Living nano-micro fibrous woven fabric/hydrogel composite scaffolds for heart valve engineering.

PubMed

Wu, Shaohua; Duan, Bin; Qin, Xiaohong; Butcher, Jonathan T

2017-03-15

Regeneration and repair of injured or diseased heart valves remains a clinical challenge. Tissue engineering provides a promising treatment approach to facilitate living heart valve repair and regeneration. Three-dimensional (3D) biomimetic scaffolds that possess heterogeneous and anisotropic features that approximate those of native heart valve tissue are beneficial to the successful in vitro development of tissue engineered heart valves (TEHV). Here we report the development and characterization of a novel composite scaffold consisting of nano- and micro-scale fibrous woven fabrics and 3D hydrogels by using textile techniques combined with bioactive hydrogel formation. Embedded nano-micro fibrous scaffolds within hydrogel enhanced mechanical strength and physical structural anisotropy of the composite scaffold (similar to native aortic valve leaflets) and also reduced its compaction. We determined that the composite scaffolds supported the growth of human aortic valve interstitial cells (HAVIC), balanced the remodeling of heart valve ECM against shrinkage, and maintained better physiological fibroblastic phenotype in both normal and diseased HAVIC over single materials. These fabricated composite scaffolds enable the engineering of a living heart valve graft with improved anisotropic structure and tissue biomechanics important for maintaining valve cell phenotypes. Heart valve-related disease is an important clinical problem, with over 300,000 surgical repairs performed annually. Tissue engineering offers a promising strategy for heart valve repair and regeneration. In this study, we developed and tissue engineered living nano-micro fibrous woven fabric/hydrogel composite scaffolds by using textile technique combined with bioactive hydrogel formation. The novelty of our technique is that the composite scaffolds can mimic physical structure anisotropy and the mechanical strength of natural aortic valve leaflet. Moreover, the composite scaffolds prevented the

A novel nano-structured porous polycaprolactone scaffold improves hyaline cartilage repair in a rabbit model compared to a collagen type I/III scaffold: in vitro and in vivo studies.

PubMed

Christensen, Bjørn Borsøe; Foldager, Casper Bindzus; Hansen, Ole Møller; Kristiansen, Asger Albæk; Le, Dang Quang Svend; Nielsen, Agnete Desirée; Nygaard, Jens Vinge; Bünger, Cody Erik; Lind, Martin

2012-06-01

To develop a nano-structured porous polycaprolactone (NSP-PCL) scaffold and compare the articular cartilage repair potential with that of a commercially available collagen type I/III (Chondro-Gide) scaffold. By combining rapid prototyping and thermally induced phase separation, the NSP-PCL scaffold was produced for matrix-assisted autologous chondrocyte implantation. Lyophilizing a water-dioxane-PCL solution created micro and nano-pores. In vitro: The scaffolds were seeded with rabbit chondrocytes and cultured in hypoxia for 6 days. qRT-PCR was performed using primers for sox9, aggrecan, collagen type 1 and 2. In vivo: 15 New Zealand White Rabbits received bilateral osteochondral defects in the femoral intercondylar grooves. Autologous chondrocytes were harvested 4 weeks prior to surgery. There were 3 treatment groups: (1) NSP-PCL scaffold without cells. (2) The Chondro-Gide scaffold with autologous chondrocytes and (3) NSP-PCL scaffold with autologous chondrocytes. Observation period was 13 weeks. Histological evaluation was made using the O'Driscoll score. In vitro: The expressions of sox9 and aggrecan were higher in the NSP-PCL scaffold, while expression of collagen 1 was lower compared to the Chondro-Gide scaffold. In vivo: Both NSP-PCL scaffolds with and without cells scored significantly higher than the Chondro-Gide scaffold when looking at the structural integrity and the surface regularity of the repair tissue. No differences were found between the NSP-PCL scaffold with and without cells. The NSP-PCL scaffold demonstrated higher in vitro expression of chondrogenic markers and had higher in vivo histological scores compared to the Chondro-Gide scaffold. The improved chondrocytic differentiation can potentially produce more hyaline cartilage during clinical cartilage repair. It appears to be a suitable cell-free implant for hyaline cartilage repair and could provide a less costly and more effective treatment option than the Chondro-Gide scaffold with cells.

Nano-structured polymer composites and process for preparing same

DOEpatents

Hillmyer, Marc; Chen, Liang

2013-04-16

A process for preparing a polymer composite that includes reacting (a) a multi-functional monomer and (b) a block copolymer comprising (i) a first block and (ii) a second block that includes a functional group capable of reacting with the multi-functional monomer, to form a crosslinked, nano-structured, bi-continuous composite. The composite includes a continuous matrix phase and a second continuous phase comprising the first block of the block copolymer.

The fabrication of PLGA microvessel scaffolds with nano-patterned inner walls.

PubMed

Wang, Gou-Jen; Lin, Yan-Cheng; Hsu, Shan-Hui

2010-10-01

Poly (lactic-co-glycolic acid) (PLGA) is one of the most commonly used biodegradable, biocompatible materials. Nanostructured PLGA has immense potential for application in tissue engineering. In this article we discuss a novel approach for the fabrication of PLGA microvessel scaffolds with nanostructured inner walls. In this novel nano-patterning approach, the thermal reflow technique is first adapted to fabricate a semi-cylindrical photoresist master mold. A thin film of titanium and a thin film of aluminum are sputtered in sequence on the semi-cylindrical microvessel network. Aluminum foil anodization is then executed to transform the aluminum thin film into a porous anodic aluminum oxide (AAO) film. During the casting process a PLGA solution is cast on the AAO film to build up semi-cylindrical PLGA microstructures with nanostructured inner walls after which inductive coupled plasma (ICP) is implemented to assist bonding of the two PLGA structures. The result is the building of a network of microchannels with nano-patterned inner walls. Bovine endothelial cells (BECs) are carefully cultured in the scaffold via semi-dynamic seeding for 7 days. Observations show that the BECs grew more separately in a nano-patterned microvessel scaffold than they did in a smooth surface scaffold.

Preparation and biological properties of a novel composite scaffold of nano-hydroxyapatite/chitosan/carboxymethyl cellulose for bone tissue engineering

PubMed Central

Liuyun, Jiang; Yubao, Li; Chengdong, Xiong

2009-01-01

In this study, we report the physico-chemical and biological properties of a novel biodegradable composite scaffold made of nano-hydroxyapatite and natural derived polymers of chitosan and carboxymethyl cellulose, namely, n-HA/CS/CMC, which was prepared by freeze-drying method. The physico-chemical properties of n-HA/CS/CMC scaffold were tested by infrared absorption spectra (IR), transmission electron microscope(TEM), scanning electron microscope(SEM), universal material testing machine and phosphate buffer solution (PBS) soaking experiment. Besides, the biological properties were evaluated by MG63 cells and Mesenchymal stem cells (MSCs) culture experiment in vitro and a short period implantation study in vivo. The results show that the composite scaffold is mainly formed through the ionic crossing-linking of the two polyions between CS and CMC, and n-HA is incorporated into the polyelectrolyte matrix of CS-CMC without agglomeration, which endows the scaffold with good physico-chemical properties such as highly interconnected porous structure, high compressive strength and good structural stability and degradation. More important, the results of cells attached, proliferated on the scaffold indicate that the scaffold is non-toxic and has good cell biocompatibility, and the results of implantation experiment in vivo further confirm that the scaffold has good tissue biocompatibility. All the above results suggest that the novel degradable n-HA/CS/CMC composite scaffold has a great potential to be used as bone tissue engineering material. PMID:19594953

Selective laser sintering fabrication of nano-hydroxyapatite/poly-ε-caprolactone scaffolds for bone tissue engineering applications

PubMed Central

Xia, Yan; Zhou, Panyu; Cheng, Xiaosong; Xie, Yang; Liang, Chong; Li, Chao; Xu, Shuogui

2013-01-01

The regeneration of functional tissue in osseous defects is a formidable challenge in orthopedic surgery. In the present study, a novel biomimetic composite scaffold, here called nano-hydroxyapatite (HA)/poly-ε-caprolactone (PCL) was fabricated using a selective laser sintering technique. The macrostructure, morphology, and mechanical strength of the scaffolds were characterized. Scanning electronic microscopy (SEM) showed that the nano-HA/PCL scaffolds exhibited predesigned, well-ordered macropores and interconnected micropores. The scaffolds have a range of porosity from 78.54% to 70.31%, and a corresponding compressive strength of 1.38 MPa to 3.17 MPa. Human bone marrow stromal cells were seeded onto the nano-HA/PCL or PCL scaffolds and cultured for 28 days in vitro. As indicated by the level of cell attachment and proliferation, the nano-HA/PCL showed excellent biocompatibility, comparable to that of PCL scaffolds. The hydrophilicity, mineralization, alkaline phosphatase activity, and Alizarin Red S staining indicated that the nano-HA/PCL scaffolds are more bioactive than the PCL scaffolds in vitro. Measurements of recombinant human bone morphogenetic protein-2 (rhBMP-2) release kinetics showed that after nano-HA was added, the material increased the rate of rhBMP-2 release. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both nano-HA/PCL scaffolds and PCL scaffolds were implanted in rabbit femur defects for 3, 6, and 9 weeks. The wounds were studied radiographically and histologically. The in vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility. However, the nano-HA/PCL scaffolds enhanced the efficiency of new bone formation more than PCL scaffolds and fulfilled all the basic requirements of bone tissue engineering scaffolds. Thus, they show large potential for use in orthopedic and reconstructive surgery. PMID:24204147

Mechanical Properties of Polymer Nano-composites

NASA Astrophysics Data System (ADS)

Srivastava, Iti

-dimensional carbon nanomaterials as fillers for high-performance polymer nano-composites. The extensive studies performed on graphene provide a strong foundation for graphene as a potential candidate for reinforcing polymers. The superior performance of graphene as a filler is attributed to graphene's high specific surface area, two-dimensional sheet geometry, strong filler-matrix adhesion and the outstanding mechanical properties of the sp2 carbon-bonding network in graphene. The improved mechanical properties of the graphene-polymer nano-composites, concurrent with the cost-effective production are both vital requirements of the industry in adoption of high strength-to-weight ratio polymer composites for various structural applications.

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

PubMed Central

Lech, Christopher Jacques

2017-01-01

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

Laser-assisted nanoceramics reinforced polymer scaffolds for tissue engineering: additional heating and stem cells behavior

NASA Astrophysics Data System (ADS)

Shishkovsky, Igor; Scherbakov, Vladimir; Volchkov, Vladislav; Volova, Larisa

2018-02-01

The conditions of selective laser melting (SLM) of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation, and differentiation. In the present study, the influence of additional heating during SLM process on stem cell viability near biopolymer matrix reinforced by nanoceramics additives was carried out. We used the biocompatible and bioresorbable polymers (polyetheretherketone /PEEK/ and polycaprolactone /PCL/) as a matrix and nano-oxide ceramics - TiO2, Al2O3, ZrO2, FexOy and/or hydroxyapatite as a basis of the additives. The rate of pure PEEK and PCL bio-resorption and in mixtures with nano oxides on the matrix was studied by the method of mass loss on bacteria of hydroxylase and enzyme complex. The stem cellular morphology, proliferative MMSC activity, and adhesion of the 2D and 3D nanocomposite matrices were the subjects of comparison. Medical potential of the SLS/M-fabricated nano-oxide ceramics after additional heating as the basis for tissue engineering scaffolds and cell targeting systems were discussed.

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

PubMed

Lech, Christopher Jacques; Phan, Anh Tuân

2017-06-20

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

Characterization of Silk/Poly 3-Hydroxybutyrate-chitosan-multi-walled Carbon Nanotube Micro-nano Scaffold: A New Hybrid Scaffold for Tissue Engineering Applications.

PubMed

Mirmusavi, Mohammad Hossein; Karbasi, Saeed; Semnani, Dariush; Kharazi, Anousheh Zargar

2018-01-01

Long-term healing tissue engineering scaffolds must hold its full mechanical strength at least for 12 weeks. Nano-micro scaffolds consist of electrospinning nanofibers and textile microfibers to support cell behavior and mechanical strength, respectively. The new nano-micro hybrid scaffold was fabricated by electrospinning poly 3-hydroxybutyrate-chitosan-multi-walled carbon nanotube (MWNT functionalized by COOH) solution on knitted silk in a random manner with different amounts of MWNT. The physical, mechanical, and biodegradation properties were assessed through scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, water contact angle test, tensile strength test, and weight loss test. The scaffold without MWNT was chosen as control sample. An increase in the amount of MWNT up to 1 wt% leads to better fiber diameter distribution, more hydrophilicity, biodegradation rate, and higher tensile strength in comparison with other samples. The porosity percentage of all scaffolds is more than 80%. According to FTIR spectra, the nanofibrous coat on knitted silk did not have any effect on silk fibroin crystallinity structures, and according to tensile strength test, the coat had a significant effect on tensile strength in comparison with pure knitted silk ( P ≤ 0.05). The average fiber diameter decreased due to an increase in electrical conductivity of the solution and fiber stretch in electrical field due to MWNTs. The scaffold containing 1 wt% MWNT was more hydrophilic due to the presence of many COOH groups of functionalized MWNT, thus an increase in the hydrolysis and degradation rate of this sample. High intrinsic tensile strength of MWNTs and improvement of nano-micro interface connection lead to an increase in tensile strength in scaffolds containing MWNT.

Characterization of Silk/Poly 3-Hydroxybutyrate-chitosan-multi-walled Carbon Nanotube Micro-nano Scaffold: A New Hybrid Scaffold for Tissue Engineering Applications

PubMed Central

Mirmusavi, Mohammad Hossein; Karbasi, Saeed; Semnani, Dariush; Kharazi, Anousheh Zargar

2018-01-01

Background: Long-term healing tissue engineering scaffolds must hold its full mechanical strength at least for 12 weeks. Nano-micro scaffolds consist of electrospinning nanofibers and textile microfibers to support cell behavior and mechanical strength, respectively. Methods: The new nano-micro hybrid scaffold was fabricated by electrospinning poly 3-hydroxybutyrate-chitosan-multi-walled carbon nanotube (MWNT functionalized by COOH) solution on knitted silk in a random manner with different amounts of MWNT. The physical, mechanical, and biodegradation properties were assessed through scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, water contact angle test, tensile strength test, and weight loss test. The scaffold without MWNT was chosen as control sample. Results: An increase in the amount of MWNT up to 1 wt% leads to better fiber diameter distribution, more hydrophilicity, biodegradation rate, and higher tensile strength in comparison with other samples. The porosity percentage of all scaffolds is more than 80%. According to FTIR spectra, the nanofibrous coat on knitted silk did not have any effect on silk fibroin crystallinity structures, and according to tensile strength test, the coat had a significant effect on tensile strength in comparison with pure knitted silk (P ≤ 0.05). The average fiber diameter decreased due to an increase in electrical conductivity of the solution and fiber stretch in electrical field due to MWNTs. The scaffold containing 1 wt% MWNT was more hydrophilic due to the presence of many COOH groups of functionalized MWNT, thus an increase in the hydrolysis and degradation rate of this sample. Conclusions: High intrinsic tensile strength of MWNTs and improvement of nano-micro interface connection lead to an increase in tensile strength in scaffolds containing MWNT. PMID:29535924

Analysis of sintered polymer scaffolds using concomitant synchrotron computed tomography and in situ mechanical testing.

PubMed

Dhillon, A; Schneider, P; Kuhn, G; Reinwald, Y; White, L J; Levchuk, A; Rose, F R A J; Müller, R; Shakesheff, K M; Rahman, C V

2011-12-01

The mechanical behaviour of polymer scaffolds plays a vital role in their successful use in bone tissue engineering. The present study utilised novel sintered polymer scaffolds prepared using temperature-sensitive poly(DL-lactic acid-co-glycolic acid)/poly(ethylene glycol) particles. The microstructure of these scaffolds was monitored under compressive strain by image-guided failure assessment (IGFA), which combined synchrotron radiation computed tomography (SR CT) and in situ micro-compression. Three-dimensional CT data sets of scaffolds subjected to a strain rate of 0.01%/s illustrated particle movement within the scaffolds with no deformation or cracking. When compressed using a higher strain rate of 0.02%/s particle movement was more pronounced and cracks between sintered particles were observed. The results from this study demonstrate that IGFA based on simultaneous SR CT imaging and micro-compression testing is a useful tool for assessing structural and mechanical scaffold properties, leading to further insight into structure-function relationships in scaffolds for bone tissue engineering applications.

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Li, Shichun; Peng, Cheng

2018-03-01

Interface induced polarization has a prominent influence on dielectric properties of 0-3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz ( 3.3 times of polymer), loss of 0.07@100 Hz ( 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm ( 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm ( 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

Hydrophilization of synthetic biodegradable polymer scaffolds for improved cell/tissue compatibility.

PubMed

Oh, Se Heang; Lee, Jin Ho

2013-02-01

Porous scaffolds have been widely used in tissue engineering because they can guide cells and tissues to grow, synthesize extracellular matrix and other biological molecules, and facilitate the formation of functional tissues and organs. Although various natural and synthetic biodegradable polymers have been used to fabricate the scaffolds, synthetic polymers have been more widely used for scaffolds since they have good mechanical strength, reproducible/controllable mechanical-chemical properties, and controllable biodegradation rates. However, the 'hydrophobic character' of common synthetic polymers is considered a limitation for tissue engineering applications because it can lead to a low initial cell seeding density, heterogeneous cell distribution in the scaffold, and slow cell growth due to insufficient absorption/diffusion of cell culture medium into scaffold and lack of specific interaction sites with cells. The hydrophilization of porous synthetic polymer scaffolds has been considered as one of the simple but effective approaches to achieve desirable in vitro cell culture and in vivo tissue regeneration within the scaffolds. In this review paper, representative synthetic biodegradable polymers and techniques to fabricate porous scaffolds are briefly summarized and their hydrophilization techniques to improve cell/tissue compatibility are discussed.

Mechanism of the dielectric enhancement in polymer-alumina nano-particle composites

NASA Astrophysics Data System (ADS)

Jacob, Rebecca; Jacob, Anne Pavitra; Mainwaring, David E.

2009-09-01

Polymer-alumina nano-composites with enhanced dielectric properties as a possibility to enable the miniaturization of devices have been reported. The enhancement of dielectric properties was found to be unique to the polymer. In the present work, the mechanism of the dielectric enhancement is established by performing ab initio molecular orbital calculations in order to study the molecular interactions in the interfacial region between the alumina-nano-particle surface and the polymer medium. The calculations predict the existence of strong electrostatic attraction between the positive charge on the aluminium of the alumina clusters and the negative charge of the oxygens of the polymer at the polymer-nano-particle interface resulting in an increase in the dipole moment and the polarization of the system leading to enhanced dielectric properties. The oxygen thus plays a dual role by involving in covalent bonding with the polymer chain and electrostatic bonding interactions with the alumina nano-particles. The unique structure of the polymer provides the highly electronegative oxygens, as carbonyl groups or ether linkages in conjugation with aromatic rings in an extended polymer chain system, facilitating this type of bonding at the interface.

Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2009-01-01

Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

Three-dimensional printed bone scaffolds: The role of nano/micro-hydroxyapatite particles on the adhesion and differentiation of human mesenchymal stem cells.

PubMed

Domingos, Marco; Gloria, Antonio; Coelho, Jorge; Bartolo, Paulo; Ciurana, Joaquim

2017-06-01

Bone tissue engineering is strongly dependent on the use of three-dimensional scaffolds that can act as templates to accommodate cells and support tissue ingrowth. Despite its wide application in tissue engineering research, polycaprolactone presents a very limited ability to induce adhesion, proliferation and osteogenic cell differentiation. To overcome some of these limitations, different calcium phosphates, such as hydroxyapatite and tricalcium phosphate, have been employed with relative success. This work investigates the influence of nano-hydroxyapatite and micro-hydroxyapatite (nHA and mHA, respectively) particles on the in vitro biomechanical performance of polycaprolactone/hydroxyapatite scaffolds. Morphological analysis performed with scanning electron microscopy allowed us to confirm the production of polycaprolactone/hydroxyapatite constructs with square interconnected pores of approximately 350 µm and to assess the distribution of hydroxyapatite particles within the polymer matrix. Compression mechanical tests showed an increase in polycaprolactone compressive modulus ( E) from 105.5 ± 11.2 to 138.8 ± 12.9 MPa (PCL_nHA) and 217.2 ± 21.8 MPa (PCL_mHA). In comparison to PCL_mHA scaffolds, the addition of nano-hydroxyapatite enhanced the adhesion and viability of human mesenchymal stem cells as confirmed by Alamar Blue assay. In addition, after 14 days of incubation, PCL_nHA scaffolds showed higher levels of alkaline phosphatase activity compared to polycaprolactone or PCL_mHA structures.

Semi-flexible polymer engendered aggregation/dispersion of fullerene (C60) nano-particles: An atomistic investigation

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Pattanayek, Sudip K.

2018-06-01

Semi flexible polymer chain has been modeled by choosing various values of persistent length (stiffness). As the polymer chain stiffness increases, the shape of polymer chain changes from globule to extended cigar to toroid like structure during cooling from a high temperature. The aggregation of fullerene nano-particles is found to depend on the morphology of polymer chain. To maximize, the number of polymer bead-nanoparticle contacts, all nano-particle have positioned inside the polymer globule. To minimize, the energy penalty, due to bending of the polymer chain, all nano-particle have positioned on the surface of the polymer's cigar and toroid morphology.

Nano-Particle Enhanced Polymer Materials for Space Flight Applications

NASA Technical Reports Server (NTRS)

Criss, Jim M., Jr.; Powell, William D.; Connell, John W.; Stallworth-Bordain, Yemaya; Brown, Tracy R.; Mintz, Eric A.; Schlea, Michelle R.; Shofne, Meisha L.

2009-01-01

Recent advances in materials technology both in polymer chemistry and nano-materials warrant development of enhanced structures for space flight applications. This work aims to develop spacecraft structures based on polymer matrix composites (PMCs) that utilize these advancements.. Multi-wall carbon nano-tubes (MWCNTs) are expected ·to increase mechanical performance, lower coefficient of thermal expansion (CTE), increase electrical conductivity (mitigate electrostatic charge), increase thermal conductivity, and reduce moisture absorption of the resultant space structures. In this work, blends of MWCNTs with PETI-330 were prepared and characterized. The nano-reinforced resins were then resin transfer molded (RTM) into composite panels using M55J carbon fabric and compared to baseline panels fabricated from a cyanate ester (RS-3) or a polyimide (PETI-330) resin containing no MWCNTs. In addition, methods of pre-loading the fabric with the MWCNTs were also investigated. The effects of the MWCNTs on the resin processing properties and on the composite end-use properties were also determined.

Virus scaffolds as enzyme nano-carriers.

PubMed

Cardinale, Daniela; Carette, Noëlle; Michon, Thierry

2012-07-01

The cooperative organization of enzymes by cells is a key feature for the efficiency of living systems. In the field of nanotechnologies, effort currently aims at mimicking this natural organization. Nanoscale resolution and high-registration alignment are necessary to control enzyme distribution in nano-containers or on the surface of solid supports. Virus capsid self-assembly is driven by precise supramolecular combinations of protein monomers, which have made them attractive building blocks to engineer enzyme nano-carriers (ENCs). We discuss some examples of what in our opinion constitute the latest advances in the use of plant viruses, bacteriophages and virus-like particles (VLPs) as nano-scaffolds for enzyme selection, enzyme confinement and patterning, phage therapy, raw material processing, and single molecule enzyme kinetics studies. Copyright © 2012 Elsevier Ltd. All rights reserved.

Control of pore size and structure of tissue engineering scaffolds produced by supercritical fluid processing.

PubMed

Tai, Hongyun; Mather, Melissa L; Howard, Daniel; Wang, Wenxin; White, Lisa J; Crowe, John A; Morgan, Steve P; Chandra, Amit; Williams, David J; Howdle, Steven M; Shakesheff, Kevin M

2007-12-17

Tissue engineering scaffolds require a controlled pore size and structure to host tissue formation. Supercritical carbon dioxide (scCO2) processing may be used to form foamed scaffolds in which the escape of CO2 from a plasticized polymer melt generates gas bubbles that shape the developing pores. The process of forming these scaffolds involves a simultaneous change in phase in the CO2 and the polymer, resulting in rapid expansion of a surface area and changes in polymer rheological properties. Hence, the process is difficult to control with respect to the desired final pore size and structure. In this paper, we describe a detailed study of the effect of polymer chemical composition, molecular weight and processing parameters on final scaffold characteristics. The study focuses on poly(DL-lactic acid) (PDLLA) and poly(DL-lactic acid-co-glycolic acid) (PLGA) as polymer classes with potential application as controlled release scaffolds for growth factor delivery. Processing parameters under investigation were temperature (from 5 to 55 degrees C) and pressure (from 60 to 230 bar). A series of amorphous PDLLA and PLGA polymers with various molecular weights (from 13 KD to 96 KD) and/or chemical compositions (the mole percentage of glycolic acid in the polymers was 0, 15, 25, 35 and 50 respectively) were employed. The resulting scaffolds were characterised by optical microscopy, scanning electron microscopy (SEM), and micro X-ray computed tomography (microCT). This is the first detailed study on using these series polymers for scaffold formation by supercritical technique. This study has demonstrated that the pore size and structure of the supercritical PDLLA and PLGA scaffolds can be tailored by careful control of processing conditions.

Replication of surface nano-structure of the wing of dragonfly ( Pantala Flavescens) using nano-molding and UV nanoimprint lithography

NASA Astrophysics Data System (ADS)

Cho, Joong-Yeon; Kim, Gyutae; Kim, Sungwook; Lee, Heon

2013-07-01

The hydrophobicity of a dragonfly's wing originates from the naturally occurring nano-structure on its surface. The nano-structure on a dragonfly's wing consists of an array of nano-sized pillars, 100 nm in diameter. We re-create this hydrophobicity on various substrates, such as Si, glass, curved acrylic polymer, and flexible PET film, by replicating the nano-structure using UV curable nano-imprint lithography (NIL) and PDMS molding. The success of the nano-structure duplication was confirmed using scanning electron microscopy (SEM). The hydrophobicity was measured by water-based contact angle measurements. The water contact angle of the replica made of UV cured polymer was 135° ± 2°, which was slightly lower than that of the original dragonfly's wing (145° ± 2°), but much higher than that of the UV cured polymer surface without any nano-sized pillars (80°). The hydrophobicity was further improved by applying a coating of Teflon-like material.

Tunable Infrared Metasurface on a Soft Polymer Scaffold.

PubMed

Reeves, Jeremy B; Jayne, Rachael K; Stark, Thomas J; Barrett, Lawrence K; White, Alice E; Bishop, David J

2018-05-09

The fabrication of metallic electromagnetic meta-atoms on a soft microstructured polymer scaffold using a MEMS-based stencil lithography technique is demonstrated. Using this technique, complex metasurfaces that are generally impossible to fabricate with traditional photolithographic techniques are created. By engineering the mechanical deformation of the polymer scaffold, the metasurface reflectivity in the mid-infrared can be tuned by the application of moderate strains.

Ultrasonic-assisted synthesis of nano lead(II) coordination polymer as precursors for preparation of lead(II) oxide nano-structures: Thermal, optical properties and XRD studies.

PubMed

Ghavidelaghdam, Elham; Shahverdizadeh, Gholam Hossein; Motameni Tabatabai, Javad; Mirtamizdoust, Babak

2018-04-01

Nano structure of a lead (II) coordination polymer [Pb 2 (C 2 Cl 3 O 2 ) 2 (NO 3 ) 2 (C l2 H 8 N 2 ) 2 ] n (1), has been synthesized by a sonochemical method in different concentrations. The nano particles were characterized by scanning electron microscopy (SEM) X-ray powder diffraction (XRD), FT-IR spectroscopy and elemental analyses. The thermal stability of nano structure is closely investigated via thermal gravimetric (TGA), and compared with crystalline structure. The compounds are then heated to 600 °C to produce PbO nano particles. The resulting PbO is characterized through XRD and SEM analyses. Concentration of initial reagents effects on size and morphology of nano-structured compound 1 have been studied and show that low concentrations of initial reagents decreased particles size and leaded to uniform nano particles morphology. The photoluminescence properties of the prepared compound, as crystalline and as nanoparticles, have been investigated. The result showed a good correlation between the size and emission wavelength. Copyright © 2017. Published by Elsevier B.V.

Development of a nanostructured DNA delivery scaffold via electrospinning of PLGA and PLA-PEG block copolymers

NASA Technical Reports Server (NTRS)

Luu, Y. K.; Kim, K.; Hsiao, B. S.; Chu, B.; Hadjiargyrou, M.; Hadjiargyou, M. (Principal Investigator)

2003-01-01

The present work utilizes electrospinning to fabricate synthetic polymer/DNA composite scaffolds for therapeutic application in gene delivery for tissue engineering. The scaffolds are non-woven, nano-fibered, membranous structures composed predominantly of poly(lactide-co-glycolide) (PLGA) random copolymer and a poly(D,L-lactide)-poly(ethylene glycol) (PLA-PEG) block copolymer. Release of plasmid DNA from the scaffolds was sustained over a 20-day study period, with maximum release occurring at approximately 2 h. Cumulative release profiles indicated amounts released were approximately 68-80% of the initially loaded DNA. Variations in the PLGA to PLA-PEG block copolymer ratio vastly affected the overall structural morphology, as well as both the rate and efficiency of DNA release. Results indicated that DNA released directly from these electrospun scaffolds was indeed intact, capable of cellular transfection, and successfully encoded the protein beta-galactosidase. When tested under tensile loads, the electrospun polymer/DNA composite scaffolds exhibited tensile moduli of approximately 35 MPa, with approximately 45% strain initially. These values approximate those of skin and cartilage. Taken together, this work represents the first successful demonstration of plasmid DNA incorporation into a polymer scaffold using electrospinning.

Flash nano-precipitation of polymer blends: a role for fluid flow?

NASA Astrophysics Data System (ADS)

Grundy, Lorena; Mason, Lachlan; Chergui, Jalel; Juric, Damir; Craster, Richard V.; Lee, Victoria; Prudhomme, Robert; Priestley, Rodney; Matar, Omar K.

2017-11-01

Porous structures can be formed by the controlled precipitation of polymer blends; ranging from porous matrices, with applications in membrane filtration, to porous nano-particles, with applications in catalysis, targeted drug delivery and emulsion stabilisation. Under a diffusive exchange of solvent for non-solvent, prevailing conditions favour the decomposition of polymer blends into multiple phases. Interestingly, dynamic structures can be `trapped' via vitrification prior to thermodynamic equilibrium. A promising mechanism for large-scale polymer processing is flash nano-precipitation (FNP). FNP particle formation has recently been modelled using spinodal decomposition theory, however the influence of fluid flow on structure formation is yet to be clarified. In this study, we couple a Navier-Stokes equation to a Cahn-Hilliard model of spinodal decomposition. The framework is implemented using Code BLUE, a massively scalable fluid dynamics solver, and applied to flows within confined impinging jet mixers. The present method is valid for a wide range of mixing timescales spanning FNP and conventional immersion precipitation processes. Results aid in the fabrication of nano-scale polymer particles with tuneable internal porosities. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM), PETRONAS.

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

PubMed Central

Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

2014-01-01

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications. PMID:24736662

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance.

PubMed

Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

2014-04-16

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa · m(1/2) with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications.

Fabrication of conductive polymer-based nanofiber scaffolds for tissue engineering applications.

PubMed

Gu, Bon Kang; Kim, Min Sup; Kang, Chang Mo; Kim, Jong-Ll; Park, Sang Jun; Kim, Chun-Ho

2014-10-01

Natural and synthetic polymers, in particular those that are conductive, are of great interest in the field of tissue engineering and the pursuit of biomimetic extracellular matrix (ECM) structures for adhesion, proliferation, and differentiation of cells. In the present study, natural chitin and conductive polyaniline (PANi) blended solutions were electrospun to produce biodegradable and conductive biomimetic nanostructured scaffolds. The chitin/PANi (Chi-PANi) nanofibrous materials were characterized using field emission scanning electron microscopy, Fourier transform-infrared spectroscopy, wettability analysis, mechanical testing, and electrical conductivity measurements using a 4-point probe method. The calculated electrical conductivities of the PANi-containing nanofiber scaffolds significantly increased as the amount of PANi increased, reaching 5.21 ± 0.28 x 10(-3) S/cm for 0.3 wt% content of the conducting polymer. In addition, the viability of human mesenchymal stem cells (hMSCs) cultured on the Chi-PANi nanofiber scaffolds in vitro was found to be excellent. These results suggest that the Chi-PANi nanofiber scaffolds have great potential for use in tissue engineering applications that involve electrical stimulation.

Electrodeposition on nanofibrous polymer scaffolds: Rapid mineralization, tunable calcium phosphate composition and topography

PubMed Central

He, Chuanglong; Xiao, Guiyong; Jin, Xiaobing; Sun, Chenghui; Ma, Peter X.

2011-01-01

We developed a straightforward, fast, and versatile technique to fabricate mineralized nanofibrous polymer scaffolds for bone regeneration in this work. Nanofibrous poly(l-lactic acid) scaffolds were fabricated using both electrospinning and phase separation techniques. An electrodeposition process was designed to deposit calcium phosphate on the nanofibrous scaffolds. Such scaffolds contain a high quality mineral coating on the fiber surface with tunable surface topography and chemical composition by varying the processing parameters, which can mimic the composition and structure of natural bone extracellular matrix and provide a more biocompatible interface for bone regeneration. PMID:21673827

Manufacture and characterisation of EmDerm-novel hierarchically structured bio-active scaffolds for tissue regeneration.

PubMed

Lim, Xuxin; Potter, Matthew; Cui, Zhanfeng; Dye, Julian F

2018-06-05

There are significant challenges for using emulsion templating as a method of manufacturing macro-porous protein scaffolds. Issues include protein denaturation by adsorption at hydrophobic interfaces, emulsion instability, oil droplet and surfactant removal after protein gelation, and compatible cross-linking methods. We investigated an oil-in-water macro-emulsion stabilised with a surfactant blend, as a template for manufacturing protein-based nano-structured bio-intelligent scaffolds (EmDerm) with tuneable micro-scale porosity for tissue regeneration. Prototype EmDerm scaffolds were made using either collagen, through thermal gelation, fibrin, through enzymatic coagulation or collagen-fibrin composite. Pore size was controlled via surfactant-to-oil phase ratio. Scaffolds were crosslink-stabilised with EDC/NHS for varying durations. Scaffold micro-architecture and porosity were characterised with SEM, and mechanical properties by tensiometry. Hydrolytic and proteolytic degradation profiles were quantified by mass decrease over time. Human dermal fibroblasts, endothelial cells and bone marrow derived mesenchymal stem cells were used to investigate cytotoxicity and cell proliferation within each scaffold. EmDerm scaffolds showed nano-scale based hierarchical structures, with mean pore diameters ranging from 40-100 microns. The Young's modulus range was 1.1-2.9 MPa, and ultimate tensile strength was 4-16 MPa. Degradation rate was related to cross-linking duration. Each EmDerm scaffold supported excellent cell ingress and proliferation compared to the reference materials Integra™ and Matriderm™. Emulsion templating is a novel rapid method of fabricating nano-structured fibrous protein scaffolds with micro-scale pore dimensions. These scaffolds hold promising clinical potential for regeneration of the dermis and other soft tissues, e.g., for burns or chronic wound therapies.

Periodontal tissue engineering by nano beta-tricalcium phosphate scaffold and fibroblast growth factor-2 in one-wall infrabony defects of dogs.

PubMed

Ogawa, K; Miyaji, H; Kato, A; Kosen, Y; Momose, T; Yoshida, T; Nishida, E; Miyata, S; Murakami, S; Takita, H; Fugetsu, B; Sugaya, T; Kawanami, M

2016-12-01

Nanoparticle bioceramics are being investigated for biomedical applications. We fabricated a regenerative scaffold comprising type I collagen and beta-tricalcium phosphate (β-TCP) nanoparticles. Fibroblast growth factor-2 (FGF-2) is a bioeffective signaling molecule that stimulates cell proliferation and wound healing. This study examined the effects, on bioactivity, of a nano-β-TCP/collagen scaffold loaded with FGF-2, particularly on periodontal tissue wound healing. Beta-tricalcium phosphate was pulverized into nanosize particles (84 nm) and was then dispersed. A nano-β-TCP scaffold was prepared by coating the surface of a collagen scaffold with a nanosize β-TCP dispersion. Scaffolds were characterized using scanning electron microscopy, compressive testing, cell seeding and rat subcutaneous implant testing. Then, nano-β-TCP scaffold, nano-β-TCP scaffold loaded with FGF-2 and noncoated collagen scaffold were implanted into a dog one-wall infrabony defect model. Histological observations were made at 10 d and 4 wk postsurgery. Scanning electron microscopy images show that TCP nanoparticles were attached to collagen fibers. The nano-β-TCP scaffold showed higher compressive strength and cytocompatibility compared with the noncoated collagen scaffold. Rat subcutaneous implant tests showed that the DNA contents of infiltrating cells in the nano-β-TCP scaffold and the FGF-2-loaded scaffold were approximately 2.8-fold and 3.7-fold greater, respectively, than in the collagen scaffold. Histological samples from the periodontal defect model showed about five-fold greater periodontal tissue repair following implantation of the nano-β-TCP scaffold loaded with FGF-2 compared with the collagen scaffold. The β-TCP nanoparticle coating strongly improved the collagen scaffold bioactivity. Nano-β-TCP scaffolds containing FGF-2 are anticipated for use in periodontal tissue engineering. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Advanced Ceramics from Preceramic Polymers Modified at the Nano-Scale: A Review.

PubMed

Bernardo, Enrico; Fiocco, Laura; Parcianello, Giulio; Storti, Enrico; Colombo, Paolo

2014-03-06

Preceramic polymers, i.e. , polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their main advantages is the possibility of combining the shaping and synthesis of ceramics: components can be shaped at the precursor stage by conventional plastic-forming techniques, such as spinning, blowing, injection molding, warm pressing and resin transfer molding, and then converted into ceramics by treatments typically above 800 °C. The extension of the approach to a wider range of ceramic compositions and applications, both structural and thermo-structural (refractory components, thermal barrier coatings) or functional (bioactive ceramics, luminescent materials), mainly relies on modifications of the polymers at the nano-scale, i.e. , on the introduction of nano-sized fillers and/or chemical additives, leading to nano-structured ceramic components upon thermal conversion. Fillers and additives may react with the main ceramic residue of the polymer, leading to ceramics of significant engineering interest (such as silicates and SiAlONs), or cause the formation of secondary phases, significantly affecting the functionalities of the polymer-derived matrix.

Advanced Ceramics from Preceramic Polymers Modified at the Nano-Scale: A Review

PubMed Central

Bernardo, Enrico; Fiocco, Laura; Parcianello, Giulio; Storti, Enrico; Colombo, Paolo

2014-01-01

Preceramic polymers, i.e., polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their main advantages is the possibility of combining the shaping and synthesis of ceramics: components can be shaped at the precursor stage by conventional plastic-forming techniques, such as spinning, blowing, injection molding, warm pressing and resin transfer molding, and then converted into ceramics by treatments typically above 800 °C. The extension of the approach to a wider range of ceramic compositions and applications, both structural and thermo-structural (refractory components, thermal barrier coatings) or functional (bioactive ceramics, luminescent materials), mainly relies on modifications of the polymers at the nano-scale, i.e., on the introduction of nano-sized fillers and/or chemical additives, leading to nano-structured ceramic components upon thermal conversion. Fillers and additives may react with the main ceramic residue of the polymer, leading to ceramics of significant engineering interest (such as silicates and SiAlONs), or cause the formation of secondary phases, significantly affecting the functionalities of the polymer-derived matrix. PMID:28788548

Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds.

PubMed

Zanin, H; Rosa, C M R; Eliaz, N; May, P W; Marciano, F R; Lobo, A O

2015-06-14

Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.

Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds

NASA Astrophysics Data System (ADS)

Zanin, H.; Rosa, C. M. R.; Eliaz, N.; May, P. W.; Marciano, F. R.; Lobo, A. O.

2015-05-01

Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.

Polysaccharide nano-vesicular multidrug carriers for synergistic killing of cancer cells.

PubMed

Pramod, P S; Shah, Ruchira; Chaphekar, Sonali; Balasubramanian, Nagaraj; Jayakannan, Manickam

2014-10-21

Multi-drug delivery based on polymer nano-scaffolds is an essential protocol to be developed for better administration of anticancer drugs to enhance their therapeutic efficacies against cancer cells. Here, we report dual delivery polysaccharide nano-vesicles that are capable of loading and delivering both water soluble and water insoluble drugs together in a single polymer scaffold. The selective rupture of the nano-vesicular assembly under intracellular enzyme conditions allowed the simultaneous delivery of a hydrophobic drug camptothecin (CPT) and hydrophilic drug doxorubicin (DOX) supporting their synergistic killing of breast and colon cancer cells. The polysaccharide nano-vesicles have allowed us to address a few important questions regarding the need for multiple drug administration in cancer cells including (a) the role of simultaneous drug release, (b) antagonistic versus synergistic effects of drug combinations and (c) how these are affected by the ratio of drugs. Further, evaluation of the role of caveolae in endocytosis of these polymer scaffolds was also made. The vesicular scaffolds were found to preserve and deliver DOX resulting in 50-60% better killing of cancer cells than the free drug. Additionally, dual loaded nano-vesicles when compared to drug cocktails with individual drugs in separate nano-vesicles (at comparable molar ratios) suggest the relative drug concentration following release and mode of delivery to be both important in cancer cell killing. Results from these experiments have revealed newly developed polysaccharide nano-vesicles loaded with DOX and CPT drugs as potential candidates for improved breast cancer cell killing. Thus, these custom-designed polysaccharide nano-vesicles provide a new perspective on multi-anticancer drug delivery systems and their efficacy.

Towards an ideal polymer scaffold for tendon/ligament tissue engineering

NASA Astrophysics Data System (ADS)

Sahoo, Sambit; Ouyang, Hong Wei; Goh, James Cho-Hong; Tay, Tong-Earn; Toh, Siew Lok

2005-04-01

Tissue engineering holds promise in treating injured tendons and ligaments by replacing the injured tissues with "engineered tissues" with identical mechanical and functional characteristics. A biocompatible, biodegradable, porous scaffold with optimized architecture, sufficient surface area for cell attachment, growth and proliferation, faborable mechanical properties, and suitable degradation rate is a pre-requisite to achieve success with this aproach. Knitted poly(lactide-co-glycolide) (PLGA) scaffolds comprising of microfibers of 25 micron diameter were coated with PLGA nanofibers on their surfaces by electrospinning technique. A cell suspension of pig bone marrow stromal cells (BMSC) was seeded on the scaffolds by pipetting, and the cell-scaffold constructs were cultured in a CO2 incubator, at 37°C for 1-2 weeks. The "engineered tissues" were then assessed for cell attachment and proliferation, tissue formation, and mechanical properties. Nanofibers, of diameter 300-900 nm, were spread randomly over the knitted scaffold. The reduction in pore-size from about 1 mm (in the knitted scaffold) to a few micrometers (in the nano-microscaffold) allowed cell seeding by direct pipetting, and eliminated the need of a cell-delivery system like fibrin gel. BMSCs were seen to attach and proliferate well on the nano-microscaffold, producing abundant extracellular matrix. Mechanical testing revealed that the cell-seeded nano-microscaffolds possessed slightly higher values of failure load, elastic-region stiffness and toe-region stiffness, than the unseeded scaffolds. The combination of superior mechanical strength and integrity of knitted microfibers, with the large surface area and improved hydrophilicity of the electrospun nanofibers facilitated cell attachment and new tissue formation. This holds promise in tissue engineering of tendon/ligament.

Periodontal regeneration with nano-hyroxyapatite-coated silk scaffolds in dogs

PubMed Central

Yang, Cheryl; Lee, Jung-Seok; Jung, Ui-Won; Seo, Young-Kwon; Park, Jung-Keug

2013-01-01

Purpose In this study, we investigated the effect of silk scaffolds on one-wall periodontal intrabony defects. We conjugated nano-hydroxyapatite (nHA) onto a silk scaffold and then seeded periodontal ligament cells (PDLCs) or dental pulp cells (DPCs) onto the scaffold. Methods Five dogs were used in this study. Bilateral 4 mm×2 mm (depth×mesiodistal width), one-wall intrabony periodontal defects were surgically created on the distal side of the mandibular second premolar and the mesial side of the mandibular fourth premolar. In each dog, four of the defects were separately and randomly assigned to the following groups: the PDLC-cultured scaffold transplantation group (PDLC group), the DPC-cultured scaffold transplantation group (DPC group), the normal saline-soaked scaffold transplantation group, and the control group. The animals were euthanized following an 8-week healing interval for clinical, scanning electron microscopy (SEM), and histologic evaluations. Results There was no sign of inflammation or other clinical signs of postoperative complications. The examination of cell-seeded constructs by SEM provided visual confirmation of the favorable characteristics of nHA-coated silk scaffolds for tissue engineering. The scaffolds exhibited a firm connective porous structure in cross section, and after PDLCs and DPCs were seeded onto the scaffolds and cultured for 3 weeks, the attachment of well-spread cells and the formation of extracellular matrix (ECM) were observed. The histologic analysis revealed that a well-maintained grafted volume was present at all experimental sites for 8 weeks. Small amounts of inflammatory cells were seen within the scaffolds. The PDLC and DPC groups did not have remarkably different histologic appearances. Conclusions These observations indicate that nHA-coated silk scaffolds can be considered to be potentially useful biomaterials for periodontal regeneration. PMID:24455445

Electrospinning polymer blends for biomimetic scaffolds for ACL tissue engineering

NASA Astrophysics Data System (ADS)

Garcia, Vanessa Lizeth

The anterior cruciate ligament (ACL) rupture is one of the most common knee injuries. Current ACL reconstructive strategies consist of using an autograft or an allograft to replace the ligament. However, limitations have led researchers to create tissue engineered grafts, known as scaffolds, through electrospinning. Scaffolds made of natural and synthetic polymer blends have the potential to promote cell adhesion while having strong mechanical properties. However, enzymes found in the knee are known to degrade tissues and affect the healing of intra-articular injuries. Results suggest that the natural polymers used in this study modify the thermal properties and tensile strength of the synthetic polymers when blended. Scanning electron microscopy display bead-free and enzyme biodegradability of the fibers. Raman spectroscopy confirms the presence of the natural and synthetic polymers in the scaffolds while, amino acid analysis present the types of amino acids and their concentrations found in the natural polymers.

Macroporous nanowire nanoelectronic scaffolds for synthetic tissues

NASA Astrophysics Data System (ADS)

Tian, Bozhi; Liu, Jia; Dvir, Tal; Jin, Lihua; Tsui, Jonathan H.; Qing, Quan; Suo, Zhigang; Langer, Robert; Kohane, Daniel S.; Lieber, Charles M.

2012-11-01

The development of three-dimensional (3D) synthetic biomaterials as structural and bioactive scaffolds is central to fields ranging from cellular biophysics to regenerative medicine. As of yet, these scaffolds cannot electrically probe the physicochemical and biological microenvironments throughout their 3D and macroporous interior, although this capability could have a marked impact in both electronics and biomaterials. Here, we address this challenge using macroporous, flexible and free-standing nanowire nanoelectronic scaffolds (nanoES), and their hybrids with synthetic or natural biomaterials. 3D macroporous nanoES mimic the structure of natural tissue scaffolds, and they were formed by self-organization of coplanar reticular networks with built-in strain and by manipulation of 2D mesh matrices. NanoES exhibited robust electronic properties and have been used alone or combined with other biomaterials as biocompatible extracellular scaffolds for 3D culture of neurons, cardiomyocytes and smooth muscle cells. Furthermore, we show the integrated sensory capability of the nanoES by real-time monitoring of the local electrical activity within 3D nanoES/cardiomyocyte constructs, the response of 3D-nanoES-based neural and cardiac tissue models to drugs, and distinct pH changes inside and outside tubular vascular smooth muscle constructs.

Self-Assembled Polymeric Ionic Liquid-Functionalized Cellulose Nano-crystals: Constructing 3D Ion-conducting Channels Within Ionic Liquid-based Composite Polymer Electrolytes.

PubMed

Shi, Qing Xuan; Xia, Qing; Xiang, Xiao; Ye, Yun Sheng; Peng, Hai Yan; Xue, Zhi Gang; Xie, Xiao Lin; Mai, Yiu-Wing

2017-09-04

Composite polymeric and ionic liquid (IL) electrolytes are some of the most promising electrolyte systems for safer battery technology. Although much effort has been directed towards enhancing the transport properties of polymer electrolytes (PEs) through nanoscopic modification by incorporating nano-fillers, it is still difficult to construct ideal ion conducting networks. Here, a novel class of three-dimensional self-assembled polymeric ionic liquid (PIL)-functionalized cellulose nano-crystals (CNC) confining ILs in surface-grafted PIL polymer chains, able to form colloidal crystal polymer electrolytes (CCPE), is reported. The high-strength CNC nano-fibers, decorated with PIL polymer chains, can spontaneously form three-dimensional interpenetrating nano-network scaffolds capable of supporting electrolytes with continuously connected ion conducting networks with IL being concentrated in conducting domains. These new CCPE have exceptional ionic conductivities, low activation energies (close to bulk IL electrolyte with dissolved Li salt), high Li + transport numbers, low interface resistances and improved interface compatibilities. Furthermore, the CCPE displays good electrochemical properties and a good battery performance. This approach offers a route to leak-free, non-flammable and high ionic conductivity solid-state PE in energy conversion devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polysaccharide nano-vesicular multidrug carriers for synergistic killing of cancer cells

NASA Astrophysics Data System (ADS)

Pramod, P. S.; Shah, Ruchira; Chaphekar, Sonali; Balasubramanian, Nagaraj; Jayakannan, Manickam

2014-09-01

Multi-drug delivery based on polymer nano-scaffolds is an essential protocol to be developed for better administration of anticancer drugs to enhance their therapeutic efficacies against cancer cells. Here, we report dual delivery polysaccharide nano-vesicles that are capable of loading and delivering both water soluble and water insoluble drugs together in a single polymer scaffold. The selective rupture of the nano-vesicular assembly under intracellular enzyme conditions allowed the simultaneous delivery of a hydrophobic drug camptothecin (CPT) and hydrophilic drug doxorubicin (DOX) supporting their synergistic killing of breast and colon cancer cells. The polysaccharide nano-vesicles have allowed us to address a few important questions regarding the need for multiple drug administration in cancer cells including (a) the role of simultaneous drug release, (b) antagonistic versus synergistic effects of drug combinations and (c) how these are affected by the ratio of drugs. Further, evaluation of the role of caveolae in endocytosis of these polymer scaffolds was also made. The vesicular scaffolds were found to preserve and deliver DOX resulting in 50-60% better killing of cancer cells than the free drug. Additionally, dual loaded nano-vesicles when compared to drug cocktails with individual drugs in separate nano-vesicles (at comparable molar ratios) suggest the relative drug concentration following release and mode of delivery to be both important in cancer cell killing. Results from these experiments have revealed newly developed polysaccharide nano-vesicles loaded with DOX and CPT drugs as potential candidates for improved breast cancer cell killing. Thus, these custom-designed polysaccharide nano-vesicles provide a new perspective on multi-anticancer drug delivery systems and their efficacy.Multi-drug delivery based on polymer nano-scaffolds is an essential protocol to be developed for better administration of anticancer drugs to enhance their therapeutic

Asphaltenes-based polymer nano-composites

DOEpatents

Bowen, III, Daniel E

2013-12-17

Inventive composite materials are provided. The composite is preferably a nano-composite, and comprises an asphaltene, or a mixture of asphaltenes, blended with a polymer. The polymer can be any polymer in need of altered properties, including those selected from the group consisting of epoxies, acrylics, urethanes, silicones, cyanoacrylates, vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, imides, esters, cyanate esters, allyl resins.

