Jian Xin Wang

GRADED POROUS TITANIUM SCAFFOLDS FABRICATED USING POWDER METALLURGY TECHNIQUE

Graded porous titanium scaffolds with a pore size of 300–400 μm are prepared by sintering. Their mechanical properties and porosity are investigated. Compared with common titanium scaffolds, the mechanical properties of graded specimens can be improved by introducing graded structure. The graded porous titanium scaffold consists of inner, middle, and outer layers. When the outer layer porosity of the graded specimen is increased from 67 to 72%, the Young’s modulus of the graded specimen increases from 3.29 to 4.72 GPa, meanwhile the compressive strength increases from 131.9 to 165 MPa, respectively. These results suggest that the graded porous titanium scaffold has potential application for tissue engineering scaffolds under load-bearing conditions.

In Situ Growth of Carbon Nanotubes in Hydroxyapatite Matrix by Chemical Vapor Deposition

Carbon nanotubes (CNTs)/hydroxyapatite (HA) nanocomposites have been successfully fabricated by a novel method for the biomedical applications, which is in situ growing CNTs in HA matrix in a chemical vapor deposition (CVD) system. The results show that it is feasible to in situ grow CNTs in HA matrix by CVD for the fabrication of CNTs/HA nanocomposites. Multi-walled CNTs with 50-80 nm in diameter have been grown in situ from HA matrix with the pretreatment of sintering at 1473K in air. The nanocomposites are composed with carbon crystals in CNTs form, HA crystallites and calcium phosphate crystallites, one of most important CaP bioceramics. And the CNTs content is about 1% proportion by weight among the composites in our experiments, which can enhance the HA mechanical properties and the CNTs content does not affect the HA performances. These CNTs/HA nanocomposites have the potential application in the biomedical fields.

Preparation of Porous Titanium by a Novel Foaming Process and MG63 Cell Behavior In Vitro

A novel two-step foaming process has been developed to prepare the porous titanium implant. By using H2O2 and stearic acid as foaming reagent ordinally, a foamed structure with an open, interconnected pore morphology was obtained. The mechanical property was determined by compressive test. In vitro study was conducted to evaluate the ability of the porous titanium to support the growth and differentiation of Human osteosarcoma cell line MG63. The results show that the porous titanium has better interconnection compared to that obtained by traditional slurry foaming and its compressive strength and Young’s modulus were approximate 23.6 MPa and 2.1 GPa, respectively. Cell culture experiment results indicate that the porous titanium has good biocompatibility and acid-alkali treatment facilitates the adherence and proliferation of cells.

Sb2O3 doped and microwave assisted sintering of ITO

Abstract Indium tin oxide (ITO) ceramics with high densities are difficult to achieve using conventional heating because of the volatilisation of both indium oxide and tin oxide at high temperatures. In our present study, we proposed to use a Sb2O3 doped and microwave hybrid sintering approach to prepare for ITO ceramics. The effects of the Sb2O3 content on the microstructure, densification and electrical properties of ITO ceramics were investigated. The results show that the relative density has reached 98·3% by using the hybrid sintering approach. The resistivity of the obtained ceramics showed a decrease tendency with increasing Sb2O3 content in the range of 0–1·5 wt-%. We speculate that the formation of electrons and vacancies caused by the doping of Sb2O3 and the ‘microwave effect’ might be the main reason responsible for the increase in the densification. As a result, these, in turn, further enhanced the electronic conductivity of the obtained ITO ceramics.

Morphological Characterization of Chitosan in the Hydroxyapatite/Chitosan Nanocomposites

The morphological differences of chitosan (CS) in the hydroxyapatite (HA)/CS nanocomposites were investigated in detailed, which were prepared via in situ hydrothermal precipitation. The results show that the obtained nanocomposites have excellent crystallinity and the crystal has excellent ordered structure, which is important to the composites performances in the biomedical application. Moreover, the CS arrangement and crystallinity in the composites greatly depend on the hydrothermal temperature and the pH value of precipitating agent. The temperature ranging from 373 to 413K and pH value of precipitating agent ranging from 12 to 14 were favorable to the crystallization and oriented growth of CS molecules in the composites. The CS crystals with better arrangement are assembled in the order of layer-by-layer in these composites.

