Xing Dong Zhang

Preparation of Bioactive Tantalum Metal via Anodic Oxidation Treatment

After the Tantalum metal was subjected to the anodic oxidation at suitable voltage in 2M H2SO4 solution, tantalum oxide with rhombic or amorphous structure formed on the metal surface. The Oxide showed apatite formation ability in simulative body fluid at 6d. It meant the anodic oxidation treatment ia an effective method to accelerate the bioactivity of tantalum metal.

Evaluation of Bioactivity and Cytocompatibility of Nano-Hydroxyapatite/Collagen Composite In Vitro

A nano-hydroxyapatie/collagen composite was fabricated by an in situ synthesis technique. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analyses for the composite indicated crystals on the collagen fibril matrix exhibited certain orientation. Bioactivity of the composite was investigated through in vitro tests in a sterile simulated body fluid (SBF) system. Scanning electron microscopy and energy-dispersive X-ray analysis of the composite showed that the composite had the ability to induce the formation of calcium phosphate crystals on the surface of the composite in SBF. The cytocompatibility of the composite was evaluated by in vitro cytotoxicity test. Both the results from MTT assay and scanning electron microscope (SEM) observations indicated that the composite had no adverse impact on cell proliferation and morphology. The results imply the composite is high bioactive and has good cytocompatibility.

Reinforcement and chemical cross-linking in collagen-based scaffolds in cartilage tissue engineering: a comparative study

Mechanical strength and biocompatibility are issues of most concern for scaffolds in cartilage tissue engineering. Collagen modification is always used to strengthen scaffolds. There are mainly two ways for collagen modification: inclusion of reinforcing phase to form composites and chemical cross-linking. To explore an alternative approach, the collagen hydrogel modified by a reinforcement phase was compared with cross-linking. Collagen-alginate hydrogel (CAH) and collagen hydrogel cross-linked by genipin (CGH), which were different in modification methods, were chosen candidates. A comprehensive study was carried out on mechanical, structural and biological properties including swelling ratio measurement, in vitro degradation, AFM, mechanical test, thermogravimetric analysis, and in vitro cartilage tissue engineering. The results showed that mechanical strength of collagen was more enhanced for CGH than CAH, as evidenced by analysis of swelling ratio, in vitro degradation, AFM, mechanical test and thermostability. MTT and histological results showed that CGH was superior to CAH with less cytotoxicity and more chondrocytes distributed as well as more aggrecan secreted. With the increase in culture time, the cytotoxicity of cross-linker may be alleviated. CGH may provide a more favorable biomimetic environment for cartilage growth. All these indicated that selecting a cross-linker with a minimal cytotoxicity could be more promising for collagen modification, with improvements observed in both physical and biological properties. For reinforcement, it was required that the incorporated component should be equipped with better or equivalent properties compared with collagen. This study provided important implications to engineering collagen-based hydrogels for cartilage graft applications.

Preparation of Electrospun PLA Nanofiber Scaffold and the Evaluation In Vitro

A electrospinning process to prepare soft tissue engineering scaffold was introduced in this study. This kind of scaffold was composed with ultrathin fiber and characterized with high porosity, well-interconnected pores and high surface-to-volume ratio. Biodegradable polylaticacid (PLA) was used to spin the scaffold and the scaffold was evaluated in vitro by analysis the microscopic structure, porosity, mechanical property, especially cytocompatibility. The results indicated that the electrospun PLA scaffold showed good cytocompatibility and the tensile property of electrospun scaffold was similar to human’s soft tissue. It could be expected that the electrospun scaffold would be potential in soft tissue engineering or soft tissue repair.

