Biomedical subjects

Kuangshin Tai

Publications and source records attributed to Kuangshin Tai.

3 recordsLinked to original sources

PubMed2006

Structural and nanoindentation studies of stem cell-based tissue-engineered bone.

Stem cell-based gene therapy and tissue engineering have been shown to be an efficient method for the regeneration of critical-sized bone defects. Despite being an area of active research over the last decade, no knowledge of the intrinsic ultrastructural and nanomechanical properties of such bone tissue exists. In this study, we report the nanomechanical properties of engineered bone tissue derived from genetically modified mesenchymal stem cells (MSCs) overexpressing the rhBMP2 gene, grown in vivo in the thigh muscle of immunocompetent mice for 4 weeks, compared to femoral bone adjacent to the transplantation site. The two types of bone had similar mineral contents (61 and 65 wt% for engineered and femoral bone, respectively), overall microstructures showing lacunae and canaliculi (both measured by back-scattered electron microscopy), chemical compositions (measured by energy dispersive X-ray analysis), and nanoscale topographical morphologies (measured by tapping-mode atomic force microscopy imaging or TMAFM). Nanoindentation experiments revealed that the small length scale mechanical properties were statistically different with the femoral bone (indented parallel to the bone long axis) being stiffer and harder (apparent elastic modulus, E approximately 27.3+/-10.5 GPa and hardness, H approximately 1.0+/-0.7G Pa) than the genetically engineered bone (E approximately 19.8+/-5.6 GPa, H approximately 0.9+/-0.4G Pa). TMAFM imaging showed clear residual indents characteristic of viscoelastic plastic deformation for both types of bone. However, fine differences in the residual indent area (smaller for the engineered bone), pile up (smaller for the engineered bone), and fracture mechanisms (microcracks for the engineered bone) were observed with the genetically engineered bone behaving more brittle than the femoral control.

Biomechanical Phenomena↗

PubMed2006

Nanogranular origins of the strength of bone.

Here, we investigate the ultrastructural origins of the strength of bone, which is critical for proper physiological function. A combination of dual nanoindentation, three-dimensional elastic-plastic finite element analysis using a Mohr-Coulomb cohesive-frictional strength criterion, and angle of repose measurements was employed. Our results suggest that nanogranular friction between mineral particles is responsible for increased yield resistance in compression relative to tension and that cohesion originates from within the organic matrix itself, rather than organic-mineral bonding.

Animals↗

PubMed2005

Effect of mineral content on the nanoindentation properties and nanoscale deformation mechanisms of bovine tibial cortical bone.

In this paper, a multitechnique experimental and numerical modeling methodology was used to show that mineral content had a significant effect on both nanomechanical properties and ultrastructural deformation mechanisms of samples derived from adult bovine tibial bone. Partial and complete demineralization was carried out using phosphoric and ethylenediamine tetraacetic acid treatments to produce samples with mineral contents that varied between 37 and 0 weight percent (wt%). The undemineralized samples were found to have a mineral content of approximately 58 wt%. Nanoindentation experiments (maximum loads approximately 1000 microN and indentation depths approximately 500 nm) perpendicular to the osteonal axis for the approximately 58 wt% samples were found to have an estimated elastic modulus of approximately 7-12 GPa, which was 4-6x greater than that obtained for the approximately 0 wt% samples. The yield strength of the approximately 58 wt% samples was found to be approximately 0.24 GPa; 3.4x greater than that of the approximately 0 wt% sample. These results are discussed in the context of in situ and post-mortem atomic force microscopy imaging studies which show clear residual deformation after indentation for all samples studied. The partially demineralized samples underwent collagen fibril deformation and kinking without loss of the characteristic banding structure at low maximum loads (approximately 300 microN). At higher maximum loads (approximately 700 microN) mechanical denaturation of collagen fibrils was observed within the indent region, as well as disruption of interfibril interfaces and slicing through the thickness of individual fibrils leading to microcracks along the tip apex lines and outside the indent regions. A finite element elastic-plastic continuum mechanical model was able to predict the nanomechanical behavior of all samples on loading and unloading.

Animals↗