Papers by Author: Zhi Ming Yang

Abstract: Many scaffolds are candidates for use in tissue engineering approaches for the repair or replacement of bone defects. Among the scaffolds tested for tissue engineering of bone, bio-derived compact bone scaffold (BDCBS) containing mineralized collagen fibers, phosphorus and calcium, as natural bone does, is one of the most promising candidates for this purpose. To analyze how appropriate the BDCBS would be for tissue engineering purposes, we established an in vitro characterization system to describe the surface properties and cytocompaibility of the scaffold. Surface properties were determined by means of scanning electron microscope and scanning probe microscope. The surface phase was examined with the Fourier transform infrared spectroscopy and X-ray diffraction. Osteoblasts from human embryos were isolated from the periosteum. After in vitro expansion, cells were cultivated on the BDCBS. Real-time cell culture was used to monitor the growth process of cells seeded on the scaffold. Using this in vitro characterization, we were able to demonstrate effective growth of osteoblasts on this scaffold. In summary, BDCBS has the surface characterization similar to a natural bone and also has strong affinity for osteoblast attachment and proliferation, indicating the potential as an effective scaffold used in tissue engineering bone.

Abstract: To compare the chemical composition and mechanical properties of the bio-derived compact bone scaffold (BDCBS) with the normal compact bone in human. Human compact bone were harvested and divided into control and experimental group. For the latter, BDCBS was prepared with physical and chemical methods. The major components (calcium, phosphorus, collagen protein) and heavy metal contents of the two groups were determined with biochemical assay. Histological examinations were performed to investigate the structure. Cylindroids from the normal compact bone and the BDCBS (6 in each group) were tested under compression. There was no significant difference between the two groups for major components. In addition, there were a few amounts of heavy metal components in BDCBS and control. Histological examinations confirmed the acellular structure in the BDCBS. Results from mechanical testing showed the compressive strength, elastic modulus and ultimate strain (193MPa, 13.76GPa, and 2.3%) of the BDCBS were a bit lower than those (205MPa, 15.67GPa, and 2.5% respectively) of control, but the differences were not statistically significant. In conclusion, there are almost the same matrix structure and composition with similar biomechanical properties between the BDCBS and the control. These results may underscore the potential of the BDCBS in tissue engineering bone.

Abstract: The purpose of this research is to find out the interaction between histological alterations and mechanical properties of engineered tendon implanted in situ. Defects of 0.5cm-1.0cm were made at deep flexor tendons by surgical procedure. Engineered tendons using degradable scaffolds polyglytic acid (PGA) mesh and tendon cells were implanted to repair the defects. Chickens were killed respectively at 2 weeks, 4 weeks, 6 weeks, and 8 weeks after surgery. The implants were taken out for histological examination, biomechanical test, and collagen synthesis assay. The results showed that after surgery the PGA scaffolds degraded fast and took precedence of collagen synthesis. There were not enough amount and maturation of the collagen fibers of the new tendon at 2-8 weeks after surgery. The biomechanical properties of new tendons were less than those of the normal tendon. Therefore, it is necessary to construct engineered tendons with better degradation rate of scaffolds and suitable biomechanical stimulation so that more collagen synthesis and better biomechanical properties of new tendons can be developed early after implantation.