| A biomimetic tubular scaffold with spatially designed nanofibers of protein/PDS bio-blends.
December 17, 2009 at 6:21 am
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| | A biomimetic tubular scaffold with spatially designed nanofibers of protein/PDS bio-blends. Biotechnol Bioeng. 2009 Dec 1;104(5):1025-33 Authors: Thomas V, Zhang X, Vohra YK Electrospun tubular conduit (4 mm inner diameter) based on blends of polydioxanone (PDS II(R)) and proteins such as gelatin and elastin having a spatially designed trilayer structure was prepared for arterial scaffolds. SEM analysis of scaffolds showed random nanofibrous morphology and well-interconnected pore network. Due to protein blending, the fiber diameter was reduced from 800-950 nm range to 300-500 nm range. Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results confirmed the blended composition and crystallinity of fibers. Pure PDS scaffold under hydrated state exhibited a tensile strength of 5.61 +/- 0.42 MPa and a modulus of 17.11 +/- 1.13 MPa with a failure strain of 216.7 +/- 13%. The blending of PDS with elastin and gelatin has decreased the tensile properties. A trilayer tubular scaffold was fabricated by sequential electrospinning of blends of elastin/gelatin, PDS/elastin/gelatin, and PDS/gelatin (EG/PEG/PG) to mimic the complex matrix structure of native arteries. Under hydrated state, the trilayer conduit exhibited tensile properties (tensile strength of 1.77 +/- 0.2 MPa and elastic modulus of 5.74 +/- 3 MPa with a failure strain of 75.08 +/- 10%) comparable to those of native arteries. In vitro degradation studies for up to 30 days showed about 40% mass loss and increase in crystallinity due to the removal of proteins and "cleavage-induced crystallization" of PDS. PMID: 19575442 [PubMed - indexed for MEDLINE] |
| Analysis of the mechanical behavior of a titanium scaffold with a repeating unit-cell substructure.
December 17, 2009 at 6:21 am
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| | Analysis of the mechanical behavior of a titanium scaffold with a repeating unit-cell substructure. J Biomed Mater Res B Appl Biomater. 2009 Aug;90(2):894-906 Authors: Ryan G, McGarry P, Pandit A, Apatsidis D Titanium scaffolds with controlled microarchitecture have been developed for load bearing orthopedic applications. The controlled microarchitecture refers to a repeating array of unit-cells, composed of sintered titanium powder, which make up the scaffold structure. The objective of this current research was to characterize the mechanical performance of three scaffolds with increasing porosity, using finite element analysis (FEA) and to compare the results with experimental data. Scaffolds were scanned using microcomputed tomography and FEA models were generated from the resulting computer models. Macroscale and unit-cell models of the scaffolds were created. The material properties of the sintered titanium powders were first evaluated in mechanical tests and the data used in the FEA. The macroscale and unit-cell FEA models proved to be a good predictor of Young's modulus and yield strength. Although macroscale models showed similar failure patterns and an expected trend in UCS, strain at UCS did not compare well with experimental data. Since a rapid prototyping method was used to create the scaffolds, the original CAD geometries of the scaffold were also evaluated using FEA but they did not reflect the mechanical properties of the physical scaffolds. This indicates that at present, determining the actual geometry of the scaffold through computed tomography imaging is important. Finally, a fatigue analysis was performed on the scaffold to simulate the loading conditions it would experience as a spinal interbody fusion device. PMID: 19360888 [PubMed - indexed for MEDLINE] |
| Procyanidins-crosslinked heart valve matrix: anticalcification effect.
December 17, 2009 at 6:21 am
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| | Procyanidins-crosslinked heart valve matrix: anticalcification effect. J Biomed Mater Res B Appl Biomater. 2009 Aug;90(2):913-21 Authors: Zhai W, Chang J, Lü X, Wang Z Calcification is one of the key factors for short durability of glutaraldehyde-crosslinked bioprosthetic heart valves. We have shown previously that procyanidins (PC)-crosslinked heart valve matrix has low cytotoxicity, perfect mechanical properties, and ideal stability. The aim of this study is to investigate the anticalcification effect of procyanidins and its crosslinked heart valves. Porcine aortic heart valve leaflets were decellularized and crosslinked with PC solution. The inhibition of calcification on PC-crosslinked heart valves was evaluated by soaking valves in simulated body fluid. The anticalcification effect of PC on valvular related cells was evaluated by culturing cells in the presence of PC. The results showed that minerals deposited on non- and glutaraldehyde-crosslinked valvular matrix in simulated body fluid, and PC could inhibit valve matrix mineralization in a dose-dependant manner. In addition, PC inhibited osteodifferentiation and calcification of valvular related cells by suppressing alkaline phosphatase activity and mineral deposition of cells. In conclusion, procyanidins can inhibit calcification of valvular matrix effectively by blocking mineral deposition and suppressing alkaline phosphatase activity and calcification of valvular related cells. Therefore, procyanindins-crosslinked heart valve matrix may be a potential candidate as new bioprosthetic heart valve implants. PMID: 19353570 [PubMed - indexed for MEDLINE] |
| Development of a 3D collagen scaffold coated with multiwalled carbon nanotubes.
