteria, making them attractive targets for the development of novel antibiotics. This review examines the biochemical and structural features of these enzymes and presents the main families of inhibitors described so far. Over the last 20 years, 7 structures of DD-ligases have been solved by X-ray crystallography, giving a detailed view of the general topology of the active site and of the residues in the catalytic pocket that play a central role in substrate recognition. This has paved the way to the rational design of inhibitors, which can be classified as (i) analogues of substrates, (ii) analogues of the product of the reaction, (iii) analogues of the transition state, and (iv) original scaffolds discovered by screening or by rational computer-aided design. The three first strategies have led to molecules that are polar by nature and have therefore poor access to their cytosolic target. The fourth one is potentially most promising as it yields more diverse structures. The most active molecules show affinity constants in the microM range, but microbiological evaluation remains scarce (typical MIC 1-8 mg/L for the tested compounds). These data strongly suggest targeting DD-ligases is a promising approach for discovery of new antibiotics. Future research should, however, aim at finding more potent inhibitors endowed with the appropriate pharmacokinetic properties that ensure access to their intracellular target.

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

Biomechanical properties of 3D-printed bone scaffolds are improved by treatment with CRFP.

PubMed

Helguero, Carlos G; Mustahsan, Vamiq M; Parmar, Sunjit; Pentyala, Sahana; Pfail, John L; Kao, Imin; Komatsu, David E; Pentyala, Srinivas

2017-12-22

One of the major challenges in orthopedics is to develop implants that overcome current postoperative problems such as osteointegration, proper load bearing, and stress shielding. Current implant techniques such as allografts or endoprostheses never reach full bone integration, and the risk of fracture due to stress shielding is a major concern. To overcome this, a novel technique of reverse engineering to create artificial scaffolds was designed and tested. The purpose of the study is to create a new generation of implants that are both biocompatible and biomimetic. 3D-printed scaffolds based on physiological trabecular bone patterning were printed. MC3T3 cells were cultured on these scaffolds in osteogenic media, with and without the addition of Calcitonin Receptor Fragment Peptide (CRFP) in order to assess bone formation on the surfaces of the scaffolds. Integrity of these cell-seeded bone-coated scaffolds was tested for their mechanical strength. The results show that cellular proliferation and bone matrix formation are both supported by our 3D-printed scaffolds. The mechanical strength of the scaffolds was enhanced by trabecular patterning in the order of 20% for compression strength and 60% for compressive modulus. Furthermore, cell-seeded trabecular scaffolds modulus increased fourfold when treated with CRFP. Upon mineralization, the cell-seeded trabecular implants treated with osteo-inductive agents and pretreated with CRFP showed a significant increase in the compressive modulus. This work will lead to creating 3D structures that can be used in the replacement of not only bone segments, but entire bones.

A poly(glycerol sebacate)-coated mesoporous bioactive glass scaffold with adjustable mechanical strength, degradation rate, controlled-release and cell behavior for bone tissue engineering.

PubMed

Lin, Dan; Yang, Kai; Tang, Wei; Liu, Yutong; Yuan, Yuan; Liu, Changsheng

2015-07-01

Various requirements in the field of tissue engineering have motivated the development of three-dimensional scaffold with adjustable physicochemical properties and biological functions. A series of multiparameter-adjustable mesoporous bioactive glass (MBG) scaffolds with uncrosslinked poly(glycerol sebacate) (PGS) coating was prepared in this article. MBG scaffold was prepared by a modified F127/PU co-templating process and then PGS was coated by a simple adsorption and lyophilization process. Through controlling macropore parameters and PGS coating amount, the mechanical strength, degradation rate, controlled-release and cell behavior of the composite scaffold could be modulated in a wide range. PGS coating successfully endowed MBG scaffold with improved toughness and adjustable mechanical strength covering the bearing range of trabecular bone (2-12MPa). Multilevel degradation rate of the scaffold and controlled-release rate of protein from mesopore could be achieved, with little impact on the protein activity owing to an "ultralow-solvent" coating and "nano-cavity entrapment" immobilization method. In vitro studies indicated that PGS coating promoted cell attachment and proliferation in a dose-dependent manner, without affecting the osteogenic induction capacity of MBG substrate. These results first provide strong evidence that uncrosslinked PGS might also yield extraordinary achievements in traditional MBG scaffold. With the multiparameter adjustability, the composite MBG/PGS scaffolds would have a hopeful prospect in bone tissue engineering. The design considerations and coating method of this study can also be extended to other ceramic-based artificial scaffolds and are expected to provide new thoughts on development of future tissue engineering materials. Copyright © 2015 Elsevier B.V. All rights reserved.