Polyurethane foam/nano hydroxyapatite composite as a suitable scaffold for bone tissue regeneration.

PubMed

Meskinfam, M; Bertoldi, S; Albanese, N; Cerri, A; Tanzi, M C; Imani, R; Baheiraei, N; Farokhi, M; Farè, S

2018-01-01

In bone tissue regeneration, the use of biomineralized scaffolds to create the 3D porous structure needed for well-fitting with defect size and appropriate cell interactions, is a promising alternative to autologous and heterologous bone grafts. Biomineralized polyurethane (PU) foams are here investigated as scaffold for bone tissue regeneration. Biomineralization of the foams was carried out by activation of PU surface by a two steps procedure performed for different times (1 to 4 weeks). Scaffolds were investigated for morphological, chemico-physical and mechanical properties, as well as for in vitro interaction with rat Bone Marrow Mesenchymal Stem Cells (BMSCs). Untreated and biomineralized PU samples showed a homogenous morphology and regular pore size (average Ø=407μm). Phase and structure of formed calcium phosphates (CaPs) layer onto the PU foam were analyzed by Fourier Transform Infrared spectroscopy and X-ray diffraction, proving the formation of bone-like nano hydroxyapatite. Biomineralization caused a significant increase of mechanical properties of treated foams compared to untreated ones. Biomineralization also affected the PU scaffold cytocompatibility providing a more appropriate surface for cell attachment and proliferation. Considering the obtained results, the proposed scaffold can be considered suitable for bone tissue regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Four-Dimensional Printing Hierarchy Scaffolds with Highly Biocompatible Smart Polymers for Tissue Engineering Applications.

PubMed

Miao, Shida; Zhu, Wei; Castro, Nathan J; Leng, Jinsong; Zhang, Lijie Grace

2016-10-01

The objective of this study was to four-dimensional (4D) print novel biomimetic gradient tissue scaffolds with highly biocompatible naturally derived smart polymers. The term "4D printing" refers to the inherent smart shape transformation of fabricated constructs when implanted minimally invasively for seamless and dynamic integration. For this purpose, a series of novel shape memory polymers with excellent biocompatibility and tunable shape changing effects were synthesized and cured in the presence of three-dimensional printed sacrificial molds, which were subsequently dissolved to create controllable and graded porosity within the scaffold. Surface morphology, thermal, mechanical, and biocompatible properties as well as shape memory effects of the synthesized smart polymers and resultant porous scaffolds were characterized. Fourier transform infrared spectroscopy and gel content analysis confirmed the formation of chemical crosslinking by reacting polycaprolactone triol and castor oil with multi-isocyanate groups. Differential scanning calorimetry revealed an adjustable glass transition temperature in a range from -8°C to 35°C. Uniaxial compression testing indicated that the obtained polymers, possessing a highly crosslinked interpenetrating polymeric networks, have similar compressive modulus to polycaprolactone. Shape memory tests revealed that the smart polymers display finely tunable recovery speed and exhibit greater than 92% shape fixing at -18°C or 0°C and full shape recovery at physiological temperature. Scanning electron microscopy analysis of fabricated scaffolds revealed a graded microporous structure, which mimics the nonuniform distribution of porosity found within natural tissues. With polycaprolactone serving as a control, human bone marrow-derived mesenchymal stem cell adhesion, proliferation, and differentiation greatly increased on our novel smart polymers. The current work will significantly advance the future design and development of

Four-Dimensional Printing Hierarchy Scaffolds with Highly Biocompatible Smart Polymers for Tissue Engineering Applications

PubMed Central

Miao, Shida; Zhu, Wei; Castro, Nathan J.; Leng, Jinsong

2016-01-01

The objective of this study was to four-dimensional (4D) print novel biomimetic gradient tissue scaffolds with highly biocompatible naturally derived smart polymers. The term “4D printing” refers to the inherent smart shape transformation of fabricated constructs when implanted minimally invasively for seamless and dynamic integration. For this purpose, a series of novel shape memory polymers with excellent biocompatibility and tunable shape changing effects were synthesized and cured in the presence of three-dimensional printed sacrificial molds, which were subsequently dissolved to create controllable and graded porosity within the scaffold. Surface morphology, thermal, mechanical, and biocompatible properties as well as shape memory effects of the synthesized smart polymers and resultant porous scaffolds were characterized. Fourier transform infrared spectroscopy and gel content analysis confirmed the formation of chemical crosslinking by reacting polycaprolactone triol and castor oil with multi-isocyanate groups. Differential scanning calorimetry revealed an adjustable glass transition temperature in a range from −8°C to 35°C. Uniaxial compression testing indicated that the obtained polymers, possessing a highly crosslinked interpenetrating polymeric networks, have similar compressive modulus to polycaprolactone. Shape memory tests revealed that the smart polymers display finely tunable recovery speed and exhibit greater than 92% shape fixing at −18°C or 0°C and full shape recovery at physiological temperature. Scanning electron microscopy analysis of fabricated scaffolds revealed a graded microporous structure, which mimics the nonuniform distribution of porosity found within natural tissues. With polycaprolactone serving as a control, human bone marrow-derived mesenchymal stem cell adhesion, proliferation, and differentiation greatly increased on our novel smart polymers. The current work will significantly advance the future design and

Development of core-shell coaxially electrospun composite PCL/chitosan scaffolds.

PubMed

Surucu, Seda; Turkoglu Sasmazel, Hilal

2016-11-01

This study was related to combining of synthetic Poly (ε-caprolactone) (PCL) and natural chitosan polymers to develop three dimensional (3D) PCL/chitosan core-shell scaffolds for tissue engineering applications. The scaffolds were fabricated with coaxial electrospinning technique and the characterizations of the samples were done by thickness and contact angle (CA) measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS) analyses, mechanical and PBS absorption and shrinkage tests. The average inter-fiber diameter values were calculated for PCL (0.717±0.001μm), chitosan (0.660±0.007μm) and PCL/chitosan core-shell scaffolds (0.412±0.003μm), also the average inter-fiber pore size values exhibited decreases of 66.91% and 61.90% for the PCL and chitosan scaffolds respectively, compared to PCL/chitosan core-shell ones. XPS analysis of the PCL/chitosan core-shell structures exhibited the characteristic peaks of PCL and chitosan polymers. The cell culture studies (MTT assay, Confocal Laser Scanning Microscope (CLSM) and SEM analyses) carried out with L929 ATCC CCL-1 mouse fibroblast cell line proved that the biocompatibility performance of the scaffolds. The obtained results showed that the created micro/nano fibrous structure of the PCL/chitosan core-shell scaffolds in this study increased the cell viability and proliferation on/within scaffolds. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Peracetic Acid: A Practical Agent for Sterilizing Heat-Labile Polymeric Tissue-Engineering Scaffolds

PubMed Central

Yoganarasimha, Suyog; Trahan, William R.; Best, Al M.; Bowlin, Gary L.; Kitten, Todd O.; Moon, Peter C.

2014-01-01

Advanced biomaterials and sophisticated processing technologies aim at fabricating tissue-engineering scaffolds that can predictably interact within a biological environment at the cellular level. Sterilization of such scaffolds is at the core of patient safety and is an important regulatory issue that needs to be addressed before clinical translation. In addition, it is crucial that meticulously engineered micro- and nano- structures are preserved after sterilization. Conventional sterilization methods involving heat, steam, and radiation are not compatible with engineered polymeric systems because of scaffold degradation and loss of architecture. Using electrospun scaffolds made from polycaprolactone, a low melting polymer, and employing spores of Bacillus atrophaeus as biological indicators, we compared ethylene oxide, autoclaving and 80% ethanol to a known chemical sterilant, peracetic acid (PAA), for their ability to sterilize as well as their effects on scaffold properties. PAA diluted in 20% ethanol to 1000 ppm or above sterilized electrospun scaffolds in 15 min at room temperature while maintaining nano-architecture and mechanical properties. Scaffolds treated with PAA at 5000 ppm were rendered hydrophilic, with contact angles reduced to 0°. Therefore, PAA can provide economical, rapid, and effective sterilization of heat-sensitive polymeric electrospun scaffolds that are used in tissue engineering. PMID:24341350

3D printing nano conductive multi-walled carbon nanotube scaffolds for nerve regeneration

NASA Astrophysics Data System (ADS)

Lee, Se-Jun; Zhu, Wei; Nowicki, Margaret; Lee, Grace; Nyoung Heo, Dong; Kim, Junghoon; Zuo, Yi Y.; Zhang, Lijie Grace

2018-02-01

Objective. Nanomaterials, such as carbon nanotubes (CNTs), have been introduced to modify the surface properties of scaffolds, thus enhancing the interaction between the neural cells and biomaterials. In addition to superior electrical conductivity, CNTs can provide nanoscale structures similar to those present in the natural neural environment. The primary objective of this study is to investigate the proliferative capability and differential potential of neural stem cells (NSCs) seeded on a CNT incorporated scaffold. Approach. Amine functionalized multi-walled carbon nanotubes (MWCNTs) were incorporated with a PEGDA polymer to provide enhanced electrical properties as well as nanofeatures on the surface of the scaffold. A stereolithography 3D printer was employed to fabricate a well-dispersed MWCNT-hydrogel composite neural scaffold with a tunable porous structure. 3D printing allows easy fabrication of complex 3D scaffolds with extremely intricate microarchitectures and controlled porosity. Main results. Our results showed that MWCNT-incorporated scaffolds promoted neural stem cell proliferation and early neuronal differentiation when compared to those scaffolds without the MWCNTs. Furthermore, biphasic pulse stimulation with 500 µA current promoted neuronal maturity quantified through protein expression analysis by quantitative polymerase chain reaction. Significance. Results of this study demonstrated that an electroconductive MWCNT scaffold, coupled with electrical stimulation, may have a synergistic effect on promoting neurite outgrowth for therapeutic application in nerve regeneration.

[Experimental study on tissue engineered cartilage complex three-dimensional nano-scaffold with collagen type II and hyaluronic acid in vitro].

PubMed

Yang, Zelong; Chen, Zhu; Liu, Kang; Bai, Yiguang; Jiang, Ting; Feng, Daxiong; Feng, Gang

2013-10-01

To explore the possibility of constructing tissue engineered cartilage complex three-dimensional nano-scaffold with collagen type II and hyaluronic acid (HA) by electrospinning. The three-dimensional porous nano-scaffolds were prepared by electrospinning techniques with collagen type II and HA (8 : 1, W : W), which was dissolved in mixed solvent of 3-trifluoroethanol and water (1 : 1, V : V). The morphology were observed by light microscope and scanning electron microscope (SEM). And the porosity, water absorption rate, contact angle, and degradation rate were detected. Chondrocytes were harvested from 1-week-old Japanese white rabbit, which was disgested by 0.25% trypsin 30 minutes and 1% collagenase overlight. The passage 2 chondrocytes were seeded on the nano-scaffold. The cell adhesion and proliferation were evaluated by cell counting kit 8 (CCK-8). The cell-scaffold composites were cultured for 2 weeks in vitro, and the biological morphology and extracelluar matrix (ECM) secretion were observed by histological analysis. The optimal electrospinning condition of nano-scaffold was 10% electrospinning solution concentration, 10 cm receiver distance, 5 mL/h spinning injection speed. The scaffold had uniform diameter and good porosity through the light microscope and SEM. The diameter was 300-600 nm, and the porosity was 89.5% +/- 25.0%. The contact angle was (35.6 +/- 3.4) degrees, and the water absorption was 1 120% +/- 34% at 24 hours, which indicated excellent hydrophilicity. The degradation rate was 42.24% +/- 1.51% at 48 days. CCK-8 results showed that the adhesive rate of cells with scaffold was 169.14% +/- 11.26% at 12 hours, and the cell survival rate was 126.03% +/- 4.54% at 7 days. The histological and immunohistochemical staining results showed that the chondrocytes could grow well on the scaffold and secreted ECM. And the similar cartilage lacuma structure could be found at 2 weeks after co-culture, which suggested that hyaline cartilage formed. The

Glass transition temperature of polymer nano-composites with polymer and filler interactions

NASA Astrophysics Data System (ADS)

Hagita, Katsumi; Takano, Hiroshi; Doi, Masao; Morita, Hiroshi

2012-02-01

We systematically studied versatile coarse-grained model (bead spring model) to describe filled polymer nano-composites for coarse-grained (Kremer-Grest model) molecular dynamics simulations. This model consists of long polymers, crosslink, and fillers. We used the hollow structure as the filler to describe rigid spherical fillers with small computing costs. Our filler model consists of surface particles of icosahedra fullerene structure C320 and a repulsive force from the center of the filler is applied to the surface particles in order to make a sphere and rigid. The filler's diameter is 12 times of beads of the polymers. As the first test of our model, we study temperature dependence of volumes of periodic boundary conditions under constant pressures through NPT constant Andersen algorithm. It is found that Glass transition temperature (Tg) decrease with increasing filler's volume fraction for the case of repulsive interaction between polymer and fillers and Tg weakly increase for attractive interaction.

Micro/Nano Multilayered Scaffolds of PLGA and Collagen by Alternately Electrospinning for Bone Tissue Engineering

NASA Astrophysics Data System (ADS)

Kwak, Sanghwa; Haider, Adnan; Gupta, Kailash Chandra; Kim, Sukyoung; Kang, Inn-Kyu

2016-07-01

The dual extrusion electrospinning technique was used to fabricate multilayered 3D scaffolds by stacking microfibrous meshes of poly(lactic acid-co-glycolic acid) (PLGA) in alternate fashion to micro/nano mixed fibrous meshes of PLGA and collagen. To fabricate the multilayered scaffold, 35 wt% solution of PLGA in THF-DMF binary solvent (3:1) and 5 wt% solution of collagen in hexafluoroisopropanol (HFIP) with and without hydroxyapatite nanorods (nHA) were used. The dual and individual electrospinning of PLGA and collagen were carried out at flow rates of 1.0 and 0.5 mL/h, respectively, at an applied voltage of 20 kV. The density of collagen fibers in multilayered scaffolds has controlled the adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells. The homogeneous dispersion of glutamic acid-modified hydroxyapatite nanorods (nHA-GA) in collagen solution has improved the osteogenic properties of fabricated multilayered scaffolds. The fabricated multilayered scaffolds were characterized using FT-IR, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). The scanning electron microscopy (FE-SEM) was used to evaluate the adhesion and spreads of MC3T3-E1 cells on multilayered scaffolds. The activity of MC3T3-E1 cells on the multilayered scaffolds was evaluated by applying MTT, alkaline phosphatase, Alizarin Red, von Kossa, and cytoskeleton F-actin assaying protocols. The micro/nano fibrous PLGA-Col-HA scaffolds were found to be highly bioactive in comparison to pristine microfibrous PLGA and micro/nano mixed fibrous PLGA and Col scaffolds.

Preparation and characterization of shape memory polymer scaffolds via solvent casting/particulate leaching.

PubMed

De Nardo, Luigi; Bertoldi, Serena; Cigada, Alberto; Tanzi, Maria Cristina; Haugen, Håvard Jostein; Farè, Silvia

2012-09-27

Porous Shape Memory Polymers (SMPs) are ideal candidates for the fabrication of defect fillers, able to support tissue regeneration via minimally invasive approaches. In this regard, control of pore size, shape and interconnection is required to achieve adequate nutrient transport and cell ingrowth. Here, we assessed the feasibility of the preparation of SMP porous structures and characterized their chemico-physical properties and in vitro cell response. SMP scaffolds were obtained via solvent casting/particulate leaching of gelatin microspheres, prepared via oil/water emulsion. A solution of commercial polyether-urethane (MM-4520, Mitsubishi Heavy Industries) was cast on compacted microspheres and leached-off after polymer solvent evaporation. The obtained structures were characterized in terms of morphology (SEM and micro-CT), thermo-mechanical properties (DMTA), shape recovery behavior in compression mode, and in vitro cytocompatibility (MG63 Osteoblast-like cell line). The fabrication process enabled easy control of scaffold morphology, pore size, and pore shape by varying the gelatin microsphere morphology. Homogeneous spherical and interconnected pores have been achieved together with the preservation of shape memory ability, with recovery rate up to 90%. Regardless of pore dimensions, MG63 cells were observed adhering and spreading onto the inner surface of the scaffolds obtained for up to seven days of static in vitro tests. A new class of SMP porous structures has been obtained and tested in vitro: according to these preliminary results reported, SMP scaffolds can be further exploited in the design of a new class of implantable devices.

Amorphous blue phase III polymer scaffold as a sub-millisecond switching electro-optical memory device

NASA Astrophysics Data System (ADS)

Gandhi, Sahil Sandesh; Kim, Min Su; Hwang, Jeoung-Yeon; Chien, Liang-Chy

2017-02-01

We demonstrate the application of the nanostructured scaffold of BPIII as a resuable EO device that retains the BPIII ordering and sub-millisecond EO switching characteristics, that is, "EO-memory" of the original BPIII even after removal of the cholesteric blue phase liquid crystal (LC) and subsequent refilling with different nematic LCs. We also fabricate scaffolds mimicking the isotropic phase and cubic blue phase I (BPI) to demonstrate the versatility of our material system to nano-engineer EO-memory scaffolds of various structures. We envisage that this work will promote new experimental investigations of the mysterious BPIII and the development of novel device architectures and optically functional nanomaterials.

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.

Novel synthesis strategies for natural polymer and composite biomaterials as potential scaffolds for tissue engineering

PubMed Central

Ko, Hsu-Feng; Sfeir, Charles; Kumta, Prashant N.

2010-01-01

Recent developments in tissue engineering approaches frequently revolve around the use of three-dimensional scaffolds to function as the template for cellular activities to repair, rebuild and regenerate damaged or lost tissues. While there are several biomaterials to select as three-dimensional scaffolds, it is generally agreed that a biomaterial to be used in tissue engineering needs to possess certain material characteristics such as biocompatibility, suitable surface chemistry, interconnected porosity, desired mechanical properties and biodegradability. The use of naturally derived polymers as three-dimensional scaffolds has been gaining widespread attention owing to their favourable attributes of biocompatibility, low cost and ease of processing. This paper discusses the synthesis of various polysaccharide-based, naturally derived polymers, and the potential of using these biomaterials to serve as tissue engineering three-dimensional scaffolds is also evaluated. In this study, naturally derived polymers, specifically cellulose, chitosan, alginate and agarose, and their composites, are examined. Single-component scaffolds of plain cellulose, plain chitosan and plain alginate as well as composite scaffolds of cellulose–alginate, cellulose–agarose, cellulose–chitosan, chitosan–alginate and chitosan–agarose are synthesized, and their suitability as tissue engineering scaffolds is assessed. It is shown that naturally derived polymers in the form of hydrogels can be synthesized, and the lyophilization technique is used to synthesize various composites comprising these natural polymers. The composite scaffolds appear to be sponge-like after lyophilization. Scanning electron microscopy is used to demonstrate the formation of an interconnected porous network within the polymeric scaffold following lyophilization. It is also established that HeLa cells attach and proliferate well on scaffolds of cellulose, chitosan or alginate. The synthesis protocols reported

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

Engineering and Modeling Carbon Nanofiller-Based Scaffolds for Tissue Regeneration

NASA Astrophysics Data System (ADS)

Al Habis, Nuha Hamad

Conductive biopolymers are starting to emerge as potential scaffolds of the future. These scaffolds exhibit some unique properties such as inherent conductivity, mechanical and surface properties. Traditionally, a conjugated polymer is used to constitute a conductive network. An alternative method currently being used is nanofillers as additives in the polymer. In this dissertation, we fabricated an intelligent scaffold for use in tissue engineering applications. The main idea was to enhance the mechanical, electrical properties and cell growth of scaffolds by using distinct types of nanofillers such as graphene, carbon nanofiber and carbon black. We identified the optimal concentrations of nano-additive in both fibrous and film scaffolds to obtain the highest mechanical and electrical properties without neglecting any of them. Lastly, we investigated the performance of these scaffold with cell biology. To accomplish these tasks, we first studied the mechanical properties of the scaffold as a function of morphology, concentration and variety of carbon nanofillers. Results showed that there was a gradual increase of the modulus and the fracture strength while using carbon black, carbon nanofiber and graphene, due to the small and strong carbon-to-carbon bonds and the length of the interlayer spacing. Moreover, regardless of the fabrication method, there was an increase in mechanical properties as the concentration of nanofillers increased until a threshold of 7 wt% was reached for the nanofiller film scaffold and 1%wt for the fibrous scaffold. Experimental results of carbon black exhibited a good agreement when compared with data obtained using numerical approaches and analytical models, especially in the case of lower carbon black fractions. Second, we examined the influence of electrical properties of nanofillers based on the concentration and the geometry of carbon nanofillers in the polymer matrix using experimental and numerical simulation approaches. The

Bioactive nano-fibrous scaffold for vascularized craniofacial bone regeneration.

PubMed

Prabha, Rahul Damodaran; Kraft, David Christian Evar; Harkness, Linda; Melsen, Birte; Varma, Harikrishna; Nair, Prabha D; Kjems, Jorgen; Kassem, Moustapha

2018-03-01

There has been a growing demand for bone grafts for correction of bone defects in complicated fractures or tumours in the craniofacial region. Soft flexible membrane like material that could be inserted into defect by less invasive approaches; promote osteoconductivity and act as a barrier to soft tissue in growth while promoting bone formation is an attractive option for this region. Electrospinning has recently emerged as one of the most promising techniques for fabrication of extracellular matrix such as nano-fibrous scaffolds that can serve as a template for bone formation. To overcome the limitation of cell penetration of electrospun scaffolds and improve on its osteoconductive nature, in this study, we fabricated a novel electrospun composite scaffold of polyvinyl alcohol (PVA)-poly (ε) caprolactone (PCL)-Hydroxyapatite based bioceramic (HAB), namely, PVA-PCL-HAB. The scaffold prepared by dual electrospinning of PVA and PCL with HAB overcomes reduced cell attachment associated with hydrophobic PCL by combination with a hydrophilic PVA and the HAB can contribute to enhance osteoconductivity. We characterized the physicochemical and biocompatibility properties of the new scaffold material. Our results indicate PVA-PCL-HAB scaffolds support attachment and growth of stromal stem cells; [human bone marrow skeletal (mesenchymal) stem cells and dental pulp stem cells]. In addition, the scaffold supported in vitro osteogenic differentiation and in vivo vascularized bone formation. Thus, PVA-PCL-HAB scaffold is a suitable potential material for therapeutic bone regeneration in dentistry and orthopaedics. Copyright © 2017 John Wiley & Sons, Ltd.

Impact of polymer structure and composition on fully resorbable endovascular scaffold performance

PubMed Central

Ferdous, Jahid; Kolachalama, Vijaya B.; Shazly, Tarek

2014-01-01

Fully erodible endovascular scaffolds are being increasingly considered for the treatment of obstructive arterial disease owing to their potential to mitigate long-term risks associated with permanent alternatives. While complete scaffold erosion facilitates vessel healing, generation and release of material degradation by-products from candidate materials such as poly-l-lactide (PLLA) may elicit local inflammatory responses that limit implant efficacy. We developed a computational framework to quantify how the compositional and structural parameters of PLLA-based fully erodible endovascular scaffolds affect degradation kinetics, erosion kinetics and the transient accumulation of material by-products within the arterial wall. Parametric studies reveal that, while some material properties have similar effects on these critical processes, others induce qualitatively opposing responses. For example, scaffold degradation is only mildly responsive to changes in either PLLA polydispersity or the initial degree of crystallinity, while the erosion kinetics is comparatively sensitive to crystallinity. Moreover, lactide doping can effectively tune both scaffold degradation and erosion, but a concomitant increase in local byproduct accumulation raises concerns about implant safety. Optimized erodible endovascular scaffolds must precisely balance therapeutic function and biological response over the implant lifetime, where compositional and structural parameters will have differential effects on implant performance. PMID:23261926

Fabrication of Microfibrous and Nano-/Microfibrous Scaffolds: Melt and Hybrid Electrospinning and Surface Modification of Poly(L-lactic acid) with Plasticizer

PubMed Central

Yoon, Young Il; Park, Ko Eun; Lee, Seung Jin; Park, Won Ho

2013-01-01

Biodegradable poly(L-lactic acid) (PLA) fibrous scaffolds were prepared by electrospinning from a PLA melt containing poly(ethylene glycol) (PEG) as a plasticizer to obtain thinner fibers. The effects of PEG on the melt electrospinning of PLA were examined in terms of the melt viscosity and fiber diameter. Among the parameters, the content of PEG had a more significant effect on the average fiber diameter and its distribution than those of the spinning temperature. Furthermore, nano-/microfibrous silk fibroin (SF)/PLA and PLA/PLA composite scaffolds were fabricated by hybrid electrospinning, which involved a combination of solution electrospinning and melt electrospinning. The SF/PLA (20/80) scaffolds consisted of a randomly oriented structure of PLA microfibers (average fiber diameter = 8.9 µm) and SF nanofibers (average fiber diameter = 820 nm). The PLA nano-/microfiber (20/80) scaffolds were found to have similar pore parameters to the PLA microfiber scaffolds. The PLA scaffolds were treated with plasma in the presence of either oxygen or ammonia gas to modify the surface of the fibers. This approach of controlling the surface properties and diameter of fibers could be useful in the design and tailoring of novel scaffolds for tissue engineering. PMID:24381937

Polymer scaffold degradation control via chemical control

DOEpatents

Hedberg-Dirk, Elizabeth L.; Dirk, Shawn; Cicotte, Kirsten

2016-01-05

A variety of polymers and copolymers suitable for use as biologically compatible constructs and, as a non-limiting specific example, in the formation of degradable tissue scaffolds as well methods for synthesizing these polymers and copolymers are described. The polymers and copolymers have degradation rates that are substantially faster than those of previously described polymers suitable for the same uses. Copolymers having a synthesis route which enables one to fine tune the degradation rate by selecting the specific stoichiometry of the monomers in the resulting copolymer are also described. The disclosure also provides a novel synthesis route for maleoyl chloride which yields monomers suitable for use in the copolymer synthesis methods described herein.

Towards ultraporous poly(L-lactide) scaffolds from quaternary immiscible polymer blends.

PubMed

Virgilio, N; Sarazin, P; Favis, B D

2010-08-01

Ultraporous poly(l-lactide) (PLLA) scaffolds were prepared by melt-processing quaternary ethylene propylene diene rubber/poly(epsilon-caprolactone)/polystyrene/poly(l-lactide) (EPDM/PCL/PS/PLLA) 45/45/5/5 %vol. polymer blends modified with a PS-b-PLLA diblock copolymer. The morphology consists of a PS+PLLA+copolymer sub-blend layer forming at the interface of the EPDM and PCL phases. Quiescent annealing and interfacial modification using the block copolymer are used to control the blend microstructure. The ultraporous structure is subsequently obtained by selectively extracting the EPDM, PS and PCL phases. The PLLA scaffolds modified with the PS-b-PLLA copolymer present themselves as fully interconnected porous networks with asymmetric channel walls, one side being smooth while the other is covered with an array of submicron-sized PLLA droplets. They are prepared with a high degree of control over the pore size, with averages ranging from 5microm to over 100microm and a specific surface from 9.1 to 23.1m(2)/g of PLLA, as annealing is carried out from 0 to 60min. The void volume reaches values as high as 95% and in all cases the shape and dimensions of the scaffolds are maintained with a high level of integrity. The proposed method represents a comprehensive approach towards the design and generation of porous PLLA scaffolds based on complex morphologies from melt-processed multiphase polymer systems. Copyright 2010 Elsevier Ltd. All rights reserved.

Mechanical properties and cell-culture characteristics of a polycaprolactone kagome-structure scaffold fabricated by a precision extruding deposition system.

PubMed

Lee, Se-Hwan; Cho, Yong Sang; Hong, Myoung Wha; Lee, Bu-Kyu; Park, Yongdoo; Park, Sang-Hyug; Kim, Young Yul; Cho, Young-Sam

2017-09-13

To enhance the mechanical properties of three-dimensional (3D) scaffolds used for bone regeneration in tissue engineering, many researchers have studied their structure and chemistry. In the structural engineering field, the kagome structure has been known to have an excellent relative strength. In this study, to enhance the mechanical properties of a synthetic polymer scaffold used for tissue engineering, we applied the 3D kagome structure to a porous scaffold for bone regeneration. Prior to fabricating the biocompatible-polymer scaffold, the ideal kagome structure, which was manufactured by a 3D printer of the digital light processing type, was compared with a grid-structure, which was used as the control group, using a compressive experiment. A polycaprolactone (PCL) kagome-structure scaffold was successfully fabricated by additive manufacturing using a 3D printer with a precision extruding deposition head. To assess the physical characteristics of the fabricated PCL-kagome-structure scaffold, we analyzed its porosity, pore size, morphological structure, surface roughness, compressive stiffness, and mechanical bending properties. The results showed that, the mechanical properties of proposed kagome-structure scaffold were superior to those of a grid-structure scaffold. Moreover, Sarcoma osteogenic (Saos-2) cells were used to evaluate the characteristics of in vitro cell proliferation. We carried out cell counting kit-8 (CCK-8) and DNA contents assays. Consequently, the cell proliferation of the kagome-structure scaffold was increased; this could be because the surface roughness of the kagome-structure scaffold enhances initial cell attachment.

Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

NASA Astrophysics Data System (ADS)

Dyartanti, Endah R.; Purwanto, Agus; Widiasa, I. Nyoman; Susanto, Heru

2016-02-01

Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is also investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.

Biomimetic mineralized hierarchical hybrid scaffolds based on in situ synthesis of nano-hydroxyapatite/chitosan/chondroitin sulfate/hyaluronic acid for bone tissue engineering.

PubMed

Hu, Yimin; Chen, Jingdi; Fan, Tiantang; Zhang, Yujue; Zhao, Yao; Shi, Xuetao; Zhang, Qiqing

2017-09-01

Biomimetic mineralized hybrid scaffolds are widely used as natural bone substitute materials in tissue engineering by mimicking vital characters of extracellular matrix (ECM). However, the fabrication of hybrid scaffolds with suitable mechanical properties and good biocompatibility remains a challenge. To solve the problems mentioned above, biomimetic calcium phosphate mineralized organic-inorganic hybrid scaffold composed of nano hydroxyapatite (nHAP), Chitosan (CS), Chondroitin sulfate (CSA) and hyaluronic acid (HA) with hierarchical micro/nano structures was successfully developed. In this process, an efficient and easy-to-accomplish method combining in situ biomimetic synthesis with freeze-drying technology was applied. The chemical structure of the scaffolds was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Surface morphology of scaffolds was characterized by Scanning electron microscopy (SEM). The nHAP/CS/CSA/HA hybrid scaffolds with a well-distributed pore size showed suitable mechanical strength which is not only due to the addition of the nHAP but also the interaction between the positively charged CS and the negatively charged CSA and HA. Simultaneously, the biocompatibility was evaluated by the MTT cytotoxicity assay, alkaline phosphatase (ALP) activity, Hoechst 33258 fluorescence staining. All those results proved that the scaffolds possess good biocompatibility and the components added have enhanced the proliferation and differentiation of osteoblast. Thus, it can be anticipated that the in situ biomimetic mineralized nHAP/CS/CAS/HA hybrid scaffolds will be promising candidates for bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of the effects of nano-TiO2 on bioactivity and mechanical properties of nano bioglass-P3HB composite scaffold for bone tissue engineering.

PubMed

Bakhtiyari, Sanaz Soleymani Eil; Karbasi, Saeed; Monshi, Ahmad; Montazeri, Mahbobeh

2016-01-01

To emulate bone structure, porous composite scaffold with suitable mechanical properties should be designed. In this research the effects of nano-titania (nTiO2) on the bioactivity and mechanical properties of nano-bioglass-poly-3-hydroxybutyrate (nBG/P3HB)-composite scaffold were evaluated. First, nBG powder was prepared by melting method of pure raw materials at a temperature of 1400 °C and then the porous ceramic scaffold of nBG/nTiO2 with 30 wt% of nBG containing different weight ratios of nTiO2 (3, 6, and 9 wt% of nTiO2 with grain size of 35-37 nm) was prepared by using polyurethane sponge replication method. Then the scaffolds were coated with P3HB in order to increase the scaffold's mechanical properties. Mechanical strength and modulus of scaffolds were improved by adding nTiO2 to nBG scaffold and adding P3HB to nBG/nTiO2 composite scaffold. The results of the compressive strength and porosity tests showed that the best scaffold is 30 wt% of nBG with 6 wt% of nTiO2 composite scaffold immersed for 30 s in P3HB with 79.5-80 % of porosity in 200-600 μm, with a compressive strength of 0.15 MPa and a compressive modulus of 30 MPa, which is a good candidate for bone tissue engineering. To evaluate the bioactivity of the scaffold, the simulated body fluid (SBF) solution was used. The best scaffold with 30 wt% of nBG, 6 wt% of P3HB and 6 wt% of nTiO2 was immersed in SBF for 4 weeks at an incubation temperature of 37 °C. The bioactivity of the scaffolds was characterized by AAS, SEM, EDXA and XRD. The results of bioactivity showed that bone-like apatite layer formed well at scaffold surface and adding nTiO2 to nBG/P3HB composite scaffold helped increase the bioactivity rate.

Multi-component nanofibrous scaffolds with tunable properties for bone tissue engineering

NASA Astrophysics Data System (ADS)

Jose, Moncy V.

Bone is a highly complex tissue which is an integral part of vertebrates and hence any damage has a major negative effect on the quality of life. Tissue engineering is regarded as an ideal route to resolve the issues related to the scarcity of tissue and organ for transplantation. Apart from cell line and growth factors, the choice of materials and fabrication technique for scaffold are equally important. The goal of this work was to develop a multi-component nanofibrous scaffold based on a synthetic polymer (poly(lactic-co-glycolide) (PLGA)), a biopolymer (collagen) and a biomineral (nano-hydroxyapatite (nano-HA)) by electrospinning technique, which mimics the nanoscopic, chemical, and anisotropic features of bone. Preliminary studies involved fabrication of nanocomposite scaffolds based on PLGA and nano-HA. Morphological and mechanical characterizations revealed that at low concentrations, nano-HA acted as reinforcements, whereas at higher concentrations the presence of aggregation was detrimental to the scaffold. Hydrolytic degradation studies revealed the scaffold had a little mass loss and the mechanical property was maintained for a period of 6 weeks. This study was followed by evaluation of a blend system based on PLGA and collagen. Collagen addition provides hydrophilicity and the necessary cell binding sites in PLGA. The structural characterization revealed that the blend had limited interactions between the two components. The mechanical characterization revealed that with increasing collagen concentration, there was a decline in mechanical properties. However, crosslinking of the blend system, with carbodiimide (EDC) resulted in improving the mechanical properties of the scaffolds. A multi-component system was developed by adding different concentrations of nano-HA to a fixed PLGA/collagen blend composition (80/20). Morphological and mechanical characterizations revealed properties similar to the PLGA/HA system. Cyto-compatibility studies revealed

Fabrication of chitin-chitosan/nano TiO2-composite scaffolds for tissue engineering applications.

PubMed

Jayakumar, R; Ramachandran, Roshni; Divyarani, V V; Chennazhi, K P; Tamura, H; Nair, S V

2011-03-01

In this study, we prepared chitin-chitosan/nano TiO(2) composite scaffolds using lyophilization technique for bone tissue engineering. The prepared composite scaffold was characterized using SEM, XRD, FTIR and TGA. In addition, swelling, degradation and biomineralization capability of the composite scaffolds were evaluated. The developed composite scaffold showed controlled swelling and degradation when compared to the control scaffold. Cytocompatibility of the scaffold was assessed by MTT assay and cell attachment studies using osteoblast-like cells (MG-63), fibroblast cells (L929) and human mesenchymal stem cells (hMSCs). Results indicated no sign of toxicity and cells were found attached to the pore walls within the scaffolds. These results suggested that the developed composite scaffold possess the prerequisites for tissue engineering scaffolds and it can be used for tissue engineering applications. Copyright © 2010 Elsevier B.V. All rights reserved.

Surface-enrichment with hydroxyapatite nanoparticles in stereolithography-fabricated composite polymer scaffolds promotes bone repair.

PubMed

Guillaume, O; Geven, M A; Sprecher, C M; Stadelmann, V A; Grijpma, D W; Tang, T T; Qin, L; Lai, Y; Alini, M; de Bruijn, J D; Yuan, H; Richards, R G; Eglin, D

2017-05-01

Fabrication of composite scaffolds using stereolithography (SLA) for bone tissue engineering has shown great promises. However, in order to trigger effective bone formation and implant integration, exogenous growth factors are commonly combined to scaffold materials. In this study, we fabricated biodegradable composite scaffolds using SLA and endowed them with osteopromotive properties in the absence of biologics. First we prepared photo-crosslinkable poly(trimethylene carbonate) (PTMC) resins containing 20 and 40wt% of hydroxyapatite (HA) nanoparticles and fabricated scaffolds with controlled macro-architecture. Then, we conducted experiments to investigate how the incorporation of HA in photo-crosslinked PTMC matrices improved human bone marrow stem cells osteogenic differentiation in vitro and kinetic of bone healing in vivo. We observed that bone regeneration was significantly improved using composite scaffolds containing as low as 20wt% of HA, along with difference in terms of osteogenesis and degree of implant osseointegration. Further investigations revealed that SLA process was responsible for the formation of a rich microscale layer of HA corralling scaffolds. To summarize, this work is of substantial importance as it shows how the fabrication of hierarchical biomaterials via surface-enrichment of functional HA nanoparticles in composite polymer stereolithographic structures could impact in vitro and in vivo osteogenesis. This study reports for the first time the enhance osteopromotion of composite biomaterials, with controlled macro-architecture and microscale distribution of hydroxyapatite particles, manufactured by stereolithography. In this process, the hydroxyapatite particles are not only embedded into an erodible polymer matrix, as reported so far in the literature, but concentrated at the surface of the structures. This leads to robust in vivo bone formation at low concentration of hydroxyapatite. The reported 3D self-corralling composite

Nano polypeptide particles reinforced polymer composite fibers.

PubMed

Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

2015-02-25

Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers.

Modulation of mesenchymal stem cell behavior by nano- and micro-sized β-tricalcium phosphate particles in suspension and composite structures

NASA Astrophysics Data System (ADS)

Smoak, Mollie; Hogan, Katie; Kriegh, Lisa; Chen, Cong; Terrell, LeKeith B.; Qureshi, Ammar T.; Todd Monroe, W.; Gimble, Jeffrey M.; Hayes, Daniel J.

2015-04-01

Interest has grown in the use of microparticles and nanoparticles for modifying the mechanical and biological properties of synthetic bone composite structures. Micro- and nano-sized calcium phosphates are of interest for their osteoinductive behavior. Engineered composites incorporating polymers and ceramics, such as poly-l-lactic acid (PLLA) and beta-tricalcium phosphate (β-TCP), for bone tissue regeneration have been well investigated for their proliferative and osteoinductive abilities. Only limited research has been done to investigate the effects of different sizes of β-TCP particles on human mesenchymal stromal cell behavior. As such, the aim of this study was to investigate the modulations of human adipose-derived stem cell (hASCs) behavior within cell/particle and cell/composite systems as functions of particle size, concentration, and exposure time. The incorporation of nanoscale calcium phosphate resulted in improved mechanical properties and osteogenic behavior within the scaffold compared to the microscale calcium phosphate additives. Particle exposure results indicate that cytotoxicity on hASCs correlates inversely with particle size and increases with the increasing exposure time and particle concentration. Composites with increasing β-TCP content, whether microparticles or nanoparticles, were less toxic than colloidal micro- and nano-sized β-TCP particles directly supplied to hASCs. The difference in viability observed as a result of varying exposure route is likely related to the increased cell-particle interactions in the direct exposure compared to the particles becoming trapped within the scaffold/polymer matrix.

Nano-ceramic composite scaffolds for bioreactor-based bone engineering.

PubMed

Lv, Qing; Deng, Meng; Ulery, Bret D; Nair, Lakshmi S; Laurencin, Cato T

2013-08-01

Composites of biodegradable polymers and bioactive ceramics are candidates for tissue-engineered scaffolds that closely match the properties of bone. We previously developed a porous, three-dimensional poly (D,L-lactide-co-glycolide) (PLAGA)/nanohydroxyapatite (n-HA) scaffold as a potential bone tissue engineering matrix suitable for high-aspect ratio vessel (HARV) bioreactor applications. However, the physical and cellular properties of this scaffold are unknown. The present study aims to evaluate the effect of n-HA in modulating PLAGA scaffold properties and human mesenchymal stem cell (HMSC) responses in a HARV bioreactor. By comparing PLAGA/n-HA and PLAGA scaffolds, we asked whether incorporation of n-HA (1) accelerates scaffold degradation and compromises mechanical integrity; (2) promotes HMSC proliferation and differentiation; and (3) enhances HMSC mineralization when cultured in HARV bioreactors. PLAGA/n-HA scaffolds (total number = 48) were loaded into HARV bioreactors for 6 weeks and monitored for mass, molecular weight, mechanical, and morphological changes. HMSCs were seeded on PLAGA/n-HA scaffolds (total number = 38) and cultured in HARV bioreactors for 28 days. Cell migration, proliferation, osteogenic differentiation, and mineralization were characterized at four selected time points. The same amount of PLAGA scaffolds were used as controls. The incorporation of n-HA did not alter the scaffold degradation pattern. PLAGA/n-HA scaffolds maintained their mechanical integrity throughout the 6 weeks in the dynamic culture environment. HMSCs seeded on PLAGA/n-HA scaffolds showed elevated proliferation, expression of osteogenic phenotypic markers, and mineral deposition as compared with cells seeded on PLAGA scaffolds. HMSCs migrated into the scaffold center with nearly uniform cell and extracellular matrix distribution in the scaffold interior. The combination of PLAGA/n-HA scaffolds with HMSCs in HARV bioreactors may allow for the generation of engineered

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

PubMed

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

2017-04-01

Polymer biomaterials are used to construct scaffolds in tissue engineering applications to assist in mechanical support, organization, and maturation of tissues. Given the flexibility, electrical conductance, and contractility of native cardiac tissues, it is desirable that polymeric scaffolds for cardiac tissue regeneration exhibit elasticity and high electrical conductivity. Herein, we developed a facile approach to introduce carbon nanotubes (CNTs) into poly(octamethylene maleate (anhydride) 1,2,4-butanetricarboxylate) (124 polymer), and developed an elastomeric scaffold for cardiac tissue engineering that provides electrical conductivity and structural integrity to 124 polymer. 124 polymer-CNT materials were developed by first dispersing CNTs in poly(ethylene glycol) dimethyl ether porogen and mixing with 124 prepolymer for molding into shapes and crosslinking under ultraviolet light. 124 polymers with 0.5% and 0.1% CNT content (wt) exhibited improved conductivity against pristine 124 polymer. With increasing the CNT content, surface moduli of hybrid polymers were increased, while their bulk moduli were decreased. Furthermore, increased swelling of hybrid 124 polymer-CNT materials was observed, suggesting their improved structural support in an aqueous environment. Finally, functional characterization of engineered cardiac tissues using the 124 polymer-CNT scaffolds demonstrated improved excitation threshold in materials with 0.5% CNT content (3.6±0.8V/cm) compared to materials with 0% (5.1±0.8V/cm) and 0.1% (5.0±0.7V/cm), suggesting greater tissue maturity. 124 polymer-CNT materials build on the advantages of 124 polymer elastomer to give a versatile biomaterial for cardiac tissue engineering applications. Achieving a high elasticity and a high conductivity in a single cardiac tissue engineering material remains a challenge. We report the use of CNTs in making electrically conductive and mechanically strong polymeric scaffolds in cardiac tissue regeneration

Optimization of Polymer-ECM Composite Scaffolds for Tissue Engineering: Effect of Cells and Culture Conditions on Polymeric Nanofiber Mats

PubMed Central

Goyal, Ritu; Guvendiren, Murat; Freeman, Onyi; Mao, Yong; Kohn, Joachim

2017-01-01

The design of composite tissue scaffolds containing an extracellular matrix (ECM) and synthetic polymer fibers is a new approach to create bioactive scaffolds that can enhance cell function. Currently, studies investigating the effects of ECM-deposition and decellularization on polymer degradation are still lacking, as are data on optimizing the stability of the ECM-containing composite scaffolds during prolonged cell culture. In this study, we develop fibrous scaffolds using three polymer compositions, representing slow (E0000), medium (E0500), and fast (E1000) degrading materials, to investigate the stability, degradation, and mechanics of the scaffolds during ECM deposition and decellularization, and during the complete cellularization-decell-recell cycle. We report data on percent molecular weight (% Mw) retention of polymeric fiber mats, changes in scaffold stiffness, ECM deposition, and the presence of fibronectin after decellularization. We concluded that the fast degrading E1000 (Mw retention ≤ 50% after 28 days) was not sufficiently stable to allow scaffold handling after 28 days in culture, while the slow degradation of E0000 (Mw retention ≥ 80% in 28 days) did not allow deposited ECM to replace the polymer support. The scaffolds made from medium degrading E0500 (Mw retention about 60% at 28 days) allowed the gradual replacement of the polymer network with cell-derived ECM while maintaining the polymer network support. Thus, polymers with an intermediate rate of degradation, maintaining good scaffold handling properties after 28 days in culture, seem best suited for creating ECM-polymer composite scaffolds. PMID:28085047

Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

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

Dyartanti, Endah R., E-mail: heru.susanto@undip.ac.id, E-mail: endah-rd@uns.ac.id; Department of Chemical Engineering, Diponegoro University, Semarang; Purwanto, Agus

2016-02-08

Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is alsomore » investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF{sub 6}) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.« less

Studies on Effective Elastic Properties of CNT/Nano-Clay Reinforced Polymer Hybrid Composite

NASA Astrophysics Data System (ADS)

Thakur, Arvind Kumar; Kumar, Puneet; Srinivas, J.

2016-02-01

This paper presents a computational approach to predict elastic propertiesof hybrid nanocomposite material prepared by adding nano-clayplatelets to conventional CNT-reinforced epoxy system. In comparison to polymers alone/single-fiber reinforced polymers, if an additional fiber is added to the composite structure, it was found a drastic improvement in resultant properties. In this regard, effective elastic moduli of a hybrid nano composite are determined by using finite element (FE) model with square representative volume element (RVE). Continuum mechanics based homogenization of the nano-filler reinforced composite is considered for evaluating the volumetric average of the stresses and the strains under different periodic boundary conditions.A three phase Halpin-Tsai approach is selected to obtain the analytical result based on micromechanical modeling. The effect of the volume fractions of CNTs and nano-clay platelets on the mechanical behavior is studied. Two different RVEs of nano-clay platelets were used to investigate the influence of nano-filler geometry on composite properties. The combination of high aspect ratio of CNTs and larger surface area of clay platelets contribute to the stiffening effect of the hybrid samples. Results of analysis are validated with Halpin-Tsai empirical formulae.

Exploring 'new' bioactivities of polymers at the nano-bio interface.

PubMed

Wang, Chunming; Dong, Lei

2015-01-01

A biological system is essentially an elegant assembly of polymeric nanostructures. The polymers in the body, biomacromolecules, are both building blocks and versatile messengers. We propose that non-biologically derived polymers can be potential therapeutic candidates with unique advantages. Emerging findings about polycations, polysaccharides, immobilised multivalent ligands, and biomolecular coronas provide evidence that polymers are activated at the nano-bio interface, while emphasising the current theoretical and practical challenges. Our increasing understanding of the nano-bio interface and evolving approaches to establish the therapeutic potential of polymers enable the development of polymer drugs with high specificities for broad applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Preparation of foam-like carbon nanotubes/hydroxyapatite composite scaffolds with superparamagnetic properties

NASA Astrophysics Data System (ADS)

Lu, X. Y.; Qiu, T.; Wang, X. F.; Zhang, M.; Gao, X. L.; Li, R. X.; Lu, X.; Weng, J.

2012-12-01

In this paper, the foam-like composite scaffolds composed of hydroxyapatite (HA) and carbon nanotubes (CNTs) were prepared by a new method, where a polymer impregnating method was used for porous HA-based scaffold and a chemical vapor deposition (CVD) method was used for the growth of CNTs from the HA-based scaffold. The process produces the CNTs/HA scaffolds that have a foam-like structure with better mechanical property, better microstructure and a high degree of interconnection. A favorable pore size with big pores of 1-2 mm and small pores of 20-300 μm for osteoconduction and bone ingrowth is presented in these scaffolds. About 2 wt% multi-walled CNTs with the diameter of 60-100 nm are observed to be in situ grown from deficient nano-HA crystallites. Magnetic measurement exhibits these scaffolds are superparamagnetic with a saturation magnetization of 1.14 emu g-1 at a room temperature, benefiting the scaffolds to take up growth factors in vivo, stem cell or other bioactive molecules easily. This new type of CNTs/HA scaffolds is expected to have a promising applications in bone tissue engineering, targeted drug delivery system and other biomedical fields.

Conducting polymer scaffolds for electrical control of cellular functions (Conference Presentation)

NASA Astrophysics Data System (ADS)

Inal, Sahika; Wan, Alwin M.; Williams, Tiffany V.; Giannelis, Emmanuel P.; Fischbach-Teschl, Claudia; Gourdon, Delphine; Owens, Róisín. M.; Malliaras, George G.

