Papers by Author: Xing Dong Zhang

Abstract: Collagen has been widely used in biomedical field, such as scaffolds for tissue engineering. However, the rapidly biodegradation and weak mechanical strength of collagen limited its application. In this study, an insoluble collagen extracted from cattle hide was designed as scaffold to act as a three-dimensional substrate for tissue engineering. The received insoluble collagen sponge was analyzed by scanning electron microscopy, infrared spectroscopy, mechanical testing and thermogravimetric-differential thermal analysis. In addition, the degradation was performed in vitro using collagenase. The results showed that the insoluble collagen had the same triple helical domain as acid-soluble collagen, while the compression strength was greatly improved and the degradation rate was reduced. The insoluble collagen sponge with good stability should be promising in tissue engineering scaffold applications.

Abstract: In the present study, three types of tetracalcium phosphate (TTCP) were prepared by solid-solid reaction or co-precipitation method and by different cooling modes. The effect of TTCP on the performance of calcium phosphate cement (CPC) was investigated. The result showed that the characteristic of TTCP varied with preparation method and played an important role in CPC performance. A solid-solid reacted TTCP yielded smaller particle size and resulted in bad workability and mechanical strength of CPC. The fast cooling of sintering TTCP by liquid nitrogen could avoid the decomposition of TTCP and make pure TTCP. TTCP prepared by wet-precipitation could improve performance of CPC and was promising to optimization of CPC.

Abstract: With good biocompatibility, collagen is often used in cartilage tissue engineering. Collagen/alginate composite was hoped to improve the poor mechanical property of pure collagen but the biocompatibity was decreased. In this study, hydroxyapatite (HA) particles were used to get collagen/alginate/HA (CAHA) composite film to enhance the bioactivity properties. The bioactivity of the composite was investigated by in vitro co-culture with chondrocytes. During the 6-day cell culture in vitro, the composite showed a significant improvement in promoting proliferation and maintaining morphology/phenotype of the chondrocytes over collagen/alginate composite by MTT, SEM, fluorescent and immunohistochemical assays. Cytocompatibility and cytoviablility of CAHA even come up to that of collagen film alone. The results indicated that the composite film may provide an appropriate environment for the proliferation and maintaining the morphology and phenotype of chondrocytes and have a potential clinical application in the cartilage tissue engineering field.

Abstract: Porous HA/TCP bioceramics were immersed in pure bovine serum to observe the growth and formation of apatite. HRTEM, FTIR, and SEM coupled with EDS were used for the characterization of immersed samples. SEM results showed that some beamed crystals formed on the surface of ceramics granules, and with postponement of immersion time, crystals extended and became bigger, strap-like crystals became sheet-like crystals. HRTEM observations indicated that new-formed crystals developed along axes direction according to parallel layers. IR spectrum showed CO3 2- characteristic peaks existed besides O-P-O and OH- characteristic peaks. EDS results showed that calcium and phosphor ratio was 1.95 (mol ratio). The results indicated that bovine serums were advantaged to bone-like apatite formation.

Abstract: It is well known that the cellular responses are related with both physical and chemical characteristics of substrate, including surface topography. In the present study，the effect of surface topography of hydroxyapatite (HA) on rat bone marrow cell (rBMCs) response was investigated. HA disc-shaped pellets with various topography were manufactured by single-axis pressing methods. The rBMCs responses on materials including cell morphology and proliferation were evaluated by SEM and MTT methods respectively, and the differentiation potential was assessed by total protein content and alkaline phosphatase (ALP) activity testing. The results showed that the cell porliferation was higher on HA surfaces with macropore structure, while ALP activity was lower. No significant difference in the cellular responses on the pore distribution and orietation was observed. However, the pore structure had a potential to guide cell orientation by gathering the cells inside the pores rather than on the ridges. Since ALP served as an indicator of early osteoblast differentiation, in this study its higher expression on HA surface with micropores suggested that surface microtopograhy exhibited an important effect on early osteoblast differentiation process.

Abstract: As a natural biomaterial, collagen especially pepsin-solubilized collagen (type I) has been used widely in biomedical fields due to its excellent biocompatibility. In this preliminary study, we investigate the effect of some inorganic ions which are frequently utilized in the preparation of collagen on the morphology and crystallinity of fibrils. The scanning electron microscope and x-ray diffraction were applied to analyze the morphology and the crystallization of the reconstituted collagen fibrils, respectively. Although further studies are needed, these initial results indicate that by controlling the self-assembly conditions of collagen molecules, we may achieve the desired properties of fibrillar collagen products.

Abstract: Nano-titania ceramics is a potential biomaterial for orthopaedic application. In our previous studies, a bioactive nano-titania ceramics was prepared by using alkali-heat treatment. In this paper, hydroxyapatite was used as a grain growth inhibitor additive to get nano-titania ceramics with different grain size, and the effect of grain size on the bioactivity was studied in vitro.

Abstract: This study was carried out to investigate the effect of acid-alkali treatment and alkaliheat treatment on the push-out strength and tissue response of the porous titanium in vivo. Porous titanium with different treatment was implanted in dog bony site for 2 months and 5 months and the push-out strength was tested. At 2 months, the mean push-out strengths of the acid-alkali treated and alkali-heat treated porous titanium were 11.3 and 15 MPa, respectively. At 5 months, the values reached 29.8 and 35 MPa, respectively. Histological observation showed a close contact between implants and bone, and more bone tissue filled inside the pores of porous titanium increasing with implantation time. The results indicated higher bonding strength between bone and porous titanium in alkali-heat treated samples. Therefore, alkali-heat treatment can provide porous titanium implants with better fixation as a bone substitute for clinical use under load-bearing conditions.

Abstract: The bioactivities of titanium oxide film on titanium surface received from different chemical treatment methods were studied in SBF in vitro and mechanically and histologically investigated in vivo. Three groups of titanium specimens were prepared: untreated titanium(S), acid-alkali treated titanium (H), and acid-alkali and heat-treated titanium(X). The oxide film of X surface resulted in more apatite formation and significantly higher strength of the interface between the samples and bone than those of the other titanium groups. The surface of the acid-alkali treated titanium and that further treated by heat treatment had higher bioactivity and stronger bone-bonding ability.

Abstract: Fixation nail systems , such as DHS, DCS and the standard Gamma-nail, are widely applied for the 31-A2 intertrochanteric unstable fractures treatment, but which one would be of more curative effect is still remained as a disputed problem. In this work, precise femur model with 31-A2 fracture was rebuilt based on the CT data, and fixation nail models were built by CAD. By the means of finite element analysis (FEA), the biomechanical data of femur and nail systems were achieved under typical loading. The results show that under the same load, the maximal stresses on the fracture sections for DCS, DHS and Gamma nail systems are 48MPa, 24MPa and 19MPa, separately; and the directional deformation is the highest with DCS fixation systems, while lowest with Gamma nail fixation system. Considering the mechanical safety, Gamma nail is more suitable for 31-A2 intertrochanteric unstable fractures treatment.