Design properties of hydrogel tissue-engineering scaffolds

PubMed Central

Zhu, Junmin; Marchant, Roger E

2011-01-01

This article summarizes the recent progress in the design and synthesis of hydrogels as tissue-engineering scaffolds. Hydrogels are attractive scaffolding materials owing to their highly swollen network structure, ability to encapsulate cells and bioactive molecules, and efficient mass transfer. Various polymers, including natural, synthetic and natural/synthetic hybrid polymers, have been used to make hydrogels via chemical or physical crosslinking. Recently, bioactive synthetic hydrogels have emerged as promising scaffolds because they can provide molecularly tailored biofunctions and adjustable mechanical properties, as well as an extracellular matrix-like microenvironment for cell growth and tissue formation. This article addresses various strategies that have been explored to design synthetic hydrogels with extracellular matrix-mimetic bioactive properties, such as cell adhesion, proteolytic degradation and growth factor-binding. PMID:22026626

Scaffold translation: barriers between concept and clinic.

PubMed

Hollister, Scott J; Murphy, William L

2011-12-01

Translation of scaffold-based bone tissue engineering (BTE) therapies to clinical use remains, bluntly, a failure. This dearth of translated tissue engineering therapies (including scaffolds) remains despite 25 years of research, research funding totaling hundreds of millions of dollars, over 12,000 papers on BTE and over 2000 papers on BTE scaffolds alone in the past 10 years (PubMed search). Enabling scaffold translation requires first an understanding of the challenges, and second, addressing the complete range of these challenges. There are the obvious technical challenges of designing, manufacturing, and functionalizing scaffolds to fill the Form, Fixation, Function, and Formation needs of bone defect repair. However, these technical solutions should be targeted to specific clinical indications (e.g., mandibular defects, spine fusion, long bone defects, etc.). Further, technical solutions should also address business challenges, including the need to obtain regulatory approval, meet specific market needs, and obtain private investment to develop products, again for specific clinical indications. Finally, these business and technical challenges present a much different model than the typical research paradigm, presenting the field with philosophical challenges in terms of publishing and funding priorities that should be addressed as well. In this article, we review in detail the technical, business, and philosophical barriers of translating scaffolds from Concept to Clinic. We argue that envisioning and engineering scaffolds as modular systems with a sliding scale of complexity offers the best path to addressing these translational challenges. © Mary Ann Liebert, Inc.

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

Biomimetic stratified scaffold design for ligament-to-bone interface tissue engineering.

PubMed

Lu, Helen H; Spalazzi, Jeffrey P

2009-07-01

The emphasis in the field of orthopaedic tissue engineering is on imparting biomimetic functionality to tissue engineered bone or soft tissue grafts and enabling their translation to the clinic. A significant challenge in achieving extended graft functionality is engineering the biological fixation of these grafts with each other as well as with the host environment. Biological fixation will require re-establishment of the structure-function relationship inherent at the native soft tissue-to-bone interface on these tissue engineered grafts. To this end, strategic biomimicry must be incorporated into advanced scaffold design. To facilitate integration between distinct tissue types (e.g., bone with soft tissues such as cartilage, ligament, or tendon), a stratified or multi-phasic scaffold with distinct yet continuous tissue regions is required to pre-engineer the interface between bone and soft tissues. Using the ACL-to-bone interface as a model system, this review outlines the strategies for stratified scaffold design for interface tissue engineering, focusing on identifying the relevant design parameters derived from an understanding of the structure-function relationship inherent at the soft-to-hard tissue interface. The design approach centers on first addressing the challenge of soft tissue-to-bone integration ex vivo, and then subsequently focusing on the relatively less difficult task of bone-to-bone integration in vivo. In addition, we will review stratified scaffold design aimed at exercising spatial control over heterotypic cellular interactions, which are critical for facilitating the formation and maintenance of distinct yet continuous multi-tissue regions. Finally, potential challenges and future directions in this emerging area of advanced scaffold design will be discussed.

Multiscale Mathematical Modeling in Dental Tissue Engineering: Toward Computer-Aided Design of a Regenerative System Based on Hydroxyapatite Granules, Focussing on Early and Mid-Term Stiffness Recovery

PubMed Central

Scheiner, Stefan; Komlev, Vladimir S.; Gurin, Alexey N.; Hellmich, Christian

2016-01-01

We here explore for the very first time how an advanced multiscale mathematical modeling approach may support the design of a provenly successful tissue engineering concept for mandibular bone. The latter employs double-porous, potentially cracked, single millimeter-sized granules packed into an overall conglomerate-type scaffold material, which is then gradually penetrated and partially replaced by newly grown bone tissue. During this process, the newly developing scaffold-bone compound needs to attain the stiffness of mandibular bone under normal physiological conditions. In this context, the question arises how the compound stiffness is driven by the key design parameters of the tissue engineering system: macroporosity, crack density, as well as scaffold resorption/bone formation rates. We here tackle this question by combining the latest state-of-the-art mathematical modeling techniques in the field of multiscale micromechanics, into an unprecedented suite of highly efficient, semi-analytically defined computation steps resolving several levels of hierarchical organization, from the millimeter- down to the nanometer-scale. This includes several types of homogenization schemes, namely such for porous polycrystals with elongated solid elements, for cracked matrix-inclusion composites, as well as for assemblies of coated spherical compounds. Together with the experimentally known stiffnesses of hydroxyapatite crystals and mandibular bone tissue, the new mathematical model suggests that early stiffness recovery (i.e., within several weeks) requires total avoidance of microcracks in the hydroxyapatite scaffolds, while mid-term stiffness recovery (i.e., within several months) is additionally promoted by provision of small granule sizes, in combination with high bone formation and low scaffold resorption rates. PMID:27708584

SNP Assay Development for Linkage Map Construction, Anchoring Whole-Genome Sequence, and Other Genetic and Genomic Applications in Common Bean

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

Song, Qijian; Jia, Gaofeng; Hyten, David L.