2016-09-01

Considering the limited physiological relevance of 2D cell culture experiments, significant effort was devoted to the development of materials that could more accurately recreate the in vivo cellular microenvironment, and support 3D cell cultures in vitro. (1) One such class of materials is conducting polymers, which are promising due to their compliant mechanical properties, compatibility with biological systems, mixed electrical and ionic conductivity, and ability to form porous structures. (2) In this work, we report the fabrication of a single component, macroporous scaffold made from poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) via an ice-templating method. (3) PEDOT:PSS scaffolds offer tunable pore size, morphology and shape through facile changes in preparation conditions, and are capable of supporting 3D cell cultures due to their biocompatibility and tissue-like elasticity. Moreover, these materials are functional: they exhibit excellent electrochemical switching behavior and significantly lower impedance compared to films. Their electrochemical activity enables their use in the active channel of a state of the art diagnostic tool in the field of bioelectronics, i.e., the organic electrochemical transistor (OECT). The inclusion of cells within the porous architecture affects the impedance of the electrically-conducting polymer network and, thus, may be used as a method to quantify cell growth. The adhesion and pro-angiogenic secretions of mouse fibroblasts cultured within the scaffolds can be controlled by switching the electrochemical state of the polymer prior to cell-seeding. In summary, these smart materials hold promise not only as extracellular matrix-mimicking structures for cell culture, but also as high-performance bioelectronic tools for diagnostic and signaling applications. References [1] M. Holzwarth, P. X. Ma, Journal of Materials Chemistry, 21, 10243-10251 (2011). [2] L. H. Jimison, J. Rivnay, R. M. Owens, in Organic

Poly(ε-caprolactone)/nano fluoridated hydroxyapatite scaffolds for bone tissue engineering: in vitro degradation and biocompatibility study.

PubMed

Johari, N; Fathi, M H; Golozar, M A; Erfani, E; Samadikuchaksaraei, A

2012-03-01

In this study, biodegradation and biocompatibility of novel poly(ε-caparolactone)/nano fluoridated hydroxyapatite (PCL-FHA) scaffolds were investigated. The FHA nanopowders were prepared via mechanical alloying method and had a chemical composition of Ca(10)(PO(4))(6)OH(2-x )F(x) (where x values were selected equal to 0.5 and 2.0). In order to fabricate PCL-FHA scaffolds, 10, 20, 30 and 40 wt% of the FHA were added to the PCL. The PCL-FHA scaffolds were produced by the solvent casting/particulate leaching using sodium chloride particles (with diameters of 300-500 μm) as the porogen. The phase structure, microstructure and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques. Porosity of the scaffolds was measured using the Archimedes' Principle. In vitro degradation of PCL-FHA scaffolds was studied by incubating the samples in phosphate buffered saline at 37°C and pH 7.4 for 30 days. Moreover, biocompatibility was evaluated by MTT assay after seeding and culture of osteoblast-like cells on the scaffolds. Results showed that the osteoblast-like cells attached to and proliferated on PCL-FHA and increasing the porosity of the scaffolds increased the cell viability. Also, degradation rate of scaffolds were increased with increasing the fluorine content in scaffolds composition.

Design of polymer-biopolymer-hydroxyapatite biomaterials for bone tissue engineering: Through molecular control of interfaces

NASA Astrophysics Data System (ADS)

Verma, Devendra

In this dissertation, novel biomaterials are designed for bone biomaterials and bone tissue engineering applications. Novel biomaterials of hydroxyapatite with synthetic and natural polymers have been fabricated using a combination of processing routes. Initially, we investigated hydroxyapatite-polycaprolactone-polyacrylic acid composites and observed that minimal interfacial interactions between polymer and mineral led to inadequate improvement in the mechanical properties. Bioactivity experiments on these composites showed that the presence of functional groups, such as carboxylate groups, influence bioactivity of the composites. We have developed and investigated composites of hydroxyapatite with chitosan and polygalacturonic acid (PgA). Chitosan and PgA are biocompatible, biodegradable, and also electrostatically complementary to each other. This strategy led to significant improvement in mechanical properties of new composites. The nanostructure analysis using atomic force microscopy revealed a multilevel organization in these composites. Enhancement in mechanical response was attributed to stronger interfaces due to strong electrostatic interaction between oppositely charged chitosan and PgA. Further analysis using the Rietveld method showed that biopolymers have marked impact on hydroxyapatite crystal growth and also on its crystal structure. Significant changes were observed in the lattice parameters of hydroxyapatite synthesized by following biomineralization method (organics mediated mineralization). For scaffold preparation, chitosan and PgA were mixed first, and then, nano-hydroxyapatite was added. Oppositely charged polyelectrolytes, such as chitosan and PgA, spontaneously form complex upon mixing. The poly-electrolyte complex exists as nano-sized particles. Chitosan/PgA scaffolds with and without hydroxyapatite were prepared by the freeze drying method. By controlling the rate of cooling and concentration, we have produced both fibrous and sheet

Synthesis and characterization of nanocomposite scaffolds based on triblock copolymer of L-lactide, ε-caprolactone and nano-hydroxyapatite for bone tissue engineering.

PubMed

Torabinejad, Bahman; Mohammadi-Rovshandeh, Jamshid; Davachi, Seyed Mohammad; Zamanian, Ali

2014-09-01

The employment of biodegradable polymer scaffolds is one of the main approaches for achieving a tissue engineered construct to reproduce bone tissues, which provide a three dimensional template to regenerate desirable tissues for different applications. The main goal of this study is to design a novel triblock scaffold reinforced with nano-hydroxyapatite (nHA) for hard tissue engineering using gas foaming/salt leaching method with minimum solvent usage. With this end in view, the biodegradable triblock copolymers of l-lactide and ε-caprolactone with different mol% were synthesized by ring-opening polymerization method in the presence of Sn(Oct)2 catalyst as initiator and ethylene glycol as co-initiator. The chemical compositions of biodegradable copolymers were characterized by means of FTIR and NMR. The thermal and crystallization behaviors of copolymers were characterized using TGA and DSC thermograms. Moreover, nano-hydroxyapatite was synthesized by the chemical precipitation process and was thoroughly characterized by FTIR, XRD and TEM. Additionally, the nanocomposites with different contents of nHA were prepared by mixing triblock copolymer with nHA. Mechanical properties of the prepared nanocomposites were evaluated by stress-strain measurements. It was found that the nanocomposite with 30% of nHA showed the optimum result. Therefore, nanocomposite scaffolds with 30% nHA were fabricated by gas foaming/salt leaching method and SEM images were used to observe the microstructure and morphology of nanocomposites and nanocomposite scaffolds before and after cell culture. The in-vitro and cell culture tests were also carried out to further evaluate the biological properties. The results revealed that the porous scaffolds were biocompatible to the osteoblast cells because the cells spread and grew well. The resultant nanocomposites could be considered as good candidates for use in bone tissue engineering. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of polymer architecture on curcumin encapsulation and release from PEGylated polymer nanoparticles: Toward a drug delivery nano-platform to the CNS.

PubMed

Rabanel, Jean-Michel; Faivre, Jimmy; Paka, Ghislain Djiokeng; Ramassamy, Charles; Hildgen, Patrice; Banquy, Xavier

2015-10-01

We developed a nanoparticles (NPs) library from poly(ethylene glycol)-poly lactic acid comb-like polymers with variable amount of PEG. Curcumin was encapsulated in the NPs with a view to develop a delivery platform to treat diseases involving oxidative stress affecting the CNS. We observed a sharp decrease in size between 15 and 20% w/w of PEG which corresponds to a transition from a large solid particle structure to a "micelle-like" or "polymer nano-aggregate" structure. Drug loading, loading efficacy and release kinetics were determined. The diffusion coefficients of curcumin in NPs were determined using a mathematical modeling. The higher diffusion was observed for solid particles compared to "polymer nano-aggregate" particles. NPs did not present any significant toxicity when tested in vitro on a neuronal cell line. Moreover, the ability of NPs carrying curcumin to prevent oxidative stress was evidenced and linked to polymer architecture and NPs organization. Our study showed the intimate relationship between the polymer architecture and the biophysical properties of the resulting NPs and sheds light on new approaches to design efficient NP-based drug carriers. Copyright © 2015 Elsevier B.V. All rights reserved.

3D-printed scaffolds based on PLA/HA nanocomposites for trabecular bone reconstruction

NASA Astrophysics Data System (ADS)

Niaza, K. V.; Senatov, F. S.; Kaloshkin, S. D.; Maksimkin, A. V.; Chukov, D. I.

2016-08-01

In the present work porous PLA scaffolds filled with micro- and nano- HA were studied. Both composites with micro- and nano-HA were obtained by extrusion in the same conditions. Scaffolds were obtained by 3D-printing by fused filament fabrication method. Structure of porous scaffolds was pre-modeled by computer software. Compression and three - point flexural tests were used to study mechanical properties of the scaffolds.

Aligned and Electrospun Piezoelectric Polymer Fiber Assembly and Scaffold

NASA Technical Reports Server (NTRS)

Holloway, Nancy M. (Inventor); Scott-Carnell, Lisa A. (Inventor); Siochi, Emilie J. (Inventor); Leong, Kam W. (Inventor); Kulangara, Karina (Inventor)

2015-01-01

A scaffold assembly and related methods of manufacturing and/or using the scaffold for stem cell culture and tissue engineering applications are disclosed which at least partially mimic a native biological environment by providing biochemical, topographical, mechanical and electrical cues by using an electroactive material. The assembly includes at least one layer of substantially aligned, electrospun polymer fiber having an operative connection for individual voltage application. A method of cell tissue engineering and/or stem cell differentiation uses the assembly seeded with a sample of cells suspended in cell culture media, incubates and applies voltage to one or more layers, and thus produces cells and/or a tissue construct. In another aspect, the invention provides a method of manufacturing the assembly including the steps of providing a first pre-electroded substrate surface; electrospinning a first substantially aligned polymer fiber layer onto the first surface; providing a second pre-electroded substrate surface; electrospinning a second substantially aligned polymer fiber layer onto the second surface; and, retaining together the layered surfaces with a clamp and/or an adhesive compound.

Aligned and Electrospun Piezoelectric Polymer Fiber Assembly and Scaffold

NASA Technical Reports Server (NTRS)

Kulangara, Karina (Inventor); Scott Carnell, Lisa A. (Inventor); Holloway, Nancy M. (Inventor); Leong, Kam W. (Inventor); Siochi, Emilie J. (Inventor)

2017-01-01

A method of manufacturing and/or using a scaffold assembly for stem cell culture and tissue engineering applications is disclosed. The scaffold at least partially mimics a native biological environment by providing biochemical, topographical, mechanical and electrical cues by using an electroactive material. The assembly includes at least one layer of substantially aligned, electrospun polymer fiber having an operative connection for individual voltage application. A method of cell tissue engineering and/or stem cell differentiation that uses the assembly seeded with a sample of cells suspended in cell culture media, incubates and applies voltage to one or more layers, and thus produces cells and/or a tissue construct. In another aspect, the invention provides a method of manufacturing the assembly including the steps of providing a first pre-electroded substrate surface; electrospinning a first substantially aligned polymer fiber layer onto the first surface; providing a second pre-electroded substrate surface; electrospinning a second substantially aligned polymer fiber layer onto the second surface; and, retaining together the layered surfaces with a clamp and/or an adhesive compound.

Electrophoretic deposition of mesoporous bioactive glass on glass-ceramic foam scaffolds for bone tissue engineering.

PubMed

Fiorilli, Sonia; Baino, Francesco; Cauda, Valentina; Crepaldi, Marco; Vitale-Brovarone, Chiara; Demarchi, Danilo; Onida, Barbara

2015-01-01

In this work, the coating of 3-D foam-like glass-ceramic scaffolds with a bioactive mesoporous glass (MBG) was investigated. The starting scaffolds, based on a non-commercial silicate glass, were fabricated by the polymer sponge replica technique followed by sintering; then, electrophoretic deposition (EPD) was applied to deposit a MBG layer on the scaffold struts. EPD was also compared with other techniques (dipping and direct in situ gelation) and it was shown to lead to the most promising results. The scaffold pore structure was maintained after the MBG coating by EPD, as assessed by SEM and micro-CT. In vitro bioactivity of the scaffolds was assessed by immersion in simulated body fluid and subsequent evaluation of hydroxyapatite (HA) formation. The deposition of a MBG coating can be a smart strategy to impart bioactive properties to the scaffold, allowing the formation of nano-structured HA agglomerates within 48 h from immersion, which does not occur on uncoated scaffold surfaces. The mechanical properties of the scaffold do not vary after the EPD (compressive strength ~19 MPa, fracture energy ~1.2 × 10(6) J m(-3)) and suggest the suitability of the prepared highly bioactive constructs as bone tissue engineering implants for load-bearing applications.

Remote Determination of Time-Dependent Stiffness of Surface-Degrading-Polymer Scaffolds Via Synchrotron-Based Imaging.

PubMed

Bawolin, N K; Chen, X B

2017-04-01

Surface-degrading polymers have been widely used to fabricate scaffolds with the mechanical properties appropriate for tissue regeneration/repair. During their surface degradation, the material properties of polymers remain approximately unchanged, but the scaffold geometry and thus mechanical properties vary with time. This paper presents a novel method to determine the time-dependent mechanical properties, particularly stiffness, of scaffolds from the geometric changes captured by synchrotron-based imaging, with the help of finite element analysis (FEA). Three-dimensional (3D) tissue scaffolds were fabricated from surface-degrading polymers, and during their degradation, the tissue scaffolds were imaged via the synchrotron-based imaging to characterize their changing geometry. On this basis, the stiffness behavior of scaffolds was estimated from the FEA, and the results obtained were compared to the direct measurements of scaffold stiffness from the load-displacement material testing. The comparison illustrates that the Young's moduli estimated from the FEA and characterized geometry are in agreement with the ones of direct measurements. The developed method of estimating the mechanical behavior was also demonstrated effective with a nondegrading scaffold that displays the nonlinear stress-strain behavior. The in vivo monitoring of Young's modulus by morphology characterization also suggests the feasibility of characterizing experimentally the difference between in vivo and in vitro surface degradation of tissue engineering constructs.

Hybrid 3D-2D printing of bone scaffolds Hybrid 3D-2D printing methods for bone scaffolds fabrication.

PubMed

Prinz, V Ya; Seleznev, Vladimir

2016-12-13

It is a well-known fact that bone scaffold topography on micro- and nanometer scale influences the cellular behavior. Nano-scale surface modification of scaffolds allows the modulation of biological activity for enhanced cell differentiation. To date, there has been only a limited success in printing scaffolds with micro- and nano-scale features exposed on the surface. To improve on the currently available imperfect technologies, in our paper we introduce new hybrid technologies based on a combination of 2D (nano imprint) and 3D printing methods. The first method is based on using light projection 3D printing and simultaneous 2D nanostructuring of each of the layers during the formation of the 3D structure. The second method is based on the sequential integration of preliminarily created 2D nanostructured films into a 3D printed structure. The capabilities of the developed hybrid technologies are demonstrated with the example of forming 3D bone scaffolds. The proposed technologies can be used to fabricate complex 3D micro- and nanostructured products for various fields. Copyright 2016 IOP Publishing Ltd.

Dynamic studies of nano-confined polymer thin films

NASA Astrophysics Data System (ADS)

Geng, Kun

Polymer thin films with the film thickness (h0 ) below 100 nm often exhibit physical properties different from the bulk counterparts. In order to make the best use of polymer thin films in applications, it is important to understand the physical origins of these deviations. In this dissertation, I will investigate how different factors influence dynamic properties of polymer thin films upon nano-confinement, including glass transition temperature (Tg), effective viscosity (etaeff) and self-diffusion coefficient (D ). The first part of this dissertation concerns the impacts of the molecular weight (MW) and tacticity on the Tg's of nano-confined polymer films. Previous experiments showed that the Tg of polymer films could be depressed or increased as h0 decreases. While these observations are usually attributed to the effects of the interfaces, some experiments suggested that MW's and tacticities might also play a role. To understand the effects of these factors, the Tg's of silica-based poly(alpha-methyl styrene) (PalphaMS/SiOx) and poly(methyl methacrylate) (PMMA/SiOx) thin films were studied, and the results suggested that MW's and tacticities influence Tg in nontrivial ways. The second part concerns an effort to resolve the long-standing controversy about the correlation between different dynamics of polymer thin films upon nano-confinement. Firstly, I discuss the experimental results of Tg, D and etaeff of poly(isobutyl methacrylate) films supported by silica (PiBMA/SiOx). Both T g and D were found to be independent of h 0, but etaeff decreased with decreasing h 0. Since both D and etaeff describe transport phenomena known to depend on the local friction coefficient or equivalently the local viscosity, it is questionable why D and etaeff displayed seemingly inconsistent h 0 dependencies. We envisage the different h0 dependencies to be caused by Tg, D and etaeff being different functions of the local T g's (Tg,i) or viscosities (eta i). By assuming a three

Selective Photophysical Modification on Light-Emitting Polymer Films for Micro- and Nano-Patterning

PubMed Central

Zhang, Xinping; Liu, Feifei; Li, Hongwei

2016-01-01

Laser-induced cross-linking in polymeric semiconductors was utilized to achieve micro- and nano-structuring in thin films. Single- and two-photon cross-linking processes led to the reduction in both the refractive index and thickness of the polymer films. The resultant photonic structures combine the features of both relief- and phase-gratings. Selective cross-linking in polymer blend films based on different optical response of different molecular phases enabled “solidification” of the phase-separation scheme, providing a stable template for further photonic structuring. Dielectric and metallic structures are demonstrated for the fabrication methods using cross-linking in polymer films. Selective cross-linking enables direct patterning into polymer films without introducing additional fabrication procedures or additional materials. The diffraction processes of the emission of the patterned polymeric semiconductors may provide enhanced output coupling for light-emitting diodes or distributed feedback for lasers. PMID:28773248

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.

A polymer scaffold for self-healing perovskite solar cells

NASA Astrophysics Data System (ADS)

Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

2016-01-01

Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ~16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.

A polymer scaffold for self-healing perovskite solar cells.

PubMed

Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

2016-01-06

Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ∼ 16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.

Direct ink writing of silica-bonded calcite scaffolds from preceramic polymers and fillers.

PubMed

Fiocco, L; Elsayed, H; Badocco, D; Pastore, P; Bellucci, D; Cannillo, V; Detsch, R; Boccaccini, A R; Bernardo, E

2017-05-11

Silica-bonded calcite scaffolds have been successfully 3D-printed by direct ink writing, starting from a paste comprising a silicone polymer and calcite powders, calibrated in order to match a SiO 2 /CaCO 3 weight balance of 35/65. The scaffolds, fabricated with two slightly different geometries, were first cross-linked at 350 °C, then fired at 600 °C, in air. The low temperature adopted for the conversion of the polymer into amorphous silica, by thermo-oxidative decomposition, prevented the decomposition of calcite. The obtained silica-bonded calcite scaffolds featured open porosity of about 56%-64% and compressive strength of about 2.9-5.5 MPa, depending on the geometry. Dissolution studies in SBF and preliminary cell culture tests, with bone marrow stromal cells, confirmed the in vitro bioactivity of the scaffolds and their biocompatibility. The seeded cells were found to be alive, well anchored and spread on the samples surface. The new silica-calcite composites are expected to be suitable candidates as tissue-engineering 3D scaffolds for regeneration of cancellous bone defects.

Enhanced bone regeneration using an insulin-loaded nano-hydroxyapatite/collagen/PLGA composite scaffold.

PubMed

Wang, Xing; Zhang, Guilan; Qi, Feng; Cheng, Yongfeng; Lu, Xuguang; Wang, Lu; Zhao, Jing; Zhao, Bin

2018-01-01

Insulin is widely considered as a classical hormone and drug in maintaining energy and glucose homeostasis. Recently, insulin has been increasingly recognized as an indispensable factor for osteogenesis and bone turnover, but its applications in bone regeneration have been restricted because of the short periods of activity and uncontrolled release. In this study, we incorporated insulin-loaded poly lactic-co-glycolic-acid (PLGA) nanospheres into nano-hydroxyapatite/collagen (nHAC) scaffolds and investigated the bioactivity of the composite scaffolds in vitro and in vivo. Bioactive insulin was successfully released from the nanospheres within the scaffold, and the release kinetics of insulin could be efficiently controlled by uniform-sized nanospheres. The physical characterizations of the composite scaffolds demonstrated that incorporation of nanospheres in nHAC scaffolds using this method did not significantly change the porosity, pore diameters, and compressive strengths of nHAC. In vitro, the insulin-loaded nHAC/PLGA composite scaffolds possessed favorable biological function for bone marrow mesenchymal stem cells adhesion and proliferation, as well as the differentiation into osteoblasts. In vivo, the optimized bone regenerative capability of this composite scaffold was confirmed in rabbit mandible critical size defects. These results demonstrated successful development of a functional insulin-PLGA-nHAC composite scaffold that enhances the bone regeneration capability of nHAC.

Mechanical Behavior of Polymer Nano Bio Composite for Orthopedic Implants

NASA Astrophysics Data System (ADS)

Marimuthu, K., Dr.; Rajan, Sankar

2018-04-01

The bio-based polymer composites have been the focus of many scientific and research projects, as well as many commercial programs. In recent years, scientists and engineers have been working together to use the inherent strength and performance of the new class of bio-based composites which is compactable with human body and can act as a substitute for living cells. In this stage the polymer composites also stepped into human bone implants as a replacement for metallic implants which was problems like corrosion resistance and high cost. The polymer composite have the advantage that it can be molded to the required shape, the polymers have high corrosion resistance, less weight and low cost. The aim of this research is to develop and analyze the suitable bio compactable polymer composite for human implants. The nano particles reinforced polymer composites provides good mechanical properties and shows good tribological properties especially in the total hip and knee replacements. The graphene oxide powders are bio compactable and acts as anti biotic. GO nano powder where reinforced into High-density polyethylene in various weight percentage of 0.5% to 2%. The performance of GO nano powder shows better tribological properties. The material produced does not cause any pollution to the environment and at the same time it can be bio compactable and sustainable. The product will act environmentally friendly.

Polymer powder processing of cryomilled polycaprolactone for solvent-free generation of homogeneous bioactive tissue engineering scaffolds.

PubMed

Lim, Jing; Chong, Mark Seow Khoon; Chan, Jerry Kok Yen; Teoh, Swee-Hin

2014-06-25

Synthetic polymers used in tissue engineering require functionalization with bioactive molecules to elicit specific physiological reactions. These additives must be homogeneously dispersed in order to achieve enhanced composite mechanical performance and uniform cellular response. This work demonstrates the use of a solvent-free powder processing technique to form osteoinductive scaffolds from cryomilled polycaprolactone (PCL) and tricalcium phosphate (TCP). Cryomilling is performed to achieve micrometer-sized distribution of PCL and reduce melt viscosity, thus improving TCP distribution and improving structural integrity. A breakthrough is achieved in the successful fabrication of 70 weight percentage of TCP into a continuous film structure. Following compaction and melting, PCL/TCP composite scaffolds are found to display uniform distribution of TCP throughout the PCL matrix regardless of composition. Homogeneous spatial distribution is also achieved in fabricated 3D scaffolds. When seeded onto powder-processed PCL/TCP films, mesenchymal stem cells are found to undergo robust and uniform osteogenic differentiation, indicating the potential application of this approach to biofunctionalize scaffolds for tissue engineering applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A polymer scaffold for self-healing perovskite solar cells

PubMed Central

Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

2016-01-01

Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ∼16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization. PMID:26732479

Biofunctionalization of scaffold material with nano-scaled diamond particles physisorbed with angiogenic factors enhances vessel growth after implantation.

PubMed

Schimke, Magdalena M; Stigler, Robert; Wu, Xujun; Waag, Thilo; Buschmann, Peter; Kern, Johann; Untergasser, Gerold; Rasse, Michael; Steinmüller-Nethl, Doris; Krueger, Anke; Lepperdinger, Günter

2016-04-01

Biofunctionalized scaffold facilitates complete healing of large defects. Biological constraints are induction and ingrowth of vessels. Angiogenic growth factors such as vascular endothelial growth factor or angiopoietin-1 can be bound to nano-scaled diamond particles. Corresponding bioactivities need to be examined after biofunctionalization. We therefore determined the physisorptive capacity of distinctly manufactured, differently sized nDP and the corresponding activities of bound factors. The properties of biofunctionalized nDPs were investigated on cultivated human mesenchymal stem cells and on the developing chicken embryo chorio-allantoic membrane. Eventually porous bone substitution material was coated with nDP to generate an interface that allows biofactor physisorption. Angiopoietin-1 was applied shortly before scaffold implantation into an osseous defect in sheep calvaria. Biofunctionalized scaffolds exhibited significantly increased rates of angiogenesis already one month after implantation. Conclusively, nDP can be used to ease functionalization of synthetic biomaterials. With the advances in nanotechnology, many nano-sized materials have been used in the biomedical field. This is also true for nano-diamond particles (nDP). In this article, the authors investigated the physical properties of functionalized nano-diamond particles in both in-vitro and in-vivo settings. The positive findings would help improve understanding of these nanomaterials in regenerative medicine. Copyright © 2015 Elsevier Inc. All rights reserved.

Cold atmospheric plasma (CAP) surface nanomodified 3D printed polylactic acid (PLA) scaffolds for bone regeneration.

PubMed

Wang, Mian; Favi, Pelagie; Cheng, Xiaoqian; Golshan, Negar H; Ziemer, Katherine S; Keidar, Michael; Webster, Thomas J

2016-12-01

Three-dimensional (3D) printing is a new fabrication method for tissue engineering which can precisely control scaffold architecture at the micron-scale. However, scaffolds not only need 3D biocompatible structures that mimic the micron structure of natural tissues, they also require mimicking of the nano-scale extracellular matrix properties of the tissue they intend to replace. In order to achieve this, the objective of the present in vitro study was to use cold atmospheric plasma (CAP) as a quick and inexpensive way to modify the nano-scale roughness and chemical composition of a 3D printed scaffold surface. Water contact angles of a normal 3D printed poly-lactic-acid (PLA) scaffold dramatically dropped after CAP treatment from 70±2° to 24±2°. In addition, the nano-scale surface roughness (Rq) of the untreated 3D PLA scaffolds drastically increased (up to 250%) after 1, 3, and 5min of CAP treatment from 1.20nm to 10.50nm, 22.90nm, and 27.60nm, respectively. X-ray photoelectron spectroscopy (XPS) analysis showed that the ratio of oxygen to carbon significantly increased after CAP treatment, which indicated that the CAP treatment of PLA not only changed nano-scale roughness but also chemistry. Both changes in hydrophilicity and nano-scale roughness demonstrated a very efficient plasma treatment, which in turn significantly promoted both osteoblast (bone forming cells) and mesenchymal stem cell attachment and proliferation. These promising results suggest that CAP surface modification may have potential applications for enhancing 3D printed PLA bone tissue engineering materials (and all 3D printed materials) in a quick and an inexpensive manner and, thus, should be further studied. Three-dimensional (3D) printing is a new fabrication method for tissue engineering which can precisely control scaffold architecture at the micron-scale. Although their success is related to their ability to exactly mimic the structure of natural tissues and control mechanical

A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite-polyetheretherketone scaffolds.

PubMed

Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

2016-01-01

A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite-polyetheretherketone (HAP-PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP-PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP-PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering.

A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite–polyetheretherketone scaffolds

PubMed Central

Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

2016-01-01

A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite–polyetheretherketone (HAP–PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP–PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP–PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering. PMID:27555770

SHI induced nano track polymer filters and characterization

NASA Astrophysics Data System (ADS)

Vijay, Y. K.

2009-07-01

Swift heavy ion irradiation produces damage in polymers in the form of latent tracks. Latent tracks can be enlarged by etching it in a suitable etchant and thus nuclear track etch membrane can be formed for gas permeation / purification in particular for hydrogen where the molecular size is very small. By applying suitable and controlled etching conditions well defined tracks can be formed for specific applications of the membranes. After etching gas permeation method is used for characterizing the tracks. In the present work polycarbonate (PC) of various thickness were irradiated with energetic ion beam at Inter University Accelerator Centre (IUAC), New Delhi. Nuclear tracks were modified by etching the PC in 6N NaOH at 60 (±1) °C from both sides for different times to produce track etch membranes. At critical etch time the etched pits from both the sides meet a rapid increase in gas permeation was observed. Permeability of hydrogen and carbon dioxide has been measured in samples etched for different times. The latent tracks produced by SHI irradiation in the track etch membranes show enhancement of free volume of the polymer. Nano filters are separation devices for the mixture of gases, different ions in the solution and isotopes and isobars separations. The polymer thin films with controlled porosity finding it self as best choice. However, the permeability and selectivity of these polymer based membrane filters are very important at the nano scale separation. The Swift Heavy Ion (SHI) induced nuclear track etched polymeric films with controlled etching have been attempted and characterized as nano scale filters.

Supramolecular structure of polymer binders and composites: targeted control based on the hierarchy

NASA Astrophysics Data System (ADS)

Matveeva, Larisa; Belentsov, Yuri

2017-10-01

The article discusses the problem of targeted control over properties by modifying the supramolecular structure of polymer binders and composites based on their hierarchy. Control over the structure formation of polymers and introduction of modifying additives should be tailored to the specific hierarchical structural levels. Characteristics of polymer materials are associated with structural defects, which also display a hierarchical pattern. Classification of structural defects in polymers is presented. The primary structural level (nano level) of supramolecular formations is of great importance to the reinforcement and regulation of strength characteristics.

Hybrid 3D-2D printing for bone scaffolds fabrication

NASA Astrophysics Data System (ADS)

Seleznev, V. A.; Prinz, V. Ya

2017-02-01

It is a well-known fact that bone scaffold topography on micro- and nanometer scale influences the cellular behavior. Nano-scale surface modification of scaffolds allows the modulation of biological activity for enhanced cell differentiation. To date, there has been only a limited success in printing scaffolds with micro- and nano-scale features exposed on the surface. To improve on the currently available imperfect technologies, in our paper we introduce new hybrid technologies based on a combination of 2D (nano imprint) and 3D printing methods. The first method is based on using light projection 3D printing and simultaneous 2D nanostructuring of each of the layers during the formation of the 3D structure. The second method is based on the sequential integration of preliminarily created 2D nanostructured films into a 3D printed structure. The capabilities of the developed hybrid technologies are demonstrated with the example of forming 3D bone scaffolds. The proposed technologies can be used to fabricate complex 3D micro- and nanostructured products for various fields.

3D-Printed Bioactive Ca3SiO5 Bone Cement Scaffolds with Nano Surface Structure for Bone Regeneration.

PubMed

Yang, Chen; Wang, Xiaoya; Ma, Bing; Zhu, Haibo; Huan, Zhiguang; Ma, Nan; Wu, Chengtie; Chang, Jiang

2017-02-22

Silicate bioactive materials have been widely studied for bone regeneration because of their eminent physicochemical properties and outstanding osteogenic bioactivity, and different methods have been developed to prepare porous silicate bioactive ceramics scaffolds for bone-tissue engineering applications. Among all of these methods, the 3D-printing technique is obviously the most efficient way to control the porous structure. However, 3D-printed bioceramic porous scaffolds need high-temperature sintering, which will cause volume shrinkage and reduce the controllability of the pore structure accuracy. Unlike silicate bioceramic, bioactive silicate cements such as tricalcium silicate (Ca 3 SiO 5 and C 3 S) can be self-set in water to obtain high mechanical strength under mild conditions. Another advantage of using C 3 S to prepare 3D scaffolds is the possibility of simultaneous drug loading. Herein, we, for the first time, demonstrated successful preparation of uniform 3D-printed C 3 S bone cement scaffolds with controllable 3D structure at room temperature. The scaffolds were loaded with two model drugs and showed a loading location controllable drug-release profile. In addition, we developed a surface modification process to create controllable nanotopography on the surface of pore wall of the scaffolds, which showed activity to enhance rat bone-marrow stem cells (rBMSCs) attachment, spreading, and ALP activities. The in vivo experiments revealed that the 3D-printed C 3 S bone cement scaffolds with nanoneedle-structured surfaces significantly improved bone regeneration, as compared to pure C 3 S bone cement scaffolds, suggesting that 3D-printed C 3 S bone cement scaffolds with controllable nanotopography surface are bioactive implantable biomaterials for bone repair.

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.

A synergistic approach to the design, fabrication and evaluation of 3D printed micro and nano featured scaffolds for vascularized bone tissue repair

PubMed Central

Holmes, Benjamin; Bulusu, Kartik; Plesniak, Michael; Zhang, Lijie Grace

2016-01-01

3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechanical testing, hydrodynamic measurements and in vitro human mesenchymal stem cell (hMSC) adhesion (4 h), proliferation (1, 3 and 5 d) and osteogenic differentiation (1, 2 and 3 weeks). These tests confirmed bone-like physical properties and vascular-like flow profiles, as well as demonstrated enhanced hMSC adhesion, proliferation and osteogenic differentiation. Additional in vitro experiments with human umbilical vein endothelial cells also demonstrated improved vascular cell growth, migration and organization on micro-nano featured scaffolds. PMID:26758780

A synergistic approach to the design, fabrication and evaluation of 3D printed micro and nano featured scaffolds for vascularized bone tissue repair.

PubMed

Holmes, Benjamin; Bulusu, Kartik; Plesniak, Michael; Zhang, Lijie Grace

2016-02-12

3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechanical testing, hydrodynamic measurements and in vitro human mesenchymal stem cell (hMSC) adhesion (4 h), proliferation (1, 3 and 5 d) and osteogenic differentiation (1, 2 and 3 weeks). These tests confirmed bone-like physical properties and vascular-like flow profiles, as well as demonstrated enhanced hMSC adhesion, proliferation and osteogenic differentiation. Additional in vitro experiments with human umbilical vein endothelial cells also demonstrated improved vascular cell growth, migration and organization on micro-nano featured scaffolds.

A synergistic approach to the design, fabrication and evaluation of 3D printed micro and nano featured scaffolds for vascularized bone tissue repair

NASA Astrophysics Data System (ADS)

Holmes, Benjamin; Bulusu, Kartik; Plesniak, Michael; Zhang, Lijie Grace

2016-02-01

3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechanical testing, hydrodynamic measurements and in vitro human mesenchymal stem cell (hMSC) adhesion (4 h), proliferation (1, 3 and 5 d) and osteogenic differentiation (1, 2 and 3 weeks). These tests confirmed bone-like physical properties and vascular-like flow profiles, as well as demonstrated enhanced hMSC adhesion, proliferation and osteogenic differentiation. Additional in vitro experiments with human umbilical vein endothelial cells also demonstrated improved vascular cell growth, migration and organization on micro-nano featured scaffolds.

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

Substrate-oriented nanorod scaffolds in polymer-fullerene bulk heterojunction solar cells.

PubMed

Ogawa, Yuta; White, Matthew S; Sun, Lina; Scharber, Markus C; Sariciftci, Niyazi Serdar; Yoshida, Tsukasa

2014-04-14

The use of a p-type inorganic semiconductor to form a nanorod scaffold within a polymer-fullerene bulk heterojunction solar cell is reported. The performance of this cell is compared to those made of the commonly used n-type scaffold of ZnO, which has been reported many times in the literature. The scaffold is designed to improve charge-carrier collection by increased mobility in thicker samples. Observations show that generally the device performance shows a negative correlation to nanorod length. By using CuSCN as a p-type inorganic scaffold, a very similar trend is observed. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Fabrication and characterization of drug-loaded nano-hydroxyapatite/polyamide 66 scaffolds modified with carbon nanotubes and silk fibroin

PubMed Central

Yao, Meng-Zhu; Huang-Fu, Ming-Yi; Liu, Hui-Na; Wang, Xia-Rong; Sheng, Xiaoxia; Gao, Jian-Qing

2016-01-01

Nano-hydroxyapatite/polyamide 66 (nHA/PA66) porous scaffolds were fabricated by a phase inversion method. Carbon nanotubes (CNTs) and silk fibroin (SF) were used to modify the surface of the nHA/PA66 scaffolds by freeze-drying and cross-linking. Dexamethasone was absorbed to the CNTs to promote the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). The cell viability of BMSCs was investigated by changing the concentration of the CNT dispersion, and the most biocompatible scaffold was selected. In addition, the morphology and mechanical property of the scaffolds were investigated. The results showed that the nHA/PA66 scaffolds modified with CNTs and SF met the requirements of bone tissue engineering scaffolds. The dexamethasone-loaded CNT/SF-nHA/PA66 composite scaffold promoted the osteogenic differentiation of BMSCs, and the drug-loaded scaffolds are expected to function as effective bone tissue engineering scaffolds. PMID:27920525

Electromagnetic and thermal properties of three-dimensional printed multilayered nano-carbon/poly(lactic) acid structures

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

Paddubskaya, A.; Center for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius; Valynets, N.

A new type of light-weight material produced by 3D printing consisting of nano-carbon doped polymer layer followed by a dielectric polymer layer is proposed. We performed temperature dependent characterization and measured the electromagnetic (EM) response of the samples in the GHz and THz range. The temperature dependent structural characteristics, crystallization, and melting were observed to be strongly affected by the presence and the number of nano-carbon doped layers in the sandwich structure. The electromagnetic measurements show a great potential of such a type of periodic material for electromagnetic compatibility applications in microwave frequency range. Sandwich structures containing only two nano-carbonmore » layers already become not transparent to the microwaves, giving an electromagnetic interference shielding efficiency at the level of 8–15 dB. A sandwich consisting of one nano-carbon doped and one polymer layer is opaque for THz radiation, because of 80% of absorption. These studies serve as a basis for design and realization of specific optimal geometries of meta-surface type with the 3D printing technique, in order to reach a high level of electromagnetic interference shielding performance for real world EM cloaking and EM ecology applications.« less

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

Fabrication of a biomimetic elastic intervertebral disk scaffold using additive manufacturing.

PubMed

Whatley, Benjamin R; Kuo, Jonathan; Shuai, Cijun; Damon, Brooke J; Wen, Xuejun

2011-03-01

A custom-designed three-dimensional additive manufacturing device was developed to fabricate scaffolds for intervertebral disk (IVD) regeneration. This technique integrated a computer with a device capable of 3D movement allowing for precise motion and control over the polymer scaffold resolution. IVD scaffold structures were designed using computer-aided design to resemble the natural IVD structure. Degradable polyurethane (PU) was used as an elastic scaffold construct to mimic the elastic nature of the native IVD tissue and was deposited at a controlled rate using ultra-fine micropipettes connected to a syringe pump. The elastic PU was extruded directly onto a collecting substrate placed on a freezing stage. The three-dimensional movement of the computer-controlled device combined with the freezing stage enabled precise control of polymer deposition using extrusion. The addition of the freezing stage increased the polymer solution viscosity and hardened the polymer solution as it was extruded out of the micropipette tip. This technique created scaffolds with excellent control over macro- and micro-structure to influence cell behavior, specifically for cell adhesion, proliferation, and alignment. Concentric lamellae were printed at a high resolution to mimic the native shape and structure of the IVD. Seeded cells aligned along the concentric lamellae and acquired cell morphology similar to native tissue in the outer portion of the IVD. The fabricated scaffolds exhibited elastic behavior during compressive and shear testing, proving that the scaffolds could support loads with proper fatigue resistance without permanent deformation. Additionally, the mechanical properties of the scaffolds were comparable to those of native IVD tissue.

Well-ordered polymer nano-fibers with self-cleaning property by disturbing crystallization process

NASA Astrophysics Data System (ADS)

Yang, Qin; Luo, Zhuangzhu; Tan, Sheng; Luo, Yimin; Wang, Yunjiao; Zhang, Zhaozhu; Liu, Weimin

2014-07-01

Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5-10 μm) polymer nano-fibers with a certain direction are fabricated by external macroscopic force ( F blow) interference introduced by H2 gas flow, leading to superior superhydrophobicity with a water contact angle (WCA) of 170° and a water sliding angle (WSA) of 0-1°. In contrast, nano-wires and nano-bridges (1-8 μm in length/10-80 nm in width) are generated by "spinning/stretching" under internal microscopic force ( F T) interference due to significant temperature difference in the non-uniform cooling medium. The findings provide a novel theoretical basis for controllable polymer "bionic lotus" surface and will further promote practical application in many engineering fields such as drag-reduction and anti-icing.

Large animal in vivo evaluation of a binary blend polymer scaffold for skeletal tissue-engineering strategies; translational issues.

PubMed

Smith, James O; Tayton, Edward R; Khan, Ferdous; Aarvold, Alexander; Cook, Richard B; Goodship, Allen; Bradley, Mark; Oreffo, Richard O C

2017-04-01

Binary blend polymers offer the opportunity to combine different desirable properties into a single scaffold, to enhance function within the field of tissue engineering. Previous in vitro and murine in vivo analysis identified a polymer blend of poly(l-lactic acid)-poly(ε-caprolactone) (PLLA:PCL 20:80) to have characteristics desirable for bone regeneration. Polymer scaffolds in combination with marrow-derived skeletal stem cells (SSCs) were implanted into mid-shaft ovine 3.5 cm tibial defects, and indices of bone regeneration were compared to groups implanted with scaffolds alone and with empty defects after 12 weeks, including micro-CT, mechanical testing and histological analysis. The critical nature of the defect was confirmed via all modalities. Both the scaffold and scaffold/SSC groups showed enhanced quantitative bone regeneration; however, this was only found to be significant in the scaffold/SSCs group (p = 0.04) and complete defect bridging was not achieved in any group. The mechanical strength was significantly less than that of contralateral control tibiae (p < 0.01) and would not be appropriate for full functional loading in a clinical setting. This study explored the hypothesis that cell therapy would enhance bone formation in a critical-sized defect compared to scaffold alone, using an external fixation construct, to bridge the scale-up gap between small animal studies and potential clinical translation. The model has proved a successful critical defect and analytical techniques have been found to be both valid and reproducible. Further work is required with both scaffold production techniques and cellular protocols in order to successfully scale-up this stem cell/binary blend polymer scaffold. © 2015 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd. © 2015 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.

A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

NASA Astrophysics Data System (ADS)

Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

2015-05-01

Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

Design of water-soluble, thiol-reactive polymers of controlled molecular weight: a novel multivalent scaffold

NASA Astrophysics Data System (ADS)

Carrillo, Alvaro; Gujraty, Kunal V.; Rai, Prakash R.; Kane, Ravi S.

2005-07-01

Multivalent molecules, i.e. scaffolds presenting multiple copies of a suitable ligand, constitute an emerging class of nanoscale therapeutics. We present a novel approach for the design of multivalent ligands, which allows the biofunctionalization of polymers with proteins or peptides in a controlled orientation. It consists of the synthesis of water-soluble, activated polymer scaffolds of controlled molecular weight, which can be biofunctionalized with various thiolated ligands in aqueous media under mild conditions. These polymers were synthesized by ring-opening metathesis polymerization (ROMP) and further modified to make them water-soluble. The incorporation of chloride groups activated the polymers to react with thiol-containing peptides or proteins, and the formation of multivalent ligands in aqueous media was demonstrated. This strategy represents a convenient route for synthesizing multivalent ligands of controlled dimensions and valency.

Rate-programming of nano-particulate delivery systems for smart bioactive scaffolds in tissue engineering.

PubMed

Izadifar, Mohammad; Haddadi, Azita; Chen, Xiongbiao; Kelly, Michael E

2015-01-09

Development of smart bioactive scaffolds is of importance in tissue engineering, where cell proliferation, differentiation and migration within scaffolds can be regulated by the interactions between cells and scaffold through the use of growth factors (GFs) and extra cellular matrix peptides. One challenge in this area is to spatiotemporally control the dose, sequence and profile of release of GFs so as to regulate cellular fates during tissue regeneration. This challenge would be addressed by rate-programming of nano-particulate delivery systems, where the release of GFs via polymeric nanoparticles is controlled by means of the methods of, such as externally-controlled and physicochemically/architecturally-modulated so as to mimic the profile of physiological GFs. Identifying and understanding such factors as the desired release profiles, mechanisms of release, physicochemical characteristics of polymeric nanoparticles, and externally-triggering stimuli are essential for designing and optimizing such delivery systems. This review surveys the recent studies on the desired release profiles of GFs in various tissue engineering applications, elucidates the major release mechanisms and critical factors affecting release profiles, and overviews the role played by the mathematical models for optimizing nano-particulate delivery systems. Potentials of stimuli responsive nanoparticles for spatiotemporal control of GF release are also presented, along with the recent advances in strategies for spatiotemporal control of GF delivery within tissue engineered scaffolds. The recommendation for the future studies to overcome challenges for developing sophisticated particulate delivery systems in tissue engineering is discussed prior to the presentation of conclusions drawn from this paper.

A novel two-step sintering for nano-hydroxyapatite scaffolds for bone tissue engineering

PubMed Central

Feng, Pei; Niu, Man; Gao, Chengde; Peng, Shuping; Shuai, Cijun

2014-01-01

In this study, nano-hydroxyapatite scaffolds with high mechanical strength and an interconnected porous structure were prepared using NTSS for the first time. The first step was performed using a laser characterized by the rapid heating to skip the surface diffusion and to obtain the driving force for grain boundary diffusion. Additionally, the interconnected porous structure was achieved by SLS. The second step consisted of isothermal heating in a furnace at a lower temperature (T2) than that of the laser beam to further increase the density and to suppress grain growth by exploiting the difference in kinetics between grain-boundary diffusion and grain-boundary migration. The results indicated that the mechanical properties first increased and then decreased as T2 was increased from 1050 to 1250°C. The optimal fracture toughness, compressive strength and stiffness were 1.69 MPam1/2, 18.68 MPa and 245.79 MPa, respectively. At the optimal point, the T2 was 1100°C, the grain size was 60 nm and the relative density was 97.6%. The decrease in mechanical properties was due to the growth of grains and the decomposition of HAP. The cytocompatibility test results indicated that cells adhered and spread well on the scaffolds. A bone-like apatite layer formed, indicating good bioactivity. PMID:24998362

Optimization of mechanical performance of oxidative nano-particle electrode nitrile butadiene rubber conducting polymer actuator.

PubMed

Kim, Baek-Chul; Park, S J; Cho, M S; Lee, Y; Nam, J D; Choi, H R; Koo, J C

2009-12-01

Present work delivers a systematical evaluation of actuation efficiency of a nano-particle electrode conducting polymer actuator fabricated based on Nitrile Butadiene Rubber (NBR). Attempts are made for maximizing mechanical functionality of the nano-particle electrode conducting polymer actuator that can be driven in the air. As the conducting polymer polypyrrole of the actuator is to be fabricated through a chemical oxidation polymerization process that may impose certain limitations on both electrical and mechanical functionality of the actuator, a coordinated study for optimization process of the actuator is necessary for maximizing its performance. In this article actuation behaviors of the nano-particle electrode polypyrrole conducting polymer is studied and an optimization process for the mechanical performance maximization is performed.

Well-ordered polymer nano-fibers with self-cleaning property by disturbing crystallization process.

PubMed

Yang, Qin; Luo, Zhuangzhu; Tan, Sheng; Luo, Yimin; Wang, Yunjiao; Zhang, Zhaozhu; Liu, Weimin

2014-01-01

Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5-10 μm) polymer nano-fibers with a certain direction are fabricated by external macroscopic force (F blow) interference introduced by H2 gas flow, leading to superior superhydrophobicity with a water contact angle (WCA) of 170° and a water sliding angle (WSA) of 0-1°. In contrast, nano-wires and nano-bridges (1-8 μm in length/10-80 nm in width) are generated by "spinning/stretching" under internal microscopic force (F T) interference due to significant temperature difference in the non-uniform cooling medium. The findings provide a novel theoretical basis for controllable polymer "bionic lotus" surface and will further promote practical application in many engineering fields such as drag-reduction and anti-icing.

Polyphosphazene/Nano-Hydroxyapatite Composite Microsphere Scaffolds for Bone Tissue Engineering

PubMed Central

Nukavarapu, Syam P.; Kumbar, Sangamesh G.; Brown, Justin L.; Krogman, Nicholas R.; Weikel, Arlin L.; Hindenlang, Mark D.; Nair, Lakshmi S.; Allcock, Harry R; Laurencin, Cato T.

2009-01-01

The non-toxic, neutral degradation products of amino acid ester polyphosphazenes make them ideal candidates for in vivo orthopaedic applications. The quest for new osteocompatible materials for load bearing tissue engineering applications has led us to investigate mechanically competent amino acid ester substituted polyphosphazenes. In this study, we have synthesized three biodegradable polyphosphazenes substituted with side groups namely leucine, valine and phenylalanine ethyl esters. Of these polymers, the phenylalanine ethyl ester substituted polyphosphazene showed the highest glass transition temperature (41.6 °C) and hence was chosen as a candidate material for forming composite microspheres with 100 nm sized hydroxyapatite (nHAp). The fabricated composite microspheres were sintered into a three-dimensional (3-D) porous scaffold by adopting a dynamic solvent sintering approach. The composite microsphere scaffolds showed compressive moduli of 46–81 MPa with mean pore diameters in the range of 86–145 µm. The three-dimensional polyphosphazene-nHAp composite microsphere scaffolds showed good osteoblast cell adhesion, proliferation and alkaline phosphatase expression, and are potential suitors for bone tissue engineering applications. PMID:18517248

Fabrication of high aspect ratio nanopillars and micro/nano combined structures with hydrophobic surface characteristics by injection molding

NASA Astrophysics Data System (ADS)

Zhou, Mingyong; Xiong, Xiang; Jiang, Bingyan; Weng, Can

2018-01-01

Polymer products with micro/nano-structures have excellent mechanical and optical properties, chemical resistance, and other advantages. Injection molding is one of the most potential techniques to fabricate polymer products with micro/nano-structures artificially in large numbers. In this study, a surface approach to fabricate high aspect ratio nanopillars and micro/nano combined structures was presented. Mold insert with micropillar arrays and nanopillars on its surface was prepared by combing anodic aluminum oxide (AAO) template and etched plate. Anti-sticking modification was done on the template to realize a better demolding quality. The influences of mold temperature and polymer material on the final replication quality were investigated. The results showed that the final replication quality of high aspect ratio nanopillars was greatly improved as compared with the unprocessed template. Polymer with low elongation at break was not suitable to fabricate structures with high aspect ratio via injection molding. For polypropylene surface, the experimental results of static contact angles were almost consistent with Cassie-Baxter equation. When the mold temperature reached 178 °C, hair-like polycarbonate nanopillars were observed, resulting in an excellent hydrophobic characteristic.

Fabrication of scalable and structured tissue engineering scaffolds using water dissolvable sacrificial 3D printed moulds.