December 17, 2009 at 6:21 am
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| | Development of a 3D collagen scaffold coated with multiwalled carbon nanotubes. J Biomed Mater Res B Appl Biomater. 2009 Aug;90(2):629-34 Authors: Hirata E, Uo M, Takita H, Akasaka T, Watari F, Yokoyama A Carbon nanotubes (CNTs) have attractive biochemical properties such as strong cell adhesion and protein absorption, which are very useful for a cell cultivation scaffold. In this study, we prepared a multiwalled carbon nanotube-coated collagen sponge (MWCNT-coated sponge) to improve the surface properties of the collagen sponge, and its cell culturing properties were examined. The suface of the collagen sponge was homogeneously coated with MWCNTs by dispersion. MC3T3-E1 cells were cultured on and inside the MWCNT-coated sponge. The DNA content on the MWCNT-coated sponge after 1 week of culture was significantly higher than on an uncoated collagen sponge (p < 0.05). There was no significant difference between the estimated ALP activity normalized by DNA quantity on the MWCNT-coated sponge and that on the uncoated collagen sponge which is well known as one of the best scaffolds for cell cultivation. In addition, the MWCNT-coated surface shows strong cell adhesion. Therefore, the MWCNT-coated collagen sponge is expected to be a useful 3D scaffold for cell cultivation. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009. PMID: 19213050 [PubMed - indexed for MEDLINE] |
| Novel fabrication of PCL porous beads for use as an injectable cell carrier system.
December 17, 2009 at 6:21 am
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| | Novel fabrication of PCL porous beads for use as an injectable cell carrier system. J Biomed Mater Res B Appl Biomater. 2009 Aug;90(2):521-30 Authors: Lim SM, Lee HJ, Oh SH, Kim JM, Lee JH Injectable polycaprolactone (PCL) porous beads were fabricated for use as cell carriers by a novel isolated particle-melting method (for nonporous beads) and the following melt-molding particulate-leaching method (for porous beads). The prepared beads showed highly porous and uniform pore structures with almost the same surface and interior porosities (porosity, over 90%). The PCL porous beads (bead size, 400-550 microm) with different pore sizes (25-50 and 50-100 microm) were compared for their in vitro cell (human chondrocyte) growth behavior with the nonporous beads. The porous beads showed higher cell seeding density and growth than the nonporous beads. The pore size effect between the porous beads was not significant up to 7 days, but after that time the beads with pore sizes of 50-100 microm showed significantly higher cell growth than those of 25-50 microm. To evaluate the tissue compatibility of the PCL porous beads, the beads were dispersed, uniformly, in cold Pluronic F127 solution and injected into hairless mice, subcutaneously, in the gel state of Pluronic F127 at room temperature, leading to the homogeneous bead delivery. The histological findings confirmed that the PCL porous beads in Pluronic F127 gel are biocompatible: surrounding tissues gradually infiltrated into the porous beads for up to 4 weeks with little inflammatory response. The PCL porous beads with highly porous and uniform pore structures fabricated in this study can be widely applicable as cell carriers. PMID: 19145632 [PubMed - indexed for MEDLINE] |
| Physically crosslinked composite hydrogels of PVA with natural macromolecules: structure, mechanical properties, and endothelial cell compatibility.
December 17, 2009 at 6:21 am
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| | Physically crosslinked composite hydrogels of PVA with natural macromolecules: structure, mechanical properties, and endothelial cell compatibility. J Biomed Mater Res B Appl Biomater. 2009 Aug;90(2):492-502 Authors: Liu Y, Vrana NE, Cahill PA, McGuinness GB Polyvinyl alcohol (PVA) hydrogels have been considered potentially suitable for applications as engineered blood vessels because of their structure and mechanical properties. However, PVA's hydrophilicity hinders its capacity to act as a substrate for cell attachment. As a remedy, PVA was blended with chitosan, gelatin, or starch, and hydrogels were formed by subjecting the solutions to freeze-thaw cycles followed by coagulation bath immersion. The structure-property relationships for these hydrogels were examined by measurement of their swelling, rehydration, degradation, and mechanical properties. For the case of pure PVA hydrogels, the equilibrium swelling ratio was used to predict the effect of freeze thaw cycles and coagulation bath on average molecular weights between crosslinks and on mesh size. For all hydrogels, trends for the reswelling ratio, which is indicative of the crosslinked polymer fraction, were consistent with relative tensile properties. The coagulation bath treatment increased the degradation resistance of the hydrogels significantly. The suitability of each hydrogel for cell attachment and proliferation was examined by protein adsorption and bovine vascular endothelial cell culture experiments. Protein adsorption and cell proliferation was highest on the PVA/gelatin hydrogels. This study demonstrates that the potential of PVA hydrogels for artificial blood vessel applications can be improved by the addition of natural polymers, and that freeze-thawing and coagulation bath treatment can be utilized for fine adjustment of the physical characteristics. PMID: 19145629 [PubMed - indexed for MEDLINE] |
| Spherical indentation of soft matter beyond the Hertzian regime: numerical and experimental validation of hyperelastic models.
December 17, 2009 at 6:21 am
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| | Spherical indentation of soft matter beyond the Hertzian regime: numerical and experimental validation of hyperelastic models. Biomech Model Mechanobiol. 2009 Oct;8(5):345-58 Authors: Lin DC, Shreiber DI, Dimitriadis EK, Horkay F The lack of practicable nonlinear elastic contact models frequently compels the inappropriate use of Hertzian models in analyzing indentation data and likely contributes to inconsistencies associated with the results of biological atomic force microscopy measurements. We derived and validated with the aid of the finite element method force-indentation relations based on a number of hyperelastic strain energy functions. The models were applied to existing data from indentation, using microspheres as indenters, of synthetic rubber-like gels, native mouse cartilage tissue, and engineered cartilage. For the biological tissues, the Fung and single-term Ogden models achieved the best fits of the data while all tested hyperelastic models produced good fits for the synthetic gels. The Hertz model proved to be acceptable for the synthetic gels at small deformations (strain < 0.05 for the samples tested), but not for the biological tissues. Although this finding supports the generally accepted view that many soft materials can be assumed to be linear elastic at small deformations, the nonlinear models facilitate analysis of intrinsically nonlinear tissues and large-strain indentation behavior. PMID: 18979205 [PubMed - indexed for MEDLINE] | | | 
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