A total of 992,682 single-nucleotide polymorphisms (SNPs) was identified as ideal for Illumina Infinium II BeadChip design after sequencing a diverse set of 17 common bean (Phaseolus vulgaris L) varieties with the aid of next-generation sequencing technology. From these, two BeadChips each with >5000 SNPs were designed. The BARCBean6K_1 BeadChip was selected for the purpose of optimizing polymorphism among market classes and, when possible, SNPs were targeted to sequence scaffolds in the Phaseolus vulgaris 14× genome assembly with sequence lengths >10 kb. The BARCBean6K_2 BeadChip was designed with the objective of anchoring additional scaffolds and to facilitate orientation of largemore » scaffolds. Analysis of 267 F2 plants from a cross of varieties Stampede × Red Hawk with the two BeadChips resulted in linkage maps with a total of 7040 markers including 7015 SNPs. With the linkage map, a total of 432.3 Mb of sequence from 2766 scaffolds was anchored to create the Phaseolus vulgaris v1.0 assembly, which accounted for approximately 89% of the 487 Mb of available sequence scaffolds of the Phaseolus vulgaris v0.9 assembly. A core set of 6000 SNPs (BARCBean6K_3 BeadChip) with high genotyping quality and polymorphism was selected based on the genotyping of 365 dry bean and 134 snap bean accessions with the BARCBean6K_1 and BARCBean6K_2 BeadChips. The BARCBean6K_3 BeadChip is a useful tool for genetics and genomics research and it is widely used by breeders and geneticists in the United States and abroad.« less

SNP Assay Development for Linkage Map Construction, Anchoring Whole-Genome Sequence, and Other Genetic and Genomic Applications in Common Bean

DOE PAGES

Song, Qijian; Jia, Gaofeng; Hyten, David L.; ...

2015-08-28

A total of 992,682 single-nucleotide polymorphisms (SNPs) was identified as ideal for Illumina Infinium II BeadChip design after sequencing a diverse set of 17 common bean (Phaseolus vulgaris L) varieties with the aid of next-generation sequencing technology. From these, two BeadChips each with >5000 SNPs were designed. The BARCBean6K_1 BeadChip was selected for the purpose of optimizing polymorphism among market classes and, when possible, SNPs were targeted to sequence scaffolds in the Phaseolus vulgaris 14× genome assembly with sequence lengths >10 kb. The BARCBean6K_2 BeadChip was designed with the objective of anchoring additional scaffolds and to facilitate orientation of largemore » scaffolds. Analysis of 267 F2 plants from a cross of varieties Stampede × Red Hawk with the two BeadChips resulted in linkage maps with a total of 7040 markers including 7015 SNPs. With the linkage map, a total of 432.3 Mb of sequence from 2766 scaffolds was anchored to create the Phaseolus vulgaris v1.0 assembly, which accounted for approximately 89% of the 487 Mb of available sequence scaffolds of the Phaseolus vulgaris v0.9 assembly. A core set of 6000 SNPs (BARCBean6K_3 BeadChip) with high genotyping quality and polymorphism was selected based on the genotyping of 365 dry bean and 134 snap bean accessions with the BARCBean6K_1 and BARCBean6K_2 BeadChips. The BARCBean6K_3 BeadChip is a useful tool for genetics and genomics research and it is widely used by breeders and geneticists in the United States and abroad.« less

SNP Assay Development for Linkage Map Construction, Anchoring Whole-Genome Sequence, and Other Genetic and Genomic Applications in Common Bean.

PubMed

Song, Qijian; Jia, Gaofeng; Hyten, David L; Jenkins, Jerry; Hwang, Eun-Young; Schroeder, Steven G; Osorno, Juan M; Schmutz, Jeremy; Jackson, Scott A; McClean, Phillip E; Cregan, Perry B