PubMed

Mohanty, Soumyaranjan; Larsen, Layla Bashir; Trifol, Jon; Szabo, Peter; Burri, Harsha Vardhan Reddy; Canali, Chiara; Dufva, Marin; Emnéus, Jenny; Wolff, Anders

2015-10-01

One of the major challenges in producing large scale engineered tissue is the lack of ability to create large highly perfused scaffolds in which cells can grow at a high cell density and viability. Here, we explore 3D printed polyvinyl alcohol (PVA) as a sacrificial mould in a polymer casting process. The PVA mould network defines the channels and is dissolved after curing the polymer casted around it. The printing parameters determined the PVA filament density in the sacrificial structure and this density resulted in different stiffness of the corresponding elastomer replica. It was possible to achieve 80% porosity corresponding to about 150 cm(2)/cm(3) surface to volume ratio. The process is easily scalable as demonstrated by fabricating a 75 cm(3) scaffold with about 16,000 interconnected channels (about 1m(2) surface area) and with a channel to channel distance of only 78 μm. To our knowledge this is the largest scaffold ever to be produced with such small feature sizes and with so many structured channels. The fabricated scaffolds were applied for in-vitro culturing of hepatocytes over a 12-day culture period. Smaller scaffolds (6×4 mm) were tested for cell culturing and could support homogeneous cell growth throughout the scaffold. Presumably, the diffusion of oxygen and nutrient throughout the channel network is rapid enough to support cell growth. In conclusion, the described process is scalable, compatible with cell culture, rapid, and inexpensive. Copyright © 2015. Published by Elsevier B.V.

Optimized composition of nanocomposite scaffolds formed from silk fibroin and nano-TiO2 for bone tissue engineering.

PubMed

Johari, N; Madaah Hosseini, H R; Samadikuchaksaraei, A

2017-10-01

Natural silk fibroin (SF) polymer has biomedical and mechanical properties as a biomaterial for bone tissue engineering scaffolds. Freeze-dried porous nanocomposite scaffolds were prepared from silk fibroin and titanium dioxide (TiO 2 ) nanoparticles as a bioactive reinforcing agent by a phase separation method. In order to fabricate SF/TiO 2 scaffolds, 5, 10, 15 and 20wt% of the TiO 2 were added to the SF. The phase structure, functional groups and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques, respectively. Porosity of the scaffolds was measured by Archimedes' Principle. In addition, mechanical properties of prepared scaffolds were evaluated by measuring the compressive strength and compressive modulus. The bioactivity property of these scaffolds was examined for 7, 14, 21 and 28days immersion in simulated body fluid (SBF) at 37°C and the in vitro degradation was studied by incubation in phosphate buffered saline (PBS) at 37°C and pH7.4 for up to 30days. Moreover, the scaffolds' biocompatibility was evaluated by seeding and culture of SaOS-2 osteoblast-like cells and assessment of their proliferation with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Results showed that the prepared scaffolds had directional porosity and the reduction of porosity in composite scaffolds with higher contents of TiO 2 nanoparticles resulted to an improvement of the mechanical strength. The macroporous structures with open interconnected and directional pores were successfully obtained without applying any porogen or inorganic solvent. The bioactivity of these scaffolds was confirmed by scanning electron microscopy (SEM) showing surface crystallization of the apatite layer proportional to the duration of immersion in the SBF and the degradation rate of scaffolds were increased by increasing the TiO 2 content. The osteoblast-like cells showed a high

Effect of milling time on microstructure and properties of Nano-titanium polymer by high-energy ball milling

NASA Astrophysics Data System (ADS)

Wang, Bo; Wei, Shicheng; Wang, Yujiang; Liang, Yi; Guo, Lei; Xue, Junfeng; Pan, Fusheng; Tang, Aitao; Chen, Xianhua; Xu, Binshi

2018-03-01

Nano-titanium (Nano-Ti) was prepared by high-energy ball milling from pure Ti power and grinding agents (Epoxy resin) at room temperature. The effect of milling time on structure and properties of Nano-Ti polymer were investigated systematically. The results show that high-energy ball milling is an effective way to produce Nano-Ti polymer. The dispersion stability and compatibility between Ti power and grinding agents are improved by prolonging the milling time at a certain degree, that is to say, the optimization milling time is 240 min. The particle size of Ti powder and the diffraction peaks intensity of Ti decrease obviously as the milling time increases due to the compression stress, shear friction and other mechanical forces are formed during ball milling. FT-IR result displays that the wavenumber of all the bands move to lower wavenumber after ball milling, and the epoxy ring is open. The system internal energy rises owing to the broken epoxy group and much more Nano-Ti is formed to promote the grafting reaction between Nano-Ti and epoxy resin. The results from TEM and XPS also prove that. And the grafting ration is maximum as the milling time is 240 min, the mass loss ratio is 17.53%.

Optical, thermal and morphological study of ZnS doped PVA polymer nano composites

NASA Astrophysics Data System (ADS)

Guruswamy, B.; Ravindrachary, V.; Shruthi, C.; Sagar, Rohan N.; Hegde, Shreedatta

2018-05-01

The effect of ZnS nano particle doping on optical, thermal properties and morphological study of the PVA polymer has been investigated using FTIR, UV-Visible and TGA, FESEM techniques. Nano sized ZnS particles were synthesized by a simple wet chemical route. Pure and ZnS/PVA nano composites were prepared using solution casting technique. The FTIR study confirms that the ZnS nano particles interacts with the OH group of PVA polymer and forms the complex. The formation of these complexes affects the optical and thermal properties of the composite. The changes in optical properties were studied using UV-Vis absorption method. The variation in thermal property was analysed using TGA results. The modified surface morphology analysis was carried out using FESEM.

Bioactive Nano-Fibrous Scaffolds for Bone and Cartilage Tissue Engineering

NASA Astrophysics Data System (ADS)

Feng, Kai

Scaffolds that can mimic the structural features of natural extracellular matrix and can deliver biomolecules in a controlled fashion may provide cells with a favorable microenvironment to facilitate tissue regeneration. Biodegradable nanofibrous scaffolds with interconnected pore network have previously been developed in our laboratory to mimic collagen matrix and advantageously support both bone and cartilage regeneration. This dissertation project aims to expand both the structural complexity and the biomolecule delivery capacity of such biomimetic scaffolds for tissue engineering. We first developed a nanofibrous scaffold that can release an antibiotic (doxycycline) with a tunable release rate and a tunable dosage, which was demonstrated to be able to inhibit bacterial growth over a prolonged time period. We then developed a nanofibrous tissue-engineciing scaffold that can release basic fibroblast growth factor (bFGF) in a spatially and temporally controlled fashion. In a mouse subcutaneous implantation model, the bFGF-releasing scaffold was shown to enhance cell penetration, tissue ingrowth and angiogenesis. It was also found that both the dose and the release rate of bFGF play roles in the biologic function of the scaffold. After that, we developed a nanofibrous PLLA scaffold that can release both bone morphogenetic protein 7 (BMP-7) and platelet-derived growth factor (PDGF) with distinct dosages and release kinetics. It was demonstrated that BMP-7 and PDGF could synergistically enhance bone regeneration using a mouse ectopic bone formation model and a rat periodontal fenestration defect regeneration model. The regeneration outcome was dependent on the dosage, the ratio and the release kinetics of the two growth factors. Last, we developed an anisotropic composite scaffold with an upper layer mimicking the superficial zone of cartilage and a lower layer mimicking the middle zone of cartilage. The thin superficial layer was fabricated using an electrospinning

Comparative Study of the Physical, Topographical and Biological Properties of Electrospinning PCL, PLLA, their Blend and Copolymer Scaffolds

NASA Astrophysics Data System (ADS)

Bolbasov, E.; Goreninskii, S.; Tverdokhlebov, S.; Mishanin, A.; Viknianshchuk, A.; Bezuidenhout, D.; Golovkin, A.

2018-05-01

Biodegradable polymers (blends, copolymers) could be the ideal materials for manufacturing of scaffolds for small diameter vascular graft. Such material characteristics as mechanical properties, chemical structure, nano- and micro topography, surface charge, porosity, wettability etc. are becoming the most important aspects for effectiveness of prosthesis biofunctionalization because of their great impact on cell adhesion, spreading, cell proliferation, differentiation and cell function. The aim of the study is to compare physical, topographical and biological properties of polycaprolactone (PCL), poly-L-lactic acid (PLLA), polycaprolactone + poly-L-lactic acid blend (PCL PLLA), L-lactide/Caprolactone copolymer (PLC7015) scaffolds fabricated with the same fiber thickness using electrospun technology. PCL PLLA scaffolds had the highest average pore area (p<0.01) and the lowest strength (p<0.01). PLC7015 scaffolds had the significantly lower average pore area (p=0.03) but the highest elastic deformation (p<0.01). Biological testing with MMSC (multipotent mesenchyme stem cells) demonstrated that after 72 hours of co-cultivation only on PCL and PLLA scaffolds cells entered to the active phase of adhesion process. We propose that physical and topographical properties of PCL, PLLA, their blend and copolymer are of a great dependence of chemical structure but could be changed during the manufacturing process that will lead to changes in biological properties.

Application of conductive polymers, scaffolds and electrical stimulation for nerve tissue engineering.

PubMed

Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P; Morshed, Mohammad; Nasr-Esfahani, Mohammad Hossein; Baharvand, Hossein; Kiani, Sahar; Al-Deyab, Salem S; Ramakrishna, Seeram

2011-04-01

Among the numerous attempts to integrate tissue engineering concepts into strategies to repair nearly all parts of the body, neuronal repair stands out. This is partially due to the complexity of the nervous anatomical system, its functioning and the inefficiency of conventional repair approaches, which are based on single components of either biomaterials or cells alone. Electrical stimulation has been shown to enhance the nerve regeneration process and this consequently makes the use of electrically conductive polymers very attractive for the construction of scaffolds for nerve tissue engineering. In this review, by taking into consideration the electrical properties of nerve cells and the effect of electrical stimulation on nerve cells, we discuss the most commonly utilized conductive polymers, polypyrrole (PPy) and polyaniline (PANI), along with their design and modifications, thus making them suitable scaffolds for nerve tissue engineering. Other electrospun, composite, conductive scaffolds, such as PANI/gelatin and PPy/poly(ε-caprolactone), with or without electrical stimulation, are also discussed. Different procedures of electrical stimulation which have been used in tissue engineering, with examples on their specific applications in tissue engineering, are also discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Antibacterial TAP-mimic electrospun polymer scaffold: effects on P. gingivalis-infected dentin biofilm.

PubMed

Albuquerque, Maria Tereza P; Evans, Joshua D; Gregory, Richard L; Valera, Marcia C; Bottino, Marco C

2016-03-01

This study sought to investigate, in vitro, the effects of a recently developed triple antibiotic paste (TAP)-mimic polymer nanofibrous scaffold against Porphyromonas gingivalis-infected dentin biofilm. Dentin specimens (4 × 4 × 1 mm(3)) were prepared from human canines. The specimens were sterilized, inoculated with P. gingivalis (ATCC 33277), and incubated for 1 week to allow for biofilm formation. Infected dentin specimens were exposed for 3 days to the following treatments: antibiotic-free polydioxanone scaffold (PDS, control), PDS + 25 wt% TAP [25 mg of each antibiotic (metronidazole, ciprofloxacin, and minocycline) per mL of the PDS polymer solution], or a saturated TAP-based solution (50 mg of each antibiotic per mL of saline solution). In order to serve as the negative control, infected dentin specimens were left untreated (bacteria only). To determine the antimicrobial efficacy of the TAP-mimic scaffold, a colony-forming unit (CFU) per milliliter (n = 10/group) measurement was performed. Furthermore, additional specimens (n = 2/group) were prepared to qualitatively study biofilm inhibition via scanning electron microscopy (SEM). Statistics were performed, and significance was set at the 5% level. Both the TAP-mimic scaffold and the positive control (TAP solution) led to complete bacterial elimination, differing statistically (p < 0.05) from the negative control group (bacteria only). No statistical differences were observed for CFU per milliliter data between antibiotic-free scaffolds (2.7 log10 CFU/mL) and the negative control (5.9 log10 CFU/mL). The obtained data revealed significant antimicrobial properties of the novel PDS-based TAP-mimic scaffold against an established P. gingivalis-infected dentin biofilm. Collectively, the data suggest that the proposed nanofibrous scaffold might be used as an alternative to the advocated clinical gold standard (i.e., TAP) for intracanal disinfection prior to regenerative endodontics.

Structure and Dynamics of Polymer/Polymer grafted nanoparticle composite

NASA Astrophysics Data System (ADS)

Archer, Lynden

Addition of nanoparticles to polymers is a well-practiced methodology for augmenting various properties of the polymer host, including mechanical strength, thermal stability, barrier properties, dimensional stability and wear resistance. Many of these property changes are known to arise from nanoparticle-induced modification of polymer structure and chain dynamics, which are strong functions of the dispersion state of the nanoparticles' and on their relative size (D) to polymer chain dimensions (e.g. Random coil radius Rg or entanglement mesh size a) . This talk will discuss polymer nanocomposites (PNCs) comprised of Polyethylene Glycol (PEG) tethered silica nanoparticles (SiO2-PEG) dispersed in polymers as model systems for investigating phase stability and dynamics of PNCs. On the basis of small-angle X-ray Scattering, it will be shown that favorable enthalpic interactions between particle-tethered chains and a polymer host provides an important mechanism for creating PNCs in which particle aggregation is avoided. The talk will report on polymer and particle scale dynamics in these materials and will show that grafted nanoparticles well dispersed in a polymer host strongly influence the host polymer relaxation dynamics on all timescales and the polymers in turn produce dramatic changes in the nature (from diffusive to hyperdiffusive) and speed of nano particle decorrelation dynamics at the polymer entanglement threshold. A local viscosity model capable of explaining these observations is discussed and the results compared with scaling theories for NP motions in polymers This material is based on work supported by the National Science Foundation Award Nos. DMR-1609125 and CBET-1512297.

Biostable scaffolds of polyacrylate polymers implanted in the articular cartilage induce hyaline-like cartilage regeneration in rabbits.

PubMed

Sancho-Tello, María; Forriol, Francisco; Martín de Llano, José J; Antolinos-Turpin, Carmen; Gómez-Tejedor, José A; Gómez Ribelles, José L; Carda, Carmen

2017-07-05

To study the influence of scaffold properties on the organization of in vivo cartilage regeneration. Our hypothesis was that stress transmission to the cells seeded inside the pores of the scaffold or surrounding it, which is highly dependent on the scaffold properties, determines the differentiation of both mesenchymal cells and dedifferentiated autologous chondrocytes. 4 series of porous scaffolds made of different polyacrylate polymers, previously seeded with cultured rabbit chondrocytes or without cells, were implanted in cartilage defects in rabbits. Subchondral bone was injured during the surgery to allow blood to reach the implantation site and fill the scaffold pores. At 3 months after implantation, excellent tissue regeneration was obtained, with a well-organized layer of hyaline-like cartilage at the condylar surface in most cases of the hydrophobic or slightly hydrophilic series. The most hydrophilic material induced the poorest regeneration. However, no statistically significant difference was observed between preseeded and non-preseeded scaffolds. All of the materials used were biocompatible, biostable polymers, so, in contrast to some other studies, our results were not perturbed by possible effects attributable to material degradation products or to the loss of scaffold mechanical properties over time due to degradation. Cartilage regeneration depends mainly on the properties of the scaffold, such as stiffness and hydrophilicity, whereas little difference was observed between preseeded and non-preseeded scaffolds.

PREFACE: International Conference on Structural Nano Composites (NANOSTRUC 2012)

NASA Astrophysics Data System (ADS)

Njuguna, James

2012-09-01

Dear Colleagues It is a great pleasure to welcome you to NanoStruc2012 at Cranfield University. The purpose of the 2012 International Conference on Structural Nano Composites (NanoStruc2012) is to promote activities in various areas of materials and structures by providing a forum for exchange of ideas, presentation of technical achievements and discussion of future directions. NanoStruc brings together an international community of experts to discuss the state-of-the-art, new research results, perspectives of future developments, and innovative applications relevant to structural materials, engineering structures, nanocomposites, modelling and simulations, and their related application areas. The conference is split in 7 panel sessions, Metallic Nanocomposites and Coatings, Silica based Nanocomposites, safty of Nanomaterials, Carboin based Nanocomposites, Multscale Modelling, Bio materials and Application of Nanomaterials. All accepted Papers will be published in the IOP Conference Series: Materials Science and Engineering (MSE), and included in the NanoStruc online digital library. The abstracts will be indexed in Scopus, Compedex, Inspec, INIS (International Nuclear Information System), Chemical Abstracts, NASA Astrophysics Data System and Polymer Library. Before ending this message, I would like to acknowledge the hard work, professional skills and efficiency of the team which ensured the general organisation. As a conclusion, I would like to Welcome you to the Nanostruc2012 and wish you a stimulating Conference and a wonderful time. On behalf of the scientific committee, Signature James Njuguna Conference Chair The PDF of this preface also contains committee listings and associates logos.

Antibacterial chitosan coating on nano-hydroxyapatite/polyamide66 porous bone scaffold for drug delivery.

PubMed

Huang, Di; Zuo, Yi; Zou, Qin; Zhang, Li; Li, Jidong; Cheng, Lin; Shen, Juan; Li, Yubao

2011-01-01

This study describes a new drug-loaded coating scaffold applied in infection therapy during bone regeneration. Chitosan (CS) containing antibacterial berberine was coated on a nano-hydroxyapatite/polyamide66 (n-HA/PA66) scaffold to realize bone regeneration together with antimicrobial properties. The porous scaffold was fabricated using the phase-inversion method with a porosity of about 84% and macropore size of 400-600 μm. The morphology, mechanical properties and drug-release behavior were investigated at different ratios of chitosan to berberine. The results show that the elastic modulus and compressive strength of the coated scaffolds were improved to 35.4 MPa and 1.7 MPa, respectively, about 7 times and 3 times higher than the uncoated scaffolds. After a burst release of berberine within the first 3 h in PBS solution, a continuous berberine release can last 150 h, which is highly dependent on the coating concentration and suitable for antibacterial requirement of orthopaedic surgery. The bactericidal test confirms a strong antibiotic effect of the delivery system and the minimum inhibitory concentration of the drug is 0.02 mg/ml. Moreover, in vitro biological evaluation demonstrates that the coating scaffolds act as a good matrix for MG63 adhesion, crawl, growth and proliferation, suggesting that the antibacterial delivery system has no cytotoxicity. We expect the drug-delivery system to have a potential application in bone regeneration or defect repair.

Evaluation of dose dependent antimicrobial activity of self-assembled chitosan, nano silver and chitosan-nano silver composite against several pathogens.

PubMed

Tareq, Foysal Kabir; Fayzunnesa, Mst; Kabir, Md Shahariar; Nuzat, Musrat

2018-01-01

The aim of this investigation to preparation of silver nanoparticles organized chitosan nano polymer, which effective against microbial and pathogens, when apply to liquid medium and edible food products surface, will rescue the growth of microbes. Self-assembly approach used to synthesis of silver nanoparticles and silver nanoparticles organized chitosan nano polymer. Silver nanoparticles and silver nanoparticles organized chitosan nano polymer and film characterized using Ultra-violate visible spectrometer (UV-vis), X-ray diffraction (X-ray), and Scanning electronic microscope (SEM). The crystalline structured protein capped nano silver successfully synthesized at range of 12 nm-29 nm and organized into chitosan nano polymer. Antimicrobial ingredient in liquid medium and food product surface provide to rescue oxidative change and growth of microorganism to provide higher safety. The silver nanoparticles organized chitosan nano polymer caused the death of microorganism. The materials in nano scale synthesized successfully using self-assembly method, which showed good antimicrobial properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Could Nano-Structured Materials Enable the Improved Pressure Vessels for Deep Atmospheric Probes?

NASA Technical Reports Server (NTRS)

Srivastava, D.; Fuentes, A.; Bienstock, B.; Arnold, J. O.

2005-01-01

A viewgraph presentation on the use of Nano-Structured Materials to enable pressure vessel structures for deep atmospheric probes is shown. The topics include: 1) High Temperature/Pressure in Key X-Environments; 2) The Case for Use of Nano-Structured Materials Pressure Vessel Design; 3) Carbon based Nanomaterials; 4) Nanotube production & purification; 5) Nanomechanics of Carbon Nanotubes; 6) CNT-composites: Example (Polymer); 7) Effect of Loading sequence on Composite with 8% by volume; 8) Models for Particulate Reinforced Composites; 9) Fullerene/Ti Composite for High Strength-Insulating Layer; 10) Fullerene/Epoxy Composite for High Strength-Insulating Layer; 11) Models for Continuous Fiber Reinforced Composites; 12) Tensile Strength for Discontinuous Fiber Composite; 13) Ti + SWNT Composites: Thermal/Mechanical; 14) Ti + SWNT Composites: Tensile Strength; and 15) Nano-structured Shell for Pressure Vessels.

Fabrication of a Bioactive, PCL-based "Self-fitting" Shape Memory Polymer Scaffold.

PubMed

Nail, Lindsay N; Zhang, Dawei; Reinhard, Jessica L; Grunlan, Melissa A

2015-10-23

Tissue engineering has been explored as an alternative strategy for the treatment of critical-sized cranio-maxillofacial (CMF) bone defects. Essential to the success of this approach is a scaffold that is able to conformally fit within an irregular defect while also having the requisite biodegradability, pore interconnectivity and bioactivity. By nature of their shape recovery and fixity properties, shape memory polymer (SMP) scaffolds could achieve defect "self-fitting." In this way, following exposure to warm saline (~60 ºC), the SMP scaffold would become malleable, permitting it to be hand-pressed into an irregular defect. Subsequent cooling (~37 ºC) would return the scaffold to its relatively rigid state within the defect. To meet these requirements, this protocol describes the preparation of SMP scaffolds prepared via the photochemical cure of biodegradable polycaprolactone diacrylate (PCL-DA) using a solvent-casting particulate-leaching (SCPL) method. A fused salt template is utilized to achieve pore interconnectivity. To realize bioactivity, a polydopamine coating is applied to the surface of the scaffold pore walls. Characterization of self-fitting and shape memory behaviors, pore interconnectivity and in vitro bioactivity are also described.

Fabrication and characterization of poly(propylene fumarate) scaffolds with controlled pore structures using 3-dimensional printing and injection molding.

PubMed

Lee, Kee-Won; Wang, Shanfeng; Lu, Lichun; Jabbari, Esmaiel; Currier, Bradford L; Yaszemski, Michael J

2006-10-01

Poly(propylene fumarate) (PPF) is an injectable, biodegradable polymer that has been used for fabricating preformed scaffolds in tissue engineering applications because of in situ crosslinking characteristics. Aiming for understanding the effects of pore structure parameters on bone tissue ingrowth, 3-dimensional (3D) PPF scaffolds with controlled pore architecture have been produced in this study from computer-aided design (CAD) models. We have created original scaffold models with 3 pore sizes (300, 600, and 900 microm) and randomly closed 0%, 10%, 20%, or 30% of total pores from the original models in 3 planes. PPF scaffolds were fabricated by a series steps involving 3D printing of support/build constructs, dissolving build materials, injecting PPF, and dissolving support materials. To investigate the effects of controlled pore size and interconnectivity on scaffolds, we compared the porosities between the models and PPF scaffolds fabricated thereby, examined pore morphologies in surface and cross-section using scanning electron microscopy, and measured permeability using the falling head conductivity test. The thermal properties of the resulting scaffolds as well as uncrosslinked PPF were determined by differential scanning calorimetry and thermogravimetric analysis. Average pore sizes and pore shapes of PPF scaffolds with 600- and 900-microm pores were similar to those of CAD models, but they depended on directions in those with 300-microm pores. Porosity and permeability of PPF scaffolds decreased as the number of closed pores in original models increased, particularly when the pore size was 300 microm as the result of low porosity and pore occlusion. These results show that 3D printing and injection molding technique can be applied to crosslinkable polymers to fabricate 3D porous scaffolds with controlled pore structures, porosity, and permeability using their CAD models.

Uniform Deposition of Protein Incorporated Mineral Layer on Three-Dimensional Porous Polymer Scaffolds

PubMed Central

Segvich, Sharon; Smith, Hayes C.; Luong, Linh N.; Kohn, David H.

2009-01-01

Inorganic–organic hybrid materials designed to facilitate bone tissue regeneration use a calcium phosphate mineral layer to encourage cell adhesion, proliferation, and osteogenic differentiation. Mineral formed on porous materials is often discontinuous through the thickness of the scaffold. This study aimed to uniformly coat the pores of three-dimensional (3D) porous, polymer scaffolds with a bone-like mineral layer in addition to uniformly incorporating a model protein within this mineral layer. A filtration system designed to induce simulated body fluid flow through the interstices of 3D polylactic-co-glycolic acid scaffolds (10-mm diameter × 2-mm thickness) illustrated that a uniform, continuous mineral layer can be precipitated on the pore surfaces of a 3D porous structure within 5 days. MicroCT analysis showed increased mineral volume percent (MV%) (7.86 ± 3.25 MV%, p = 0.029) and continuous mineralization of filtered scaffolds compared with two static control groups (floating, 0.16 ± 0.26 MV% and submerged, 0.20 ± 0.01 MV%). Furthermore, the system was effective in coprecipitating a model protein, bone sialoprotein (BSA), within the mineral layer. A 10-fold increase in BSA incorporation was seen when coprecipitated filtered scaffolds (1308 ± 464 μg) were compared to a submerged static control group (139 ± 45 μg), p < 0.001. Confocal microscopy visually confirmed uniform coprecipitation of BSA throughout the thickness of the filtration scaffolds. The designed system enables 3D mineralization through the thickness of porous materials, and provides the option of including coprecipitated biomolecular cues within the mineral layer. This approach of providing a 3D conductive and osteoinductive environment could be conducive to bone tissue regeneration. PMID:17618505

Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique.

PubMed

Yang, Tae Young; Lee, Jung Min; Yoon, Seog Young; Park, Hong Chae

2010-05-01

A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled "designer" pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180-360 microm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (approximately 4.5 microm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 microm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths.

Nano-imprint lithography using poly (methyl methacrylate) (PMMA) and polystyrene (PS) polymers

NASA Astrophysics Data System (ADS)

Ting, Yung-Chiang; Shy, Shyi-Long

2016-04-01

Nano-imprinting lithography (NIL) technology, as one of the most promising fabrication technologies, has been demonstrated to be a powerful tool for large-area replication up to wafer-level, with features down to nanometer scale. The cost of resists used for NIL is important for wafer-level large-area replication. This study aims to develop capabilities in patterning larger area structure using thermal NIL. The commercial available Poly (Methyl Methacrylate) (PMMA) and Polystyrene (PS) polymers possess a variety of characteristics desirable for NIL, such as low material cost, low bulkvolumetric shrinkage, high spin coating thickness uniformity, high process stability, and acceptable dry-etch resistance. PMMA materials have been utilized for positive electron beam lithography for many years, offering high resolution capability and wide process latitude. In addition, it is preferable to have a negative resist like PMMA, which is a simple polymer with low cost and practically unlimited shelf life, and can be dissolved easily using commercial available Propylene glycol methyl ether acetate (PGMEA) safer solvent to give the preferred film thickness. PS is such a resist, as it undergoes crosslinking when exposed to deep UV light or an electron beam and can be used for NIL. The result is a cost effective patterning larger area structure using thermal nano-imprint lithography (NIL) by using commercial available PMMA and PS ploymers as NIL resists.

Behavior of a nano-particle and a polymer molecule in a nano-scale four-roll mill

NASA Astrophysics Data System (ADS)

Vo, Minh; Papavassiliou, Dimitrios

2016-11-01

The four-roll mill device could be used to create a mixed flow from purely extensional stresses to completely rotational through the proper selection of speed and direction of each of the four cylindrical rollers. Considerable research has been done with this device for macroscale rheological studies.. In our study, the dissipative particle dynamics (DPD) method was employed to investigate the behavior of a nano-sphere and a polymer molecule in different conditions within a four-roll mill device. Hydrophilic properties of each roll were generated by adjusting interaction parameters and using bounce back boundary condition at the solid surface. All simulations were run up to 4x106 time steps at room temperature using the open source LAMMPS package. After the flow in the system reached equilibrium, a nano-sphere and then a polymer chain were released at the center of the simulation box. Their trajectories were recorded at different shear rate conditions. The propagation of nanosphere in different rotational flow will be discussed. Additionally, the deformation of polymer chains will be compared to that in a simple shear flow.

Preparation and characterization of PVP-PVA–ZnO blend polymer nano composite films

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

Divya, S., E-mail: divi.fysics@gmail.com; Saipriya, G.; Hemalatha, J., E-mail: hemalatha@nitt.edu

Flexible self-standing films of PVP-PVA blend composites are prepared by using ZnO as a nano filler at different concentrations. The structural, compositional, morphological and optical studies made with the help of X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), Scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-vis) and Photoluminescence (PL) spectra are presented in this paper. The results of XRD indicate that ZnO nanoparticles are formed with hexagonal phase in the polymeric matrix. SEM images show the dispersion of ZnO nano filler in the polymer matrix. UV–vis spectra reveal that the absorption peak is centered around 235more » nm and 370 nm for the nano composite films. The blue shift is observed with decrease in the concentration of the nano filler. PL spectra shows the excitation wavelength is given at 320 nm.The emission peaks were observed at 383 nm ascribing to the electronic transitions between valence band and conduction band and the peak at 430 nm.« less

Three-dimensional nano-architected scaffolds with tunable stiffness for efficient bone tissue growth.

PubMed

Maggi, Alessandro; Li, Hanqing; Greer, Julia R

2017-11-01

The precise mechanisms that lead to orthopedic implant failure are not well understood; it is believed that the micromechanical environment at the bone-implant interface regulates structural stability of an implant. In this work, we seek to understand how the 3D mechanical environment of an implant affects bone formation during early osteointegration. We employed two-photon lithography (TPL) direct laser writing to fabricate 3-dimensional rigid polymer scaffolds with tetrakaidecahedral periodic geometry, herewith referred to as nanolattices, whose strut dimensions were on the same order as osteoblasts' focal adhesions (∼2μm) and pore sizes on the order of cell size, ∼10μm. Some of these nanolattices were subsequently coated with thin conformal layers of Ti or W, and a final outer layer of 18nm-thick TiO 2 was deposited on all samples to ensure biocompatibility. Nanomechanical experiments on each type of nanolattice revealed the range of stiffnesses of 0.7-100MPa. Osteoblast-like cells (SAOS-2) were seeded on each nanolattice, and their mechanosensitve response was explored by tracking mineral secretions and intracellular f-actin and vinculin concentrations after 2, 8 and 12days of cell culture in mineralization media. Experiments revealed that the most compliant nanolattices had ∼20% more intracellular f-actin and ∼40% more Ca and P secreted onto them than the stiffer nanolattices, where such cellular response was virtually indistinguishable. We constructed a simple phenomenological model that appears to capture the observed relation between scaffold stiffness and f-actin concentration. This model predicts a range of optimal scaffold stiffnesses for maximum f-actin concentration, which appears to be directly correlated with osteoblast-driven mineral deposition. This work suggests that three-dimensional scaffolds with titania-coated surfaces may provide an optimal microenvironment for cell growth when their stiffness is similar to that of cartilage (∼0

Nanomechanics of cellulose crystals and cellulose-based polymer composites

NASA Astrophysics Data System (ADS)

Pakzad, Anahita

Cellulose-polymer composites have potential applications in aerospace and transportation areas where lightweight materials with high mechanical properties are needed. In addition, these economical and biodegradable composites have been shown to be useful as polymer electrolytes, packaging structures, optoelectronic devices, and medical implants such as wound dressing and bone scaffolds. In spite of the above mentioned advantages and potential applications, due to the difficulties associated with synthesis and processing techniques, application of cellulose crystals (micro and nano sized) for preparation of new composite systems is limited. Cellulose is hydrophilic and polar as opposed to most of common thermoplastics, which are non-polar. This results in complications in addition of cellulose crystals to polymer matrices, and as a result in achieving sufficient dispersion levels, which directly affects the mechanical properties of the composites. As in other composite materials, the properties of cellulose-polymer composites depend on the volume fraction and the properties of individual phases (the reinforcement and the polymer matrix), the dispersion quality of the reinforcement through the matrix and the interaction between CNCs themselves and CNC and the matrix (interphase). In order to develop economical cellulose-polymer composites with superior qualities, the properties of individual cellulose crystals, as well as the effect of dispersion of reinforcements and the interphase on the properties of the final composites should be understood. In this research, the mechanical properties of CNC polymer composites were characterized at the macro and nano scales. A direct correlation was made between: - Dispersion quality and macro-mechanical properties - Nanomechanical properties at the surface and tensile properties - CNC diameter and interphase thickness. Lastly, individual CNCs from different sources were characterized and for the first time size-scale effect on

Nano scaffolds and stem cell therapy in liver tissue engineering

NASA Astrophysics Data System (ADS)

Montaser, Laila M.; Fawzy, Sherin M.

2015-08-01

Tissue engineering and regenerative medicine have been constantly developing of late due to the major progress in cell and organ transplantation, as well as advances in materials science and engineering. Although stem cells hold great potential for the treatment of many injuries and degenerative diseases, several obstacles must be overcome before their therapeutic application can be realized. These include the development of advanced techniques to understand and control functions of micro environmental signals and novel methods to track and guide transplanted stem cells. A major complication encountered with stem cell therapies has been the failure of injected cells to engraft to target tissues. The application of nanotechnology to stem cell biology would be able to address those challenges. Combinations of stem cell therapy and nanotechnology in tissue engineering and regenerative medicine have achieved significant advances. These combinations allow nanotechnology to engineer scaffolds with various features to control stem cell fate decisions. Fabrication of Nano fiber cell scaffolds onto which stem cells can adhere and spread, forming a niche-like microenvironment which can guide stem cells to proceed to heal damaged tissues. In this paper, current and emergent approach based on stem cells in the field of liver tissue engineering is presented for specific application. The combination of stem cells and tissue engineering opens new perspectives in tissue regeneration for stem cell therapy because of the potential to control stem cell behavior with the physical and chemical characteristics of the engineered scaffold environment.

Bioresorbable Ca-phosphate-polymer/metal and Fe-Ag nanocomposites for macro-porous scaffolds with tunable degradation and drug release

NASA Astrophysics Data System (ADS)

Gotman, I.; Swain, S. K.; Sharipova, A.; Gutmanas, E. Y.

2016-11-01

Bioresorbable implants are increasingly gaining popularity as an attractive alternative to traditional permanent bone healing devices. The advantage of bioresorbable implantable devices is that they slowly degrade over time and disappear once their "mission" is accomplished. Thus, no foreign material is left behind that can cause adverse effects on the host, such as long term local or systemic immune response and stress-shielding related bone atrophy. Resorbable materials considered for surgical implant applications include degradable polymers, Ca phosphate ceramics (CaP) and corrodible metals. Degradable polymers, such as polycaprolactone and lactic acid are weak, lack osteoconductivity and degrade to acidic products that can cause late inflammation. Resorbable CaP ceramics (e.g., β-TCP) are attractive materials for bone regeneration bear close resemblance to the bone mineral, however they are intrinsically brittle and thus unsuitable for use in load-bearing sites. Moreover, introducing high porosity required to encourage better cellular ingrowth into bone regeneration scaffolds is detrimental to the mechanical strength of the material. In present work we review and discuss our results on development of strong bioresorbable Ca-phosphate-polymer/metal nanonocomposites and highly porous scaffolds from them. By introduction of nanoscale ductile polymer or metal phase into CaP ceramic an attempt was made to mimic structure of natural bone, where nanocrystallites of CaP ceramic are bonded by thin collagen layers. Recent results on development of high strength scaffolds from Fe-Ag nanocomposites are also reported. High energy milling of powders followed by cold sintering—high pressure consolidation at ambient temperature in combination with modified porogen leaching method was employed for processing. The developed nanocomposites and scaffolds exhibited high mechanical strength coupled with measurable ductility, gradual lost weight and strength during immersion in

Enhancing the mechanical and in vitro performance of robocast bioglass scaffolds by polymeric coatings: Effect of polymer composition.

PubMed

Motealleh, Azadeh; Eqtesadi, Siamak; Pajares, Antonia; Miranda, Pedro

2018-08-01

The effect of different polymeric coatings, including natural and synthetic compositions, on the mechanical performance of 45S5 bioglass robocast scaffolds is systematically analyzed in this work. Fully amorphous 45S5 bioglass robocast scaffolds sintered at 550 °C were impregnated with natural (gelatin, alginate, and chitosan) and synthetic (polycaprolactone, PCL and poly-lactic acid, PLA) polymers through a dip-coating process. Mechanical enhancement provided by these coatings in terms of both compressive strength and strain energy density was evaluated. Natural polymers, in general, and chitosan, in particular, were found to produce the greater reinforcement. The effect of these coatings on the in vitro bioactivity and degradation behavior of 45S5 bioglass robocast scaffolds was also investigated through immersion tests in simulated body fluid (SBF). Coatings from natural polymers, especially chitosan, are shown to have a positive effect on the bioactivity of 45S5 bioglass, accelerating the formation of an apatite-like layer. Besides, most coating compositions reduced the degradation (weight loss) rate of the scaffold, which has a positive impact on the evolution of their mechanical properties. Copyright © 2018 Elsevier Ltd. All rights reserved.

3D structural patterns in scalable, elastomeric scaffolds guide engineered tissue architecture.

PubMed

Kolewe, Martin E; Park, Hyoungshin; Gray, Caprice; Ye, Xiaofeng; Langer, Robert; Freed, Lisa E

2013-08-27

Microfabricated elastomeric scaffolds with 3D structural patterns are created by semiautomated layer-by-layer assembly of planar polymer sheets with through-pores. The mesoscale interconnected pore architectures governed by the relative alignment of layers are shown to direct cell and muscle-like fiber orientation in both skeletal and cardiac muscle, enabling scale up of tissue constructs towards clinically relevant dimensions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of gelatin/carboxymethyl chitosan/nano-hydroxyapatite composite 3D macroporous scaffold for bone tissue engineering applications.

PubMed

Maji, Somnath; Agarwal, Tarun; Das, Joyjyoti; Maiti, Tapas Kumar

2018-06-01

The present study delineates a relatively simpler approach for fabrication of a macroporous three-dimensional scaffold for bone tissue engineering. The novelty of the work is to obtain a scaffold with macroporosity (interconnected networks) through a combined approach of high stirring induced foaming of the gelatin/carboxymethyl chitosan (CMC)/nano-hydroxyapatite (nHAp) matrix followed by freeze drying. The fabricated macroporous (SGC) scaffold had a greater pore size, higher porosity, higher water retention capacity, slow and sustained enzymatic degradation rate along with higher compressive strength compared to that of non-macroporous (NGC, prepared by conventional freeze drying methodology) scaffold. The biological studies revealed the increased percentage of viability, proliferation, and differentiation as well as higher mineralization of differentiated human Wharton's jelly MSC microtissue (wjhMSC-MT) on SGC as compared to NGC scaffold. RT-PCR also showed enhanced expression level of collagen type I, osteocalcin and Runx2 when seeded on SGC. μCT and histological analysis further revealed a penetration of cellular spheroid to a greater depth in SGC scaffold than NGC scaffold. Furthermore, the effect of cryopreservation on microtissue survival on the three-dimensional construct revealed significant higher viability upon revival in macroporous SGC scaffolds. These results together suggest that high stirring based macroporous scaffolds could have a potential application in bone tissue engineering. Copyright © 2018 Elsevier Ltd. All rights reserved.

CdO-NPs; synthesis from 1D new nano Cd coordination polymer, characterization and application as anti-cancer drug for reducing the viability of cancer cells

NASA Astrophysics Data System (ADS)

Afzalian Mend, Behnaz; Delavar, Mahmoud; Darroudi, Majid

2017-04-01

The hexagonal CdO nano-particles (CdO-NPs) was prepared using new nano Cd coordination polymer, [Cd(NO3)(bipy)(pzca)]n (1) as a precursor, through direct calcination process at 500 °C. The precursor (1) was synthesized by sonochemical method. The new nano compound (1) was characterized by IR spectroscopy, elemental analyses, X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and thermal gravimetric analyses. The structure of nano coordination polymer was determined by comparing the XRD pattern of nano and single-crystal of compound (1). The nano CdO was characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). In addition, the activity and efficiency of nano CdO as an anti-cancer drug was studied on cancer cells with different concentration. The results shows that the viability of cancer cells reduced above 2 μg/mL of CdO-NPs concentration.

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

PubMed

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

2010-05-01

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

Polymer Nanofiber Based Reversible Nano-Switch/Sensor Diode (Nanosssd) Device

NASA Technical Reports Server (NTRS)

Theofylaktos, Onoufrios (Inventor); Meador, Michael A. (Inventor); Miranda, Felix A. (Inventor); Pinto, Nicholas (Inventor); Mueller, Carl H. (Inventor); Santos-Perez, Javier (Inventor)

2017-01-01

A nanostructure device is provided and performs dual functions as a nano-switching/sensing device. The nanostructure device includes a doped semiconducting substrate, an insulating layer disposed on the doped semiconducting substrate, an electrode formed on the insulating layer, and at least one polymer nanofiber deposited on the electrode. The at least one polymer nanofiber provides an electrical connection between the electrode and the substrate and is the electroactive element in the device.

Effect of ionic activity products on the structure and composition of mineral self assembled on three-dimensional poly(lactide-co-glycolide) scaffolds

PubMed Central

Shin, Kyungsup; Jayasuriya, Ambalangodage C.; Kohn, David H.

2009-01-01

A biomimetic approach involving the self-assembly of mineral within the pores of three-dimensional porous polymer scaffolds is a promising strategy to integrate advantages of inorganic and organic phases into a single material for hard tissue engineering. Such a material enhances the ability of progenitor cells to differentiate down an osteoblast lineage in vitro and in vivo, compared with polymer scaffolds. The mechanisms regulating mineral formation in this one-step process, however, are poorly understood, especially the effects of ionic activity products (IP) of the mineralizing solution and incubation time. The aims of this study were to define the structure and composition of mineral formed within the pores of biodegradable polymer scaffolds as a function of IP and time. Three-dimensional poly(lactide-co-glycolide) scaffolds were fabricated by solvent casting/particulate leaching and incubated for 4–16 days in six variants of simulated body fluid whose IPs were varied by adjusting ionic concentrations. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy demonstrated the formation of carbonated apatite with sub-micrometer sized crystals that grew into spherical globules extending out of the scaffold pore surfaces. As IP increased, more mineral grew on the scaffold pore surfaces, but the apatite became less crystalline and the Ca/P molar ratio decreased from 1.63 ± 0.005 to 1.51 ± 0.002. Since morphology, composition, and structure of mineral are factors that affect cell function, this study demonstrates that the IP of the mineralizing solution is an important modulator of material properties, potentially leading to enhanced control of cell function. PMID:17584901

Rapid Prototyping Amphiphilic Polymer/Hydroxyapatite Composite Scaffolds with Hydration-Induced Self-Fixation Behavior

PubMed Central

Kutikov, Artem B.; Gurijala, Anvesh

2015-01-01

Two major factors hampering the broad use of rapid prototyped biomaterials for tissue engineering applications are the requirement for custom-designed or expensive research-grade three-dimensional (3D) printers and the limited selection of suitable thermoplastic biomaterials exhibiting physical characteristics desired for facile surgical handling and biological properties encouraging tissue integration. Properly designed thermoplastic biodegradable amphiphilic polymers can exhibit hydration-dependent hydrophilicity changes and stiffening behavior, which may be exploited to facilitate the surgical delivery/self-fixation of the scaffold within a physiological tissue environment. Compared to conventional hydrophobic polyesters, they also present significant advantages in blending with hydrophilic osteoconductive minerals with improved interfacial adhesion for bone tissue engineering applications. Here, we demonstrated the excellent blending of biodegradable, amphiphilic poly(D,L-lactic acid)-poly(ethylene glycol)-poly(D,L-lactic acid) (PLA-PEG-PLA) (PELA) triblock co-polymer with hydroxyapatite (HA) and the fabrication of high-quality rapid prototyped 3D macroporous composite scaffolds using an unmodified consumer-grade 3D printer. The rapid prototyped HA-PELA composite scaffolds and the PELA control (without HA) swelled (66% and 44% volume increases, respectively) and stiffened (1.38-fold and 4-fold increases in compressive modulus, respectively) in water. To test the hypothesis that the hydration-induced physical changes can translate into self-fixation properties of the scaffolds within a confined defect, a straightforward in vitro pull-out test was designed to quantify the peak force required to dislodge these scaffolds from a simulated cylindrical defect at dry versus wet states. Consistent with our hypothesis, the peak fixation force measured for the PELA and HA-PELA scaffolds increased 6-fold and 15-fold upon hydration, respectively. Furthermore, we showed that

Effects of Structural Properties of Electrospun TiO2 Nano-fiber Meshes on their Osteogenic Potential

PubMed Central

Wang, Xiaokun; Gittens, Rolando A.; Song, Rosemary; Tannenbaum, Rina; Olivares-Navarrete, Rene; Schwartz, Zvi; Chen, Haifeng; Boyan, Barbara D.

2011-01-01

Ideal outcomes in the field of tissue engineering and regenerative medicine involve biomaterials that can enhance cell differentiation and production of local factors for natural tissue regeneration without the use of systemic drugs. Biomaterials typically used in tissue engineering applications include polymeric scaffolds that mimic the 3-D structural environment of the native tissue, but these are often functionalized with proteins or small peptides to improve their biological performance. For bone applications, titanium (Ti) implants, or more appropriately the titania (TiO2) passive oxide layer formed on their surface, have been shown to enhance osteoblast differentiation in vitro and to promote osseointegration in vivo. In this study we evaluated the effect on osteoblast differentiation of pure TiO2 nano-fiber meshes with different surface micro-roughness and nano-fiber diameters, prepared by the electrospinning method. MG63 cells were seeded on TiO2 meshes, and cell number, differentiation markers and local factor production were analyzed. The results showed that cells grew throughout the entire surfaces and with similar morphology in all groups. Cell number was sensitive to surface micro-roughness, whereas cell differentiation and local factor production was regulated by both surface roughness and nano-fiber diameter. These results indicate that scaffold structural cues alone can be used to drive cell differentiation and create an osteogenic environment without the use of exogenous factors. PMID:22075122

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

Association of 17-β Estradiol with Adipose-Derived Stem Cells: New Strategy to Produce Functional Myogenic Differentiated Cells with a Nano-Scaffold for Tissue Engineering.

PubMed

Feng, Chunxiang; Hu, Jinqian; Liu, Chang; Liu, Shiliang; Liao, Guiying; Song, Linjie; Zeng, Xiaoyong

2016-01-01

The increased incidence of stress urinary incontinence (SUI) in postmenopausal women has been proposed to be associated with a reduction in the level of 17-β estradiol (E2). E2 has also been shown to enhance the multi-differentiation ability of adipose-derived stem cells (ASCs) in vitro. However, studies on the potential value of E2 for tissue engineering in SUI treatment are rare. In the present study, we successfully fabricated myogenically differentiated ASCs (MD-ASCs), which were seeded onto a Poly(l-lactide)/Poly(e-caprolactone) electrospinning nano-scaffold, and incorporated E2 into the system, with the aim of improving the proliferation and myogenic differentiation of ASCs. ASCs were collected from the inguinal subcutaneous fat of rats. The proliferation and myogenic differentiation of ASCs, as well as the nano-scaffold biocompatibility of MD-ASCs, with or without E2 supplementation, were investigated. We demonstrated that E2 incorporation enhanced the proliferation of ASCs in vitro, and the most optimal concentration was 10-9 M. E2 also led to modulation of the MD-ASCs phenotype toward a concentrated type with smooth muscle-inductive medium. The expression of early (alpha-smooth muscle actin), mid (calponin), and late-stage (myosin heavy chain) contractile markers in MD-ASCs was enhanced by E2 during the different differentiation stages. Furthermore, the nano-scaffold was biocompatible with MD-ASCs, and cell proliferation was significantly enhanced by E2. Taken together, these results demonstrate that E2 can enhance the proliferation and myogenic differentiation of ASCs and can be used to construct a biocompatible cell/nano-scaffold. These scaffolds with desirable differentiation cells show promising applications for tissue engineering.

Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review

PubMed Central

Yusop, A. H.; Bakir, A. A.; Shaharom, N. A.; Abdul Kadir, M. R.; Hermawan, H.

2012-01-01

Scaffolds have been utilized in tissue regeneration to facilitate the formation and maturation of new tissues or organs where a balance between temporary mechanical support and mass transport (degradation and cell growth) is ideally achieved. Polymers have been widely chosen as tissue scaffolding material having a good combination of biodegradability, biocompatibility, and porous structure. Metals that can degrade in physiological environment, namely, biodegradable metals, are proposed as potential materials for hard tissue scaffolding where biodegradable polymers are often considered as having poor mechanical properties. Biodegradable metal scaffolds have showed interesting mechanical property that was close to that of human bone with tailored degradation behaviour. The current promising fabrication technique for making scaffolds, such as computation-aided solid free-form method, can be easily applied to metals. With further optimization in topologically ordered porosity design exploiting material property and fabrication technique, porous biodegradable metals could be the potential materials for making hard tissue scaffolds. PMID:22919393

3-dimensional free standing micro-structures by proton beam writing of Su 8-silver nanoParticle polymeric composite

NASA Astrophysics Data System (ADS)

Igbenehi, H.; Jiguet, S.

2012-09-01

Proton beam lithography a maskless direct-write lithographic technique (well suited for producing 3-Dimensional microstructures in a range of resist and semiconductor materials) is demonstrated as an effective tool in the creation of electrically conductive freestanding micro-structures in an Su 8 + Nano Silver polymer composite. The structures produced show non-ohmic conductivity and fit the percolation theory conduction model of tunneling of separated nanoparticles. Measurements show threshold switching and a change in conductivity of at least 4 orders of magnitude. The predictable range of protons in materials at a given energy is exploited in the creation of high aspect ratio, free standing micro-structures, made from a commercially available SU8 Silver nano-composite (GMC3060 form Gersteltec Inc. a negative tone photo-epoxy with added metallic nano-particles(Silver)) to create films with enhanced electrical properties when exposed and cured. Nano-composite films are directly written on with a finely focused MeV accelerated Proton particle beam. The energy loss of the incident proton beams in the target polymer nano- composite film is concentrated at the end of its range, where damage occurs; changing the chemistry of the nano-composite film via an acid initiated polymerization - creating conduction paths. Changing the energy of the incident beams provide exposed regions with different penetration and damage depth - exploited in the demonstrated cantilever microstructure.

Development of Useful Biomaterial for Bone Tissue Engineering by Incorporating Nano-Copper-Zinc Alloy (nCuZn) in Chitosan/Gelatin/Nano-Hydroxyapatite (Ch/G/nHAp) Scaffold.