Compare of Electrospinning PLA and PLA/β-TCP Scaffold in Vitro

In recent years, electrospinning process is gradually applied in producing tissue-engineering scaffold. In this study, we chose polylacticacid(PLA) and β-tertiary calcium phosphate(β-TCP) as raw materials to fabricate PLA/β-TCP biodegradable composite scaffold by electrospinning process. The characteristics of the scaffold and effect of the scaffolds to cell proliferation and cell adhesion was studied. Compare with pure PLA scaffold, blendingβ-TCP in the spinning process of the scaffold could improve the properties of the scaffold, especially the hydrophilicity and the proliferation and adhesion of cells, this means that the material is more potential to be used as tissue engineering scaffolds.

Preparation and Characterization of Nano Hydroxyapatite

The aim of this study is to prepare nano hydroxyapatite powder. Hydroxyapatite powder was prepared via co-precipitated method with the addition of citric acid at pH 9-11 in ambient environment. The precipitates were aged for 24hs, and then milled into powder after washed and dried. The particle morphology and particle size of as prepared HA powders were characterized. The results showed that hydroxyapatite powder with width of 10-30nm and length of 30-100nm was prepared by wet co-precipitation.

3D Finite Element Analysis of Bone Stress around Distally Osteointegrated Implant for Artificial Limb Attachment

Stress shielding, which occurred always around traditional one part implant applied for prosthetic artificial lower limb attachment, would cause osteoporosis and thus result in the loose and extrusion, and then the malfunction of the implant. To improve the structure of the implant, a new type of implant—multi-part implant was developed in this article. Based on CT data and under the maximal load during a normal walking cycle, 3D finite element analysis (FEA) was carried out to analyze the stress of bone around the new implant in three cases of distally truncated femur at high position、middle-position and low-position. Results reveal that stress shielding and stress concentration under the new type of implant reduced effectively compared with the traditional one-part implant, and the stress distribution is much close to the natural bone. Application for distally truncated femur at middle-position and low-position was much better, while stress concentration was marked at high-position. Meanwhile, the stability in vivo can also be maintained with the multi-part implant. The new implant is promising applied for prosthetic limb.

Fabrication of Porous Hydroxyapatite Ceramics by Microwave Sintering Method

Microwave processing of porous hydroxyapatite ceramics was investigated in a dual frequency microwave-sintering furnace. The results revealed that microwave-sintering process could get sintered ceramics at much shorter sintering time and at lower sintering temperature than that of the conventionally heat-sintering process. Further, the microwave-sintered samples showed much smaller grain size and more uniform microstructure and reached a comparable compressive strength. The mechanism of rapid heating behavior of hydroxyapatite ceramics in microwave was also discussed. The results revealed that microwave processing was a promising method for sintering porous hydroxyapatite ceramics.

Preparation and Characterization of Collagen by Hydrogel Formation Method

A kind of medical collagen was prepared by hydrogel formation method. Chemical and physical properties were investigated by FTIR, amino acid analysis, SDS-PAGE, carbohydrate content analysis, heavy metal content analysis. Degradation experiments in vivo and subsequent histological investigations were carried out to evaluate the biological performance. The results suggested that the collagen achieved is promising in tissue engineering scaffold materials for a long-term (more than 12 weeks) implantation application.

Synthesis of Nanosized Carbonated Hydroxyapatite under Microwave Irradiation

In order to solve the problems on synthesizing carbonated hydroxyapatites (CHA) by the conventional heating precipitation method, such as long reaction and large particle size, poor crystallinity of CHA etc, the nanosized CHA particles have been synthesized by microwave heating method using phosphoric acid (H3PO4), calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3 ) as starting materials in the present paper. The influences of power level and time of microwave irradiation on synthesis of CHA have been investigated. The X-ray diffraction (XRD) analysis has indicated that microwave heating will reduce CHA crystallization time and improve crystallinity of CHA. Scanning electron microscope (SEM) analysis has showed that CHA particles are of rod like morphology with about 60nm width and 200nm length respectively. Infrared spectroscopy (IR) analysis has confirmed the B-type CHA precipitate can be formed under microwave irradiation. The microwave irradiation plays an important role to promote the reaction and the synthesis of nanosized CHA particles.