2015-08-28

A total of 992,682 single-nucleotide polymorphisms (SNPs) was identified as ideal for Illumina Infinium II BeadChip design after sequencing a diverse set of 17 common bean (Phaseolus vulgaris L) varieties with the aid of next-generation sequencing technology. From these, two BeadChips each with >5000 SNPs were designed. The BARCBean6K_1 BeadChip was selected for the purpose of optimizing polymorphism among market classes and, when possible, SNPs were targeted to sequence scaffolds in the Phaseolus vulgaris 14× genome assembly with sequence lengths >10 kb. The BARCBean6K_2 BeadChip was designed with the objective of anchoring additional scaffolds and to facilitate orientation of large scaffolds. Analysis of 267 F2 plants from a cross of varieties Stampede × Red Hawk with the two BeadChips resulted in linkage maps with a total of 7040 markers including 7015 SNPs. With the linkage map, a total of 432.3 Mb of sequence from 2766 scaffolds was anchored to create the Phaseolus vulgaris v1.0 assembly, which accounted for approximately 89% of the 487 Mb of available sequence scaffolds of the Phaseolus vulgaris v0.9 assembly. A core set of 6000 SNPs (BARCBean6K_3 BeadChip) with high genotyping quality and polymorphism was selected based on the genotyping of 365 dry bean and 134 snap bean accessions with the BARCBean6K_1 and BARCBean6K_2 BeadChips. The BARCBean6K_3 BeadChip is a useful tool for genetics and genomics research and it is widely used by breeders and geneticists in the United States and abroad. Copyright © 2015 Song et al.

Novel technique for repair of severed peripheral nerves in rats using polyurea crosslinked silica aerogel scaffold.

PubMed

Sabri, Firouzeh; Gerth, David; Tamula, George-Rudolph M; Phung, Thien-Chuong N; Lynch, Kyle J; Boughter, John D

2014-10-01

To design, synthesize, and test in vivo an aerogel-based top-open peripheral nerve scaffold to simultaneously support and guide multiple completely severed peripheral nerves in a rat model. Also, to explore options for immobilizing severed nerves on the aerogel material without the use of sutures resulting in reduced surgical time. A novel material and approach was developed for the reattachment of severed peripheral nerves. Nerve confinement and alignment in this case relies on the surface properties of a lightweight, highly porous, polyurea crosslinked silica aerogel scaffold. The distal and proximal ends of completely transected nerve terminals were positioned inside prefabricated "top-open" corrugated channels that cradled approximately two thirds of the circumference of the nerve trunk and connectivity of the severed nerves was evaluated using sciatic function index (SFI) technique for five months post-surgery on 10 female Sprague-Dawley rats then compared with the gold standard for peripheral nerve repair. The interaction of nerves with the surface of the scaffold was investigated also. Multichannel aerogel-based nerve support scaffold showed similar SFI recovery trend as the case suture repair technique. Usage of an adhesion-promoting coating reduced the friction between the nerve and the scaffold leading to slippage and lack of attachment between nerve and surface. The aerogel scaffold used in this study did not collapse under pressure during the incubation period and allowed for a rapid and non-invasive peripheral nerve repair approach without the demands of microsurgery on both time and surgical expertise. This technique may allow for simultaneous repair and reconnection of multiple severed nerves particularly relevant to nerve branching sites.

Numerical optimization of open-porous bone scaffold structures to match the elastic properties of human cortical bone.

PubMed

Wieding, Jan; Wolf, Andreas; Bader, Rainer

2014-09-01

Treatment of large segmental bone defects, especially in load bearing areas, is a complex procedure in orthopedic surgery. The usage of additive manufacturing processes enables the creation of customized bone implants with arbitrary open-porous structure satisfying both the mechanical and the biological requirements for a sufficient bone ingrowth. Aim of the present numerical study was to optimize the geometrical parameters of open-porous titanium scaffolds to match the elastic properties of human cortical bone with respect to an adequate pore size. Three different scaffold designs (cubic, diagonal and pyramidal) were numerically investigated by using an optimization approach. Beam elements were used to create the lattice structures of the scaffolds. The design parameters strut diameter and pore size ranged from 0.2 to 1.5mm and from 0 to 3.0mm, respectively. In a first optimization step, the geometrical parameters were varied under uniaxial compression to obtain a structural modulus of 15GPa (Young׳s modulus of cortical bone) and a pore size of 800µm was aimed to enable cell ingrowth. Furthermore, the mechanical behavior of the optimized structures under bending and torsion was investigated. Results for bending modulus were between 9.0 and 14.5GPa. In contrast, shear modulus was lowest for cubic and pyramidal design of approximately 1GPa. Here, the diagonal design revealed a modulus of nearly 20GPa. In a second step, large-sized bone scaffolds were created and placed in a biomechanical loading situation within a 30mm segmental femoral defect, stabilized with an osteosynthesis plate and loaded with physiological muscle forces. Strut diameter for the 17 sections of each scaffold was optimized independently in order to match the biomechanical stability of intact bone. For each design, highest strut diameter was found at the dorsal/medial site of the defect and smallest strut diameter in the center. In conclusion, we demonstrated the possibility of providing optimized open-porous scaffolds for bone regeneration by considering both mechanical and biological aspects. Furthermore, the results revealed the need of the investigation and comparison of different load scenarios (compression, bending and torsion) as well as complex biomechanical loading for a profound characterization of different scaffold designs. The usage of a numerical optimization process was proven to be a feasible tool to reduce the amount of the required titanium material without influencing the biomechanical performance of the scaffold negatively. By using fully parameterized models, the optimization approach is adaptable to other scaffold designs and bone defect situations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hydrogel scaffolds for tissue engineering: Progress and challenges

PubMed Central

El-Sherbiny, Ibrahim M.; Yacoub, Magdi H.