PubMed

Forero, Juan Carlos; Roa, Eduardo; Reyes, Juan G; Acevedo, Cristian; Osses, Nelson

2017-10-17

Ceramic and metallic nanoparticles can improve the mechanical and biological properties of polymeric scaffolds for bone tissue engineering (BTE). In this work, nanohydroxyapatite (nHAp) and nano-copper-zinc alloy (nCuZn) were added to a chitosan/gelatin (Ch/G) scaffold in order to investigate the effects on morphological, physical, and biocompatibility properties. Scaffolds were fabricated by a freeze-drying technique using different pre-freezing temperatures. Microstructure and morphology were studied by scanning electron microscopy (SEM), glass transition ( T g ) was studied using differential scanning calorimetry (DSC), cell growth was estimated by MTT assay, and biocompatibility was examined in vitro and in vivo by histochemistry analyses. Scaffolds and nanocomposite scaffolds presented interconnected pores, high porosity, and pore size appropriate for BTE. T g of Ch/G scaffolds was diminished by nanoparticle inclusion. Mouse embryonic fibroblasts (MEFs) cells loaded in the Ch/G/nHAp/nCuZn nanocomposite scaffold showed suitable behavior, based on cell adhesion, cell growth, alkaline phosphatase (ALP) activity as a marker of osteogenic differentiation, and histological in vitro cross sections. In vivo subcutaneous implant showed granulation tissue formation and new tissue infiltration into the scaffold. The favorable microstructure, coupled with the ability to integrate nanoparticles into the scaffold by freeze-drying technique and the biocompatibility, indicates the potential of this new material for applications in BTE.

Polymer scaffolds with no skin-effect for tissue engineering applications fabricated by thermally induced phase separation.

PubMed

Kasoju, Naresh; Kubies, Dana; Sedlačík, Tomáš; Janoušková, Olga; Koubková, Jana; Kumorek, Marta M; Rypáček, František

2016-01-11

Thermally induced phase separation (TIPS) based methods are widely used for the fabrication of porous scaffolds for tissue engineering and related applications. However, formation of a less-/non-porous layer at the scaffold's outer surface at the air-liquid interface, often known as the skin-effect, restricts the cell infiltration inside the scaffold and therefore limits its efficacy. To this end, we demonstrate a TIPS-based process involving the exposure of the just quenched poly(lactide-co-caprolactone):dioxane phases to the pure dioxane for a short time while still being under the quenching strength, herein after termed as the second quenching (2Q). Scanning electron microscopy, mercury intrusion porosimetry and contact angle analysis revealed a direct correlation between the time of 2Q and the gradual disappearance of the skin, followed by the widening of the outer pores and the formation of the fibrous filaments over the surface, with no effect on the internal pore architecture and the overall porosity of scaffolds. The experiments at various quenching temperatures and polymer concentrations revealed the versatility of 2Q in removing the skin. In addition, the in vitro cell culture studies with the human primary fibroblasts showed that the scaffolds prepared by the TIPS based 2Q process, with the optimal exposure time, resulted in a higher cell seeding and viability in contrast to the scaffolds prepared by the regular TIPS. Thus, TIPS including the 2Q step is a facile, versatile and innovative approach to fabricate the polymer scaffolds with a skin-free and fully open porous surface morphology for achieving a better cell response in tissue engineering and related applications.

Sonochemical syntheses of a new nano-sized porous lead(II) coordination polymer as precursor for preparation of lead(II) oxide nanoparticles

NASA Astrophysics Data System (ADS)

Ranjbar, Zohreh Rashidi; Morsali, Ali

2009-11-01

Nano-scale of a new Pb(II) coordination polymer, {[Pb(bpacb)(OAc)]·DMF} n ( 1); bpacbH = 3,5-bis[(4-pyridylamino)carbonyl]benzoic acid], were synthesized by a sonochemical method. The nano-material was characterized by scanning electron microscopy, X-ray powder diffraction (XRD), 1H, 13C NMR, IR spectroscopy and elemental analyses. Crystal structure of compound 1 was determined by X-ray crystallography. Calcination of the nano-sized compound 1 at 700 °C under air atmospheres yields PbO nanoparticles. Thermal stability of nano-sized and single crystalline samples of compound 1 were studied and compared with each other.

A Novel Polymer-Synthesized Ceramic Composite Based System for Bone Repair: Osteoblast Growth on Scaffolds with Varied Calcium Phosphate Content

DTIC Science & Technology

2005-01-01

demongtrated the synthesis of degradable scaffolds from PLAGA /calcium phosphate composite microspheres in which an amorphous calcium phosphate is...EXPERIMENTAL DETAILS Scaffold Preparation Scaffolds were prepared as described in detail previously [3]. Briefly, PLAGA /calcium phosphate composite...culture polystyrene (TCPS) 2- pure PLAGA microspheres 64 3- composite microsphere matrices with a low polymer/ceramic ratio 4- composite microsphere

Design of 3D scaffolds for tissue engineering testing a tough polylactide-based graft copolymer.

PubMed

Dorati, R; Colonna, C; Tomasi, C; Genta, I; Bruni, G; Conti, B

2014-01-01

The aim of this research was to investigate a tough polymer to develop 3D scaffolds and 2D films for tissue engineering applications, in particular to repair urethral strictures or defects. The polymer tested was a graft copolymer of polylactic acid (PLA) synthesized with the rationale to improve the toughness of the related PLA homopolymer. The LMP-3055 graft copolymer (in bulk) demonstrated to have negligible cytotoxicity (bioavailability >85%, MTT test). Moreover, the LMP-3055 sterilized through gamma rays resulted to be cytocompatible and non-toxic, and it has a positive effect on cell biofunctionality, promoting the cell growth. 3D scaffolds and 2D film were prepared using different LMP-3055 polymer concentrations (7.5, 10, 12.5 and 15%, w/v), and the effect of polymer concentration on pore size, porosity and interconnectivity of the 3D scaffolds and 2D film was investigated. 3D scaffolds got better results for fulfilling structural and biofunctional requirements: porosity, pore size and interconnectivity, cell attachment and proliferation. 3D scaffolds obtained with 10 and 12.5% polymer solutions (3D-2 and 3D-3, respectively) were identified as the most suitable construct for the cell attachment and proliferation presenting pore size ranged between 100 and 400μm, high porosity (77-78%) and well interconnected pores. In vitro cell studies demonstrated that all the selected scaffolds were able to support the cell proliferation, the cell attachment and growth resulting to their dependency on the polymer concentration and structural features. The degradation test revealed that the degradation of polymer matrix (ΔMw) and water uptake of 3D scaffolds exceed those of 2D film and raw polymer (used as control reference), while the mass loss of samples (3D scaffold and 2D film) resulted to be controlled, they showed good stability and capacity to maintain the physical integrity during the incubation time. © 2013.

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.

A review: fabrication of porous polyurethane scaffolds.

PubMed

Janik, H; Marzec, M

2015-03-01

The aim of tissue engineering is the fabrication of three-dimensional scaffolds that can be used for the reconstruction and regeneration of damaged or deformed tissues and organs. A wide variety of techniques have been developed to create either fibrous or porous scaffolds from polymers, metals, composite materials and ceramics. However, the most promising materials are biodegradable polymers due to their comprehensive mechanical properties, ability to control the rate of degradation and similarities to natural tissue structures. Polyurethanes (PUs) are attractive candidates for scaffold fabrication, since they are biocompatible, and have excellent mechanical properties and mechanical flexibility. PU can be applied to various methods of porous scaffold fabrication, among which are solvent casting/particulate leaching, thermally induced phase separation, gas foaming, emulsion freeze-drying and melt moulding. Scaffold properties obtained by these techniques, including pore size, interconnectivity and total porosity, all depend on the thermal processing parameters, and the porogen agent and solvents used. In this review, various polyurethane systems for scaffolds are discussed, as well as methods of fabrication, including the latest developments, and their advantages and disadvantages. Copyright © 2014. Published by Elsevier B.V.

Coordinative nanoporous polymers synthesized with hydrogen-bonded columnar liquid crystals.

PubMed

Ishihara, Shinsuke; Furuki, Yusuke; Hill, Jonathan P; Ariga, Katsuhiko; Takeoka, Shinji

2012-10-01

In this paper, we report the development of nanoporous polymer which demonstrates the coordination property toward zinc porphyrin. A hydrogen-bonded columnar liquid crystalline precursor composed of a triphenylene template and three equivalent of the surrounding dendric amphiphile bearing a pyridyl head group and a polymerizable aliphatic chain, was covalently fixed by photopolymerization, and then the subsequent selective removal of the template successively resulted in a nanoporous polymer in which the pore wall is modified with pyridyl groups. The nanoporous polymer reflected the conformation of template, and displayed considerable coordination ability of the pyridyl groups towards zinc porphyrin. The coordinative nanoporous polymer is promising as a nano-scaled scaffold for the organization of dyes into functional supramolecular architectures.

Delivery of S1P Receptor-Targeted Drugs via Biodegradable Polymer Scaffolds Enhances Bone Regeneration in a Critical Size Cranial Defect*

PubMed Central

Das, Anusuya; Tanner, Shaun; Barker, Daniel A.; Green, David; Botchwey, Edward A.

2014-01-01

Biodegradable polymer scaffolds can be used to deliver soluble factors to enhance osseous remodeling in bone defects. To this end, we designed a poly(lactic-co-glycolic acid) (PLAGA) microsphere scaffold to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors. The microsphere scaffolds were created from fast degrading 50:50 PLAGA and/or from slow-degrading 85:15 PLAGA. Temporal and spatial regulation of bone remodeling depended on the use of appropriate scaffolds for drug delivery. The release profiles from the scaffolds were used to design an optimal delivery system to treat critical size cranial defects in a rodent model. The ability of local FTY720 delivery to maximize bone regeneration was evaluated with microcomputed tomography (microCT) and histology. Following 4 weeks of defect healing, FTY720 delivery from 85:15 PLAGA scaffolds resulted in a significant increase in bone volumes in the defect region compared to the controls. 85:15 microsphere scaffolds maintain their structural integrity over a longer period of time, and cause an initial burst release of FTY720 due to surface localization of the drug. This encourages cellular in-growth and an increase in new bone formation. PMID:23640833

Delivery of S1P receptor-targeted drugs via biodegradable polymer scaffolds enhances bone regeneration in a critical size cranial defect.

PubMed

Das, Anusuya; Tanner, Shaun; Barker, Daniel A; Green, David; Botchwey, Edward A

2014-04-01

Biodegradable polymer scaffolds can be used to deliver soluble factors to enhance osseous remodeling in bone defects. To this end, we designed a poly(lactic-co-glycolic acid) (PLAGA) microsphere scaffold to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors. The microsphere scaffolds were created from fast degrading 50:50 PLAGA and/or from slow-degrading 85:15 PLAGA. Temporal and spatial regulation of bone remodeling depended on the use of appropriate scaffolds for drug delivery. The release profiles from the scaffolds were used to design an optimal delivery system to treat critical size cranial defects in a rodent model. The ability of local FTY720 delivery to maximize bone regeneration was evaluated with micro-computed tomography (microCT) and histology. Following 4 weeks of defect healing, FTY720 delivery from 85:15 PLAGA scaffolds resulted in a significant increase in bone volumes in the defect region compared to the controls. A 85:15 microsphere scaffolds maintain their structural integrity over a longer period of time, and cause an initial burst release of FTY720 due to surface localization of the drug. This encourages cellular in-growth and an increase in new bone formation. Copyright © 2013 Wiley Periodicals, Inc.

3D Printing Polymers with Supramolecular Functionality for Biological Applications.

PubMed

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

2017-09-11

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

Nano silver diffusion behaviour on conductive polymer during doping process for high voltage application

NASA Astrophysics Data System (ADS)

Mohammad, A.; Mahmood, A.; Chin, K. T.; Danquah, M. K.; van Stratan, S.

2017-06-01

Conductive polymer had opened a new era of engineering for microelectronics and semiconductor applications. However, it is still a challenge for high voltage applications due to lower electrical conductivity compare to metals. This results tremendous energy losses during transmission and restricts its usage. In order to address such problem a novel method was investigated using nano silver particle doped iodothiophene since silver is the highest electrical conductive material. The experiments were carried out to study the organometallic diffusion behaviour of nanosilver doped iodothiophene with different concentration of iodothiophene. Five different mixing ratio between nanosilver and the solution of iodothiophene dissolved in diethyl ether were used which are 1:1.25, 1:1.5, 1:2.5, 1:3 and l:5. It was revealed that there is an effective threshold concentration of which the nano silver evenly distributed and there was no coagulation observed. These parameters laid the foundation of better doping process between the nano silver and the polymer significantly which would contribute developing conductive polymer towards high voltage application for industries that are vulnerable to corrosive environment.

Application of Wikis with Scaffolding Structure in Laboratory Reporting

ERIC Educational Resources Information Center

Ge, Changfeng

2012-01-01

This work demonstrates how a Wiki can be mapped into different learning stages during group-based lab reporting via an adequate scaffolding structure. The scaffolding structure of the Wiki-based group report is comprised of six constructs in sequence: Appendix, Methods, Results, Analysis, Introduction and Conclusion. The scaffolding structure was…

Glycodendritic structures based on Boltorn hyperbranched polymers and their interactions with Lens culinaris lectin.

PubMed

Arce, Eva; Nieto, Pedro M; Díaz, Vicente; Castro, Rossana García; Bernad, Antonio; Rojo, Javier

2003-01-01

Multivalent scaffolds bearing carbohydrates have been prepared to mediate biological processes where carbohydrates are involved. These systems consist of dendritic structures based on Boltorn H20 and H30 hyperbranched polymers to which carbohydrates are linked through a convenient spacer. Mannose has been chosen as a sugar unit to test the viability of this strategy. These glycodendritic compounds have been prepared in a few steps with good yields, showing a high solubility in physiological media and low toxicity. The binding of these dendritic polymers to the mannose-binding lectin Lens culinaris (LCA) was studied using STD-NMR experiments and quantitative precipitation assays. The results demonstrate the existence of a clear interaction between the mannose derivative systems and the Lens lectin where the dendritic scaffold does not have an important role in mannose binding but supplies the necessary multivalence for lectin cluster formation. These glycodendritic structures are able to interact with a receptor, and therefore they can be considered as promising tools for biological studies.

Design of nano- and microfiber combined scaffolds by electrospinning of collagen onto starch-based fiber meshes: a man-made equivalent of natural extracellular matrix.

PubMed

Tuzlakoglu, Kadriye; Santos, Marina I; Neves, Nuno; Reis, Rui L

2011-02-01

Mimicking the structural organization and biologic function of natural extracellular matrix has been one of the main goals of tissue engineering. Nevertheless, the majority of scaffolding materials for bone regeneration highlights biochemical functionality in detriment of mechanical properties. In this work we present a rather innovative construct that combines in the same structure electrospun type I collagen nanofibers with starch-based microfibers. These combined structures were obtained by a two-step methodology and structurally consist in a type I collagen nano-network incorporated on a macro starch-based support. The morphology of the developed structures was assessed by several microscopy techniques and the collagenous nature of the nano-network was confirmed by immunohistochemistry. In addition, and especially regarding the requirements of large bone defects, we also successfully introduced the concept of layer by layer, as a way to produce thicker structures. In an attempt to recreate bone microenvironment, the design and biochemical composition of the combined structures also envisioned bone-forming cells and endothelial cells (ECs). The inclusion of a type I collagen nano-network induced a stretched morphology and improved the metabolic activity of osteoblasts. Regarding ECs, the presence of type I collagen on the combined structures provided adhesive support and obviated the need of precoating with fibronectin. It was also importantly observed that ECs on the nano-network organized into circular structures, a three-dimensional arrangement distinct from that observed for osteoblasts and resembling the microcappillary-like organizations formed during angiogenesis. By providing simultaneously physical and chemical cues for cells, the herein-proposed combined structures hold a great potential in bone regeneration as a man-made equivalent of extracellular matrix.

Hyper-elastic modeling and mechanical behavior investigation of porous poly-D-L-lactide/nano-hydroxyapatite scaffold material.

PubMed

Han, Quan Feng; Wang, Ze Wu; Tang, Chak Yin; Chen, Ling; Tsui, Chi Pong; Law, Wing Cheung

2017-07-01

Poly-D-L-lactide/nano-hydroxyapatite (PDLLA/nano-HA) can be used as the biological scaffold material in bone tissue engineering as it can be readily made into a porous composite material with excellent performance. However, constitutive modeling for the mechanical response of porous PDLLA/nano-HA under various stress conditions has been very limited so far. In this work, four types of fundamental compressible hyper-elastic constitutive models were introduced for constitutive modeling and investigation of mechanical behaviors of porous PDLLA/nano-HA. Moreover, the unitary expressions of Cauchy stress tensor have been derived for the PDLLA/nano-HA under uniaxial compression (or stretch), biaxial compression (or stretch), pure shear and simple shear load by using the theory of continuum mechanics. The theoretical results determined from the approach based on the Ogden compressible hyper-elastic constitutive model were in good agreement with the experimental data from the uniaxial compression tests. Furthermore, this approach can also be used to predict the mechanical behaviors of the porous PDLLA/nano-HA material under the biaxial compression (or stretch), pure shear and simple shear. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication of β-tricalcium phosphate composite ceramic sphere-based scaffolds with hierarchical pore structure for bone regeneration.

PubMed

He, Fupo; Qian, Guowen; Ren, Weiwei; Li, Jiyan; Fan, Peirong; Shi, Haishan; Shi, Xuetao; Deng, Xin; Wu, Shanghua; Ye, Jiandong

2017-04-24

Polymer sphere-based scaffolds, which are prepared by bonding the adjacent spheres via sintering the randomly packed spheres, feature uniform pore structure, full three-dimensional (3D) interconnection, and considerable mechanical strength. However, bioceramic sphere-based scaffolds fabricated by this method have never been reported. Due to high melting temperature of bioceramic, only limited diffusion rate can be achieved when sintering the bioceramic spheres, which is far from enough to form robust bonding between spheres. In the present study, for the first time we fabricated 3D interconnected β-tricalcium phosphate ceramic sphere-based (PG/TCP) scaffolds by introducing phosphate-based glass (PG) as sintering additive and placing uniaxial pressure during the sintering process. The sintering mechanism of PG/TCP scaffolds was unveiled. The PG/TCP scaffolds had hierarchical pore structure, which was composed by interconnected macropores (>200 μm) among spheres, pores (20–120 μm) in the interior of spheres, and micropores (1–3 μm) among the grains. During the sintering process, partial PG reacted with β-TCP, forming β-Ca2P2O7; metal ions from PG substituted to Ca2+ sites of β-TCP. The mechanical properties (compressive strength 2.8–10.6 MPa; compressive modulus 190–620 MPa) and porosity (30%–50%) of scaffolds could be tailored by manipulating the sintering temperatures. The introduction of PG accelerated in vitro degradation of scaffolds, and the PG/TCP scaffolds showed good cytocompatibility. This work may offer a new strategy to prepare bioceramic scaffolds with satisfactory physicochemical properties for application in bone regeneration.

Laminated electrospun nHA/PHB-composite scaffolds mimicking bone extracellular matrix for bone tissue engineering.

PubMed

Chen, Zhuoyue; Song, Yue; Zhang, Jing; Liu, Wei; Cui, Jihong; Li, Hongmin; Chen, Fulin

2017-03-01

Electrospinning is an effective means to generate nano- to micro-scale polymer fibers resembling native extracellular matrix for tissue engineering. However, a major problem of electrospun materials is that limited pore size and porosity may prevent adequate cellular infiltration and tissue ingrowth. In this study, we first prepared thin layers of hydroxyapatite nanoparticle (nHA)/poly-hydroxybutyrate (PHB) via electrospinning. We then laminated the nHA/PHB thin layers to obtain a scaffold for cell seeding and bone tissue engineering. The results demonstrated that the laminated scaffold possessed optimized cell-loading capacity. Bone marrow mesenchymal stem cells (MSCs) exhibited better adherence, proliferation and osteogenic phenotypes on nHA/PHB scaffolds than on PHB scaffolds. Thereafter, we seeded MSCs onto nHA/PHB scaffolds to fabricate bone grafts. Histological observation showed osteoid tissue formation throughout the scaffold, with most of the scaffold absorbed in the specimens 2months after implantation, and blood vessels ingrowth into the graft could be observed in the graft. We concluded that electrospun and laminated nanoscaled biocomposite scaffolds hold great therapeutic potential for bone regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

Polymer-Attached Functional Inorganic-Organic Hybrid Nano-Composite Aerogels

DTIC Science & Technology

2003-01-01

drugs. The chemistry to synthesize polyamino- siloxane based aerogel composite was discussed. In addition, two approaches to synthesize PHEMA aerogel... Composite Aerogels DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Materials...Proc. Vol. 740 © 2003 Materials Research Society 112.24 Polymer-Attached Functional Inorganic-Organic Hybrid Nano- composite Aerogels Xipeng Liu, Mingzhe

Apatite nano-crystalline surface modification of poly(lactide-co-glycolide) sintered microsphere scaffolds for bone tissue engineering: implications for protein adsorption.

PubMed

Jabbarzadeh, Ehsan; Nair, Lakshmi S; Khan, Yusuf M; Deng, Meng; Laurencin, Cato T

2007-01-01

A number of bone tissue engineering approaches are aimed at (i) increasing the osteconductivity and osteoinductivity of matrices, and (ii) incorporating bioactive molecules within the scaffolds. In this study we examined the growth of a nano-crystalline mineral layer on poly(lactide-co-glycolide) (PLAGA) sintered microsphere scaffolds for tissue engineering. In addition, the influence of the mineral precipitate layer on protein adsorption on the scaffolds was studied. Scaffolds were mineralized by incubation in simulated body fluid (SBF). Scanning electron microscopy (SEM) analysis revealed that mineralized scaffolds possess a rough surface with a plate-like nanostructure covering the surface of microspheres. The results of protein adsorption and release studies showed that while the protein release pattern was similar for PLAGA and mineralized PLAGA scaffolds, precipitation of the mineral layer on PLAGA led to enhanced protein adsorption and slower protein release. Mineralization of tissue-engineered surfaces provides a method for both imparting bioactivity and controlling levels of protein adsorption and release.

Tandem SAM Domain Structure of Human Caskin1: A Presynaptic, Self-Assembling Scaffold for CASK

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

Stafford, Ryan L.; Hinde, Elizabeth; Knight, Mary Jane

2012-02-07

The synaptic scaffolding proteins CASK and Caskin1 are part of the fibrous mesh of proteins that organize the active zones of neural synapses. CASK binds to a region of Caskin1 called the CASK interaction domain (CID). Adjacent to the CID, Caskin1 contains two tandem sterile a motif (SAM) domains. Many SAM domains form polymers so they are good candidates for forming the fibrous structures seen in the active zone. We show here that the SAM domains of Caskin1 form a new type of SAM helical polymer. The Caskin1 polymer interface exhibits a remarkable segregation of charged residues, resulting in amore » high sensitivity to ionic strength in vitro. The Caskin1 polymers can be decorated with CASK proteins, illustrating how these proteins may work together to organize the cytomatrix in active zones.« 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

Impedance Biosensors and Deep Crater Salivary Gland Scaffolds for Tissue Engineering

NASA Astrophysics Data System (ADS)

Schramm, Robert A.

The salivary gland is a complex, branching organ whose primary biological function is the production of the fluid critical to alimentary function and the lubrication and maintenance of the oral cavity, saliva. The most frequent disruption of the salivary organ system is one in which the rate of supply of saliva into the oral cavity is diminished, and this may vary from a minor reduction, to near cessation. Regenerative medicine is a field which seeks to find ways to overcome the symptoms of organ malfunction or damage by inducing regrowth, repair and replacement of partial or whole organ function. Historically, the only methods available to medical experts were certain chemical drugs and transplantation, each of which suffers from significant risks and drawbacks. Tissue Engineering arose in the past few decades thanks to the seminal work of Robert Langer with the charter mission of finding new biomaterials and techniques to achieve these ends. The original concept of tissue engineering was the cell or tissue scaffold, which is supports the regrowth of cells by making intimate contact with adherent cells, and induces improved regrowth in vitro or in vivo by providing mechanical or chemical signaling cues. Epithelial cell types such as salivary glands have structural functional polarity at the cellular level, an apical side which faces a void, and a basal side which faces the support substrate. While 3D scaffolds such as hydrogels maximize interaction area between cells and substrate, they struggle to develop cohesive tissues beyond the scale of small cellular clusters . 2D scaffolds enforce a defined polarity by allowing cell interaction at only one side of the cell. Langer pioneered the use of polymer nanofibers as the premier synthetic 2D scaffold biomaterial, due to their exceptionally high nano-scale surface area, and collagen-imitating structure. Prior work has established PLGA nanofibers, which allow salivary cells to attach, proliferate, and generate a

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

Post-processing of polymer foam tissue scaffolds with high power ultrasound: a route to increased pore interconnectivity, pore size and fluid transport.

PubMed

Watson, N J; Johal, R K; Glover, Z; Reinwald, Y; White, L J; Ghaemmaghami, A M; Morgan, S P; Rose, F R A J; Povey, M J W; Parker, N G

2013-12-01

The aim of this work is to demonstrate that the structural and fluidic properties of polymer foam tissue scaffolds, post-fabrication but prior to the introduction of cells, can be engineered via exposure to high power ultrasound. Our analysis is supported by measurements of fluid uptake during insonification and imaging of the scaffold microstructure via X-ray computed tomography, scanning electron microscopy and acoustic microscopy. The ultrasonic treatment is performed with a frequency of 30 kHz, average intensities up to 80,000 Wm(-2) and exposure times up to 20 h. The treatment is found to increase the mean pore size by over 10%. More striking is the improvement in fluid uptake: for scaffolds with only 40% water uptake via standard immersion techniques, we can routinely achieve full saturation of the scaffold over approximately one hour of exposure. These desirable modifications occur with negligible loss of scaffold integrity and mass, and are optimized when the ultrasound treatment is coupled to a pre-wetting stage with ethanol. Our findings suggest that high power ultrasound is highly targeted towards flow obstructions in the scaffold architecture, thereby providing an efficient means to promote pore interconnectivity and fluid transport in thick foam tissue scaffolds. © 2013.

Ion Beam Etching: Replication of Micro Nano-structured 3D Stencil Masks

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

Weber, Patrick; Guibert, Edouard; Mikhailov, Serguei

2009-03-10

Ion beam LIGA allows the etching of 3D nano-structures by direct writing with a nano-sized beam. However, this is a relatively time consuming process. We propose here another approach for etching structures on large surfaces and faster, compared to the direct writing process. This approach consists of replicating 3D structured masks, by scanning an unfocused ion beam. A polymer substrate is placed behind the mask, as in UV photolithography. But the main advantage is that the 3D structure of the mask can be replicated into the polymer. For that purpose, the masks (developped at LMIS1, EPFL) are made of amore » silicon nitride membrane 100 nm thick, on which 3D gold structures up to 200 nm thick, are deposited. The 3D Au structures are made with the nanostencil method, based on successive gold deposition. The IMA institute, from HE-Arc, owns a High Voltage Engineering 1.7 MV Tandetron with both solid and gaseous negative ion sources, able to generate ions from almost every chemical element in a broad range of energies comprised between 400 keV and 6.8 MeV. The beam composition and energy are chosen in such a way, that ions lose a significant fraction of their energy when passing through the thickest regions of the mask. Ions passing through thinner regions of the mask loose a smaller fraction of their energy and etch the polymer with larger thicknesses, allowing a replication of the mask into the polymer. For our trials, we have used a carbon beam with an energy of 500 keV. The beam was focussed to a diameter of 5 mm with solid slits, in order to avoid border effects and thus ensure a homogeneous dose distribution on the beam diameter. The feasibility of this technique has been demonstrated, allowing industrial applications for micro-mould fabrication, micro-fluidics and micro-optics.« less

A novel albumin-based tissue scaffold for autogenic tissue engineering applications.

PubMed

Li, Pei-Shan; Lee, I-Liang; Yu, Wei-Lin; Sun, Jui-Sheng; Jane, Wann-Neng; Shen, Hsin-Hsin

2014-07-18

Tissue scaffolds provide a framework for living tissue regeneration. However, traditional tissue scaffolds are exogenous, composed of metals, ceramics, polymers, and animal tissues, and have a defined biocompatibility and application. This study presents a new method for obtaining a tissue scaffold from blood albumin, the major protein in mammalian blood. Human, bovine, and porcine albumin was polymerised into albumin polymers by microbial transglutaminase and was then cast by freeze-drying-based moulding to form albumin tissue scaffolds. Scanning electron microscopy and material testing analyses revealed that the albumin tissue scaffold possesses an extremely porous structure, moderate mechanical strength, and resilience. Using a culture of human mesenchymal stem cells (MSCs) as a model, we showed that MSCs can be seeded and grown in the albumin tissue scaffold. Furthermore, the albumin tissue scaffold can support the long-term osteogenic differentiation of MSCs. These results show that the albumin tissue scaffold exhibits favourable material properties and good compatibility with cells. We propose that this novel tissue scaffold can satisfy essential needs in tissue engineering as a general-purpose substrate. The use of this scaffold could lead to the development of new methods of artificial fabrication of autogenic tissue substitutes.

Cell-free 3D scaffold with two-stage delivery of miRNA-26a to regenerate critical-sized bone defects

PubMed Central

Zhang, Xiaojin; Li, Yan; Chen, Y. Eugene; Chen, Jihua; Ma, Peter X.

2016-01-01

MicroRNAs (miRNAs) are being developed to enhance tissue regeneration. Here we show that a hyperbranched polymer with high miRNA-binding affinity and negligible cytotoxicity can self-assemble into nano-sized polyplexes with a ‘double-shell' miRNA distribution and high transfection efficiency. These polyplexes are encapsulated in biodegradable microspheres to enable controllable two-stage (polyplexes and miRNA) delivery. The microspheres are attached to cell-free nanofibrous polymer scaffolds that spatially control the release of miR-26a. This technology is used to regenerate critical-sized bone defects in osteoporotic mice by targeting Gsk-3β to activate the osteoblastic activity of endogenous stem cells, thus addressing a critical challenge in regenerative medicine of achieving cell-free scaffold-based miRNA therapy for tissue engineering. PMID:26765931

An injection molding process for manufacturing highly porous and interconnected biodegradable polymer matrices for use as tissue engineering scaffolds.

PubMed

Kramschuster, Adam; Turng, Lih-Sheng

2010-02-01

In this research, injection molding was combined with a novel material combination, supercritical fluid processing, and particulate leaching techniques to produce highly porous and interconnected structures that have the potential to act as scaffolds for tissue engineering applications. The foamed structures, molded with polylactide (PLA) and polyvinyl alcohol (PVOH) with salt as the particulate, were processed without the aid of organic solvents, which can be detrimental to tissue growth. The pore size in the scaffolds is controlled by salt particulates and interconnectivity is achieved by the co-continuous blending morphology of biodegradable PLA matrix with water-soluble PVOH. Carbon dioxide (CO(2)) at the supercritical state is used to serve as a plasticizer, thereby imparting moldability of blends even with an ultra high salt particulate content, and allows the use of low processing temperatures, which are desirable for temperature-sensitive biodegradable polymers. Interconnected pores of approximately 200 microm in diameter and porosities of approximately 75% are reported and discussed.

Polyester type polyHIPE scaffolds with an interconnected porous structure for cartilage regeneration

NASA Astrophysics Data System (ADS)

Naranda, Jakob; Sušec, Maja; Maver, Uroš; Gradišnik, Lidija; Gorenjak, Mario; Vukasović, Andreja; Ivković, Alan; Rupnik, Marjan Slak; Vogrin, Matjaž; Krajnc, Peter

2016-06-01

Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50-170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation.

Polyester type polyHIPE scaffolds with an interconnected porous structure for cartilage regeneration

PubMed Central

Naranda, Jakob; Sušec, Maja; Maver, Uroš; Gradišnik, Lidija; Gorenjak, Mario; Vukasović, Andreja; Ivković, Alan; Rupnik, Marjan Slak; Vogrin, Matjaž; Krajnc, Peter

2016-01-01

Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50–170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation. PMID:27340110

Evaluation of mechanical property and bioactivity of nano-bioglass 45S5 scaffold coated with poly-3-hydroxybutyrate.

PubMed

Montazeri, Mahbobeh; Karbasi, Saeed; Foroughi, Mohammad Reza; Monshi, Ahmad; Ebrahimi-Kahrizsangi, Reza

2015-02-01

One of the major challenges facing researchers of tissue engineering is scaffold design with desirable physical and mechanical properties for growth and proliferation of cells and tissue formation. In this research, firstly, nano-bioglass powder with grain sizes of 55-56 nm was prepared by melting method of industrial raw materials at 1,400 °C. Then the porous ceramic scaffold of bioglass with 30, 40 and 50 wt% was prepared by using the polyurethane sponge replication method. The scaffolds were coated with poly-3-hydroxybutyrate (P3HB) for 30 s and 1 min in order to increase the scaffold's mechanical properties. XRD, XRF, SEM, FE-SEM and FT-IR were used for phase and component studies, morphology, particle size and determination of functional groups, respectively. XRD and XRF results showed that the type of the produced bioglass was 45S5. The results of XRD and FT-IR showed that the best temperature to produce bioglass scaffold was 600 °C, in which Na2Ca2Si3O9 crystal is obtained. By coating the scaffolds with P3HB, a composite scaffold with optimal porosity of 80-87% in 200-600 μm and compression strength of 0.1-0.53 MPa was obtained. According to the results of compressive strength and porosity tests, the best kind of scaffold was produced with 30 wt% of bioglass immersed for 1 min in P3HB. To evaluate the bioactivity of the scaffold, the SBF solution was used. The selected scaffold (30 wt% bioglass/6 wt% P3HB) was maintained for up to 4 weeks in this solution at an incubation temperature of 37 °C. The XRD, SEM EDXA and AAS tests were indicative of hydroxyapatite formation on the surface of bioactive scaffold. This scaffold has some potential to use in bone tissue engineering.

Fabrication and Handling of 3D Scaffolds Based on Polymers and Decellularized Tissues.

PubMed

Shpichka, Anastasia; Koroleva, Anastasia; Kuznetsova, Daria; Dmitriev, Ruslan I; Timashev, Peter

2017-01-01

Polymeric, ceramic and hybrid material-based three-dimensional (3D) scaffold or matrix structures are important for successful tissue engineering. While the number of approaches utilizing the use of cell-based scaffold and matrix structures is constantly growing, it is essential to provide a framework of their typical preparation and evaluation for tissue engineering. This chapter describes the fabrication of 3D scaffolds using two-photon polymerization, decellularization and cell encapsulation methods and easy-to-use protocols allowing assessing the cell morphology, cytotoxicity and viability in these scaffolds.

Structure formation in fibrous materials based on poly-3-hydroxybutyrate for traumatology

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Sklyanchuk, E. D.; Staroverova, O. V.; Abbasov, T. A.; Guryev, V. V.; Akatov, V. S.; Fadeyeva, I. S.; Fesenko, N. I.; Filatov, Yu. N.; Iordanskii, A. L.

2015-10-01

The paper reviews the structure formation of fibrous materials based on poly-3-hydroxybutyrate depending on parameters of electrospinning and characteristics of polymer solution. Fiber structure was studied by DSC, ESR and SEM. The molecular weight affects the diameter and uniformity of the fiber. An electromechanical impact leads to an orientation of crystalline structure in the fiber. The design of an artificial bioresorbable implant based on nano- and microfibers of poly-3-hydroxybutyrate is created. Dynamics of growth of mesenchymal stem cells on poly-3-hydroxybutyrate scaffolds is studied. Successful field tests of implants of the Achilles tendon in Wistar rats are conducted.

Cell-matrix mechanical interaction in electrospun polymeric scaffolds for tissue engineering: Implications for scaffold design and performance.

PubMed

Kennedy, Kelsey M; Bhaw-Luximon, Archana; Jhurry, Dhanjay

2017-03-01

Engineered scaffolds produced by electrospinning of biodegradable polymers offer a 3D, nanofibrous environment with controllable structural, chemical, and mechanical properties that mimic the extracellular matrix of native tissues and have shown promise for a number of tissue engineering applications. The microscale mechanical interactions between cells and electrospun matrices drive cell behaviors including migration and differentiation that are critical to promote tissue regeneration. Recent developments in understanding these mechanical interactions in electrospun environments are reviewed, with emphasis on how fiber geometry and polymer structure impact on the local mechanical properties of scaffolds, how altering the micromechanics cues cell behaviors, and how, in turn, cellular and extrinsic forces exerted on the matrix mechanically remodel an electrospun scaffold throughout tissue development. Techniques used to measure and visualize these mechanical interactions are described. We provide a critical outlook on technological gaps that must be overcome to advance the ability to design, assess, and manipulate the mechanical environment in electrospun scaffolds toward constructs that may be successfully applied in tissue engineering and regenerative medicine. Tissue engineering requires design of scaffolds that interact with cells to promote tissue development. Electrospinning is a promising technique for fabricating fibrous, biomimetic scaffolds. Effects of electrospun matrix microstructure and biochemical properties on cell behavior have been extensively reviewed previously; here, we consider cell-matrix interaction from a mechanical perspective. Micromechanical properties as a driver of cell behavior has been well established in planar substrates, but more recently, many studies have provided new insights into mechanical interaction in fibrillar, electrospun environments. This review provides readers with an overview of how electrospun scaffold mechanics and

Three-dimensional micro/nano-scale structure fabricated by combination of non-volatile polymerizable RTIL and FIB irradiation

PubMed Central

Kuwabata, Susumu; Minamimoto, Hiro; Inoue, Kosuke; Imanishi, Akihito; Hosoya, Ken; Uyama, Hiroshi; Torimoto, Tsukasa; Tsuda, Tetsuya; Seki, Shu

2014-01-01

Room-temperature ionic liquid (RTIL) has been widely investigated as a nonvolatile solvent as well as a unique liquid material because of its interesting features, e.g., negligible vapor pressure and high thermal stability. Here we report that a non-volatile polymerizable RTIL is a useful starting material for the fabrication of micro/nano-scale polymer structures with a focused-ion-beam (FIB) system operated under high-vacuum condition. Gallium-ion beam irradiation to the polymerizable 1-allyl-3-ethylimidazolium bis((trifluoromethane)sulfonyl)amide RTIL layer spread on a Si wafer induced a polymerization reaction without difficulty. What is interesting to note is that we have succeeded in provoking the polymerization reaction anywhere on the Si wafer substrate by using FIB irradiation with a raster scanning mode. By this finding, two- and three-dimensional micro/nano-scale polymer structure fabrications were possible at the resolution of 500,000 dpi. Even intricate three-dimensional micro/nano-figures with overhang and hollow moieties could be constructed at the resolution of approximately 100 nm. PMID:24430465

Rotating microgravity-bioreactor cultivation enhances the hepatic differentiation of mouse embryonic stem cells on biodegradable polymer scaffolds.

PubMed

Wang, Yingjie; Zhang, Yunping; Zhang, Shichang; Peng, Guangyong; Liu, Tao; Li, Yangxin; Xiang, Dedong; Wassler, Michael J; Shelat, Harnath S; Geng, Yongjian

2012-11-01

Embryonic stem (ES) cells are pluripotent cells that are capable of differentiating all the somatic cell lineages, including those in the liver tissue. We describe the generation of functional hepatic-like cells from mouse ES (mES) cells using a biodegradable polymer scaffold and a rotating bioreactor that allows simulated microgravity. Cells derived from ES cells cultured in the three-dimensional (3D) culture system with exogenous growth factors and hormones can differentiate into hepatic-like cells with morphologic characteristics of typical mature hepatocytes. Reverse-transcription polymerase chain-reaction testing, Western blot testing, immunostaining, and flow cytometric analysis show that these cells express hepatic-specific genes and proteins during differentiation. Differentiated cells on scaffolds further exhibit morphologic traits and biomarkers characteristic of liver cells, including albumin production, cytochrome P450 activity, and low-density lipoprotein uptake. When these stem cell-bearing scaffolds are transplanted into severe combined immunodeficient mice, the 3D constructs remained viable, undergoing further differentiation and maturation of hepatic-like cells in vivo. In conclusion, the growth and differentiation of ES cells in a biodegradable polymer scaffold and a rotating microgravity bioreactor can yield functional and organizational hepatocytes useful for research involving bioartificial liver and engineered liver tissue.

A novel enzymatic bioelectrode system combining a redox hydrogel with a carbon NanoWeb.

PubMed

Little, Shannon J; Ralph, Stephen F; Mano, Nicolas; Chen, Jun; Wallace, Gordon G

2011-08-21

A novel bioelectrode system has been prepared in which an enzyme and a conducting polymer hydrogel are combined in a nanostructured scaffold. The latter consists of fibres of carbon NanoWeb, grown by chemical vapour deposition onto reticulated vitreous carbon (RVC). The catalytic currents produced by this new bioelectrode system are significantly larger than those obtained using conventional electrodes. This journal is © The Royal Society of Chemistry 2011

Nano-Sized Cyclodextrin-Based Molecularly Imprinted Polymer Adsorbents for Perfluorinated Compounds—A Mini-Review

PubMed Central

Karoyo, Abdalla H.; Wilson, Lee D.

2015-01-01

Recent efforts have been directed towards the design of efficient and contaminant selective remediation technology for the removal of perfluorinated compounds (PFCs) from soils, sediments, and aquatic environments. While there is a general consensus on adsorption-based processes as the most suitable methodology for the removal of PFCs from aquatic environments, challenges exist regarding the optimal materials design of sorbents for selective uptake of PFCs. This article reviews the sorptive uptake of PFCs using cyclodextrin (CD)-based polymer adsorbents with nano- to micron-sized structural attributes. The relationship between synthesis of adsorbent materials and their structure relate to the overall sorption properties. Hence, the adsorptive uptake properties of CD-based molecularly imprinted polymers (CD-MIPs) are reviewed and compared with conventional MIPs. Further comparison is made with non-imprinted polymers (NIPs) that are based on cross-linking of pre-polymer units such as chitosan with epichlorohydrin in the absence of a molecular template. In general, MIPs offer the advantage of selectivity, chemical tunability, high stability and mechanical strength, ease of regeneration, and overall lower cost compared to NIPs. In particular, CD-MIPs offer the added advantage of possessing multiple binding sites with unique physicochemical properties such as tunable surface properties and morphology that may vary considerably. This mini-review provides a rationale for the design of unique polymer adsorbent materials that employ an intrinsic porogen via incorporation of a macrocyclic compound in the polymer framework to afford adsorbent materials with tunable physicochemical properties and unique nanostructure properties. PMID:28347047

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.

Electrospinning for nano- to mesoscale photonic structures

NASA Astrophysics Data System (ADS)

Skinner, Jack L.; Andriolo, Jessica M.; Murphy, John P.; Ross, Brandon M.

2017-08-01

The fabrication of photonic and electronic structures and devices has directed the manufacturing industry for the last 50 years. Currently, the majority of small-scale photonic devices are created by traditional microfabrication techniques that create features by processes such as lithography and electron or ion beam direct writing. Microfabrication techniques are often expensive and slow. In contrast, the use of electrospinning (ES) in the fabrication of micro- and nano-scale devices for the manipulation of photons and electrons provides a relatively simple and economic viable alternative. ES involves the delivery of a polymer solution to a capillary held at a high voltage relative to the fiber deposition surface. Electrostatic force developed between the collection plate and the polymer promotes fiber deposition onto the collection plate. Issues with ES fabrication exist primarily due to an instability region that exists between the capillary and collection plate and is characterized by chaotic motion of the depositing polymer fiber. Material limitations to ES also exist; not all polymers of interest are amenable to the ES process due to process dependencies on molecular weight and chain entanglement or incompatibility with other polymers and overall process compatibility. Passive and active electronic and photonic fibers fabricated through the ES have great potential for use in light generation and collection in optical and electronic structures/devices. ES produces fiber devices that can be combined with inorganic, metallic, biological, or organic materials for novel device design. Synergistic material selection and post-processing techniques are also utilized for broad-ranging applications of organic nanofibers that span from biological to electronic, photovoltaic, or photonic. As the ability to electrospin optically and/or electronically active materials in a controlled manner continues to improve, the complexity and diversity of devices fabricated from this

Hierarchical Structure and Mechanical Improvement of an n-HA/GCO-PU Composite Scaffold for Bone Regeneration.

PubMed

Li, Limei; Zuo, Yi; Zou, Qin; Yang, Boyuan; Lin, Lili; Li, Jidong; Li, Yubao

2015-10-14

To improve the mechanical properties of bone tissue and achieve the desired bone tissue regeneration for orthopedic surgery, newly designed hydroxyapatite/polyurethane (HA/PU) porous scaffolds were developed via in situ polymerization. The results showed that the molecular modification of PU soft segments by glyceride of castor oil (GCO) can increase the scaffold compressive strength by 48% and the elastic modulus by 96%. When nano-HA (n-HA) particles were incorporated into the GCO-PU matrix, the compressive strength and elastic modulus further increased by 49 and 74%, from 2.91 to 4.34 MPa and from 95 to 165.36 MPa, respectively. The n-HA particles with fine dispersity not only improved the interface bonding with the GCO-PU matrix but also provided effective bioactivity for bonding with bone tissue. The hierarchical structure and mechanical quality of the n-HA/GCO-PU composite scaffold were determined to be appropriate for the growth of cells and the regeneration of bony tissues, demonstrating promising prospects for bone repair and regeneration.

Electrospun Poly(L-lactide)/Poly(ε-caprolactone) Blend Nanofibrous Scaffold: Characterization and Biocompatibility with Human Adipose-Derived Stem Cells

PubMed Central

Liao, Guiying; Peng, Ejun; Wu, Bolin; Wang, Yuxi; Zeng, Xiaoyong; Xie, Xiaolin

2013-01-01

The essence of tissue engineering is the fabrication of autologous cells or induced stem cells in naturally derived or synthetic scaffolds to form specific tissues. Polymer is thought as an appealing source of cell-seeded scaffold owing to the diversity of its physicochemical property and can be electrospun into nano-size to mimic natural structure. Poly (L-lactic acid) (PLLA) and poly (ε-caprolactone) (PCL) are both excellent aliphatic polyester with almost “opposite” characteristics. The controlling combination of PLLA and PCL provides varying properties and makes diverse applications. Compared with the copolymers of the same components, PLLA/PCL blend demonstrates its potential in regenerative medicine as a simple, efficient and scalable alternative. In this study, we electrospun PLLA/PCL blends of different weight ratios into nanofibrous scaffolds (NFS) and their properties were detected including morphology, porosity, degradation, ATR-FTIR analysis, stress-stain assay, and inflammatory reaction. To explore the biocompatibility of the NFS we synthesized, human adipose-derived stem cells (hASCs) were used to evaluate proliferation, attachment, viability and multi-lineage differentiation. In conclusion, the electrospun PLLA/PCL blend nanofibrous scaffold with the indicated weight ratios all supported hASCs well. However, the NFS of 1/1 weight ratio showed better properties and cellular responses in all assessments, implying it a biocompatible scaffold for tissue engineering. PMID:23990941

Effect of microstructure of nano- and micro-particle filled polymer composites on their tribo-mechanical performance

NASA Astrophysics Data System (ADS)

Devaprakasam, D.; Hatton, P. V.; Möbus, G.; Inkson, B. J.

2008-08-01

In this work we have investigated the influence of nanoscale and microscale structure on the tribo-mechanical performance and failure mechanisms of two biocompatible dental polymer composites, with different reinforcing particulates, using advanced microscopy techniques. Nano- and micro structural analysis reveals the shape, size and distribution of the particles in the composites. In the microparticle filled polymer composite (microcomposite), the particles are of irregular shape with sharp edges with non-uniform distribution in the matrix. However, in the nanoparticle filled composites (nanocomposite), filler particles are spherical in shape with uniform distribution in the matrix. From nanoindentation measurements, hardness and reduced modulus of the microcomposite were found to be heterogeneous. However, the hardness and reduced modulus of the nanocomposite were found to be homogeneous. The nanocomposite shows better tribo-mechanical performance compared to that of the microcomposite.

Fabrication and in vivo evaluation of an osteoblast-conditioned nano-hydroxyapatite/gelatin composite scaffold for bone tissue regeneration.

PubMed

Samadikuchaksaraei, Ali; Gholipourmalekabadi, Mazaher; Erfani Ezadyar, Elham; Azami, Mahmoud; Mozafari, Masoud; Johari, Behrooz; Kargozar, Saeid; Jameie, Seyed Behnamedin; Korourian, Alireza; Seifalian, Alexander M

2016-08-01

In this study, the effects of osteoblast-conditioning on mechanical behavior, biocompatibility, biodegradation and osteoinductive properties of a nano-hydroxyapatite/gelatin (HA/GEL) nanocomposite scaffold was investigated. The scaffold was fabricated using the layer solvent casting combined with the freeze-drying and lamination techniques. The scaffolds were conditioned by culture of osteoblasts on their surface and their elimination by a repeated freeze-thawing process. The potential of the osteoblast-conditioned HA/GEL (HA/GEL/OC) scaffold to support cell adhesion and growth and its cytotoxicity was assessed in vitro using rat mesenchymal stem cells. For in vivo studies, the HA/GEL/OC nanocomposite was implanted in the critical size bone defect created on rat calvarium and studied after 7, 30 and 90 days. The results showed that mechanical and in vitro biological properties of the scaffold were not affected by the process of conditioning. However, in vivo studies demonstrated that osteoblast-conditioning enhanced biocompatibility and osteoinductivity and of the nanocomposite scaffold. The osteoblast conditioning also accelerated collagen content during the bone healing. In the experimental group that received the HA/GEL/OC and MSCs, the newly formed bone occupied almost the entire defect (93.4 ± 3.3%) within 3 months. In conclusion, this study indicates that osteoblast-conditioning is a viable strategy for the development of bone tissue engineering scaffolds. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2001-2010, 2016. © 2016 Wiley Periodicals, Inc.

Anterior cruciate ligament regeneration using braided biodegradable scaffolds: in vitro optimization studies.