2013-01-01

Designing of biologically active scaffolds with optimal characteristics is one of the key factors for successful tissue engineering. Recently, hydrogels have received a considerable interest as leading candidates for engineered tissue scaffolds due to their unique compositional and structural similarities to the natural extracellular matrix, in addition to their desirable framework for cellular proliferation and survival. More recently, the ability to control the shape, porosity, surface morphology, and size of hydrogel scaffolds has created new opportunities to overcome various challenges in tissue engineering such as vascularization, tissue architecture and simultaneous seeding of multiple cells. This review provides an overview of the different types of hydrogels, the approaches that can be used to fabricate hydrogel matrices with specific features and the recent applications of hydrogels in tissue engineering. Special attention was given to the various design considerations for an efficient hydrogel scaffold in tissue engineering. Also, the challenges associated with the use of hydrogel scaffolds were described. PMID:24689032

Rational design for multifunctional non-liposomal lipid-based nanocarriers for cancer management: theory to practice

PubMed Central

2013-01-01

Nanomedicines have gained more and more attention in cancer therapy thanks to their ability to enhance the tumour accumulation and the intracellular uptake of drugs while reducing their inactivation and toxicity. In parallel, nanocarriers have been successfully employed as diagnostic tools increasing imaging resolution holding great promises both in preclinical research and in clinical settings. Lipid-based nanocarriers are a class of biocompatible and biodegradable vehicles that provide advanced delivery of therapeutic and imaging agents, improving pharmacokinetic profile and safety. One of most promising engineering challenges is the design of innovative and versatile multifunctional targeted nanotechnologies for cancer treatment and diagnosis. This review aims to highlight rational approaches to design multifunctional non liposomal lipid-based nanocarriers providing an update of literature in this field. PMID:24564841

Designer bFGF-incorporated d-form self-assembly peptide nanofiber scaffolds to promote bone repair.

PubMed

He, Bin; Ou, Yunsheng; Chen, Shuo; Zhao, Weikang; Zhou, Ao; Zhao, Jinqiu; Li, Hong; Jiang, Dianming; Zhu, Yong

2017-05-01

d-Form and l-form peptide nanofiber scaffolds can spontaneously form stable β-sheet secondary structures and nanofiber hydrogel scaffolds, and hold some promise in hemostasis and wound healing. We report here on the synthetic self-assembling peptide d-RADA16 and l-RADA16 are both found to produce stable β-sheet secondary structure and nanofiber hydrogel scaffolds based on circular dichroism (CD) spectroscopy, transmission electron microscopy (TEM) and rheology analysis etc. d-RADA16 hydrogel and l-RADA16 hydrogel can enhance obvious bone repair in femoral condyle defects of the Sprague-Dawley (SD) rat model compared to PBS treatment. Based on micro-computed tomography (CT), it was revealed that d-RADA16 hydrogel and l-RADA16 hydrogel were capable to obtain the extensive bone healing. Histological evaluation also found that these two hydrogels facilitate the presence of more mature bone tissue within the femoral condyle defects. Additionally, d-RADA16 hydrogel showed some potential in storing and releasing basic-fibroblast growth factor (bFGF) which was able to further promote bone regeneration based on micro-CT analysis. These results indicate that d-form peptide nanofiber hydrogel have some special capacity for bone repair. Copyright © 2016 Elsevier B.V. All rights reserved.

A poly(glycerol sebacate) based photo/thermo dual curable biodegradable and biocompatible polymer for biomedical applications.

PubMed

Wang, Min; Lei, Dong; Liu, Zenghe; Chen, Shuo; Sun, Lijie; Lv, Ziying; Huang, Peng; Jiang, Zhongxing; You, Zhengwei

2017-10-01

Due to its biomimetic mechanical properties to soft tissues, excellent biocompatibility and biodegradability, poly (glycerol sebacate) (PGS) has emerged as a representative bioelastomer and been widely used in biomedical engineering. However, the typical curing of PGS needs high temperature (>120 °C), high vacuum (>1 Torr), and long duration (>12 h), which limit its further applications. Accordingly, we designed, synthesized and characterized a photo/thermo dual curable polymer based on PGS. Treatment of PGS with 2-isocyanatoethyl methacrylate without additional reagents readily produced a methacrylated PGS (PGS-IM). Photo-curing of PGS-IM for 10 min at room temperature using salt leaching method efficiently produced porous scaffolds with a thickness up to 1 mm. PGS-IM was adapt to thermo-curing as well. The combination of photo and thermo curing provided a further way to modulate the properties of resultant porous scaffolds. Interestingly, photo-cured scaffolds exhibited hierarchical porous structures carrying extensive micropores with a diameter from several to hundreds micrometers. All the scaffolds showed good elasticity and biodegradability. In addition, PGS-IM exhibited good compatibility with L929 fibroblast cells. We expect this new PGS based biomaterial will have a wide range of biomedical applications.