PubMed

Lu, Helen H; Cooper, James A; Manuel, Sharron; Freeman, Joseph W; Attawia, Mohammed A; Ko, Frank K; Laurencin, Cato T

2005-08-01

The anterior cruciate ligament (ACL) is the most commonly injured intra-articular ligament of the knee, and limitations in existing reconstruction grafts have prompted an interest in tissue engineered solutions. Previously, we reported on a tissue-engineered ACL scaffold fabricated using a novel, three-dimensional braiding technology. A critical factor in determining cellular response to such a graft is material selection. The objective of this in vitro study was to optimize the braided scaffold, focusing on material composition and the identification of an appropriate polymer. The selection criteria are based on cellular response, construct degradation, and the associated mechanical properties. Three compositions of poly-alpha-hydroxyester fibers, namely polyglycolic acid (PGA), poly-L-lactic acid (PLLA), and polylactic-co-glycolic acid 82:18 (PLAGA) were examined. The effects of polymer composition on scaffold mechanical properties and degradation were evaluated in physiologically relevant solutions. Prior to culturing with primary rabbit ACL cells, scaffolds were pre-coated with fibronectin (Fn, PGA-Fn, PLAGA-Fn, PLLA-Fn), an important protein which is upregulated during ligament healing. Cell attachment and growth were examined as a function of time and polymer composition. While PGA scaffolds measured the highest tensile strength followed by PLLA and PLAGA, its rapid degradation in vitro resulted in matrix disruption and cell death over time. PLLA-based scaffolds maintained their structural integrity and exhibited superior mechanical properties over time. The response of ACL cells was found to be dependent on polymer composition, with the highest cell number measured on PLLA-Fn scaffolds. Surface modification of polymer scaffolds with Fn improved cell attachment efficiency and effected the long-term matrix production by ACL cells on PLLA and PLAGA scaffolds. Therefore based on the overall cellular response and its temporal mechanical and degradation properties

Hyaluronic acid-based scaffolds for tissue engineering.

PubMed

Chircov, Cristina; Grumezescu, Alexandru Mihai; Bejenaru, Ludovic Everard

2018-01-01

Hyaluronic acid (HA) is a natural glycosaminoglycan found in the extracellular matrix of most connective tissues. Due to its chemical structure, HA is a hydrophilic polymer and it is characterized by a fast degradation rate. HA-based scaffolds for tissue engineering are intensively studied due to their increased biocompatibility, biodegradability and chemical modification. Depending on the processing technique, scaffolds can be prepared in the form of hydrogels, sponges, cryogels, and injectable hydrogels, all discussed in this review.

Nano-sponge ionic liquid-polymer composite electrolytes for solid-state lithium power sources

NASA Astrophysics Data System (ADS)

Liao, Kang-Shyang; Sutto, Thomas E.; Andreoli, Enrico; Ajayan, Pulickel; McGrady, Karen A.; Curran, Seamus A.

Solid polymer gel electrolytes composed of 75 wt.% of the ionic liquid, 1- n-butyl-2,3-dimethylimidazolium bis-trifluoromethanesulfonylimide with 1.0 M lithium bis-trifluoromethanesulfonylimide and 25 wt.% poly(vinylidenedifluoro-hexafluoropropene) are characterized as the electrolyte/separator in solid-state lithium batteries. The ionic conductivity of these gels ranges from 1.5 to 2.0 mS cm -1, which is several orders of magnitude more conductive than any of the more commonly used solid polymers, and comparable to the best solid gel electrolytes currently used in industry. TGA indicates that these polymer gel electrolytes are thermally stable to over 280 °C, and do not begin to thermally decompose until over 300 °C; exhibiting a significant advancement in the safety of lithium batteries. Atomic force microscopy images of these solid thin films indicate that these polymer gel electrolytes have the structure of nano-sponges, with a sub-micron pore size. For these thin film batteries, 150 charge-discharge cycles are run for Li xCoO 2 where x is cycled between 0.95 down to 0.55. Minimal internal resistance effects are observed over the charging cycles, indicating the high ionic conductivity of the ionic liquid solid polymer gel electrolyte. The overall cell efficiency is approximately 98%, and no significant loss in battery efficiency is observed over the 150 cycles.

Nano SiO2 and MgO improve the properties of porous β-TCP scaffolds via advanced manufacturing technology.

PubMed

Gao, Chengde; Wei, Pingpin; Feng, Pei; Xiao, Tao; Shuai, Cijun; Peng, Shuping

2015-03-25

Nano SiO2 and MgO particles were incorporated into β-tricalcium phosphate (β-TCP) scaffolds to improve the mechanical and biological properties. The porous cylindrical β-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped β-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from β-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (β-TCP) to 5.74 ± 0.62 MPa (β-TCP/SiO2), 9.02 ± 0.55 MPa (β-TCP/MgO) and 10.43 ± 0.28 MPa (β-TCP/SiO2/MgO), respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of β-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of β-TCP scaffold.

Nano SiO2 and MgO Improve the Properties of Porous β-TCP Scaffolds via Advanced Manufacturing Technology

PubMed Central

Gao, Chengde; Wei, Pingpin; Feng, Pei; Xiao, Tao; Shuai, Cijun; Peng, Shuping

2015-01-01

Nano SiO2 and MgO particles were incorporated into β-tricalcium phosphate (β-TCP) scaffolds to improve the mechanical and biological properties. The porous cylindrical β-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped β-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from β-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (β-TCP) to 5.74 ± 0.62 MPa (β-TCP/SiO2), 9.02 ± 0.55 MPa (β-TCP/MgO) and 10.43 ± 0.28 MPa (β-TCP/SiO2/MgO), respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of β-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of β-TCP scaffold. PMID:25815597

Impregnation of β-tricalcium phosphate robocast scaffolds by in situ polymerization.

PubMed

Martínez-Vázquez, Francisco J; Perera, Fidel H; van der Meulen, Inge; Heise, Andreas; Pajares, Antonia; Miranda, Pedro

2013-11-01

Ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LLA) was performed to impregnate β-tricalcium phosphate (β-TCP) scaffolds fabricated by robocasting. Concentrated colloidal inks prepared from β-TCP commercial powders were used to fabricate porous structures consisting of a 3D mesh of interpenetrating rods. ε-CL and LLA were in situ polymerized within the ceramic structure by using a lipase and stannous octanoate, respectively, as catalysts. The results show that both the macropores inside the ceramic mesh and the micropores within the ceramic rods are full of polymer in either case. The mechanical properties of scaffolds impregnated by in situ polymerization (ISP) are significantly increased over those of the bare structures, exhibiting similar values than those obtained by other, more aggressive, impregnation methods such as melt-immersion (MI). ISP using enzymatic catalysts requires a reduced processing temperature which could facilitate the incorporation of growth factors and other drugs into the polymer composition, thus enhancing the bioactivity of the composite scaffold. The implications of these results for the optimization of the mechanical and biological performance of scaffolds for bone tissue engineering applications are discussed. Copyright © 2013 Wiley Periodicals, Inc.

Functionalized scaffolds to enhance tissue regeneration

PubMed Central

Guo, Baolin; Lei, Bo; Li, Peng; Ma, Peter X.

2015-01-01

Tissue engineering scaffolds play a vital role in regenerative medicine. It not only provides a temporary 3-dimensional support during tissue repair, but also regulates the cell behavior, such as cell adhesion, proliferation and differentiation. In this review, we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nanocomposites of hydroxyapatite (HA) and bioactive glasses (BGs) with various biodegradable polymers. Furthermore, the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning, deposition and thermally induced phase separation is discussed. Moreover, bioactive molecules and surface properties of scaffolds are very important during tissue repair. Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed. PMID:25844177

Sphere-shaped nano-hydroxyapatite/chitosan/gelatin 3D porous scaffolds increase proliferation and osteogenic differentiation of human induced pluripotent stem cells from gingival fibroblasts.

PubMed

Ji, Jun; Tong, Xin; Huang, Xiaofeng; Wang, Tiancong; Lin, Zitong; Cao, Yazhou; Zhang, Junfeng; Dong, Lei; Qin, Haiyan; Hu, Qingang

2015-07-08

Hydroxyapatite (HA) is an important component of human bone and bone tissue engineering scaffolds. A plethora of bone tissue engineering scaffolds have been synthesized so far, including nano-HA/chitosan/gelatin (nHA/CG) scaffolds; and for seeding cells, stem cells, especially induced pluripotent stem cells (iPSCs), have been a promising cell source for bone tissue engineering recently. However, the influence of different HA nano-particle morphologies on the osteogenic differentiation of human iPSCs (hiPSCs) from human gingival fibroblasts (hGFs) is unknown. The purpose of this study was to investigate the osteogenic differentiation of hiPSCs from hGFs seeded on nHA/CG scaffolds with 2 shapes (rod and sphere) of nHA particles. Firstly, hGFs isolated from discarded normal gingival tissues were reprogrammed into hiPSCs. Secondly, hiPSCs were seeded on rod-like nHA/CG (rod-nHA/CG) and sphere-shaped nHA/CG (sphere-nHA/CG) scaffolds respectively and then cell/scaffold complexes were cultured in vitro. Scanning electron microscope, hematoxyline and eosin (HE) staining, Masson's staining, and quantitative real-time polymerase chain reaction techniques were used to examine hiPSC morphology, proliferation, and differentiation on rod-nHA/CG and sphere-nHA/CG scaffolds. Finally, hiPSCs composited with 2 kinds of nHA/CG were transplanted in vivo in a subcutaneous implantation model for 12 weeks; pure scaffolds were also transplanted as a blank control. HE, Masson's, and immunohistochemistry staining were applied to detect new bone regeneration ability. The results showed that sphere-nHA/CG significantly increased hiPSCs from hGF proliferation and osteogenic differentiation in vitro. hiPSCs and sphere-nHA/CG composities generated large bone, whereas hiPSCs and rod-nHA/CG composities produced tiny bone in vivo. Moreover, pure scaffolds without cells almost produced no bone. In conclusion, our work provided a potential innovative bone tissue engineering approach using

Organization of polymer chains onto long, single-wall carbon nano-tubes: effect of tube diameter and cooling method.

PubMed

Kumar, Sunil; Pattanayek, Sudip K; Pereira, Gerald G

2014-01-14

We use molecular dynamics simulations to investigate the arrangement of polymer chains when absorbed onto a long, single-wall carbon nano-tube (SWCNT). We study the conformation and organization of the polymer chains on the SWCNT and their dependence on the tube's diameter and the rate of cooling. We use two types of cooling processes: direct quenching and gradual cooling. The radial density distribution function and bond orientational order parameter are used to characterize the polymer chain structure near the surface. In the direct cooling process, the beads of the polymer chain organize in lamella-like patterns on the surface of the SWCNT with the long axis of the lamella parallel to the axis of the SWCNT. In a stepwise, gradual cooling process, the polymer beads form a helical pattern on the surface of a relatively thick SWCNT, but form a lamella-like pattern on the surface of a very thin SWCNT. We develop a theoretical (free energy) model to explain this difference in pattern structures for the gradual cooling process and also provide a qualitative explanation for the pattern that forms from the direct cooling process.

The deposition of thin titanium-nitrogen coatings on the surface of PCL-based scaffolds for vascular tissue engineering

NASA Astrophysics Data System (ADS)

Kudryavtseva, Valeriya; Stankevich, Ksenia; Kibler, Elina; Golovkin, Alexey; Mishanin, Alexander; Bolbasov, Evgeny; Choynzonov, Evgeny; Tverdokhlebov, Sergei

2018-04-01

Biodegradable polymer scaffolds for tissue engineering is a promising technology for therapies of patients suffering from the loss of tissue or its function including cardiac tissues. However, limitations such as hydrophobicity of polymers prevent cell attachment, cell conductivity, and endothelialization. Plasma modification of polymers allows producing materials for an impressive range of applications due to their unique properties. Here, we demonstrate the possibility of bioresorbable electrospun polycaprolacton (PCL) scaffold surface modification by reactive magnetron sputtering of the titanium target in a nitrogen atmosphere. The influence of the plasma treatment time on the structure and properties of electrospun PCL scaffolds was studied. We show that the plasma treatment does not change the physico-mechanical properties of electrospun PCL scaffolds, leads to an increase in PCL scaffold biocompatibility, and, simultaneously, increases their hydrophilicity. In conclusion, this modification method opens a route to producing scaffolds with enhanced biocompatibility for tissue engineered vascular grafts.

1, 6-diisocyanatohexane-extended poly (1, 4-butylene succinate / hydroxyl apatite nano particle scaffolds: Potential materials for bone regeneration applications

NASA Astrophysics Data System (ADS)

Kaur, Kulwinder; Singh, K. J.; Anand, Vikas; Bhatia, Gaurav; Nim, Lovedeep; Kaur, Manpreet; Arora, Daljit Singh

2017-05-01

Bioresorbable and bioactive scaffolds are promising materials for various biomedical applications including bone regeneration and drug delievrery. Authors present bioactive scaffolds prepared from 1, 6-diisocyanatohexane-extended poly (1, 4-butylene succinate) (PBSu-DCH) with different amount of hydroxyl apatite nanoparticles (nHAp) by solvent casting and particulate leaching techniques. Different weight ratios of nHAp (i.e. 0, 5 and 10 wt %) with fixed weight ratio (i.e. 10 wt %) of PBSu-DCH polymer have been prepared. Scaffolds have been assessed for their morphology, bioactivity, degradation, drug release and biological properties including cytotoxicity, cell attachment using MG-63 cell line and antimicrobial activity. Effectual drug release has been measured by incorporating gentamycin as an antibiotic in the scaffolds. The study is aimed at developing new biodegradable scaffolds to be used in skull, jaw and tooth socket for preserving bone mass.

Understanding selective molecular recognition in integrated carbon nanotube-polymer sensors by simulating physical analyte binding on carbon nanotube-polymer scaffolds.

PubMed

Lin, Shangchao; Zhang, Jingqing; Strano, Michael S; Blankschtein, Daniel

2014-08-28

Macromolecular scaffolds made of polymer-wrapped single-walled carbon nanotubes (SWCNTs) have been explored recently (Zhang et al., Nature Nanotechnology, 2013) as a new class of molecular-recognition motifs. However, selective analyte recognition is still challenging and lacks the underlying fundamental understanding needed for its practical implementation in biological sensors. In this report, we combine coarse-grained molecular dynamics (CGMD) simulations, physical adsorption/binding theories, and photoluminescence (PL) experiments to provide molecular insight into the selectivity of such sensors towards a large set of biologically important analytes. We find that the physical binding affinities of the analytes on a bare SWCNT partially correlate with their distribution coefficients in a bulk water/octanol system, suggesting that the analyte hydrophobicity plays a key role in determining the binding affinities of the analytes considered, along with the various specific interactions between the analytes and the polymer anchor groups. Two distinct categories of analytes are identified to demonstrate a complex picture for the correlation between optical sensor signals and the simulated binding affinities. Specifically, a good correlation was found between the sensor signals and the physical binding affinities of the three hormones (estradiol, melatonin, and thyroxine), the neurotransmitter (dopamine), and the vitamin (riboflavin) to the SWCNT-polymer scaffold. The four amino acids (aspartate, glycine, histidine, and tryptophan) and the two monosaccharides (fructose and glucose) considered were identified as blank analytes which are unable to induce sensor signals. The results indicate great success of our physical adsorption-based model in explaining the ranking in sensor selectivities. The combined framework presented here can be used to screen and select polymers that can potentially be used for creating synthetic molecular recognition motifs.

Synthesis and structural characterization of nano-hydroxyapatite biomaterials prepared by microwave processing

NASA Astrophysics Data System (ADS)

Ramli, Rosmamuhamadani; Arawi, Ainaa Zafirah Omar; Talari, Mahesh Kumar; Mahat, Mohd Muzamir; Jais, Umi Sarah

2012-07-01

Synthetic hydroxyapatite, (HA, Ca10(PO4)6(OH)2), is an attractive and widely utilized bio-ceramic material for orthopedic and dental implants because of its close resemblance of native tooth and bone crystal structure. Synthetic HA exhibits excellent osteoconductive properties. Osteoconductivity means the ability to provide the appropriate scaffold or template for bone formation. Calcium phosphate biomaterials [(HA), tri-calcium phosphate (TCP) and biphasic calcium phosphate (HA/TCP)] with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive and can be effective carriers of bone cell seeds. This HA can be used in bio-implants as well as drug delivery application due to the unique properties of HA. Biomaterials synthesized from the natural species like mussel shells have additional benefits such as high purity, less expensive and high bio compatibility. In this project, HA-nanoparticles of different crystallite size were prepared by microwave synthesis of precursors. High purity CaO was extracted from the natural mussel shells for the synthesis of nano HA. Dried nano HA powders were analyzed using X-Ray Diffraction (XRD) technique for the determination of crystal structure and impurity content. Scanning Electron Microscopic (SEM) investigation was employed for the morphological investigation of nano HA powders. From the results obtained, it was concluded that by altering the irradiation time, nano HA powders of different crystallite sizes and morphologies could be produced. Crystallite sizes calculated from the XRD patterns are found to be in the range of 10-55 nm depending on the irradiation time.

Proliferation, differentiation and gene expression of osteoblasts in boron-containing associated with dexamethasone deliver from mesoporous bioactive glass scaffolds.

PubMed

Wu, Chengtie; Miron, Richard; Sculean, Anton; Kaskel, Stefan; Doert, Thomas; Schulze, Renate; Zhang, Yufeng

2011-10-01

Boron is one of the trace elements in the human body which plays an important role in bone growth. Porous mesopore bioactive glass (MBG) scaffolds are proposed as potential bone regeneration materials due to their excellent bioactivity and drug-delivery ability. The aims of the present study were to develop boron-containing MBG (B-MBG) scaffolds by sol-gel method and to evaluate the effect of boron on the physiochemistry of B-MBG scaffolds and the response of osteoblasts to these scaffolds. Furthermore, the effect of dexamethasone (DEX) delivery in B-MBG scaffold system was investigated on the proliferation, differentiation and bone-related gene expression of osteoblasts. The composition, microstructure and mesopore properties (specific surface area, nano-pore volume and nano-pore distribution) of B-MBG scaffolds have been characterized. The effect of boron contents and large-pore porosity on the loading and release of DEX in B-MBG scaffolds were also investigated. The results have shown that the incorporation of boron into MBG scaffolds slightly decreases the specific surface area and pore volume, but maintains well-ordered mesopore structure and high surface area and nano-pore volume compared to non-mesopore bioactive glass. Boron contents in MBG scaffolds did not influence the nano-pore size distribution or the loading and release of DEX. B-MBG scaffolds have the ability to maintain a sustained release of DEX in a long-term span. Incorporating boron into MBG glass scaffolds led to a controllable release of boron ions and significantly improved the proliferation and bone-related gene expression (Col I and Runx2) of osteoblasts. Furthermore, the sustained release of DEX from B-MBG scaffolds significantly enhanced alkaline phosphatase (ALP) activity and gene expressions (Col I, Runx2, ALP and BSP) of osteoblasts. These results suggest that boron plays an important role in enhancing osteoblast proliferation in B-MBG scaffold system and DEX-loaded B-MBG scaffolds

[Histocompatibility of nano-hydroxyapatite/poly-co-glycolic acid tissue engineering bone modified by mesenchymal stem cells with vascular endothelial frowth factor].

PubMed

Zhang, Minglei; Wang, Dapeng; Yin, Ruofeng

2015-10-06

To explorec Histocompatibility of nano-hydroxyapatite/poly-co-glycolic acid tissue engineering bone modified by mesenchymal stem cells with vascular endothelial frowth factor transinfected. Rat bone marrow mesenchymal stem cells (BMSCs) was separated, using BMSCs as target cells, and then vascular endothelial growth factor (VEGF) gene was transfected. Composite bone marrow mesenchymal stem cells and cells transfected with nano-hydroxyapatite (HA)/polylactic-co-glycolic acid (PLGA). The composition of cell and scaffold was observed. The blank plasmid transfection was 39.1%, 40.1% in VEGF group. The cell adhesion and growth was found on the scaffold pore wall after 5 days, and the number of adherent cells in the nano-HA/PLGA composite scaffold material basically had no significant difference in both. Although the nano-HA/PLGA scaffold material is still not fully meet the requirements of the matrix material for bone tissue engineering, but good biocompatibility, structure is its rich microporous satisfaction in material mechanics, toughening, enhanced obviously. Composition scaffold with BMSCs transfected by VEGF plasmid, the ability of angiogenesis is promoted.

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

FINAL REPORT: Room Temperature Hydrogen Storage in Nano-Confined Liquids

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

VAJO, JOHN

2014-06-12

DOE continues to seek solid-state hydrogen storage materials with hydrogen densities of ≥6 wt% and ≥50 g/L that can deliver hydrogen and be recharged at room temperature and moderate pressures enabling widespread use in transportation applications. Meanwhile, development including vehicle engineering and delivery infrastructure continues for compressed-gas hydrogen storage systems. Although compressed gas storage avoids the materials-based issues associated with solid-state storage, achieving acceptable volumetric densities has been a persistent challenge. This project examined the possibility of developing storage materials that would be compatible with compressed gas storage technology based on enhanced hydrogen solubility in nano-confined liquid solvents. These materialsmore » would store hydrogen in molecular form eliminating many limitations of current solid-state materials while increasing the volumetric capacity of compressed hydrogen storage vessels. Experimental methods were developed to study hydrogen solubility in nano-confined liquids. These methods included 1) fabrication of composites comprised of volatile liquid solvents for hydrogen confined within the nano-sized pore volume of nanoporous scaffolds and 2) measuring the hydrogen uptake capacity of these composites without altering the composite composition. The hydrogen storage capacities of these nano-confined solvent/scaffold composites were compared with bulk solvents and with empty scaffolds. The solvents and scaffolds were varied to optimize the enhancement in hydrogen solubility that accompanies confinement of the solvent. In addition, computational simulations were performed to study the molecular-scale structure of liquid solvent when confined within an atomically realistic nano-sized pore of a model scaffold. Confined solvent was compared with similar simulations of bulk solvent. The results from the simulations were used to formulate a mechanism for the enhanced solubility and to

Microsecond MD Simulations of Nano-patterned Polymer Brushes on Self-Assembled Monolayers

NASA Astrophysics Data System (ADS)

Buie, Creighton; Qiu, Liming; Cheng, Kwan; Park, Soyeun

2010-03-01

Nano-patterned polymer brushes end-grafted onto self-assembled monolayers have gained increasing research interests due to their unique thermodynamic properties and their chemical and biomedical applications in colloids, biosensing and tissue engineering. So far, the interactions between the polymer brushes with the surrounding environments such as the floor and solvent at the nanometer length scale and microsecond time scale are still difficult to obtained experimentally and computationally. Using a Coarse-Grained MD approach, polymer brushes of different monomeric lengths, grafting density and hydrophobicity of the monomers grafted on self-assembled monolayers and in explicit solvent were studied. Molecular level information, such as lateral diffusion, transverse height and volume contour of the brushes, were calculated from our microsecond-MD simulations. Our results demonstrated the significance of the hydration of the polymer in controlling the conformational arrangement of the polymer brushes.

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.

MC3T3-E1 osteoblast attachment and proliferation on porous hydroxyapatite scaffolds fabricated with nanophase powder

PubMed Central

Smith, Ian O; McCabe, Laura R; Baumann, Melissa J

2006-01-01

Porous bone tissue engineering scaffolds were fabricated using both nano hydroxyapatite (nano HA) powder (20 nm average particle size) and micro HA powder (10 μm average particle size), resulting in sintered scaffolds of 59 vol% porosity and 8.6±1.9 μm average grain size and 72 vol% porosity and 588±55 nm average grain size, respectively. Scanning electron microscopy was used to measure both the grain size and pore size. MC3T3-E1 osteoblast (OB) attachment and proliferation on both nano HA and micro HA porous scaffolds were quantified. As expected, OB cell number was greater on nano HA scaffolds compared with similarly processed micro HA scaffolds 5 days after seeding, while OB attachment did not appear greater on the nano HA scaffolds (p<0.05). PMID:17722535

Accounting for structural compliance in nanoindentation measurements of bioceramic bone scaffolds

Treesearch

Juan Vivanco; Joseph E. Jakes; Josh Slane; Heidi-Lynn Ploeg

2014-01-01

Structural properties have been shown to be critical in the osteoconductive capacity and strength of bioactive ceramic bone scaffolds. Given the cellular foam-like structure of bone scaffolds, nanoindentation has been used as a technique to assess the mechanical properties of individual components of the scaffolds. Nevertheless, nanoindents placed on scaffolds may...

Self-organization in suspensions of end-functionalized semiflexible polymers under shear flow

NASA Astrophysics Data System (ADS)

Myung, Jin Suk; Winkler, Roland G.; Gompper, Gerhard

2015-12-01

The nonequilibrium dynamical behavior and structure formation of end-functionalized semiflexible polymer suspensions under flow are investigated by mesoscale hydrodynamic simulations. The hybrid simulation approach combines the multiparticle collision dynamics method for the fluid, which accounts for hydrodynamic interactions, with molecular dynamics simulations for the semiflexible polymers. In equilibrium, various kinds of scaffold-like network structures are observed, depending on polymer flexibility and end-attraction strength. We investigate the flow behavior of the polymer networks under shear and analyze their nonequilibrium structural and rheological properties. The scaffold structure breaks up and densified aggregates are formed at low shear rates, while the structural integrity is completely lost at high shear rates. We provide a detailed analysis of the shear- rate-dependent flow-induced structures. The studies provide a deeper understanding of the formation and deformation of network structures in complex materials.

Infinite Coordination Polymer Nano- and Micro-Particles

DTIC Science & Technology

2015-06-12

Mirkin, Tobin J. Marks, Joseph T. Hupp. SiO2 Aerogel-templated, Porous TiO2 Photoanodes for Enhanced Performances in Dye-Sensitized Solar Cells ...nano-scale ICPs and their selective surface functionalization, we examined if indeed these ICP-DNA hybrid structures could enter cells and...surface functionalization. In particular, we aimed to utilize this fundamental understanding for the realization of nano-scale ICP-biomolecule hybrids

Amorphous hydroxyapatite-sintered polymeric scaffolds for bone tissue regeneration: physical characterization studies.

PubMed

Cushnie, Emily K; Khan, Yusuf M; Laurencin, Cato T

2008-01-01

Given the inherent shortcomings of autografts and allografts, donor-site morbidity and risk of disease transmission, respectively, alternatives to traditional bone grafting options are warranted. To this end, poly(lactide-co-glycolide) (PLAGA) and in situ-synthesized amorphous hydroxyapatite (HA) were used to construct three-dimensional microsphere-based composite scaffolds of varying HA content for bone regeneration. In the current study, the effect of adding amorphous HA to the PLAGA scaffolds on their physical characteristics and in vitro degradation mechanism was investigated. Porosimetry and uniaxial compression testing were used to analyze the internal structure and elastic modulus of the scaffolds, respectively. Additionally, gel permeation chromatography (GPC) was performed to assess the polymer molecular weight over the course of an 8-week degradation study. HA content (17% or 27%) of the composite scaffolds was found to increase scaffold pore volume from 33.86% for pure polymer scaffolds, to 40.49% or 46.29%, depending on the amount of incorporated HA. This increased pore volume provided the composite scaffolds with a greater surface area and a corresponding decrease in elastic modulus. Scaffold degradation studies conducted over 8 weeks showed PLAGA to degrade in a first-order mechanism, with the rate of polymer degradation for the 27% HA composite scaffold being significantly slower than that of the pure PLAGA scaffold (degradation constants of 0.0324 and 0.0232 week(-1), respectively). These results suggest that the addition of amorphous HA to PLAGA microspheres resulted in porous, bioactive scaffolds that offer potential as alternative bone grafting materials for the field of regenerative medicine. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.

High aspect ratio template and method for producing same for central and peripheral nerve repair

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Chan, Christina (Inventor); Tuszynski, Mark Henry (Inventor); Mehrotra, Sumit (Inventor); Gros, Thomas (Inventor)

2011-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers. The scaffolds may be used in, among other applications, the repair of central and peripheral nerves. Scaffolds for the repair of peripheral nerves may include a reservoir for the sustained release of nerve growth factor. The scaffolds may also include a multifunctional polyelectrolyte layer for the sustained release of nerve growth factor and enhance biocompatibility.

Degradability, biocompatibility, and osteogenesis of biocomposite scaffolds containing nano magnesium phosphate and wheat protein both in vitro and in vivo for bone regeneration.

PubMed

Xia, Yan; Zhou, Panyu; Wang, Fei; Qiu, Chao; Wang, Panfeng; Zhang, Yuntong; Zhao, Liming; Xu, Shuogui

2016-01-01

In this study, bioactive scaffold of nano magnesium phosphate (nMP)/wheat protein (WP) composite (MWC) was fabricated. The results revealed that the MWC scaffolds had interconnected not only macropores (sized 400-600 μm) but also micropores (sized 10-20 μm) on the walls of macropores. The MWC scaffolds containing 40 w% nMP had an appropriate degradability in phosphate-buffered saline and produced a weak alkaline microenvironment. In cell culture experiments, the results revealed that the MWC scaffolds significantly promoted the MC3T3-E1 cell proliferation, differentiation, and growth into the scaffolds. The results of synchrotron radiation microcomputed tomography and analysis of the histological sections of the in vivo implantation revealed that the MWC scaffolds evidently improved the new bone formation and bone defects repair as compared with WP scaffolds. Moreover, it was found that newly formed bone tissue continued to increase with the gradual reduction of materials residual in the MWC scaffolds. Furthermore, the immunohistochemical analysis further offered the evidence of the stimulatory effects of MWC scaffolds on osteogenic-related cell differentiation and new bone regeneration. The results indicated that MWC scaffolds with good biocompability and degradability could promote osteogenesis in vivo, which would have potential for bone tissue repair.

Template-mediated nano-crystallite networks in semiconducting polymers.

PubMed

Kwon, Sooncheol; Yu, Kilho; Kweon, Kyoungchun; Kim, Geunjin; Kim, Junghwan; Kim, Heejoo; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Jehan; Lee, Seoung Ho; Lee, Kwanghee

2014-06-18

Unlike typical inorganic semiconductors with a crystal structure, the charge dynamics of π-conjugated polymers (π-CPs) are severely limited by the presence of amorphous portions between the ordered crystalline regions. Thus, the formation of interconnected pathways along crystallites of π-CPs is desired to ensure highly efficient charge transport in printable electronics. Here we report the formation of nano-crystallite networks in π-CP films by employing novel template-mediated crystallization (TMC) via polaron formation and electrostatic interaction. The lateral and vertical charge transport of TMC-treated films increased by two orders of magnitude compared with pristine π-CPs. In particular, because of the unprecedented room temperature and solution-processing advantages of our TMC method, we achieve a field-effect mobility of 0.25 cm(2) V(-1) s(-1) using a plastic substrate, which corresponds to the highest value reported thus far. Because our findings can be applied to various π-conjugated semiconductors, our approach is universal and is expected to yield high-performance printable electronics.

The effect of hydroxyapatite in biopolymer-based scaffolds on release of naproxen sodium.

PubMed

Asadian-Ardakani, Vahid; Saber-Samandari, Samaneh; Saber-Samandari, Saeed

2016-12-01

A scaffold capable of controlling drug release is highly desirable for bone tissue engineering. The objective of this study was to develop and characterize a highly porous biodegradable scaffold and evaluate the kinetic release behavior for the application of anti-inflammatory drug delivery. Porous scaffolds consisting of chitosan, poly(acrylic acid), and nano-hydroxyapatite were prepared using the freeze-drying method. The nanocomposite scaffolds were characterized for structure, pore size, porosity, and mechanical properties. The nanocomposite scaffolds were tested and characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDS), X-ray diffraction (XRD) analysis, and tensile test instrument. The results showed that the pores of the scaffolds were interconnected, and their sizes ranged from 145 µm to 213 μm. The mechanical properties were found close to those of trabecular bone of the same density. The ability of the scaffolds to deliver naproxen sodium as a model drug in vitro was investigated. The release profile of naproxen sodium was measured in a phosphate-buffered saline solution by a ultra-violet spectrophotometer that was controlled by the Fickian diffusion mechanism. These results indicated that the chitosan-graft-poly(acrylic acid)/nano-hydroxyapatite scaffold may be a promising biomedical scaffold for clinical use in bone tissue engineering with a potential for drug delivery. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2992-3003, 2016. © 2016 Wiley Periodicals, Inc.

Development of Semicrystalline Morphology of Poly(L-lactic acid) During Processing of a Vascular Scaffold

NASA Astrophysics Data System (ADS)

Ailianou, Artemis

New and promising treatments for coronary heart disease are enabled by vascular scaffolds made of poly(L-lactic acid) (PLLA), as demonstrated by Abbott Vascular's bioresorbable vascular scaffold. PLLA is a semicrystalline polymer whose degree of crystallinity and crystalline microstructure depend on the thermal and deformation history during processing. In turn, the semicrystalline morphology determines scaffold strength and biodegradation time. However, spatially-resolved information about the resulting material structure (crystallinity and crystal orientation) is needed to interpret in vivo observations. The first manufacturing step of the scaffold is tube expansion in a process similar to injection blow molding. Spatial uniformity of the tube microstructure is essential for the consistent production and performance of the final scaffold. For implantation into the artery, solid-state deformation below the glass transition temperature is imposed on a laser-cut subassembly to crimp it into a small diameter. Regions of localized strain during crimping are implicated in deployment behavior. To examine the semicrystalline microstructure development of the scaffold, we employed complementary techniques of scanning electron and polarized light microscopy, wide-angle X-ray scattering, and X-ray microdiffraction. These techniques enabled us to assess the microstructure at the micro and nano length scale. The results show that the expanded tube is very uniform in the azimuthal and axial directions and that radial variations are more pronounced. The crimping step dramatically changes the microstructure of the subassembly by imposing extreme elongation and compression. Spatial information on the degree and direction of chain orientation from X-ray microdiffraction data gives insight into the mechanism by which the PLLA dissipates the stresses during crimping, without fracture. Finally, analysis of the microstructure after deployment shows that it is inherited from the

A comparison study of nanofiber, microfiber, and new composite nano/microfiber polymers used as sorbents for on-line solid phase extraction in chromatography system.

PubMed

Háková, Martina; Havlíková, Lucie Chocholoušová; Chvojka, Jiří; Erben, Jakub; Solich, Petr; Švec, František; Šatínský, Dalibor

2018-09-06

Three different approaches has been used to obtain nano/micro fibers and their diversity and extraction properties were examined. The effect of their structure on stability in an ultra-high-performance liquid chromatography (UHPLC) system during on-line SPE procedure was monitored. Five types of various nano/micro fiber polymers were used as sorbents: polyamide 6 nanofibers, polyvinylidene difluoride nanofibers, polyethylene microfibers, and two new polycaprolactone microfiber/nanofiber and polycaprolactone microfibers/polyvinylidene difluoride nanofibers composite polymers. The fiber polymers were filled in a cartridge directly connected to the UHPLC system and tested. For each polymer, the optimal conditions of the on-line extraction were found and potential applicability on real samples was tested. The determination of ochratoxin A (OTA) in beer matrix was chosen as a case study. Relevant factors such as the mechanical and chemical stability of the nano/microfibers, filling the cartridges, fiber reusability and the possibility and the repeatability of all processes were involved in the proposed study. A new nano/micro composite sorbent consisting of polycaprolactone microfibers/polyvinylidene difluoride nanofibers was chosen as the most suitable sorbent for the on-line extraction of OTA from a beer matrix. The tested validation parameters had the value of intra-day precision lower than 1.48%, linearity in the range from 0.5 to 100 μg L -1 with r 2  ≥ 0.9999 for standard and matrix calibration curve, and recovery in the range 99.1-103.9% at five concentration levels. Long-term precision evaluated for 31 analyses over the period of three months did not exceed 2.9% RSD. It confirmed the column reusability and perfect stability of nano/micro composite sorbent in the presence of organic solvents and after repeated injection of a complex beer matrix. Copyright © 2018 Elsevier B.V. All rights reserved.

Fabrication of scalable tissue engineering scaffolds with dual-pore microarchitecture by combining 3D printing and particle leaching.

PubMed

Mohanty, Soumyaranjan; Sanger, Kuldeep; Heiskanen, Arto; Trifol, Jon; Szabo, Peter; Dufva, Marin; Emnéus, Jenny; Wolff, Anders

2016-04-01

Limitations in controlling scaffold architecture using traditional fabrication techniques are a problem when constructing engineered tissues/organs. Recently, integration of two pore architectures to generate dual-pore scaffolds with tailored physical properties has attracted wide attention in tissue engineering community. Such scaffolds features primary structured pores which can efficiently enhance nutrient/oxygen supply to the surrounding, in combination with secondary random pores, which give high surface area for cell adhesion and proliferation. Here, we present a new technique to fabricate dual-pore scaffolds for various tissue engineering applications where 3D printing of poly(vinyl alcohol) (PVA) mould is combined with salt leaching process. In this technique the sacrificial PVA mould, determining the structured pore architecture, was filled with salt crystals to define the random pore regions of the scaffold. After crosslinking the casted polymer the combined PVA-salt mould was dissolved in water. The technique has advantages over previously reported ones, such as automated assembly of the sacrificial mould, and precise control over pore architecture/dimensions by 3D printing parameters. In this study, polydimethylsiloxane and biodegradable poly(ϵ-caprolactone) were used for fabrication. However, we show that this technique is also suitable for other biocompatible/biodegradable polymers. Various physical and mechanical properties of the dual-pore scaffolds were compared with control scaffolds with either only structured or only random pores, fabricated using previously reported methods. The fabricated dual-pore scaffolds supported high cell density, due to the random pores, in combination with uniform cell distribution throughout the scaffold, and higher cell proliferation and viability due to efficient nutrient/oxygen transport through the structured pores. In conclusion, the described fabrication technique is rapid, inexpensive, scalable, and compatible

Self-assembly of silk-elastinlike protein polymers into three-dimensional scaffolds for biomedical applications

NASA Astrophysics Data System (ADS)

Zeng, Like

Production of brand new protein-based materials with precise control over the amino acid sequences at single residue level has been made possible by genetic engineering, through which artificial genes can be developed that encode protein-based materials with desired features. As an example, silk-elastinlike protein polymers (SELPs), composed of tandem repeats of amino acid sequence motifs from Bombyx mori (silkworm) silk and mammalian elastin, have been produced in this approach. SELPs have been studied extensively in the past two decades, however, the fundamental mechanism governing the self-assembly process to date still remains largely unresolved. Further, regardless of the unprecedented success when exploited in areas including drug delivery, gene therapy, and tissue augmentation, SELPs scaffolds as a three-dimensional cell culture model system are complicated by the inability of SELPs to provide the embedded tissue cells with appropriate biochemical stimuli essential for cell survival and function. In this dissertation, it is reported that the self-assembly of silk-elastinlike protein polymers (SELPs) into nanofibers in aqueous solutions can be modulated by tuning the curing temperature, the size of the silk blocks, and the charge of the elastin blocks. A core-sheath model was proposed for nanofiber formation, with the silk blocks in the cores and the hydrated elastin blocks in the sheaths. The folding of the silk blocks into stable cores -- affected by the size of the silk blocks and the charge of the elastin blocks -- plays a critical role in the assembly of silk-elastin nanofibers. The assembled nanofibers further form nanofiber clusters on the microscale, and the nanofiber clusters then coalesce into nanofiber micro-assemblies, interconnection of which eventually leads to the formation of three-dimensional scaffolds with distinct nanoscale and microscale features. SELP-Collagen hybrid scaffolds were also fabricated to enable independent control over the

Natural Polymer-Cell Bioconstructs for Bone Tissue Engineering.

PubMed

Titorencu, Irina; Albu, Madalina Georgiana; Nemecz, Miruna; Jinga, Victor V

2017-01-01

The major goal of bone tissue engineering is to develop bioconstructs which substitute the functionality of damaged natural bone structures as much as possible if critical-sized defects occur. Scaffolds that mimic the structure and composition of bone tissue and cells play a pivotal role in bone tissue engineering applications. First, composition, properties and in vivo synthesis of bone tissue are presented for the understanding of bone formation. Second, potential sources of osteoprogenitor cells have been investigated for their capacity to induce bone repair and regeneration. Third, taking into account that the main property to qualify one scaffold as a future bioconstruct for bone tissue engineering is the biocompatibility, the assessments which prove it are reviewed in this paper. Forth, various types of natural polymer- based scaffolds consisting in proteins, polysaccharides, minerals, growth factors etc, are discussed, and interaction between scaffolds and cells which proved bone tissue engineering concept are highlighted. Finally, the future perspectives of natural polymer-based scaffolds for bone tissue engineering are considered. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Collagen-grafted porous HDPE/PEAA scaffolds for bone reconstruction.

PubMed

Kim, Chang-Shik; Jung, Kyung-Hye; Kim, Hun; Kim, Chan-Bong; Kang, Inn-Kyu

2016-01-01

After tumor resection, bone reconstruction such as skull base reconstruction using interconnected porous structure is absolutely necessary. In this study, porous scaffolds for bone reconstruction were prepared using heat-pressing and salt-leaching methods. High-density polyethylene (HDPE) and poly(ethylene-co-acrylic acid) (PEAA) were chosen as the polymer composites for producing a porous scaffold of high mechanical strength and having high reactivity with biomaterials such as collagen, respectively. The porous structure was observed through surface images, and its intrusion volume and porosity were measured. Owing to the carboxylic acids on PEAA, collagen was successfully grafted onto the porous HDPE/PEAA scaffold, which was confirmed by FT-IR spectroscopy and electron spectroscopy for chemical analysis. Osteoblasts were cultured on the collagen-grafted porous scaffold, and their adhesion, proliferation, and differentiation were investigated. The high viability and growth of the osteoblasts suggest that the collagen-grafted porous HDPE/PEAA is a promising scaffold material for bone generation.

Mechanical evaluation of nHAp scaffold coated with poly-3-hydroxybutyrate for bone tissue engineering.

PubMed

Foroughi, Mohammad Reza; Karbasi, Saeed; Ebrahimi-Kahrizsangi, Reza

2013-02-01

Regeneration of bone, cartilage and osteochondral tissues by tissue engineering has attracted intense attention due to its potential advantages over the traditional replacement of tissues with synthetic implants. Nevertheless, there is still a dearth of ideal or suitable scaffolds based on porous biomaterials, and the present study was undertaken to develop and evaluate a useful porous composite scaffold system. In this study, nano hydroxyapatite (nHAp) powder made (about 35-45 nm) by heating at temperature of 900 degrees C and porous hydroxyapatite (40, 50 and 60 wt% solution) for making scaffold, by using Polyurethane sponge replication method. In order to increase the scaffolds mechanical properties, they coated with 2, 4 and 6 wt% Poly-3-hydroxybutyrate (P3HB) for 30 sec and 60 sec, respectively; after the scaffold coated by Polymer and survey results, this scaffold is nHAp/P3HB composite. Based on these results, this scaffold is an optimized one among three tested above mentioned composition and can be utilized in bone tissue engineering. In the result, the best of scaffold is with 50 wt% HAp and 6 wt% P3HB and porosity of present is between 80-90% with compressive strength and modulus 1.51 MPa and 22.73 MPa, respectively, that it can be application in bone tissue engineering.

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

PubMed Central

Liu, Cong; Li, Yanqing; Liao, Ruijin; Liao, Qiang; Tang, Chao

2018-01-01

Cellulose insulation polymer is an important component of oil-paper insulation, which is widely used in power transformer. The weight of the cellulose insulation polymer materials is as high as tens of tons in the larger converter transformer. Excellent performance of oil-paper insulation is very important for ensuring the safe operation of larger converter transformer. An effective way to improve the insulation and the physicochemical property of the oil impregnated insulation pressboard/paper is currently a popular research topic. In this paper, the polytetrafluoroethylene (PTFE) functional film was coated on the cellulose insulation pressboard by radio frequency (RF) magnetron sputtering to improve its breakdown voltage and the hydrophobicity properties. X-ray photoelectron spectroscopy (XPS) results show that the nano-structure PTFE functional film was successfully fabricated on the cellulose insulation pressboard surface. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) present that the nanoscale size PTFE particles were attached to the pressboard surface and it exists in the amorphous form. Atomic force microscopy (AFM) shows that the sputtered pressboard surface is still rough. The rough PTFE functional film and the reduction of the hydrophilic hydroxyl of the surface due to the shielding effect of PTFE improve the breakdown and the hydrophobicity properties of the cellulose insulation pressboard obviously. This paper provides an innovative way to improve the performance of the cellulose insulation polymer. PMID:29883376

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties.

PubMed

Hao, Jian; Liu, Cong; Li, Yanqing; Liao, Ruijin; Liao, Qiang; Tang, Chao

2018-05-21

Cellulose insulation polymer is an important component of oil-paper insulation, which is widely used in power transformer. The weight of the cellulose insulation polymer materials is as high as tens of tons in the larger converter transformer. Excellent performance of oil-paper insulation is very important for ensuring the safe operation of larger converter transformer. An effective way to improve the insulation and the physicochemical property of the oil impregnated insulation pressboard/paper is currently a popular research topic. In this paper, the polytetrafluoroethylene (PTFE) functional film was coated on the cellulose insulation pressboard by radio frequency (RF) magnetron sputtering to improve its breakdown voltage and the hydrophobicity properties. X-ray photoelectron spectroscopy (XPS) results show that the nano-structure PTFE functional film was successfully fabricated on the cellulose insulation pressboard surface. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) present that the nanoscale size PTFE particles were attached to the pressboard surface and it exists in the amorphous form. Atomic force microscopy (AFM) shows that the sputtered pressboard surface is still rough. The rough PTFE functional film and the reduction of the hydrophilic hydroxyl of the surface due to the shielding effect of PTFE improve the breakdown and the hydrophobicity properties of the cellulose insulation pressboard obviously. This paper provides an innovative way to improve the performance of the cellulose insulation polymer.

Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

PubMed

Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka

2013-07-01

In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next

Evaluation of the osteoinductive potential of a bio-inspired scaffold mimicking the osteogenic niche for bone augmentation.

PubMed

Minardi, Silvia; Corradetti, Bruna; Taraballi, Francesca; Sandri, Monica; Van Eps, Jeffrey; Cabrera, Fernando J; Weiner, Bradley K; Tampieri, Anna; Tasciotti, Ennio

2015-09-01

Augmentation of regenerative osteogenesis represents a premier clinical need, as hundreds of thousands of patients are left with insufficient healing of bony defects related to a host of insults ranging from congenital abnormalities to traumatic injury to surgically-induced deficits. A synthetic material that closely mimics the composition and structure of the human osteogenic niche represents great potential to successfully address this high demand. In this study, a magnesium-doped hydroxyapatite/type I collagen scaffold was fabricated through a biologically-inspired mineralization process and designed to mimic human trabecular bone. The composition of the scaffold was fully characterized by XRD, FTIR, ICP and TGA, and compared to human bone. Also, the scaffold microstructure was evaluated by SEM, while its nano-structure and nano-mechanical properties were evaluated by AFM. Human bone marrow-derived mesenchymal stem cells were used to test the in vitro capability of the scaffold to promote osteogenic differentiation. The cell/scaffold constructs were cultured up to 7 days and the adhesion, organization and proliferation of the cells were evaluated. The ability of the scaffold to induce osteogenic differentiation of the cells was assessed over 3 weeks and the correlate gene expression for classic genes of osteogenesis was assessed. Finally, when tested in an ectopic model in rabbit, the scaffold produced a large volume of trabecular bone in only two weeks, that subsequently underwent maturation over time as expected, with increased mature cortical bone formation, supporting its ability to promote bone regeneration in clinically-relevant scenarios. Altogether, these results confirm a high level of structural mimicry by the scaffold to the composition and structure of human osteogenic niche that translated to faster and more efficient osteoinduction in vivo--features that suggest such a biomaterial may have great utility in future clinical applications where bone

Enhancement in biological response of Ag-nano composite polymer membranes using plasma treatment for fabrication of efficient bio materials

NASA Astrophysics Data System (ADS)

Agrawal, Narendra Kumar; Sharma, Tamanna Kumari; Chauhan, Manish; Agarwal, Ravi; Vijay, Y. K.; Swami, K. C.

2016-05-01

Biomaterials are nonviable material used in medical devices, intended to interact with biological systems, which are becoming necessary for the development of artificial material for biological systems such as artificial skin diaphragm, valves for heart and kidney, lenses for eye etc. Polymers having novel properties like antibacterial, antimicrobial, high adhesion, blood compatibility and wettability are most suitable for synthesis of biomaterial, but all of these properties does not exist in any natural or artificial polymeric material. Nano particles and plasma treatment can offer these properties to the polymers. Hence a new nano-biomaterial has been developed by modifying the surface and chemical properties of Ag nanocomposite polymer membranes (NCPM) by Argon ion plasma treatment. These membranes were characterized using different techniques for surface and chemical modifications occurred. Bacterial adhesion and wettability were also tested for these membranes, to show direct use of this new class of nano-biomaterial for biomedical applications.

A building-block approach to 3D printing a multichannel, organ-regenerative scaffold.

PubMed

Wang, Xiaohong; Rijff, Boaz Lloyd; Khang, Gilson

2017-05-01

Multichannel scaffolds, formed by rapid prototyping technologies, retain a high potential for regenerative medicine and the manufacture of complex organs. This study aims to optimize several parameters for producing poly(lactic-co-glycolic acid) (PLGA) scaffolds by a low-temperature, deposition manufacturing, three-dimensional printing (3DP, or rapid prototyping) system. Concentration of the synthetic polymer solution, nozzle speed and extrusion rate were analysed and discussed. Polymer solution with a concentration of 12% w/v was determined as optimal for formation; large deviation of this figure failed to maintain the desired structure. The extrusion rate was also modified for better construct quality. Finally, several solid organ scaffolds, such as the liver, with proper wall thickness and intact contour were printed. This study gives basic instruction to design and fabricate scaffolds with de novo material systems, particularly by showing the approximation of variables for manufacturing multichannel PLGA scaffolds. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold.

PubMed

Lin, Hsin-Yi; Chen, Hsin-Hung; Chang, Shih-Hsin; Ni, Tsung-Sheng

2013-01-01

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young's modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds' swelling ratios decreased by 55% after 60 min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.

Preparation and characterization of poly (hydroxy butyrate)/chitosan blend scaffolds for tissue engineering applications

PubMed Central

Karbasi, Saeed; Khorasani, Saied Nouri; Ebrahimi, Somayeh; Khalili, Shahla; Fekrat, Farnoosh; Sadeghi, Davoud

2016-01-01

Background: Poly (hydroxy butyrate) (PHB) is a biodegradable and biocompatible polymer with good mechanical properties. This polymer could be a promising material for scaffolds if some features improve. Materials and Methods: In the present work, new PHB/chitosan blend scaffolds were prepared as a three-dimensional substrate in cartilage tissue engineering. Chitosan in different weight percent was added to PHB and solved in trifluoroacetic acid. Statistical Taguchi method was employed in the design of experiments. Results: The Fourier-transform infrared spectroscopy test revealed that the crystallization of PHB in these blends is suppressed with increasing the amount of chitosan. Scanning electron microscopy images showed a thin and rough top layer with a nodular structure, supported with a porous sub-layer in the surface of the scaffolds. In vitro degradation rate of the scaffolds was higher than pure PHB scaffolds. Maximum degradation rate has been seen for the scaffold with 90% wt. NaCl and 40% wt. chitosan. Conclusions: The obtained results suggest that these newly developed PHB/chitosan blend scaffolds may serve as a three-dimensional substrate in cartilage tissue engineering. PMID:28028517

Preparation and characterization of poly (hydroxy butyrate)/chitosan blend scaffolds for tissue engineering applications.