Collagenous matrix supported by a 3D-printed scaffold for osteogenic differentiation of dental pulp cells.

PubMed

Fahimipour, Farahnaz; Dashtimoghadam, Erfan; Rasoulianboroujeni, Morteza; Yazdimamaghani, Mostafa; Khoshroo, Kimia; Tahriri, Mohammadreza; Yadegari, Amir; Gonzalez, Jose A; Vashaee, Daryoosh; Lobner, Douglas C; Jafarzadeh Kashi, Tahereh S; Tayebi, Lobat

2018-02-01

A systematic characterization of hybrid scaffolds, fabricated based on combinatorial additive manufacturing technique and freeze-drying method, is presented as a new platform for osteoblastic differentiation of dental pulp cells (DPCs). The scaffolds were consisted of a collagenous matrix embedded in a 3D-printed beta-tricalcium phosphate (β-TCP) as the mineral phase. The developed construct design was intended to achieve mechanical robustness owing to 3D-printed β-TCP scaffold, and biologically active 3D cell culture matrix pertaining to the Collagen extracellular matrix. The β-TCP precursor formulations were investigated for their flow-ability at various temperatures, which optimized for fabrication of 3D printed scaffolds with interconnected porosity. The hybrid constructs were characterized by 3D laser scanning microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and compressive strength testing. The in vitro characterization of scaffolds revealed that the hybrid β-TCP/Collagen constructs offer superior DPCs proliferation and alkaline phosphatase (ALP) activity compared to the 3D-printed β-TCP scaffold over three weeks. Moreover, it was found that the incorporation of TCP into the Collagen matrix improves the ALP activity. The presented results converge to suggest the developed 3D-printed β-TCP/Collagen hybrid constructs as a new platform for osteoblastic differentiation of DPCs for craniomaxillofacial bone regeneration. Copyright © 2017. Published by Elsevier Ltd.

Fabrication of porous beta-tricalcium phosphate with microchannel and customized geometry based on gel-casting and rapid prototyping.

PubMed

Li, X; Bian, W; Li, D; Lian, Q; Jin, Z

2011-03-01

The tissue engineering scaffolds with three-dimensional porous structure are regarded to be beneficial to facilitate a sufficient supply of nutrients and enable cell ingrowth in bone reconstruction. However, the pores in scaffolds tend to be blocked by the cell ingrowth and result in a restraint of nutrient supply in the further side of the scaffold. An indirect approach of combining the rapid prototyping and gel-casting technique is introduced in this study to fabricate beta-tricalcium phosphate (beta-TCP) scaffolds which not only have interconnected porous structure, but also have a microchannel network inside. The scaffold was designed with customized geometry that matches the defect area, and a double-scale (micropores-microchannel) porous structure inside that is beneficial for cell ingrowth. The scaffolds fabricated have an open, uniform, and interconnected porous architecture with a pore size of 200-400 microm, and posses an internal channel network with a diameter of 600 microm. The porosity was controllable. The compressive yield strength was 4.5 MPa with a porosity of 70 per cent. X-ray diffraction analysis shows that these fabrication processes do not change the crystal structure and chemical composition of beta-TCP. With this technique, it was also possible to fabricate porous scaffolds with desired pore size, porosity, and microchannel, as well as customized geometries by other bioceramics.

Enhanced human bone marrow mesenchymal stem cell functions in novel 3D cartilage scaffolds with hydrogen treated multi-walled carbon nanotubes.

PubMed

Holmes, Benjamin; Castro, Nathan J; Li, Jian; Keidar, Michael; Zhang, Lijie Grace

2013-09-13

Cartilage tissue is a nanostructured tissue which is notoriously hard to regenerate due to its extremely poor inherent regenerative capacity and complex stratified architecture. Current treatment methods are highly invasive and may have many complications. Thus, the goal of this work is to use nanomaterials and nano/microfabrication methods to create novel biologically inspired tissue engineered cartilage scaffolds to facilitate human bone marrow mesenchymal stem cell (MSC) chondrogenesis. To this end we utilized electrospinning to design and fabricate a series of novel 3D biomimetic nanostructured scaffolds based on hydrogen (H2) treated multi-walled carbon nanotubes (MWCNTs) and biocompatible poly(L-lactic acid) (PLLA) polymers. Specifically, a series of electrospun fibrous PLLA scaffolds with controlled fiber dimension were fabricated in this study. In vitro MSC studies showed that stem cells prefer to attach in the scaffolds with smaller fiber diameter. More importantly, the MWCNT embedded scaffolds showed a drastic increase in mechanical strength and a compressive Young's modulus matching to natural cartilage. Furthermore, our MSC differentiation results demonstrated that incorporation of the H2 treated carbon nanotubes and poly-L-lysine coating can induce more chondrogenic differentiations of MSCs than controls. After two weeks of culture, PLLA scaffolds with H2 treated MWCNTs and poly-L-lysine can achieve the highest glycosaminoglycan synthesis, making them promising for further exploration for cartilage regeneration.

Enhanced human bone marrow mesenchymal stem cell functions in novel 3D cartilage scaffolds with hydrogen treated multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Holmes, Benjamin; Castro, Nathan J.; Li, Jian; Keidar, Michael; Zhang, Lijie Grace

2013-09-01

Cartilage tissue is a nanostructured tissue which is notoriously hard to regenerate due to its extremely poor inherent regenerative capacity and complex stratified architecture. Current treatment methods are highly invasive and may have many complications. Thus, the goal of this work is to use nanomaterials and nano/microfabrication methods to create novel biologically inspired tissue engineered cartilage scaffolds to facilitate human bone marrow mesenchymal stem cell (MSC) chondrogenesis. To this end we utilized electrospinning to design and fabricate a series of novel 3D biomimetic nanostructured scaffolds based on hydrogen (H2) treated multi-walled carbon nanotubes (MWCNTs) and biocompatible poly(L-lactic acid) (PLLA) polymers. Specifically, a series of electrospun fibrous PLLA scaffolds with controlled fiber dimension were fabricated in this study. In vitro MSC studies showed that stem cells prefer to attach in the scaffolds with smaller fiber diameter. More importantly, the MWCNT embedded scaffolds showed a drastic increase in mechanical strength and a compressive Young’s modulus matching to natural cartilage. Furthermore, our MSC differentiation results demonstrated that incorporation of the H2 treated carbon nanotubes and poly-L-lysine coating can induce more chondrogenic differentiations of MSCs than controls. After two weeks of culture, PLLA scaffolds with H2 treated MWCNTs and poly-L-lysine can achieve the highest glycosaminoglycan synthesis, making them promising for further exploration for cartilage regeneration.

The Unexamined Student Is Not Worth Teaching: Preparation, the Zone of Proximal Development, and the Socratic Model of Scaffolded Learning

ERIC Educational Resources Information Center

Colter, Robert; Ulatowski, Joseph

2017-01-01

"Scaffolded learning" describes a cluster of instructional techniques designed to move students from a novice position toward greater understanding, such that they become independent learners. Our Socratic Model of Scaffolded Learning ("SMSL") includes two phases not normally included in discussions of scaffolded learning, the…

Novel 2H-chromen-2-one derivatives of resveratrol: Design, synthesis, modeling and use as human monoamine oxidase inhibitors.

PubMed

Ruan, Ban-Feng; Cheng, Hui-Jie; Ren, Jing; Li, Hong-Lin; Guo, Lu-Lu; Zhang, Xing-Xing; Liao, Chenzhong

2015-10-20

Using a fragment-based drug design strategy, two biomedical interesting fragments, resveratrol and coumarin were linked to design a series of novel human monoamine oxidase (hMAO) inhibitors with a scaffold of 3-((E)-3-(2-((E)-styryl)phenyl)acryloyl)-2H-chromen-2-one, which demonstrated a very interesting selectivity profile against hMAO-A and hMAO-B: some compounds with this scaffold are selective hMAO-A inhibitors, whereas some are selective hMAO-B inhibitors. The small changes in the substituents of the coumarin moiety led to this interesting selectivity profile. The most potent selective hMAO-B inhibitor D7 has a selectivity ratio of 20.93, with an IC₅₀ value of 2.78 μM, similar or better than selegiline (IC₅₀ = 2.89 μM), a selective hMAO-B inhibitor currently in the market for the treatment of Parkinson's disease. Our modeling study indicates that Tyr 326 of hMAO-B (or corresponded Ile 335 of hMAO-A) may be the determinant for the specificity of these compounds. The selectivity profile of compounds reported herein suggests that we can further develop both selective hMAO-A and hMAO-B inhibitors based on this novel scaffold. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Channeled Scaffolds for Engineering Myocardium with Mechanical Stimulation

PubMed Central

Zhang, Ting; Wan, Leo Q.; Xiong, Zhuo; Marsano, Anna; Maidhof, Robert; Park, Miri; Yan, Yongnian; Vunjak-Novakovic, Gordana

2011-01-01

The characteristics of the matrix (composition, structure, mechanical properties) and external culture environment (pulsatile perfusion, physical stimulation) are critically important for engineering functional myocardial tissue. We report the development of chitosan-collagen scaffolds with micro-pores and an array of parallel channels (~200 μm in diameter) that were specifically designed for cardiac tissue engineering with mechanical stimulation. The scaffolds were designed to have the structural and mechanical properties similar to those of the native human heart matrix. Scaffolds were seeded with neonatal rat heart cells and subjected to dynamic tensile stretch using a custom-designed bioreactor. The channels enhanced oxygen transport and facilitated the establishment of cell connections within the construct. The myocardial patches (14 mm in diameter, 1–2 mm thick) consisted of metabolically active cells and started to contract synchronously after 3 days of culture. Mechanical stimulation with high tensile stresses promoted cell alignment, elongation, and the expression of connexin-43 (Cx-43). This study confirms the importance of scaffold design and mechanical stimulation for the formation of contractile cardiac constructs. PMID:22081518

Channelled scaffolds for engineering myocardium with mechanical stimulation.