PubMed

Karbasi, Saeed; Khorasani, Saied Nouri; Ebrahimi, Somayeh; Khalili, Shahla; Fekrat, Farnoosh; Sadeghi, Davoud

2016-01-01

Poly (hydroxy butyrate) (PHB) is a biodegradable and biocompatible polymer with good mechanical properties. This polymer could be a promising material for scaffolds if some features improve. In the present work, new PHB/chitosan blend scaffolds were prepared as a three-dimensional substrate in cartilage tissue engineering. Chitosan in different weight percent was added to PHB and solved in trifluoroacetic acid. Statistical Taguchi method was employed in the design of experiments. The Fourier-transform infrared spectroscopy test revealed that the crystallization of PHB in these blends is suppressed with increasing the amount of chitosan. Scanning electron microscopy images showed a thin and rough top layer with a nodular structure, supported with a porous sub-layer in the surface of the scaffolds. In vitro degradation rate of the scaffolds was higher than pure PHB scaffolds. Maximum degradation rate has been seen for the scaffold with 90% wt. NaCl and 40% wt. chitosan. The obtained results suggest that these newly developed PHB/chitosan blend scaffolds may serve as a three-dimensional substrate in cartilage tissue engineering.

Novel calcified gum Arabic porous nano-composite scaffold for bone tissue regeneration.

PubMed

Hadavi, M; Hasannia, S; Faghihi, Sh; Mashayekhi, F; Zadeh, H H; Mostofi, S B

2017-07-08

The aim of this study was to investigate the biomechanical and biological properties of a nanocomposite scaffold containing both mineral and polysaccharide constituents. Hydroxyapatite nanoparticles (n-HA) was synthesized from dead abra ovata shells using wet chemical methods and was used in different ratios in concert with gum Arabic, a branched plant polysaccharide. N-HA/gum nanocomposite was fabricated with freeze-drying process and characterized by FTIR and SEM for chemical structure and morphology. Porosity was estimated using liquid substitution method. The scaffold mechanical properties were evaluated by compressive test measurement. Osteogenic differentiation was assessed using alkaline phosphatase production and biomineralization was evaluated using Alizarin red assay. Results demonstrated that the hydroxyapatite/gum Arabic nanocomposite had favorable biocompatibility and a similar structure to natural bone matrix. Porous nanocomposite possessed macropore networks with a porosity 87-93% and mean pore size ranging between 164 and 230 μm. The gum/HA with a ratio of 50% w/w HA had the highest compressive modulus of ∼75.3 MPa Pa (MPa) and the ultimate compressive stress of ∼16.6 MPa. C2C12 cells cultured on a scaffold with higher percentage (40 and 50 w/w) of HA demonstrated increased ALP levels and calcium deposition. The data from the present study demonstrated significant changes to the biomechanical properties and osteoconductivity of the nanocomposite scaffold by modulating its mineral content. Nanocomposite scaffolds containing gum and n-HA of 40-50% exhibited highest mechanical properties, as well as supported increased biomineralization. Copyright © 2017 Elsevier Inc. All rights reserved.

Parallel fabrication of macroporous scaffolds.

PubMed

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

2018-07-01

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

Coordination polymer-derived nano-sized zinc ferrite with excellent performance in nitro-explosive detection.

PubMed

Singha, Debal Kanti; Mahata, Partha

2017-08-29

Herein, a mixed metal coordination polymer, {(H 2 pip)[Zn 1/3 Fe 2/3 (pydc-2,5) 2 (H 2 O)]·2H 2 O} 1 {where H 2 pip = piperazinediium and pydc-2,5 = pyridine-2,5-dicarboxylate}, was successfully synthesized using a hydrothermal technique. To confirm the structure and phase purity of 1, single crystals of an isomorphous pure Fe compound, {(H 2 pip)[Fe(pydc-2,5) 2 (H 2 O)]·2H 2 O} 1a, were synthesized based on similar synthetic conditions. Single crystal X-ray data of 1a confirmed the one-dimensional anionic metal-organic coordination polymer hydrogen bonded with protonated piprazine (piperazinediium) and lattice water molecules. The phase purity of 1 and 1a were confirmed via powder X-ray diffraction. Compound 1 was systematically characterized using IR, TGA, SEM, and EDX elemental mapping analysis. Compound 1 was used as a single source precursor for the preparation of nano-sized ZnFe 2 O 4 via thermal decomposition. The as-obtained ZnFe 2 O 4 was fully characterized using PXRD, SEM, TEM, and EDX elemental mapping analysis. It was found that ZnFe 2 O 4 was formed in its pure form with particle size in the nano-dimension. The aqueous dispersion of nano-sized ZnFe 2 O 4 exhibits a strong emission at 402 nm upon excitation at 310 nm. This emissive property was employed for luminescence-based detection of nitroaromatic explosives in an aqueous medium through luminescence quenching for the first time. Importantly, selective detections have been observed for phenolic nitroaromatics based on differential luminescence quenching behaviour along with a detection limit of 57 ppb for 2,4,6-trinitrophenol (TNP) in water.

Exploring the Electronic Structure and Chemical Homogeneity of Individual Bi2Te3 Nanowires by Nano-Angle-Resolved Photoemission Spectroscopy.

PubMed

Krieg, Janina; Chen, Chaoyu; Avila, José; Zhang, Zeying; Sigle, Wilfried; Zhang, Hongbin; Trautmann, Christina; Asensio, Maria Carmen; Toimil-Molares, Maria Eugenia

2016-07-13

Due to their high surface-to-volume ratio, cylindrical Bi2Te3 nanowires are employed as model systems to investigate the chemistry and the unique conductive surface states of topological insulator nanomaterials. We report on nanoangle-resolved photoemission spectroscopy (nano-ARPES) characterization of individual cylindrical Bi2Te3 nanowires with a diameter of 100 nm. The nanowires are synthesized by electrochemical deposition inside channels of ion-track etched polymer membranes. Core level spectra recorded with submicron resolution indicate a homogeneous chemical composition along individual nanowires, while nano-ARPES intensity maps reveal the valence band structure at the single nanowire level. First-principles electronic structure calculations for chosen crystallographic orientations are in good agreement with those revealed by nano-ARPES. The successful application of nano-ARPES on single one-dimensional nanostructures constitutes a new avenue to achieve a better understanding of the electronic structure of topological insulator nanomaterials.

A novel chitosan-tussah silk fibroin/nano-hydroxyapatite composite bone scaffold platform with tunable mechanical strength in a wide range.

PubMed

Ran, Jiabing; Hu, Jingxiao; Sun, Guanglin; Chen, Si; Jiang, Pei; Shen, Xinyu; Tong, Hua

2016-12-01

Currently, great efforts have been made to enhance the mechanical strength of bone tissue engineering (BTE) scaffolds, which are composed of biopolymeric matrices and inorganic nano-fillers. But the tunability of mechanical strength in a wide range for BTE scaffolds has seldom been investigated in spite of the great importance of this performance. In this work, a chitosan-tussah silk fibroin/hydroxyapatite (CS-TSF/HAp) hydrogel was synthesized by using a novel in situ precipitation method. Through in situ inducing the conformation transition of TSF in the CS-TSF/HAp hydrogel, which could be monitored by XRD, FT-IR, TGA, and DTA, the elastic modulus and fracture strength of the final CS-TSF/HAp composite could be tailored in a wide range without changing its composition, morphology, roughness, and crystal structures. The elastic modulus of the CS-TSF/HAp composite ranged from ∼250 to ∼400MPa while its fracture strength ranged from ∼45 to ∼100MPa. In order to clarify the rationale behind this process, a speculative explanation was provided. In vitro cell culture indicated that MC3T3-E1 cells cultured on the CS-TSF/HAp composite had positive adhesion, proliferation, and differentiation potential. We believed that the CS-TSF/HAp composite could be used as an ideal scaffold platform for cell culture and implantation of bone reconstruction. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterizing the macro and micro mechanical properties of scaffolds for rotator cuff repair.

PubMed

Smith, Richard D J; Zargar, Nasim; Brown, Cameron P; Nagra, Navraj S; Dakin, Stephanie G; Snelling, Sarah J B; Hakimi, Osnat; Carr, Andrew

2017-11-01

Retearing after rotator cuff surgery is a major clinical problem. Numerous scaffolds are being used to try to reduce retear rates. However, few have demonstrated clinical efficacy. We hypothesize that this lack of efficacy is due to insufficient mechanical properties. Therefore, we compared the macro and nano/micro mechanical properties of 7 commercially available scaffolds to those of the human supraspinatus tendons, whose function they seek to restore. The clinically approved scaffolds tested were X-Repair, LARS ligament, Poly-Tape, BioFiber, GraftJacket, Permacol, and Conexa. Fresh frozen cadaveric human supraspinatus tendon samples were used. Macro mechanical properties were determined through tensile testing and rheometry. Scanning probe microscopy and scanning electron microscopy were performed to assess properties of materials at the nano/microscale (morphology, Young modulus, loss tangent). None of the scaffolds tested adequately approximated both the macro and micro mechanical properties of human supraspinatus tendon. Macroscale mechanical properties were insufficient to restore load-bearing function. The best-performing scaffolds on the macroscale (X-Repair, LARS ligament) had poor nano/microscale properties. Scaffolds approximating tendon properties on the nano/microscale (BioFiber, biologic scaffolds) had poor macroscale properties. Existing scaffolds failed to adequately approximate the mechanical properties of human supraspinatus tendons. Combining the macroscopic mechanical properties of a synthetic scaffold with the micro mechanical properties of biologic scaffold could better achieve this goal. Future work should focus on advancing techniques to create new scaffolds with more desirable mechanical properties. This may help improve outcomes for rotator cuff surgery patients. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

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.

Increasing the strength and bioactivity of collagen scaffolds using customizable arrays of 3D-printed polymer fibers.

PubMed

Mozdzen, Laura C; Rodgers, Ryan; Banks, Jessica M; Bailey, Ryan C; Harley, Brendan A C

2016-03-01

Tendon is a highly aligned connective tissue which transmits force from muscle to bone. Each year, people in the US sustain more than 32 million tendon injuries. To mitigate poor functional outcomes due to scar formation, current surgical techniques rely heavily on autografts. Biomaterial platforms and tissue engineering methods offer an alternative approach to address these injuries. Scaffolds incorporating aligned structural features can promote expansion of adult tenocytes and mesenchymal stem cells capable of tenogenic differentiation. However, appropriate balance between scaffold bioactivity and mechanical strength of these constructs remains challenging. The high porosity required to facilitate cell infiltration, nutrient and oxygen biotransport within three-dimensional constructs typically results in insufficient biomechanical strength. Here we describe the use of three-dimensional printing techniques to create customizable arrays of acrylonitrile butadiene styrene (ABS) fibers that can be incorporated into a collagen scaffold under development for tendon repair. Notably, mechanical performance of scaffold-fiber composites (elastic modulus, peak stress, strain at peak stress, and toughness) can be selectively manipulated by varying fiber-reinforcement geometry without affecting the native bioactivity of the collagen scaffold. Further, we report an approach to functionalize ABS fibers with activity-inducing growth factors via sequential oxygen plasma and carbodiimide crosslinking treatments. Together, we report an adaptable approach to control both mechanical strength and presence of biomolecular cues in a manner orthogonal to the architecture of the collagen scaffold itself. Tendon injuries account for more than 32 million injuries each year in the US alone. Current techniques use allografts to mitigate poor functional outcomes, but are not ideal platforms to induce functional regeneration following injury. Tissue engineering approaches using biomaterial

β-Tricalcium phosphate/poly(glycerol sebacate) scaffolds with robust mechanical property for bone tissue engineering.

PubMed

Yang, Kai; Zhang, Jing; Ma, Xiaoyu; Ma, Yifan; Kan, Chao; Ma, Haiyan; Li, Yulin; Yuan, Yuan; Liu, Changsheng

2015-11-01

Despite good biocompatibility and osteoconductivity, porous β-TCP scaffolds still lack the structural stability and mechanical robustness, which greatly limit their application in the field of bone regeneration. The hybridization of β-TCP with conventional synthetic biodegradable PLA and PCL only produced a limited toughening effect due to the plasticity of the polymers in nature. In this study, a β-TCP/poly(glycerol sebacate) scaffold (β-TCP/PGS) with well interconnected porous structure and robust mechanical property was prepared. Porous β-TCP scaffold was first prepared with polyurethane sponge as template and then impregnated into PGS pre-polymer solution with moderate viscosity, followed by in situ heat crosslinking and freezing-drying process. The results indicated that the freezing-drying under vacuum process could further facilitate crosslinking of PGS and formation of Ca(2+)-COO(-) ionic complexing and thus synergistically improved the mechanical strength of the β-TCP/PGS with in situ heat crosslinking. Particularly, the β-TCP/PGS with 15% PGS content after heat crosslinking at 130°C and freezing-drying at -50°C under vacuum exhibited an elongation at break of 375±25% and a compressive strength of 1.73MPa, 3.7-fold and 200-fold enhancement compared to the β-TCP, respectively. After the abrupt drop of compressive load, the β-TCP/PGS scaffolds exhibited a full recovery of their original shape. More importantly, the PGS polymer in the β-TCP/PGS scaffolds could direct the biomineralization of Ca/P from particulate shape into a nanofiber-interweaved structure. Furthermore, the β-TCP/PGS scaffolds allowed for cell penetration and proliferation, indicating a good cytobiocompatibility. It is believed that β-TCP/PGS scaffolds have great potential application in rigid tissue regeneration. Copyright © 2015 Elsevier B.V. All rights reserved.

Microporous nanofibrous fibrin-based scaffolds for craniofacial bone tissue engineering

NASA Astrophysics Data System (ADS)

Osathanon, Thanaphum

The fibrotic response of the body to synthetic polymers limits their success in tissue engineering and other applications. Though porous polymers have demonstrated improved healing, difficulty in controlling their pore sizes and pore interconnections has clouded the understanding of this phenomenon. In this study, a novel method to fabricate natural polymer/calcium phosphate composite scaffolds and immobilized alkaline phosphatase fibrin scaffolds with tightly controllable pore size, pore interconnection has been investigated. Microporous, nanofibrous fibrin scaffolds (FS) were fabricated using sphere-templating method. Calcium phosphate/fibrin composite scaffolds were created by solution deposition of calcium phosphate on fibrin surfaces or by direct incorporation of nanocrystalline hydroxyapatite (nHA). The SEM results showed that fibrin scaffolds exhibited a highly porous and interconnected structure. Osteoblast-like cells, obtained from murine calvaria, attached, spread and showed a polygonal morphology on the surface of the biomaterial. Multiple cell layers and fibrillar matrix deposition were observed. Moreover, cells seeded on mineralized fibrin scaffolds (MFS) exhibited significantly higher alkaline phosphatase activity as well as osteoblast marker gene expression compared to FS and nHA incorporated fibrin scaffolds (nHA/FS). These fibrin-based scaffolds were degraded both in vitro and in vivo. Furthermore, these scaffolds promoted bone formation in a mouse calvarial defect model and the bone formation was enhanced by addition of rhBMP-2. The second approach was to immobilize alkaline phosphatase (ALP) on fibrin scaffolds. ALP enzyme was covalently immobilized on the microporous nanofibrous fibrin scaffolds using 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride (EDC). The SEM results demonstrated mineral deposition on immobilized ALP fibrin scaffolds (ALP/FS) when incubated in medium supplemented with beta-glycerophosphate, suggesting that the

Magnetic high throughput screening system for the development of nano-sized molecularly imprinted polymers for controlled delivery of curcumin.

PubMed

Piletska, Elena V; Abd, Bashar H; Krakowiak, Agata S; Parmar, Anitha; Pink, Demi L; Wall, Katie S; Wharton, Luke; Moczko, Ewa; Whitcombe, Michael J; Karim, Kal; Piletsky, Sergey A

2015-05-07

Curcumin is a versatile anti-inflammatory and anti-cancer agent known for its low bioavailability, which could be improved by developing materials capable of binding and releasing drug in a controlled fashion. The present study describes the preparation of magnetic nano-sized Molecularly Imprinted Polymers (nanoMIPs) for the controlled delivery of curcumin and their high throughput characterisation using microtitre plates modified with magnetic inserts. NanoMIPs were synthesised using functional monomers chosen with the aid of molecular modelling. The rate of release of curcumin from five polymers was studied under aqueous conditions and was found to correlate well with the binding energies obtained computationally. The presence of specific monomers was shown to be significant in ensuring effective binding of curcumin and to the rate of release obtained. Characterisation of the polymer particles was carried out using dynamic light scattering (DLS) technique and scanning electron microscopy (SEM) in order to establish the relationship between irradiation time and particle size. The protocols optimised during this study could be used as a blueprint for the development of nanoMIPs capable of the controlled release of potentially any compound of interest.

Advanced nano lithography via soft materials-derived and reversible nano-patterning methodology for molding of infrared nano lenses

NASA Astrophysics Data System (ADS)

Park, Jae Hong; Jang, Hyun Ik; Park, Jun Yong; Jeon, Seok Woo; Kim, Woo Choong; Kim, Hee Yeoun; Ahn, Chi Won

2015-03-01

The methodology suggested in this research provides the great possibility of creating nanostructures composed of various materials, such as soft polymer, hard polymer, and metal, as well as Si. Such nanostructures are required for a vast range of optical and display devices, photonic components, physical devices, energy devices including electrodes of secondary batteries, fuel cells, solar cells, and energy harvesters, biological devices including biochips, biomimetic or biosimilar structured devices, and mechanical devices including micro- or nano-scale sensors and actuators.

Quadratic Electro-optic Effect in a Novel Nano-optical Polymer (iodine-doped polyisoprene)

NASA Astrophysics Data System (ADS)

Swamy, Rajendra; Titus, Jitto; Thakur, Mrinal

2004-03-01

In this report, exceptionally large quadratic electro-optic effect in a novel nano-optical polymer will be discussed. The material involved is cis-1,4-polyisoprene or natural rubber which is a nonconjugated conductive polymer[1,2].Upon doping with an acceptor such as iodine, an electron is transferred from its isolated double bond to the dopant leading to a charge-transfer complex. The positive charge (hole) thus created is localized around the double-bond site, within a nanometer dimension - thus, forming a nano-optical material. The quadratic electro-optic measurement on the doped polyisoprene film was made using field-induced birefringence method. The measured Kerr coefficient is about sixty six times that of nitrobenzene at 632 nm. Significant electroabsorption was also observed in this material at 632 nm. 1. M. Thakur, J. Macromol. Sci. - PAC, 2001, A38(12), 1337. 2. M. Thakur, S. Khatavkar and E.J. Parish, J. Macromol. Sci. - PAC, 2003, A40 (12), 1397.

Increasing the pore sizes of bone-mimetic electrospun scaffolds comprised of polycaprolactone, collagen I and hydroxyapatite to enhance cell infiltration

PubMed Central

Phipps, Matthew C.; Clem, William C.; Grunda, Jessica M.; Clines, Gregory A.; Bellis, Susan L.

2012-01-01

Bone-mimetic electrospun scaffolds consisting of polycaprolactone (PCL), collagen I and nanoparticulate hydroxyapatite (HA) have previously been shown to support the adhesion, integrin-related signaling and proliferation of mesenchymal stem cells (MSCs), suggesting these matrices serve as promising degradable substrates for osteoregeneration. However, the small pore sizes in electrospun scaffolds hinder cell infiltration in vitro and tissue-ingrowth into the scaffold in vivo, limiting their clinical potential. In this study, three separate techniques were evaluated for their capability to increase the pore size of the PCL/col I/nanoHA scaffolds: limited protease digestion, decreasing the fiber packing density during electro-spinning, and inclusion of sacrificial fibers of the water-soluble polymer PEO. The PEO sacrificial fiber approach was found to be the most effective in increasing scaffold pore size. Furthermore, the use of sacrificial fibers promoted increased MSC infiltration into the scaffolds, as well as greater infiltration of endogenous cells within bone upon placement of scaffolds within calvarial organ cultures. These collective findings support the use of sacrificial PEO fibers as a means to increase the porosity of complex, bone-mimicking electrospun scaffolds, thereby enhancing tissue regenerative processes that depend upon cell infiltration, such as vascularization and replacement of the scaffold with native bone tissue. PMID:22014462

3D conductive nanocomposite scaffold for bone tissue engineering.

PubMed

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli.

Alliance for NanoHealth Competitive Research Program

DTIC Science & Technology

2009-10-28

25-35 Guided Microvasculature Formation and Cellular Infiltration for Tissue Regeneration Applications in Nano-Structured Silk ...V, Davis G, Gordon A, Altman A, Reece G, Gascoyne P, Mathur AB, Endothelial and Stem Cell Interactions on Dielectrophoretically Aligned Fibrous Silk ...Interactions on Dielectrophoretically Aligned Fibrous Silk Fibroin-­‐Chitosan Scaffolds, Journal of Biomedical Materials Research, Accepted October

Bio-mimetic hollow scaffolds for long bone replacement

NASA Astrophysics Data System (ADS)

Müller, Bert; Deyhle, Hans; Fierz, Fabienne C.; Irsen, Stephan H.; Yoon, Jin Y.; Mushkolaj, Shpend; Boss, Oliver; Vorndran, Elke; Gburek, Uwe; Degistirici, Özer; Thie, Michael; Leukers, Barbara; Beckmann, Felix; Witte, Frank

2009-08-01

The tissue engineering focuses on synthesis or regeneration of tissues and organs. The hierarchical structure of nearly all porous scaffolds on the macro, micro- and nanometer scales resembles that of engineering foams dedicated for technical applications, but differ from the complex architecture of long bone. A major obstacle of scaffold architecture in tissue regeneration is the limited cell infiltration as the result of the engineering approaches. The biological cells seeded on the three-dimensional constructs are finally only located on the scaffold's periphery. This paper reports on the successful realization of calcium phosphate scaffolds with an anatomical architecture similar to long bones. Two base materials, namely nano-porous spray-dried hydroxyapatite hollow spheres and tri-calcium phosphate powder, were used to manufacture cylindrically shaped, 3D-printed scaffolds with micro-passages and one central macro-canal following the general architecture of long bones. The macro-canal is built for the surgical placement of nerves or larger blood vessels. The micro-passages allow for cell migration and capillary formation through the entire scaffold. Finally, the nanoporosity is essential for the molecule transport crucial for signaling, any cell nutrition and waste removal.

Nanocomposite scaffold fabrication by incorporating gold nanoparticles into biodegradable polymer matrix: Synthesis, characterization, and photothermal effect.

PubMed

Abdelrasoul, Gaser N; Farkas, Balazs; Romano, Ilaria; Diaspro, Alberto; Beke, Szabolcs

2015-11-01

Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532nm laser, known as the photothermal effect. Copyright © 2015 Elsevier B.V. All rights reserved.

Microfluidic active mixers employing ultra-high aspect-ratio rare-earth magnetic nano-composite polymer artificial cilia

NASA Astrophysics Data System (ADS)

Rahbar, Mona; Shannon, Lesley; Gray, Bonnie L.

2014-02-01

We present a new micromixer based on highly magnetic, flexible, high aspect-ratio, artificial cilia that are fabricated as individual micromixer elements or in arrays for improved mixing performance. These new cilia enable high efficiency, fast mixing in a microchamber, and are controlled by small electromagnetic fields. The artificial cilia are fabricated using a new micromolding process for nano-composite polymers. Cilia fibers with aspect-ratios as high as 8:0.13 demonstrate the fabrication technique's capability in creating ultra-high aspect-ratio microstructures. Cilia, which are realized in polydimethylsiloxane doped with rare-earth magnetic powder, are magnetized to produce permanent magnetic structures with bidirectional deflection capabilities, making them highly suitable as mixers controlled by electromagnetic fields. Due to the high magnetization level of the polarized nano-composite polymer, we are able to use miniature electromagnets providing relatively small magnetic fields of 1.1 to 7 mT to actuate the cilia microstructures over a very wide motion range. Mixing performances of a single cilium, as well as different arrays of multiple cilia ranging from 2 to 8 per reaction chamber, are characterized and compared with passive diffusion mixing performance. The mixer cilia are actuated at different amplitudes and frequencies to optimize mixing performance. We demonstrate that more than 85% of the total volume of the reaction chamber is fully mixed after 3.5 min using a single cilium mixer at 7 mT compared with only 20% of the total volume mixed with passive diffusion. The time to achieve over 85% mixing is further reduced to 70 s using an array of eight cilia microstructures. The novel microfabrication technique and use of rare-earth permanently-magnetizable nano-composite polymers in mixer applications has not been reported elsewhere by other researchers. We further demonstrate improved mixing over other cilia micromixers as enabled by the high aspect

Direct formation of nano-pillar arrays by phase separation of polymer blend for the enhanced out-coupling of organic light emitting diodes with low pixel blurring.

PubMed

Lee, Cholho; Han, Kyung-Hoon; Kim, Kwon-Hyeon; Kim, Jang-Joo

2016-03-21

We have demonstrated a simple and efficient method to fabricate OLEDs with enhanced out-coupling efficiencies and with low pixel blurring by inserting nano-pillar arrays prepared through the lateral phase separation of two immiscible polymers in a blend film. By selecting a proper solvent for the polymer and controlling the composition of the polymer blend, the nano-pillar arrays were formed directly after spin-coating of the polymer blend and selective removal of one phase, needing no complicated processes such as nano-imprint lithography. Pattern size and distribution were easily controlled by changing the composition and thickness of the polymer blend film. Phosphorescent OLEDs using the internal light extraction layer containing the nano-pillar arrays showed a 30% enhancement of the power efficiency, no spectral variation with the viewing angle, and only a small increment in pixel blurring. With these advantages, this newly developed method can be adopted for the commercial fabrication process of OLEDs for lighting and display applications.

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'

NASA Astrophysics Data System (ADS)

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y

A review of mechanical and tribological behaviour of polymer composite materials

NASA Astrophysics Data System (ADS)

Prabhakar, K.; Debnath, S.; Ganesan, R.; Palanikumar, K.

2018-04-01

Composite materials are finding increased applications in many industrial applications. A nano-composite is a matrix to which nanosized particles have been incorporated to drastically improve the mechanical performance of the original material. The structural components produced using nano-composites will exhibit a high strength-to-weight ratio. The properties of nano-composites have caused researchers and industries to consider using this material in several fields. Polymer nanocomposites consists of a polymer material having nano-particles or nano-fillers dispersed in the polymer matrix which may be of different shapes with at least one of the dimensions less than 100nm. In this paper, comprehensive review of polymer nanocomposites was done majorly in three different areas. First, mechanical behaviour of polymer nanocomposites which focuses on the mechanical property evaluation such as tensile strength, impact strength and modulus of elasticity based on the different combination of filler materials and nanoparticle inclusion. Second, wear behavior of Polymer composite materials with respect to different impingement angles and variation of filler composition using different processing techniques. Third, tribological (Friction and Wear) behaviour of nanocomposites using various combination of nanoparticle inclusion and time. Finally, it summarized the challenges and prospects of polymer nanocomposites.

Integrating biologically inspired nanomaterials and table-top stereolithography for 3D printed biomimetic osteochondral scaffolds

NASA Astrophysics Data System (ADS)

Castro, Nathan J.; O'Brien, Joseph; Zhang, Lijie Grace

2015-08-01

The osteochondral interface of an arthritic joint is notoriously difficult to regenerate due to its extremely poor regenerative capacity and complex stratified architecture. Native osteochondral tissue extracellular matrix is composed of numerous nanoscale organic and inorganic constituents. Although various tissue engineering strategies exist in addressing osteochondral defects, limitations persist with regards to tissue scaffolding which exhibit biomimetic cues at the nano to micro scale. In an effort to address this, the current work focused on 3D printing biomimetic nanocomposite scaffolds for improved osteochondral tissue regeneration. For this purpose, two biologically-inspired nanomaterials have been synthesized consisting of (1) osteoconductive nanocrystalline hydroxyapatite (nHA) (primary inorganic component of bone) and (2) core-shell poly(lactic-co-glycolic) acid (PLGA) nanospheres encapsulated with chondrogenic transforming growth-factor β1 (TGF-β1) for sustained delivery. Then, a novel table-top stereolithography 3D printer and the nano-ink (i.e., nHA + nanosphere + hydrogel) were employed to fabricate a porous and highly interconnected osteochondral scaffold with hierarchical nano-to-micro structure and spatiotemporal bioactive factor gradients. Our results showed that human bone marrow-derived mesenchymal stem cell adhesion, proliferation, and osteochondral differentiation were greatly improved in the biomimetic graded 3D printed osteochondral construct in vitro. The current work served to illustrate the efficacy of the nano-ink and current 3D printing technology for efficient fabrication of a novel nanocomposite hydrogel scaffold. In addition, tissue-specific growth factors illustrated a synergistic effect leading to increased cell adhesion and directed stem cell differentiation.

Electrospray neutralization process and apparatus for generation of nano-aerosol and nano-structured materials

DOEpatents

Bailey, Charles L.; Morozov, Victor; Vsevolodov, Nikolai N.

2010-08-17

The claimed invention describes methods and apparatuses for manufacturing nano-aerosols and nano-structured materials based on the neutralization of charged electrosprayed products with oppositely charged electrosprayed products. Electrosprayed products include molecular ions, nano-clusters and nano-fibers. Nano-aerosols can be generated when neutralization occurs in the gas phase. Neutralization of electrospan nano-fibers with molecular ions and charged nano-clusters may result in the formation of fibrous aerosols or free nano-mats. Nano-mats can also be produced on a suitable substrate, forming efficient nano-filters.

Multilayer porous UHMWPE scaffolds for bone defects replacement.

PubMed

Maksimkin, A V; Senatov, F S; Anisimova, N Yu; Kiselevskiy, M V; Zalepugin, D Yu; Chernyshova, I V; Tilkunova, N A; Kaloshkin, S D

2017-04-01

Reconstruction of the structural integrity of the damaged bone tissue is an urgent problem. UHMWPE may be potentially used for the manufacture of porous implants simulating as closely as possible the porous cancellous bone tissue. But the extremely high molecular weight of the polymer does not allow using traditional methods of foaming. Porous and multilayer UHMWPE scaffolds with nonporous bulk layer and porous layer that mimics cancellous bone architecture were obtained by solid-state mixing, thermopressing and washing in subcritical water. Structural and mechanical properties of the samples were studied. Porous UHMWPE samples were also studied in vitro and in vivo. The pores of UHMWPE scaffold are open and interconnected. Volume porosity of the obtained samples was 79±2%; the pore size range was 80-700μm. Strong connection of the two layers in multilayer UHMWPE scaffolds was observed with decreased number of fusion defects. Functionality of implants based on multilayer UHMWPE scaffolds is provided by the fixation of scaffolds in the bone defect through ingrowths of the connective tissue into the pores, which ensures the maintenance of the animals' mobility. Copyright © 2016 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2011-01-01

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

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.

Advances in skin regeneration: application of electrospun scaffolds.

PubMed

Norouzi, Mohammad; Boroujeni, Samaneh Moghadasi; Omidvarkordshouli, Noushin; Soleimani, Masoud

2015-06-03

The paucity of cellular and molecular signals essential for normal wound healing makes severe dermatological ulcers stubborn to heal. The novel strategies of skin regenerative treatments are focused on the development of biologically responsive scaffolds accompanied by cells and multiple biomolecules resembling structural and biochemical cues of the natural extracellular matrix (ECM). Electrospun nanofibrous scaffolds provide similar architecture to the ECM leading to enhancement of cell adhesion, proliferation, migration and neo tissue formation. This Review surveys the application of biocompatible natural, synthetic and composite polymers to fabricate electrospun scaffolds as skin substitutes and wound dressings. Furthermore, the application of biomolecules and therapeutic agents in the nanofibrous scaffolds viz growth factors, genes, antibiotics, silver nanoparticles, and natural medicines with the aim of ameliorating cellular behavior, wound healing, and skin regeneration are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D printed porous polycaprolactone/oyster shell powder (PCL/OSP) scaffolds for bone tissue engineering

NASA Astrophysics Data System (ADS)

Luo, Wenfeng; Zhang, Shuangying; Lan, Yuewei; Huang, Chen; Wang, Chao; Lai, Xuexu; Chen, Hanwei; Ao, Ningjian

2018-04-01

In this work, oyster shell powder (OSP) was used as the bio-filler and combined with polycaprolactone (PCL) through melt blending methodology. The PCL and PCL/OSP scaffolds were prepared using additive manufacturing process. All the 3D printed scaffolds hold a highly porosity and interconnected pore structures. OSP particles are dispersed in the polymer matrix, which helped to improve the degree of crystallinity and mineralization ability of the scaffolds. There was no significant cytotoxicity of the prepared scaffolds towards MG-63 cells, and all the scaffolds showed a well ALP activity. Therefore, PCL/OSP scaffolds had a high potential to be employed in the bone tissue engineering.

Polyurethane/fluor-hydroxyapatite nanocomposite scaffolds for bone tissue engineering. Part I: morphological, physical, and mechanical characterization

PubMed Central

Asefnejad, Azadeh; Behnamghader, Aliasghar; Khorasani, Mohammad Taghi; Farsadzadeh, Babak

2011-01-01

In this study, new nano-fluor-hydroxyapatite (nFHA)/polyurethane composite scaffolds were fabricated for potential use in bone tissue engineering. Polyester urethane samples were synthesized from polycaprolactone, hexamethylene diisocyanate, and 1,4-butanediol as chain extender. Nano fluor-hydroxyapatite (nFHA) was successfully synthesized by sol-gel method. The solid–liquid phase separation and solvent sublimation methods were used for preparation of the porous composites. Mechanical properties, chemical structure, and morphological characteristics of the samples were investigated by compressive test, Fourier transform infrared, and scanning electron microscopy (SEM) techniques, respectively. The effect of nFHA powder content on porosity and pore morphology was investigated. SEM images demonstrated that the scaffolds were constituted of interconnected and homogeneously distributed pores. The pore size of the scaffolds was in the range 50–250 μm. The result obtained in this research revealed that the porosity and pore average size decreased and compressive modulus increased with nFHA percentage. Considering morphological, physical, and mechanical properties, the scaffold with a higher ratio of nFHA has suitable potential use in tissue regeneration. PMID:21289986

Melt electrospinning of biodegradable polyurethane scaffolds

PubMed Central

Karchin, Ari; Simonovsky, Felix I.; Ratner, Buddy D.; Sanders, Joan E.

2014-01-01

Electrospinning from the melt, in contrast to from solution, is an attractive tissue engineering scaffold manufacturing process as it allows for the formation of small diameter fibers while eliminating potentially cytotoxic solvents. Despite this, there is a dearth of literature on scaffold formation via melt electrospinning. This is likely due to the technical challenges related to the need for a well-controlled high temperature setup and the difficulty in developing an appropriate polymer. In this paper, a biodegradable and thermally stable polyurethane (PU) is described specifically for use in melt electrospinning. Polymer formulations of aliphatic PUs based on (CH2)4-content diisocyanates, polycaprolactone (PCL), 1,4-butanediamine and 1,4-butanediol (BD) were evaluated for utility in the melt electrospinning process. The final polymer formulation, a catalyst-purified PU based on 1,4-butane diisocyanate, PCL and BD in a 4/1/3 molar ratio with a weight-average molecular weight of about 40 kDa, yielded a nontoxic polymer that could be readily electrospun from the melt. Scaffolds electrospun from this polymer contained point bonds between fibers and mechanical properties analogous to many in vivo soft tissues. PMID:21640853

Highly structured and surface modified poly(epsilon-caprolactone) scaffolds derived from co-continuous polymer blends for bone tissue engineering

NASA Astrophysics Data System (ADS)

Mehr, Nima Ghavidel

Chitosan, an important member of the polysaccharide family was used to alter the chemistry of PCL scaffolds and bring hydrophilicity to the surface. The deposition of a homogeneous chitosan layer on the surface of the PCL scaffolds was carried out using a Layer-by-Layer (LbL) selfassembly of poly(dialyldemethylammunium chloride) (PDADMAC) as cationic and poly(sodium 4-styrenesulfonate) (PSS) as anionic polyelectrolytes. The final negatively charged PSS layer allows for the addition of the positively charged chitosan as the outermost layer. Gravimetric measurements revealed that the addition of up to 3 layers leads to the formation of interdiffusing polyelectrolyte layers which do not allow for the formation of defined positive or negative charges. By increasing the number of polyelectrolyte layers with alternating charges, more welldefined layers are formed. Detailed analyses of O/C, N/C and S/C ratios by X-ray photoelectron spectroscopy (XPS) show that the PSS molecule dominates the surface as the last deposited polyelectrolyte layer at higher number of depositions (n=8), which can later be the surface for the deposition of chitosan. The LbL deposition of the chitosan layer on the LbL coating was then shown to be locally homogeneous at different depths within the scaffolds which also clarified that the LbL method is superior to the dip coating strategy. SEM analysis showed that there is a rough chitosan surface on the 2D solid PCL constructs whose thickness ranges from 550-700 nanometers. These results demonstrate that the application of LbL self-assembly of polyelectrolytes followed by the addition of chitosan as the outermost layer provides a route towards stable and homogeneous surface modification and has the potential to transform a classic fully interconnected porous synthetic polymer material to one with essentially complete chitosanlike surface characteristics. The osteogenic potential of PCL scaffolds with a chitosan coating using Layer-by-Layer (Lb

3D conductive nanocomposite scaffold for bone tissue engineering

PubMed Central

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874

Tuning Fano resonances with a nano-chamber of air.

PubMed

Chen, Jianjun; He, Keke; Sun, Chengwei; Wang, Yujia; Li, Hongyun; Gong, Qihuang

2016-05-15

By designing a polymer-film-coated asymmetric metallic slit structure that only contains one nanocavity side-coupled with a subwavelength plasmonic waveguide, the Fano resonance is realized in the experiment. The Fano resonance originates from the interference between the narrow resonant spectra of the radiative light from the nanocavity and the broad nonresonant spectra of the directly transmitted light from the slit. The lateral dimension of the asymmetric slit is only 825 nm. Due to the presence of the soft polymer film, a nano-chamber of air is constructed. Based on the opto-thermal effect, the air volume in the nano-chamber is expanded by a laser beam, which blueshifts the Fano resonance. This tunable Fano resonance in such a submicron slit structure with a nano-chamber is of importance in the highly integrated plasmonic circuits.

Biomimetic Silk Scaffolds with an Amorphous Structure for Soft Tissue Engineering.

PubMed

Sang, Yonghuan; Li, Meirong; Liu, Jiejie; Yao, Yuling; Ding, Zhaozhao; Wang, Lili; Xiao, Liying; Lu, Qiang; Fu, Xiaobing; Kaplan, David L

2018-03-21

Fine tuning physical cues of silk fibroin (SF) biomaterials to match specific requirements for different soft tissues would be advantageous. Here, amorphous SF nanofibers were used to fabricate scaffolds with better hierarchical extracellular matrix (ECM) mimetic microstructures than previous silk scaffolds. Kinetic control was introduced into the scaffold forming process, resulting in the direct production of water-stable scaffolds with tunable secondary structures and thus mechanical properties. These biomaterials remained with amorphous structures, offering softer properties than prior scaffolds. The fine mechanical tunability of these systems provides a feasible way to optimize physical cues for improved cell proliferation and enhanced neovascularization in vivo. Multiple physical cues, such as partly ECM mimetic structures and optimized stiffness, provided suitable microenvironments for tissue ingrowth, suggesting the possibility of actively designing bioactive SF biomaterials. These systems suggest a promising strategy to develop novel SF biomaterials for soft tissue repair and regenerative medicine.

[Strategies to choose scaffold materials for tissue engineering].

PubMed

Gao, Qingdong; Zhu, Xulong; Xiang, Junxi; Lü, Yi; Li, Jianhui

2016-02-01

Current therapies of organ failure or a wide range of tissue defect are often not ideal. Transplantation is the only effective way for long time survival. But it is hard to meet huge patients demands because of donor shortage, immune rejection and other problems. Tissue engineering could be a potential option. Choosing a suitable scaffold material is an essential part of it. According to different sources, tissue engineering scaffold materials could be divided into three types which are natural and its modified materials, artificial and composite ones. The purpose of tissue engineering scaffold is to repair the tissues or organs damage, so could reach the ideal recovery in its function and structure aspect. Therefore, tissue engineering scaffold should even be as close as much to the original tissue or organs in function and structure. We call it "organic scaffold" and this strategy might be the drastic perfect substitute for the tissues or organs in concern. Optimized organization with each kind scaffold materials could make up for biomimetic structure and function of the tissue or organs. Scaffold material surface modification, optimized preparation procedure and cytosine sustained-release microsphere addition should be considered together. This strategy is expected to open new perspectives for tissue engineering. Multidisciplinary approach including material science, molecular biology, and engineering might find the most ideal tissue engineering scaffold. Using the strategy of drawing on each other strength and optimized organization with each kind scaffold material to prepare a multifunctional biomimetic tissue engineering scaffold might be a good method for choosing tissue engineering scaffold materials. Our research group had differentiated bone marrow mesenchymal stem cells into bile canaliculi like cells. We prepared poly(L-lactic acid)/poly(ε-caprolactone) biliary stent. The scaffold's internal played a part in the long-term release of cytokines which

Titanium-scaffolded organic-monolithic stationary phases for ultra-high-pressure liquid chromatography.

PubMed

Vonk, Rudy J; Vaast, Axel; Eeltink, Sebastiaan; Schoenmakers, Peter J

2014-09-12

Organic-polymer monoliths with overall dimensions larger than one millimetre are prone to rupture - either within the monolith itself or between the monoliths and the containing wall - due to the inevitable shrinkage accompanying the formation of a cross-linked polymeric network. This problem has been addressed by creating titanium-scaffolded poly(styrene-co-divinylbenzene) (S-co-DVB) monoliths. Titanium-scaffolded monoliths were successfully used in liquid chromatography at very high pressures (up to 80MPa) and using gradients spanning the full range of water-acetonitrile compositions (0 to 100%). The kinetic-performance of (50-mm long) titanium-scaffolded monoliths was compared to that of similar monolith created in 1-mm i.d. glass-lined tubing at pressures up to 50MPa. The peak capacities obtained with the titanium-scaffolded column was about 30% lower. An increased Eddy-diffusion, due to the pillar-structure, and a decreased permeability are thought to be the main reasons for this reduced kinetic-performance. No decrease in performance was observed when the titanium-scaffolded columns were operated at pressures of 80MPa for up to 12h. The column-to-column repeatability (n=5) was acceptable in terms of observed peak widths at half heights (RSD ca. 10%) The run-to-run repeatability (n=135) in terms of retention times and peak widths at half height were found to be good. Titanium-scaffolded columns coupled in series up to a combined length of (200mm) were used for the analyses of a complex Escherichia coli protein sample. Our experiments demonstrate that columns based on titanium-scaffolded organic-polymer monolith can be operated under strenuous conditions without loss in performance. The titanium-scaffolded approach makes it feasible to create organic-polymer monoliths in wide-bore columns with accurate temperature control. Copyright © 2014 Elsevier B.V. All rights reserved.

Replication of cicada wing's nano-patterns by hot embossing and UV nanoimprinting.

PubMed

Hong, Sung-Hoon; Hwang, Jaeyeon; Lee, Heon

2009-09-23

The hydrophobicity of the cicada wing originates from its naturally occurring, surface nano-structure. The nano-structure of the cicada wing consists of an array of nano-sized pillars, 100 nm in diameter and 300 nm in height. In this study, the nano-structure of the cicada wing was successfully duplicated by using hot embossing lithography and UV nanoimprint lithography (NIL). The diameter and pitch of replication were the same as those of the original cicada wing and the height was a little smaller than that of the original master. The transmittance of the hot embossed PVC film was increased by 2-6% compared with that of the bare PVC film. The hydrophobicity was measured by water contact angle measurements. The water contact angle of the replica, made of UV cured polymer, was 132 degrees +/- 2 degrees , which was slightly lower than that of the original cicada wing (138 degrees +/- 2 degrees ), but much higher than that of the UV cured polymer surface without any nano-sized pillars (86 degrees ).

Replication of cicada wing's nano-patterns by hot embossing and UV nanoimprinting

NASA Astrophysics Data System (ADS)

Hong, Sung-Hoon; Hwang, Jaeyeon; Lee, Heon

2009-09-01

The hydrophobicity of the cicada wing originates from its naturally occurring, surface nano-structure. The nano-structure of the cicada wing consists of an array of nano-sized pillars, 100 nm in diameter and 300 nm in height. In this study, the nano-structure of the cicada wing was successfully duplicated by using hot embossing lithography and UV nanoimprint lithography (NIL). The diameter and pitch of replication were the same as those of the original cicada wing and the height was a little smaller than that of the original master. The transmittance of the hot embossed PVC film was increased by 2-6% compared with that of the bare PVC film. The hydrophobicity was measured by water contact angle measurements. The water contact angle of the replica, made of UV cured polymer, was 132° ± 2°, which was slightly lower than that of the original cicada wing (138° ± 2°), but much higher than that of the UV cured polymer surface without any nano-sized pillars (86°).

Comparative analyses of structural features and scaffold diversity for purchasable compound libraries.

PubMed

Shang, Jun; Sun, Huiyong; Liu, Hui; Chen, Fu; Tian, Sheng; Pan, Peichen; Li, Dan; Kong, Dexin; Hou, Tingjun

2017-04-21

Large purchasable screening libraries of small molecules afforded by commercial vendors are indispensable sources for virtual screening (VS). Selecting an optimal screening library for a specific VS campaign is quite important to improve the success rates and avoid wasting resources in later experimental phases. Analysis of the structural features and molecular diversity for different screening libraries can provide valuable information to the decision making process when selecting screening libraries for VS. In this study, the structural features and scaffold diversity of eleven purchasable screening libraries and Traditional Chinese Medicine Compound Database (TCMCD) were analyzed and compared. Their scaffold diversity represented by the Murcko frameworks and Level 1 scaffolds was characterized by the scaffold counts and cumulative scaffold frequency plots, and visualized by Tree Maps and SAR Maps. The analysis demonstrates that, based on the standardized subsets with similar molecular weight distributions, Chembridge, ChemicalBlock, Mucle, TCMCD and VitasM are more structurally diverse than the others. Compared with all purchasable screening libraries, TCMCD has the highest structural complexity indeed but more conservative molecular scaffolds. Moreover, we found that some representative scaffolds were important components of drug candidates against different drug targets, such as kinases and guanosine-binding protein coupled receptors, and therefore the molecules containing pharmacologically important scaffolds found in screening libraries might be potential inhibitors against the relevant targets. This study may provide valuable perspective on which purchasable compound libraries are better for you to screen. Graphical abstract Selecting diverse compound libraries with scaffold analyses.

Cell infiltration and growth in a low density, uncompressed three-dimensional electrospun nanofibrous scaffold.

PubMed

Blakeney, Bryan A; Tambralli, Ajay; Anderson, Joel M; Andukuri, Adinarayana; Lim, Dong-Jin; Dean, Derrick R; Jun, Ho-Wook

2011-02-01

A limiting factor of traditional electrospinning is that the electrospun scaffolds consist entirely of tightly packed nanofiber layers that only provide a superficial porous structure due to the sheet-like assembly process. This unavoidable characteristic hinders cell infiltration and growth throughout the nanofibrous scaffolds. Numerous strategies have been tried to overcome this challenge, including the incorporation of nanoparticles, using larger microfibers, or removing embedded salt or water-soluble fibers to increase porosity. However, these methods still produce sheet-like nanofibrous scaffolds, failing to create a porous three-dimensional scaffold with good structural integrity. Thus, we have developed a three-dimensional cotton ball-like electrospun scaffold that consists of an accumulation of nanofibers in a low density and uncompressed manner. Instead of a traditional flat-plate collector, a grounded spherical dish and an array of needle-like probes were used to create a Focused, Low density, Uncompressed nanoFiber (FLUF) mesh scaffold. Scanning electron microscopy showed that the cotton ball-like scaffold consisted of electrospun nanofibers with a similar diameter but larger pores and less-dense structure compared to the traditional electrospun scaffolds. In addition, laser confocal microscopy demonstrated an open porosity and loosely packed structure throughout the depth of the cotton ball-like scaffold, contrasting the superficially porous and tightly packed structure of the traditional electrospun scaffold. Cells seeded on the cotton ball-like scaffold infiltrated into the scaffold after 7 days of growth, compared to no penetrating growth for the traditional electrospun scaffold. Quantitative analysis showed approximately a 40% higher growth rate for cells on the cotton ball-like scaffold over a 7 day period, possibly due to the increased space for in-growth within the three-dimensional scaffolds. Overall, this method assembles a nanofibrous scaffold

Poly(ɛ-caprolactone)/gelatin composite electrospun scaffolds with porous crater-like structures for tissue engineering.

PubMed

Hwang, Patrick T J; Murdock, Kyle; Alexander, Grant C; Salaam, Amanee D; Ng, Joshua I; Lim, Dong-Jin; Dean, Derrick; Jun, Ho-Wook

2016-04-01

Electrospinning has been widely used to fabricate scaffolds imitating the structure of natural extracellular matrix (ECM). However, conventional electrospinning produces tightly compacted nanofiber layers with only small superficial pores and a lack of bioactivity, which limit the usefulness of electrospinning in biomedical applications. Thus, a porous poly(ε-caprolactone) (PCL)/gelatin composite electrospun scaffold with crater-like structures was developed. Porous crater-like structures were created on the scaffold by a gas foaming/salt leaching process; this unique fiber structure had more large pore areas and higher porosity than the conventional electrospun fiber network. Various ratios of PCL/gelatin (concentration ratios: 100/0, 75/25, and 50/50) composite electrospun scaffolds with and without crater-like structures were characterized by their microstructures, surface chemistry, degradation, mechanical properties, and ability to facilitate cell growth and infiltration. The combination of PCL and gelatin endowed the scaffold with both structural stability of PCL and bioactivity of gelatin. All ratios of scaffolds with crater-like structures showed fairly similar surface chemistry, degradation rates, and mechanical properties to equivalent scaffolds without crater-like structures; however, craterized scaffolds displayed higher human mesenchymal stem cell (hMSC) proliferation and infiltration throughout the scaffolds after 7-day culture. Therefore, these results demonstrated that PCL/gelatin composite electrospun scaffolds with crater-like structures can provide a structurally and biochemically improved three-dimensional ECM-mimicking microenvironment. © 2016 Wiley Periodicals, Inc.