PubMed

Zhang, Ting; Wan, Leo Q; Xiong, Zhuo; Marsano, Anna; Maidhof, Robert; Park, Miri; Yan, Yongnian; Vunjak-Novakovic, Gordana

2012-10-01

The characteristics of the matrix (composition, structure, mechanical properties) and external culture environment (pulsatile perfusion, physical stimulation) of the heart are important characteristics in the engineering of functional myocardial tissue. This study reports on the development of chitosan-collagen scaffolds with micropores and an array of parallel channels (~ 200 µm in diameter) that were specifically designed for cardiac tissue engineering using mechanical stimulation. The scaffolds were designed to have similar structural and mechanical properties of those of native heart matrix. Scaffolds were seeded with neonatal rat heart cells and subjected to dynamic tensile stretch using a custom designed bioreactor. The channels enhanced oxygen transport and facilitated the establishment of cell connections within the construct. The myocardial patches (14 mm in diameter, 1-2 mm thick) consisted of metabolically active cells that began to contract synchronously after 3 days of culture. Mechanical stimulation with high tensile stress promoted cell alignment, elongation, and expression of connexin-43 (Cx-43). This study confirms the importance of scaffold design and mechanical stimulation for the formation of contractile cardiac constructs. Copyright © 2011 John Wiley & Sons, Ltd.

Protein-based hydrogels for tissue engineering

PubMed Central

Schloss, Ashley C.; Williams, Danielle M.; Regan, Lynne J.

2017-01-01

The tunable mechanical and structural properties of protein-based hydrogels make them excellent scaffolds for tissue engineering and repair. Moreover, using protein-based components provides the option to insert sequences associated with the promoting both cellular adhesion to the substrate and overall cell growth. Protein-based hydrogel components are appealing for their structural designability, specific biological functionality, and stimuli-responsiveness. Here we present highlights in the field of protein-based hydrogels for tissue engineering applications including design requirements, components, and gel types. PMID:27677513

Project-Based Learning Courses: The Relationship Between Faculty-Intended Course Implementation and Students' Perceptions

NASA Astrophysics Data System (ADS)

Simonovich, Jennifer A.; Towers, Emily; Zastavker, Yevgeniya V.

2012-02-01

Project-based learning (PjBL) has been shown to improve students' performance and satisfaction with their coursework, particularly in science and engineering courses. Specific aspects of PjBL that contribute to this improvement are student autonomy, course scaffolding, and instructor support. This study investigates two PjBL courses required for engineering majors at a small technical school, Introductory Mechanics Laboratory and Introductory Engineering Design. The three data sources used in this work are classroom observations (one laboratory and four design sessions) and semi-structured in-depth interviews with twelve students and six faculty. Grounded theory approach is used in a two-step fashion by (1) analyzing each data set individually and (2) performing full triangulation of all three data sets. In this talk, we demonstrate the relationship between faculty intentions and student perceptions regarding the three PjBL aspects -- student autonomy, course scaffolding, and instructor support -- within the context of these two courses. We further discuss implications for the course design and professional development of faculty.

A Novel Amyloid Designable Scaffold and Potential Inhibitor Inspired by GAIIG of Amyloid Beta and the HIV-1 V3 loop.

PubMed

Kokotidou, C; Jonnalagadda, S V R; Orr, A A; Seoane-Blanco, M; Apostolidou, C P; van Raaij, M J; Kotzabasaki, M; Chatzoudis, A; Jakubowski, J M; Mossou, E; Forsyth, V T; Mitchell, E P; Bowler, M W; Llamas-Saiz, A L; Tamamis, P; Mitraki, A

2018-05-17

The GAIIG sequence, common to the amyloid beta peptide (residues 29-33) and to the HIV gp 120 (residues 24-28 in a typical V3 loop) self-assembles into amyloid fibrils, as suggested by theory and the experiments presented here. The longer YATGAIIGNII sequence from the V3 loop also self-assembles into amyloid fibrils, of which the first three and the last two residues are outside the amyloid GAIIG core. We postulate that this sequence, with suitable selected replacements at the flexible positions, can serve as a designable scaffold for novel amyloid-based materials. Moreover, we report the single X-ray crystal structure of the beta-breaker peptide GAIPIG at 1.05 Å resolution. This structural information could serve as the basis for structure-based design of potential inhibitors of amyloid formation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Integrated Teaching of Structure-Based Drug Design and Biopharmaceutics: A Computer-Based Approach

ERIC Educational Resources Information Center

Sutch, Brian T.; Romero, Rebecca M.; Neamati, Nouri; Haworth, Ian S.

2012-01-01

Rational drug design requires expertise in structural biology, medicinal chemistry, physiology, and related fields. In teaching structure-based drug design, it is important to develop an understanding of the need for early recognition of molecules with "drug-like" properties as a key component. That is, it is not merely sufficient to teach…