Poly(ε-caprolactone)/gelatin composite electrospun scaffolds with porous crater-like structures for tissue engineering

PubMed Central

Hwang, Patrick T.J.; Murdock, Kyle; Alexander, Grant C.; Salaam, Amanee D.; Ng, Joshua I.; Lim, Dong-Jin; Dean, Derrick; Jun, Ho-Wook

2016-01-01

Electrospinning has been widely used to fabricate scaffolds imitating the structure of natural extracellular matrix (ECM). However, conventional electrospinning produces tightly compacted nanofiber layers with only small superficial pores and a lack of bioactivity, which limit the usefulness of electrospinning in biomedical applications. Thus, a porous poly(ε-caprolactone) (PCL)/gelatin composite electrospun scaffold with crater-like structures was developed. Porous crater-like structures were created on the scaffold by a gas foaming/salt leaching process; this unique fiber structure had more large pore areas and higher porosity than the conventional electrospun fiber network. Various ratios of PCL/gelatin (concentration ratios: 100/0, 75/25, and 50/50) composite electrospun scaffolds with and without crater-like structures were characterized by their microstructures, surface chemistry, degradation, mechanical properties, and ability to facilitate cell growth and infiltration. The combination of PCL and gelatin endowed the scaffold with both structural stability of PCL and bioactivity of gelatin. All ratios of scaffolds with crater-like structures showed fairly similar surface chemistry, degradation rates, and mechanical properties to equivalent scaffolds without crater-like structures; however, craterized scaffolds displayed higher human mesenchymal stem cell (hMSC) proliferation and infiltration throughout the scaffolds after 7-day culture. Therefore, these results demonstrated that PCL/gelatin composite electrospun scaffolds with crater-like structures can provide a structurally and biochemically improved three-dimensional ECM-mimicking microenvironment. PMID:26567028

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

Electrospun polyurethane/hydroxyapatite bioactive scaffolds for bone tissue engineering: the role of solvent and hydroxyapatite particles.

PubMed

Tetteh, G; Khan, A S; Delaine-Smith, R M; Reilly, G C; Rehman, I U

2014-11-01

Polyurethane (PU) is a promising polymer to support bone-matrix producing cells due to its durability and mechanical resistance. In this study two types of medical grade poly-ether urethanes Z3A1 and Z9A1 and PU-Hydroxyapatite (PU-HA) composites were investigated for their ability to act as a scaffold for tissue engineered bone. PU dissolved in varying concentrations of dimethylformamide (DMF) and tetrahydrofuran (THF) solvents were electrospun to attain scaffolds with randomly orientated non-woven fibres. Bioactive polymeric composite scaffolds were created using 15 wt% Z3A1 in a 70/30 DMF/THF PU solution and incorporating micro- or nano-sized HA particles in a ratio of 3:1 respectively, whilst a 25 wt% Z9A1 PU solution was doped in ratio of 5:1. Chemical properties of the resulting composites were evaluated by FTIR and physical properties by SEM. Tensile mechanical testing was carried out on all electrospun scaffolds. MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells, hES-MPs were seeded on the scaffolds to test their biocompatibility and ability to support mineralised matrix production over a 28 day culture period. Cell viability was assayed by MTT and calcium and collagen deposition by Sirius red and alizarin red respectively. SEM images of both electrospun PU scaffolds and PU-HA composite scaffolds showed differences in fibre morphology with changes in solvent combinations and size of HA particles. Inclusion of THF eliminated the presence of beads in fibres that were present in scaffolds fabricated with 100% DMF solvent, and resulted in fibres with a more uniform morphology and thicker diameters. Mechanical testing demonstrated that the Young׳s Modulus and yield strength was lower at higher THF concentrations. Inclusion of both sizes of HA particles in PU-HA solutions reinforced the scaffolds leading to higher mechanical properties, whilst FTIR characterisation confirmed the presence of HA in all composite scaffolds. Although

Production of Poly(ε-Caprolactone)/Hydroxyapatite Composite Scaffolds with a Tailored Macro/Micro-Porous Structure, High Mechanical Properties, and Excellent Bioactivity

PubMed Central

Kim, Jong-Woo; Shin, Kwan-Ha; Koh, Young-Hag; Hah, Min Jin; Moon, Jiyoung; Kim, Hyoun-Ee

2017-01-01

We produced poro-us poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) composite scaffolds for bone regeneration, which can have a tailored macro/micro-porous structure with high mechanical properties and excellent in vitro bioactivity using non-solvent-induced phase separation (NIPS)-based 3D plotting. This innovative 3D plotting technique can create highly microporous PCL/HA composite filaments by inducing unique phase separation in PCL/HA solutions through the non-solvent-solvent exchange phenomenon. The PCL/HA composite scaffolds produced with various HA contents (0 wt %, 10 wt %, 15 wt %, and 20 wt %) showed that PCL/HA composite struts with highly microporous structures were well constructed in a controlled periodic pattern. Similar levels of overall porosity (~78 vol %) and pore size (~248 µm) were observed for all the PCL/HA composite scaffolds, which would be highly beneficial to bone tissue regeneration. Mechanical properties, such as ultimate tensile strength and compressive yield strength, increased with an increase in HA content. In addition, incorporating bioactive HA particles into the PCL polymer led to remarkable enhancements in in vitro apatite-forming ability. PMID:28937605

Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration

NASA Astrophysics Data System (ADS)

Ren, Liyun; Pandit, Vaibhav; Elkin, Joshua; Denman, Tyler; Cooper, James A.; Kotha, Shiva P.

2013-02-01

PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a

Engineering dextran-based scaffolds for drug delivery and tissue repair

PubMed Central

Sun, Guoming; Mao, Jeremy J

2015-01-01

Owing to its chemically reactive hydroxyl groups, dextran can be modified with different functional groups to form spherical, tubular and 3D network structures. The development of novel functional scaffolds for efficient controlled release and tissue regeneration has been a major research interest, and offers promising therapeutics for many diseases. Dextran-based scaffolds are naturally biodegradable and can serve as bioactive carriers for many protein biomolecules. The reconstruction of the in vitro microenvironment with proper signaling cues for large-scale tissue regenerative scaffolds has yet to be fully developed, and remains a significant challenge in regenerative medicine. This paper will describe recent advances in dextran-based polymers and scaffolds for controlled release and tissue engineering. Special attention is given to the development of dextran-based hydrogels that are precisely manipulated with desired structural properties and encapsulated with defined angiogenic growth factors for therapeutic neovascularization, as well as their potential for wound repair. PMID:23210716

Nanosecond laser-induced ablation and laser-induced shockwave structuring of polymer foils down to sub-μm patterns

NASA Astrophysics Data System (ADS)

Lorenz, P.; Bayer, L.; Ehrhardt, M.; Zimmer, K.; Engisch, L.

2015-03-01

Micro- and nanostructures exhibit a growing commercial interest where a fast, cost-effective, and large-area production is attainable. Laser methods have a great potential for the easy fabrication of surface structures into flexible polymer foils like polyimide (PI). In this study two different concepts for the structuring of polymer foils using a KrF excimer laser were tested and compared: the laser-induced ablation and the laser-induced shock wave structuring. The direct front side laser irradiation of these polymers allows the fabrication of different surface structures. For example: The low laser fluence treatment of PI results in nano-sized cone structures where the cone density can be controlled by the laser parameters. This allows inter alia the laser fabrication of microscopic QR code and high-resolution grey-tone images. Furthermore, the laser treatment of the front side of the polymer foil allows the rear side structuring due to a laserinduced shock wave. The resultant surface structures were analysed by optical and scanning electron microscopy (SEM) as well as white light interferometry (WLI).

Structural Polymer-Based Carbon Nanotube Composite Fibers: Understanding the Processing–Structure–Performance Relationship

PubMed Central

Song, Kenan; Zhang, Yiying; Meng, Jiangsha; Green, Emily C.; Tajaddod, Navid; Li, Heng; Minus, Marilyn L.

2013-01-01

Among the many potential applications of carbon nanotubes (CNT), its usage to strengthen polymers has been paid considerable attention due to the exceptional stiffness, excellent strength, and the low density of CNT. This has provided numerous opportunities for the invention of new material systems for applications requiring high strength and high modulus. Precise control over processing factors, including preserving intact CNT structure, uniform dispersion of CNT within the polymer matrix, effective filler–matrix interfacial interactions, and alignment/orientation of polymer chains/CNT, contribute to the composite fibers’ superior properties. For this reason, fabrication methods play an important role in determining the composite fibers’ microstructure and ultimate mechanical behavior. The current state-of-the-art polymer/CNT high-performance composite fibers, especially in regards to processing–structure–performance, are reviewed in this contribution. Future needs for material by design approaches for processing these nano-composite systems are also discussed. PMID:28809290

Preparation and Performance of Porous Polymer Electrolytes Doped with Nano-Al₂O₃.

PubMed

Jiang, Qingbai; Liang, Bo; Tang, Siqi; Chen, Xu

2018-03-01

Porous polymer electrolytes (PPEs) doped with nano-Al2O3 were prepared by a joint application of ultrasonic treatment and control evaporation in vacuum oven. The morphology, pore size distribution, thermal, electrochemical and mechanical properties of the PPEs were investigated. The porosity distribution of PPEs was uniform and their pore size was relatively modest. The total resistance (Rt) of PPEs with 10% Al2O3 is only 9 Ω at 80 °C. The maximum tensile strength of the PPEs membranes reached to 24.43 MPa. The results show that nano-Al2O3 can improve the comprehensive performance of PPEs without compromising their conductivity and diplayed the good application prospects of Al2O3-modified PPEs for lithium-ion batteries.

Melt Electrospinning Writing of Three-dimensional Poly(ε-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications.

PubMed

Wunner, Felix M; Bas, Onur; Saidy, Navid T; Dalton, Paul D; Pardo, Elena M De-Juan; Hutmacher, Dietmar W

2017-12-23

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

Enhancement of Cell-Based Therapeutic Angiogenesis Using a Novel Type of Injectable Scaffolds of Hydroxyapatite-Polymer Nanocomposite Microspheres

PubMed Central

Koyama, Hidenori; Okada, Masahiro; Tanaka, Shinji; Shoji, Tetsuo; Emoto, Masanori; Furuzono, Tsutomu; Nishizawa, Yoshiki; Inaba, Masaaki

2012-01-01

Background Clinical trials demonstrate the effectiveness of cell-based therapeutic angiogenesis in patients with severe ischemic diseases; however, their success remains limited. Maintaining transplanted cells in place are expected to augment the cell-based therapeutic angiogenesis. We have reported that nano-hydroxyapatite (HAp) coating on medical devices shows marked cell adhesiveness. Using this nanotechnology, HAp-coated poly(l-lactic acid) (PLLA) microspheres, named nano-scaffold (NS), were generated as a non-biological, biodegradable and injectable cell scaffold. We investigate the effectiveness of NS on cell-based therapeutic angiogenesis. Methods and Results Bone marrow mononuclear cells (BMNC) and NS or control PLLA microspheres (LA) were intramuscularly co-implanted into mice ischemic hindlimbs. When BMNC derived from enhanced green fluorescent protein (EGFP)-transgenic mice were injected into ischemic muscle, the muscle GFP level in NS+BMNC group was approximate fivefold higher than that in BMNC or LA+BMNC groups seven days after operation. Kaplan-Meier analysis demonstrated that NS+BMNC markedly prevented hindlimb necrosis (P<0.05 vs. BMNC or LA+BMNC). NS+BMNC revealed much higher induction of angiogenesis in ischemic tissues and collateral blood flow confirmed by three-dimensional computed tomography angiography than those of BMNC or LA+BMNC groups. NS-enhanced therapeutic angiogenesis and arteriogenesis showed good correlations with increased intramuscular levels of vascular endothelial growth factor and fibroblast growth factor-2. NS co-implantation also prevented apoptotic cell death of transplanted cells, resulting in prolonged cell retention. Conclusion A novel and feasible injectable cell scaffold potentiates cell-based therapeutic angiogenesis, which could be extremely useful for the treatment of severe ischemic disorders. PMID:22529991

Polymer X-ray refractive nano-lenses fabricated by additive technology.

PubMed

Petrov, A K; Bessonov, V O; Abrashitova, K A; Kokareva, N G; Safronov, K R; Barannikov, A A; Ershov, P A; Klimova, N B; Lyatun, I I; Yunkin, V A; Polikarpov, M; Snigireva, I; Fedyanin, A A; Snigirev, A

2017-06-26

The present work demonstrates the potential applicability of additive manufacturing to X-Ray refractive nano-lenses. A compound refractive lens with a radius of 5 µm was produced by the two-photon polymerization induced lithography. It was successfully tested at the X-ray microfocus laboratory source and a focal spot of 5 μm was measured. An amorphous nature of polymer material combined with the potential of additive technologies may result in a significantly enhanced focusing performance compared to the best examples of modern X-ray compound refractive lenses.

Enhanced differentiation of dental pulp cells cultured on microtubular polymer scaffolds in vitro.

PubMed

Haeri, Morteza; Sagomonyants, Karen; Mina, Mina; Kuhn, Liisa T; Goldberg, A Jon

2017-06-01

Dental caries (tooth decay) is the most common chronic disease. Dental tissue engineering is a promising alternative approach to alleviate the shortcomings of the currently available restorative materials. Mimicking the natural extracellular matrix (ECM) could enhance the performance of tissue engineering scaffolds. In this study, we developed microtubular (~20 μm diameter) polymethyl methacrylate (PMMA) scaffolds resembling the tubular (~2.5 μm diameter) structure of dentin, the collagen-based mineralized tissue that forms the major portion of teeth, to study the effect of scaffold architecture on differentiation of mouse dental pulp cells in vitro . Flat (control), plasma-treated solid and microtubular PMMA scaffolds with densities of 240±15, 459±51 and 480±116 tubules/mm 2 were first characterized using scanning electron microscopy and contact angle measurements. Dental pulp cells were cultured on the surface of the scaffolds for up to 21 days and examined using various assays. Cell proliferation and mineralization were examined using Alamar Blue and Xylenol Orange (XO) staining assays, respectively. The differentiation of pulp cells into odontoblasts was examined by immunostaining for Nestin and by quantitative PCR analysis for dentin matrix protein 1 ( Dmp1 ), dentin sialophosphoprotein ( Dspp ) and osteocalcin ( Ocn ). Our results showed that the highest tubular density scaffolds significantly (p<0.05) enhanced differentiation of pulp cells into odontoblasts as compared to control flat scaffolds, as evidenced by increased expression of Nestin (5.4x). However, mineralization was suppressed on all surfaces, possibly due to low cell density. These results suggest that the microtubular architecture may be a desirable feature of scaffolds developed for clinical applications. Regenerative engineering of diseased or traumatized tooth structure could avoid the deficiencies of traditional dental restorative (filling) materials. Cells in the dental pulp have the

Cytotoxicity investigation of a new hydroxyapatite scaffold with improved structural design.

PubMed

Sjerobabin, Nikola; Čolović, Božana; Petrović, Milan; Marković, Dejan; Živković, Slavoljub; Jokanović, Vukoman

2016-01-01

Biodegradable porous scaffolds are found to be very promising bone substitutes, acting as a temporary physical support to guide new tissue regeneration, until the entire scaffold is totally degraded and replaced by the new tissue. The aim of this study was to investigate cytotoxicity of a synthesized calcium hydroxyapatitebased scaffold, named ALBO-OS, with high porosity and optimal topology. The ALBO-OS scaffold was synthesized by the method of polymer foam template. The analysis of pore geometry and scaffold walls’ topography was made by scanning electron microscope (SEM). The biological investigations assumed the examinations of ALBO-OS cytotoxicity to mouse L929 fibroblasts, using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromidefor (MTT) and lactate dehydrogenase (LDH) tests and inverse phase microscopy. The SEM analysis showed high porosity with fair pore distribution and interesting morphology from the biological standpoint. The biological investigations showed that the material is not cytotoxic to L929 cells. Comparison of ALBO-OS with Bio-Oss, as the global gold standard as a bone substitute, showed similar results in MTT test, while LDH test showed significantly higher rate of cell multiplication with ALBO-OS. The scaffold design from the aspect of pore size, distribution, and topology seems to be very convenient for cell adhesion and occupation, which makes it a promising material as a bone substitute. The results of biological assays proved that ALBO-OS is not cytotoxic for L929 fibroblasts. In comparison with Bio-Oss, similar or even better results were obtained.

Microscale diffusion measurements and simulation of a scaffold with a permeable strut.

PubMed

Lee, Seung Youl; Lee, Byung Ryong; Lee, Jongwan; Kim, Seongjun; Kim, Jung Kyung; Jeong, Young Hun; Jin, Songwan

2013-10-10

Electrospun nanofibrous structures provide good performance to scaffolds in tissue engineering. We measured the local diffusion coefficients of 3-kDa FITC-dextran in line patterns of electrospun nanofibrous structures fabricated by the direct-write electrospinning (DWES) technique using the fluorescence recovery after photobleaching (FRAP) method. No significant differences were detected between DWES line patterns fabricated with polymer supplied at flow rates of 0.1 and 0.5 mL/h. The oxygen diffusion coefficients of samples were estimated to be ~92%-94% of the oxygen diffusion coefficient in water based on the measured diffusion coefficient of 3-kDa FITC-dextran. We also simulated cell growth and distribution within spatially patterned scaffolds with struts consisting of either oxygen-permeable or non-permeable material. The permeable strut scaffolds exhibited enhanced cell growth. Saturated depths at which cells could grow to confluence were 15% deeper for the permeable strut scaffolds than for the non-permeable strut scaffold.

Toughening and functionalization of bioactive ceramic and glass bone scaffolds by biopolymer coatings and infiltration: a review of the last 5 years.

PubMed

Philippart, Anahí; Boccaccini, Aldo R; Fleck, Claudia; Schubert, Dirk W; Roether, Judith A

2015-01-01

Inorganic scaffolds with high interconnected porosity based on bioactive glasses and ceramics are prime candidates for applications in bone tissue engineering. These materials however exhibit relatively low fracture strength and high brittleness. A simple and effective approach to improve the toughness is to combine the basic scaffold structure with polymer coatings or through the formation of interpenetrating polymer-bioactive ceramic microstructures. The polymeric phase can additionally serve as a carrier for growth factors and therapeutic drugs, thus adding biological functionalities. The present paper reviews the state-of-the art in the field of polymer coated and infiltrated bioactive inorganic scaffolds. Based on the notable combination of bioactivity, improved mechanical properties and drug or growth factor delivery capability, this scaffold type is a candidate for bone and osteochondral regeneration strategies. Remaining challenges for the improvement of the materials are discussed and opportunities to broaden the application potential of this scaffold type are also highlighted.

Role of nano-range amphiphilic polymers in seed quality enhancement of soybean and imidacloprid retention capacity on seed coatings.

PubMed

Adak, Totan; Kumar, Jitendra; Shakil, Najam A; Pandey, Sushil

2016-10-01

Nano-size and wide-range solubility of amphiphilic polymers (having both hydrophilic and hydrophobic blocks) can improve uniformity in seed coatings. An investigation was carried out to assess the positive effect of amphiphilic polymers over hydrophilic or hydrophobic polymers as seed coating agents and pesticide carriers. Amphiphilic polymers with 127.5-354 nm micelle size were synthesized in the laboratory using polyethylene glycols and aliphatic di-acids. After 6 months of storage, germination of uncoated soybean seeds decreased drastically from 97.80 to 81.55%, while polymer-coated seeds showed 89.44-95.92% germination. Similarly, vigour index-1 was reduced from 3841.10 to 2813.06 for control seeds but ranged from 3375.59 to 3844.60 for polymer-coated seeds after 6 months. The developed imidacloprid formulations retained more pesticide on soybean seed coatings than did a commercial formulation (Gaucho(®) 600 FS). The time taken for 50% release of imidacloprid from seed coatings in water was 7.12-9.11 h for the developed formulations and 0.41 h for the commercial formulation. Nano-range amphiphilic polymers can be used to protect soybean seeds from ageing. Formulations as seed treatments may produce improved and sustained efficacy with minimum environmental contamination. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Mineralized polymer composites as biogenic bone substitute material

NASA Astrophysics Data System (ADS)

Shah, Rushita; Saha, Nabanita; Kitano, Takeshi; Saha, Petr

2015-05-01

Mineralized polymer composites (MPC) are recognized as potential fillers of bone defects. Though bioceramics exhibits quite a good bone-bonding and vascularization, it is considered to be too stiff and brittle for using alone. Thus, the use of polymer scaffold instead of bioceramics has several advantages including combining the osteoconductivity and bone-bonding potential of the inorganic phase with the porosity and interconnectivity of the three-dimensional construction. Aiming the advantages of ceramic-polymer composite scaffolds, the calcium carbonate (CaCO3) based biomineralized scaffold was prepared, where the PVP-CMC hydrogel was used as an extracellular matrix. This paper is reported about the morphology, swelling trend (in physiological solution) and viscoelastic behavior of (90 min mineralized) MPC. The dry MPC are off-white, coarse in texture, comparatively less flexible than the original PVP-CMC based hydrogel film, and the deposition of granular structures on the surface of the hydrogel film confirms about the development of biomineralized scaffold/polymer composites. Irrespective of thickness, the dry MPC shows higher values of swelling ratio within 30 min, which varies between 200-250 approximately. The dynamic viscoelastic nature of freshly prepared MPC was investigated applying 1% and 10% strain. At higher strain the viscoelastic moduli (G' and G") show significant change, and the nature of MPC turns from elastic to viscous. Based on the observed basic properties, the MPC (calcite based polymer composites) can be recommended for the treatment of adyanamic bone disorder.

A structural model for the flexural mechanics of nonwoven tissue engineering scaffolds.

PubMed

Engelmayr, George C; Sacks, Michael S

2006-08-01

The development of methods to predict the strength and stiffness of biomaterials used in tissue engineering is critical for load-bearing applications in which the essential functional requirements are primarily mechanical. We previously quantified changes in the effective stiffness (E) of needled nonwoven polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffolds due to tissue formation and scaffold degradation under three-point bending. Toward predicting these changes, we present a structural model for E of a needled nonwoven scaffold in flexure. The model accounted for the number and orientation of fibers within a representative volume element of the scaffold demarcated by the needling process. The spring-like effective stiffness of the curved fibers was calculated using the sinusoidal fiber shapes. Structural and mechanical properties of PGA and PLLA fibers and PGA, PLLA, and 50:50 PGA/PLLA scaffolds were measured and compared with model predictions. To verify the general predictive capability, the predicted dependence of E on fiber diameter was compared with experimental measurements. Needled nonwoven scaffolds were found to exhibit distinct preferred (PD) and cross-preferred (XD) fiber directions, with an E ratio (PD/XD) of approximately 3:1. The good agreement between the predicted and experimental dependence of E on fiber diameter (R2 = 0.987) suggests that the structural model can be used to design scaffolds with E values more similar to native soft tissues. A comparison with previous results for cell-seeded scaffolds (Engelmayr, G. C., Jr., et al., 2005, Biomaterials, 26(2), pp. 175-187) suggests, for the first time, that the primary mechanical effect of collagen deposition is an increase in the number of fiber-fiber bond points yielding effectively stiffer scaffold fibers. This finding indicated that the effects of tissue deposition on needled nonwoven scaffold mechanics do not follow a rule-of-mixtures behavior. These important results underscore

In vitro degradation and in vivo toxicity of NanoMatrix3D® polycaprolactone and poly(lactic acid) nanofibrous scaffolds.

PubMed

Pogorielov, Maksym; Hapchenko, Andrii; Deineka, Volodymyr; Rogulska, Larysa; Oleshko, Olexandr; Vodseďálková, Kateřina; Berezkinová, Liliana; Vysloužilová, Lucie; Klápšťová, Andrea; Erben, Jakub

2018-04-10

Nanofibrous materials present unique properties favorable in many biomedicine and industrial applications. In this research we evaluated biodegradation, tissue response and general toxicity of nanofibrous poly(lactic acid) (PLA) and polycaprolactone (PCL) scaffolds produced by conventional method of electrospinning and using NanoMatrix3D ® (NM3D ® ) technology. Mass density, scanning electron microscopy and in vitro degradation (static and dynamic) were used for material characterization, and subcutaneous, intramuscular and intraperitoneal implantation - for in vivo tests. Biochemical blood analysis and histology were used to assess toxicity and tissue response. Pore size and fiber diameter did not differ in conventional and NM3D ® PLA and PCL materials, but mass density was significantly lower in NM3D ® ones. Scaffolds made by conventional method showed toxic effect during the in-vivo tests due to residual concentration of chloroform that released with material degradation. NM3D ® method allowed cleaning scaffolds from residual solutions that made them nontoxic and biocompatible. Subcutaneous, intramuscular and intraperitoneal implantation of PCL and PLA NM3D ® electrospun nanofibrous scaffolds showed their appropriate cell conductive properties, tissue and vessels formation in all sites. Thus, NM3D ® PCL and PLA nanofibrous electrospun scaffolds can be used in the field of tissue engineering, surgery, wound healing, drug delivery, and so forth, due to their unique properties, nontoxicity and biocompatibility. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A:000-000, 2018. © 2018 Wiley Periodicals, Inc.

Micro- and Nano-Scale Fabrication of Fluorinated Polymers by Direct Etching Using Focused Ion Beam

NASA Astrophysics Data System (ADS)

Fukutake, Naoyuki; Miyoshi, Nozomi; Takasawa, Yuya; Urakawa, Tatsuya; Gowa, Tomoko; Okamoto, Kazumasa; Oshima, Akihiro; Tagawa, Seiichi; Washio, Masakazu

2010-06-01

Micro- and nano-scale fabrications of various fluorinated polymers were demonstrated by direct maskless etching using a focused ion beam (FIB). The etching rates of perfluorinated polymers, such as poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoroalkoxyvinylether) (PFA), were about 500-1000 times higher than those of partially fluorinated polymers, such as poly(tetrafluoroethylene-co-ethylene) (ETFE) and poly(vinilydene-fluoride) (PVdF). Controlled high quality and high aspect-ratio nanostructures of spin-coated cross-linked PTFE were obtained without solid debris. The height and diameter of the fibers were about 1.5 µm and 90 nm, respectively. Their aspect ratio was about 17.

Micro- and Nano-Scale Fabrication of Fluorinated Polymers by Direct Etching Using Focused Ion Beam

NASA Astrophysics Data System (ADS)

Naoyuki Fukutake,; Nozomi Miyoshi,; Yuya Takasawa,; Tatsuya Urakawa,; Tomoko Gowa,; Kazumasa Okamoto,; Akihiro Oshima,; Seiichi Tagawa,; Masakazu Washio,

2010-06-01

Micro- and nano-scale fabrications of various fluorinated polymers were demonstrated by direct maskless etching using a focused ion beam (FIB). The etching rates of perfluorinated polymers, such as poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoroalkoxyvinylether) (PFA), were about 500-1000 times higher than those of partially fluorinated polymers, such as poly(tetrafluoroethylene-co-ethylene) (ETFE) and poly(vinilydene-fluoride) (PVdF). Controlled high quality and high aspect-ratio nanostructures of spin-coated cross-linked PTFE were obtained without solid debris. The height and diameter of the fibers were about 1.5 μm and 90 nm, respectively. Their aspect ratio was about 17.

Three-dimensional organization of block copolymers on "DNA-minimal" scaffolds.

PubMed

McLaughlin, Christopher K; Hamblin, Graham D; Hänni, Kevin D; Conway, Justin W; Nayak, Manoj K; Carneiro, Karina M M; Bazzi, Hassan S; Sleiman, Hanadi F

2012-03-07

Here, we introduce a 3D-DNA construction method that assembles a minimum number of DNA strands in quantitative yield, to give a scaffold with a large number of single-stranded arms. This DNA frame is used as a core structure to organize other functional materials in 3D as the shell. We use the ring-opening metathesis polymerization (ROMP) to generate block copolymers that are covalently attached to DNA strands. Site-specific hybridization of these DNA-polymer chains on the single-stranded arms of the 3D-DNA scaffold gives efficient access to DNA-block copolymer cages. These biohybrid cages possess polymer chains that are programmably positioned in three dimensions on a DNA core and display increased nuclease resistance as compared to unfunctionalized DNA cages. © 2012 American Chemical Society

Soluble polymer supported divergent synthesis of tetracyclic benzene-fused pyrazino/diazepino indoles: an advanced synthetic approach to bioactive scaffolds.

PubMed

Lin, Po-Tsung; Salunke, Deepak B; Chen, Li-Hsun; Sun, Chung-Ming

2011-04-21

The synthesis of indoline substituted nitrobenzene on a PEG support and its further elaboration to structurally diverse benzene-fused pyrazino/diazepino indoles is disclosed. A reagent based diversification approach coupled with Pictet-Spengler type condensation reactions furnished these fused polycyclic scaffolds. Microwave irradiation was used as a means of rate acceleration for soluble polymer-supported reactions. The efficiency of these fused heterocyclic molecules to inhibit the vascular endothelial growth factor receptor 3 (VEGFR-3) was examined in vitro using kinase receptor activation enzyme-linked immunosorbant assay (KIRA-ELISA). Based on the preliminary results obtained, a small set of potential drug candidates were identified as novel leads in this therapeutic area to be further explored as anti-metastatic agents.

Fabrication of semiconductor-polymer compound nonlinear photonic crystal slab with highly uniform infiltration based on nano-imprint lithography technique.

PubMed

Qin, Fei; Meng, Zi-Ming; Zhong, Xiao-Lan; Liu, Ye; Li, Zhi-Yuan

2012-06-04

We present a versatile technique based on nano-imprint lithography to fabricate high-quality semiconductor-polymer compound nonlinear photonic crystal (NPC) slabs. The approach allows one to infiltrate uniformly polystyrene materials that possess large Kerr nonlinearity and ultrafast nonlinear response into the cylindrical air holes with diameter of hundred nanometers that are perforated in silicon membranes. Both the structural characterization via the cross-sectional scanning electron microscopy images and the optical characterization via the transmission spectrum measurement undoubtedly show that the fabricated compound NPC samples have uniform and dense polymer infiltration and are of high quality in optical properties. The compound NPC samples exhibit sharp transmission band edges and nondegraded high quality factor of microcavities compared with those in the bare silicon PC. The versatile method can be expanded to make general semiconductor-polymer hybrid optical nanostructures, and thus it may pave the way for reliable and efficient fabrication of ultrafast and ultralow power all-optical tunable integrated photonic devices and circuits.

Remotely Triggered Scaffolds for Controlled Release of Pharmaceuticals

PubMed Central

Roach, Paul; McGarvey, David J.; Lees, Martin R.; Hoskins, Clare

2013-01-01

Fe3O4-Au hybrid nanoparticles (HNPs) have shown increasing potential for biomedical applications such as image guided stimuli responsive drug delivery. Incorporation of the unique properties of HNPs into thermally responsive scaffolds holds great potential for future biomedical applications. Here we successfully fabricated smart scaffolds based on thermo-responsive poly(N-isopropylacrylamide) (pNiPAM). Nanoparticles providing localized trigger of heating when irradiated with a short laser burst were found to give rise to remote control of bulk polymer shrinkage. Gold-coated iron oxide nanoparticles were synthesized using wet chemical precipitation methods followed by electrochemical coating. After subsequent functionalization of particles with allyl methyl sulfide, mercaptodecane, cysteamine and poly(ethylene glycol) thiol to enhance stability, detailed biological safety was determined using live/dead staining and cell membrane integrity studies through lactate dehydrogenase (LDH) quantification. The PEG coated HNPs did not show significant cytotoxic effect or adverse cellular response on exposure to 7F2 cells (p < 0.05) and were carried forward for scaffold incorporation. The pNiPAM-HNP composite scaffolds were investigated for their potential as thermally triggered systems using a Q-switched Nd:YAG laser. These studies show that incorporation of HNPs resulted in scaffold deformation after very short irradiation times (seconds) due to internal structural heating. Our data highlights the potential of these hybrid-scaffold constructs for exploitation in drug delivery, using methylene blue as a model drug being released during remote structural change of the scaffold. PMID:23603890

Scaffolds for bone regeneration made of hydroxyapatite microspheres in a collagen matrix.

PubMed

Cholas, Rahmatullah; Kunjalukkal Padmanabhan, Sanosh; Gervaso, Francesca; Udayan, Gayatri; Monaco, Graziana; Sannino, Alessandro; Licciulli, Antonio

2016-06-01

Biomimetic scaffolds with a structural and chemical composition similar to native bone tissue may be promising for bone tissue regeneration. In the present work hydroxyapatite mesoporous microspheres (mHA) were incorporated into collagen scaffolds containing an ordered interconnected macroporosity. The mHA were obtained by spray drying of a nano hydroxyapatite slurry prepared by the precipitation technique. X-ray diffraction (XRD) analysis revealed that the microspheres were composed only of hydroxyapatite (HA) phase, and energy-dispersive x-ray spectroscopy (EDS) analysis revealed the Ca/P ratio to be 1.69 which is near the value for pure HA. The obtained microspheres had an average diameter of 6 μm, a specific surface area of 40 m(2)/g as measured by Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis showed a mesoporous structure with an average pore diameter of 16 nm. Collagen/HA-microsphere (Col/mHA) composite scaffolds were prepared by freeze-drying followed by dehydrothermal crosslinking. SEM observations of Col/mHA scaffolds revealed HA microspheres embedded within a porous collagen matrix with a pore size ranging from a few microns up to 200 μm, which was also confirmed by histological staining of sections of paraffin embedded scaffolds. The compressive modulus of the composite scaffold at low and high strain values was 1.7 and 2.8 times, respectively, that of pure collagen scaffolds. Cell proliferation measured by the MTT assay showed more than a 3-fold increase in cell number within the scaffolds after 15 days of culture for both pure collagen scaffolds and Col/mHA composite scaffolds. Attractive properties of this composite scaffold include the potential to load the microspheres for drug delivery and the controllability of the pore structure at various length scales. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel diamond micro-/nano-machining process for the generation of hierarchical micro-/nano-structures

NASA Astrophysics Data System (ADS)

Zhu, Zhiwei; To, Suet; Ehmann, Kornel F.; Xiao, Gaobo; Zhu, Wule

2016-03-01

A new mechanical micro-/nano-machining process that combines rotary spatial vibrations (RSV) of a diamond tool and the servo motions of the workpiece is proposed and applied for the generation of multi-tier hierarchical micro-/nano-structures. In the proposed micro-/nano-machining system, the servo motion, as the primary cutting motion generated by a slow-tool-servo, is adopted for the fine generation of the primary surfaces with complex shapes. The RSV, as the tertiary cutting operation, is superimposed on the secondary fundamental rotary cutting motion to construct secondary nano-structures on the primary surface. Since the RSV system generally works at much higher frequencies and motion resolution than the primary and secondary motions, it leads to an inherent hierarchical cutting architecture. To investigate the machining performance, complex micro-/nano-structures were generated and explored by both numerical simulations and actual cutting tests. Rotary vibrations of the diamond tool at a constant rotational distance offer an inherent constant cutting velocity, leading to the ability for the generation of homogeneous micro-/nano-structures with fixed amplitudes and frequencies of the vibrations, even over large-scale surfaces. Furthermore, by deliberately combining the non-resonant three-axial vibrations and the servo motion, the generation of a variety of micro-/nano-structures with complex shapes and with flexibly tunable feature sizes can be achieved.

Microporous polymeric 3D scaffolds templated by the layer-by-layer self-assembly.

PubMed

Paulraj, Thomas; Feoktistova, Natalia; Velk, Natalia; Uhlig, Katja; Duschl, Claus; Volodkin, Dmitry

2014-08-01

Polymeric scaffolds serve as valuable supports for biological cells since they offer essential features for guiding cellular organization and tissue development. The main challenges for scaffold fabrication are i) to tune an internal structure and ii) to load bio-molecules such as growth factors and control their local concentration and distribution. Here, a new approach for the design of hollow polymeric scaffolds using porous CaCO3 particles (cores) as templates is presented. The cores packed into a microfluidic channel are coated with polymers employing the layer-by-layer (LbL) technique. Subsequent core elimination at mild conditions results in formation of the scaffold composed of interconnected hollow polymer microspheres. The size of the cores determines the feature dimensions and, as a consequence, governs cellular adhesion: for 3T3 fibroblasts an optimal microsphere size is 12 μm. By making use of the carrier properties of the porous CaCO3 cores, the microspheres are loaded with BSA as a model protein. The scaffolds developed here may also be well suited for the localized release of bio-molecules using external triggers such as IR-light. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biomimetic poly(lactide) based fibrous scaffolds for ligament tissue engineering.

PubMed

Surrao, Denver C; Waldman, Stephen D; Amsden, Brian G

2012-11-01

The aim of this study was to fabricate a fibrous scaffold that closely resembled the micro-structural architecture and mechanical properties of collagen fibres found in the anterior cruciate ligament (ACL). To achieve this aim, fibrous scaffolds were made by electrospinning L-lactide based polymers. L-Lactide was chosen primarily due to its demonstrated biocompatibility, biodegradability and high modulus. The electrospun fibres were collected in tension on a rotating wire mandrel. Upon treating these fibres in a heated aqueous environment, they possessed a crimp-like pattern having a wavelength and amplitude similar to that of native ACL collagen. Of the polymer fibre scaffolds studied, those made from poly(L-lactide-co-D,L-lactide) PLDLA exhibited the highest modulus and were also the most resilient to in vitro hydrolytic degradation, undergoing a slight decrease in modulus compared to the other polymeric fibres over a 6 month period. Bovine fibroblasts seeded on the wavy, crimp-like PLDLA fibres attached, proliferated and deposited extracellular matrix (ECM) molecules on the surface of the fibrous scaffold. In addition, the deposited ECM exhibited bundle formation that resembled the fascicles found in native ACL. These findings demonstrate the importance of replicating the geometric microenvironment in developing effective tissue engineering scaffolds. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Large 3D direct laser written scaffolds for tissue engineering applications

NASA Astrophysics Data System (ADS)

Trautmann, Anika; Rüth, Marieke; Lemke, Horst-Dieter; Walther, Thomas; Hellmann, Ralf

2018-01-01

We report on the fabrication of three-dimensional direct laser written scaffolds for tissue engineering and the seeding of primary fibroblasts on these structures. Scaffolds are realized by two-photon absorption induced polymerization in the inorganic-organic hybrid polymer OrmoComp using a 515 nm femtosecond laser. A nonstop single-line single-pass writing process is implemented in order to produce periodic reproducible large scaled structures with a dimension in the range of several millimeters and reduce process time to less than one hour. This method allows us to determine optimized process parameters for writing stable structures while achieving pore sizes ranging from 5 μm to 90 μm and a scanning speed of up to 5 mm/s. After a multi-stage post-treatment, normal human dermal fibroblasts are applied to the scaffolds to test if these macroscopic structures with large surface and numerous small gaps between the pores provide nontoxic conditions. Furthermore, we study the cell behavior in this environment and observe both cell growth on as well as ingrowth on the three-dimensional structures. In particular, fibroblasts adhere and grow also on the vertical walls of the scaffolds.

Laser direct synthesis and patterning of silver nano/microstructures on a polymer substrate.

PubMed

Liu, Yi-Kai; Lee, Ming-Tsang

2014-08-27

This study presents a novel approach for the rapid fabrication of conductive nano/microscale metal structures on flexible polymer substrate (polyimide). Silver film is simultaneously synthesized and patterned on the polyimide substrate using an advanced continuous wave (CW) laser direct writing technology and a transparent, particle-free reactive silver ion ink. The location and shape of the resulting silver patterns are written by a laser beam from a digitally controlled micromirror array device. The silver patterns fabricated by this laser direct synthesis and patterning (LDSP) process exhibit the remarkably low electrical resistivity of 2.1 μΩ cm, which is compatible to the electrical resistivity of bulk silver. This novel LDSP process requires no vacuum chamber or photomasks, and the steps needed for preparation of the modified reactive silver ink are simple and straightforward. There is none of the complexity and instability associated with the synthesis of the nanoparticles that are encountered for the conventional laser direct writing technology which involves nanoparticle sintering process. This LDSP technology is an advanced method of nano/microscale selective metal patterning on flexible substrates that is fast and environmentally benign and shows potential as a feasible process for the roll-to-roll manufacturing of large area flexible electronic devices.

Modifying the mechanical properties of silk nanofiber scaffold by knitted orientation for regenerative medicine applications.

PubMed

Dodel, M; Hemmati Nejad, N; Bahrami, S H; Soleimani, M; Hanaee-Ahvaz, H

2016-08-31

Tissue reconstruction is among the increasing applications of polymer nanofibers. Fibrous scaffolds (mats) can be easily produced using the electrospinning method with structure and biomechanical properties similar to those of a cellular matrix. Electrospinning is widely used in the production of nanofibers and the GAP-method electrospinning is one of the means of producing fully aligned nanofibers. In this research, using the GAP-method, knitted fibrous scaffolds were made of silk fibroin, which is a biocompatible and biodegradable polymer. To extract fibroin from cocoons, the sodium chloride solution as well as dialysis and freeze-drying techniques were employed. The molecular weight of the extracted fibroin was measured with the SDS-Page electrophoresis technique. Moreover, the pure fibroin structure was examined using the ATR-FTIR method, and the viscosity of the solution used for electrospinning was measured with the Brookfield rotational viscometer. The scaffolds were prepared through electrospinning of the silk fibroin in pure formic acid solution. The following three structures were electrospun: 1) a random structure; 2) a knitted structure with an interstitial angle of 60 degrees; 3) a knitted structure with an interstitial angle of 90 degrees. Morphology of the resulting fibers was studied with a SEM (scanning electron microscope). Fibroin scaffolds are degradable in water. Therefore, they were fixated through immersion in methanol to be prepared for assays. The mechanical properties of the scaffolds were also studied using a tensile strength test device. The effect of methanol on the strength properties of the samples was also assessed. The hydrophilic potential of the samples was measured via a contact angle test. To increase the hydrophilicity of the scaffold surfaces, the cold oxygen plasma technique was employed. Finally, the biocompatibility and cell adhesion of the resulting scaffolds were examined through a HEK 293 cell culture, and the results

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.

Nano-structured surface plasmon resonance sensor for sensitivity enhancement

NASA Astrophysics Data System (ADS)

Kim, Jae-Ho; Kim, Hyo-Sop; Kim, Jin-Ho; Choi, Sung-Wook; Cho, Yong-Jin

2008-08-01

A new nano-structured SPR sensor was devised to improve its sensitivity. Nano-scaled silica particles were used as the template to fabricate nano-structure. The surface of the silica particles was modified with thiol group and a single layer of the modified silica particles was attached on the gold or silver thin film using Langmuir-Blodgett (LB) method. Thereafter, gold or silver was coated on the template by an e-beam evaporator. Finally, the nano-structured surface with basin-like shape was obtained after removing the silica particles by sonication. Applying the new developed SPR sensor to a model food of alcoholic beverage, the sensitivities for the gold and silver nano-structured sensors, respectively, had 95% and 126% higher than the conventional one.

Multi-Material Tissue Engineering Scaffold with Hierarchical Pore Architecture.

PubMed

Morgan, Kathy Ye; Sklaviadis, Demetra; Tochka, Zachary L; Fischer, Kristin M; Hearon, Keith; Morgan, Thomas D; Langer, Robert; Freed, Lisa E

2016-08-23

Multi-material polymer scaffolds with multiscale pore architectures were characterized and tested with vascular and heart cells as part of a platform for replacing damaged heart muscle. Vascular and muscle scaffolds were constructed from a new material, poly(limonene thioether) (PLT32i), which met the design criteria of slow biodegradability, elastomeric mechanical properties, and facile processing. The vascular-parenchymal interface was a poly(glycerol sebacate) (PGS) porous membrane that met different criteria of rapid biodegradability, high oxygen permeance, and high porosity. A hierarchical architecture of primary (macroscale) and secondary (microscale) pores was created by casting the PLT32i prepolymer onto sintered spheres of poly(methyl methacrylate) (PMMA) within precisely patterned molds followed by photocuring, de-molding, and leaching out the PMMA. Pre-fabricated polymer templates were cellularized, assembled, and perfused in order to engineer spatially organized, contractile heart tissue. Structural and functional analyses showed that the primary pores guided heart cell alignment and enabled robust perfusion while the secondary pores increased heart cell retention and reduced polymer volume fraction.

Gelatin/nano-hydroxyapatite hydrogel scaffold prepared by sol-gel technology as filler to repair bone defects.

PubMed

Raucci, Maria Grazia; Demitri, Christian; Soriente, Alessandra; Fasolino, Ines; Sannino, Alessandro; Ambrosio, Luigi

2018-03-25

This study reports on the development of a scaffold with a gradient of bioactive solid signal embedded in the biodegradable polymer matrix by combining a sol-gel approach and freeze-drying technology. The chemical approach based on the sol-gel transition of calcium phosphates ensures the particles dispersion into the gelatin matrix and a direct control of interaction among COOH gelatin /Ca 2+ ions. Morphological analysis demonstrated that on the basis of the amount of inorganic component and by using specific process conditions, it is possible to control the spatial distribution of nanoparticles around the gelatin helix. In fact, methodology and formulations were able to discriminate between the different hydroxyapatite concentrations and their respective morphology. The good biological response represented by good cell attachment, proliferation and increased levels of alkaline phosphatase as an indicator of osteoblastic differentiation of human mesenchymal stem cells toward the osteogenic lineage, demonstrating the effect of bioactive solid signals on cellular behavior. Furthermore, the inhibition of reactive oxygen species production by composite materials predicted potential anti-inflammatory properties of scaffolds thus confirming their biocompatibility. Indeed, these interesting biological results suggest good potential application of this scaffold as filler to repair bone defects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

Nano-extrusion: a promising tool for continuous manufacturing of solid nano-formulations.

PubMed

Baumgartner, Ramona; Eitzlmayr, Andreas; Matsko, Nadejda; Tetyczka, Carolin; Khinast, Johannes; Roblegg, Eva

2014-12-30

Since more than 40% of today's drugs have low stability, poor solubility and/or limited ability to cross certain biological barriers, new platform technologies are required to address these challenges. This paper describes a novel continuous process that converts a stabilized aqueous nano-suspension into a solid oral formulation in a single step (i.e., the NANEX process) in order to improve the solubility of a model drug (phenytoin). Phenytoin nano-suspensions were prepared via media milling using different stabilizers. A stable nano-suspension was obtained using Tween(®) 80 as a stabilizer. The matrix material (Soluplus(®)) was gravimetrically fed into the hot melt extruder. The suspension was introduced through a side feeding device and mixed with the molten polymer to immediately devolatilize the water in the nano-suspension. Phenytoin nano-crystals were dispersed and embedded in the molten polymer. Investigation of the nano-extrudates via transmission electron microscopy and atomic force microscopy showed that the nano-crystals were embedded de-aggregated in the extrudates. Furthermore, no changes in the crystallinity (due to the mechanical and thermal stress) occurred. The dissolution studies confirmed that the prepared nano-extrudates increased the solubility of nano-crystalline phenytoin, regardless of the polymer. Our work demonstrates that NANEX represents a promising new platform technology in the design of novel drug delivery systems to improve drug performance. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural Assessment of a Tissue Engineered Scaffold for Bone Repair

DTIC Science & Technology

2001-10-25

lactide-co- glycolide) [ PLAGA ] have been evaluated for such uses. However, structural limitations may restrict the clinical use of these scaffolds...bone specific protein. Through this work, it was shown that an osteoconductive PLAGA scaffold with a pore system equivalent to the structure of...known as poly(lactide-co-glycolide) [ PLAGA ]. Our laboratory has conducted several studies evaluating the ability of PLAGA to promote osteoblast

Antibacterial activity of combination of synthetic and biopolymer non-woven structures.

PubMed

Bhullar, Sukhwinder K; Özsel, Burcak Kaya; Yadav, Ramesh; Kaur, Ginpreet; Chintamaneni, Meena; Buttar, Harpal S

2015-12-01

Fibrous structures and synthetic polymer blends offer potential usages in making biomedical devices, textiles used in medical practices, food packaging, tissue engineering, environmental applications and biomedical arena. These products are also excellent candidates for building scaffolds to grow stem cells for implantation, to make tissue engineering grafts, to make stents to open up blood vessels caused by atherosclerosis or narrowed by blood clots, for drug delivery systems for micro- to nano-medicines, for transdermal patches, and for healing of wounds and burn care. The current study was designed to evaluate the antimicrobial activity of woven and non-woven forms of nano- and macro-scale blended polymers having biocompatible and biodegradable characteristics. The antimicrobial activity of non-woven fibrous structures created with the combination of synthetic and biopolymer was assessed using Gram-negative, Gram-positive bacteria, such as Staphylococcus aureus, Proteus vulgaris, Escherichia coli and Enterobacter aerogenes using pour plate method. Structural evaluation of the fabricated samples was performed by Fourier transform infrared spectroscopy. Broad spectrum antibacterial activities were found from the tested materials consisting of polyvinyl alcohol (PVA) with chitosan and nylon-6 combined with chitosan and formic acid. The combination of PVA with chitosan was more bactericidal or bacteriostatic than that of nylon-6 combined with chitosan and formic acid. PVA combination with chitosan appears to be a broad-spectrum antimicrobial agent.

Preparation and characterization of a three-dimensional printed scaffold based on a functionalized polyester for bone tissue engineering applications.

PubMed

Seyednejad, Hajar; Gawlitta, Debby; Dhert, Wouter J A; van Nostrum, Cornelus F; Vermonden, Tina; Hennink, Wim E

2011-05-01

At present there is a strong need for suitable scaffolds that meet the requirements for bone tissue engineering applications. The objective of this study was to investigate the suitability of porous scaffolds based on a hydroxyl functionalized polymer, poly(hydroxymethylglycolide-co-ε-caprolactone) (pHMGCL), for tissue engineering. In a recent study this polymer was shown to be a promising material for bone regeneration. The scaffolds consisting of pHMGCL or poly(ε-caprolactone) (PCL) were produced by means of a rapid prototyping technique (three-dimensional plotting) and were shown to have a high porosity and an interconnected pore structure. The thermal and mechanical properties of both scaffolds were investigated and human mesenchymal stem cells were seeded onto the scaffolds to evaluate the cell attachment properties, as well as cell viability and differentiation. It was shown that the cells filled the pores of the pHMGCL scaffold within 7 days and displayed increased metabolic activity when compared with cells cultured in PCL scaffolds. Importantly, pHMGCL scaffolds supported osteogenic differentiation. Therefore, scaffolds based on pHMGCL are promising templates for bone tissue engineering applications. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.