Nano-HA Coating on Titanium Surface Fabricated by Modulation of Self-Assembled Monolayer and Bovine Serum Albumin

Bone-like hydroxyapatite (HA) coatings were fabricated on titanium implants by a self-assembled technique and biomimetic method. After titanium plates were oxidized in a mixture of H2SO4/H2O2, a hexadecanoic acid self-assembled onto titanium surfaces. Contact angles of water and tricresyl phosphate on the surfaces were measured to characterize the self-assembled monolayer (SAM) and confirm the presence of the functional group. The titanium plates with SAM were used to fabricate HA coatings. In the simulate body fluid (SBF) with and without bovine serum albumin (BSA), Ca2+ and PO4 3- ions could spontaneously deposit onto the titanium surfaces and form bone-like HA coatings. The morphology, component and structure of samples were examined by scanning electronic microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy. The results suggested that the SAM can induce the formation of the nano-HA coating with a network and microporous structure. For the biomimetical HA coating induced by HDA-SAM, BSA could modulate the growth of HA crystal and decreased the grain size.

The Effect of Particle Morphologies on Mechanical Properties of Porous Hydroxyapatite Scaffold

Porous hydroxyapatite (HA) ceramic scaffolds are extensively used to induct the tissue growth for bone repair and replacement, and serve functions to support the adhesion, transfer, proliferation and differentiation of cells. Highly porous structure is always expected for its positive effect on the bone regeneration in vivo, nevertheless high porosity always accompanies a decrease in strength of the HA ceramic scaffolds. Therefore, it is significant to improve the strength of the HA ceramic scaffolds with highly interconnected porosity so that they are more suitable in clinic applications. The aim of this study is to investigate the effect of starting materials on mechanical property of final scaffold in order to optimize the preparation process. In this work, three starting HA particles with different morphologies are used to prepare highly porous HA ceramic scaffolds by the polymer impregnation approach in the same preparation process. The phase composition, microstructure and mechanical properties of the sintered porous HA scaffolds are investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM) and compressive test. The experimental results show that the particle morphologies have influence on the slurry viscosity and further affect the coating amount on the sponge. The porous HA ceramics fabricated by spherical HA particle hold the highest compressive strength than the other two HA scaffolds for better sintering property. It is an effectively method to improve the mechanical property of porous HA ceramic scaffolds by optimizing the starting particle morphology.

Immobilization of Bovine Serum Albumin on Titanium through Plasma Polymerization of Allylamine and Crylic Acid

In the present work, technique of plasma polymerization was used to generate amido (- NH2) and carboxyl (-COOH) on titanium surface for immobilizing bovine serum albumin (BSA). After plasma polymerization of allylamine and crylic acid, the contact angle with respect to double distilled water significantly increased. Surface components were detected by X-ray photoelectron spectroscopy and Fourier transform infrared reflection-absorption spectroscopy. The results showed that BSA was successfully immobilized on the titanium surface and the amounts of BSA on specimens were relied on the properties of thin film deposited through plasma polymerization, which was corresponding to the ultraviolet spectrophotometer result.

Hydroxyapatite Formation and Protein Absorption on Triethyl Phosphate Modified Titanium Surface

In this work, triethyl phosphate (TEP) was used to bioactivating titanium. Titanium plates grafted with TEP were immersed in a two times concentrated simulated body fluid (2SBF) to investigate deposition of hydoxyapatite (HA) on the surface. A phosphate buffer solution (PBS) with bovine serum albumin (BSA) was used to evaluate adsorption of protein on the grafted titanium surface. The morphology, component and structure of samples were examined by scanning electronic microscopy, attenuated total reflection Fourier transform infrared spectroscopy and X-ray diffraction respectively. The concentration change of BSA in adsorption test was examined with the ultraviolet-visible absorption spectra (UV). The analyses showed that TEP grafted onto the titanium surface. In 2SBF, calcium and phosphate ions deposited spontaneously onto the grafted titanium surface and formed a HA coating with a network-like microporous structure after being immersed for 3 days. The coating consisted of HA particles with 180-265nm in thickness and 72-85nm in width. The diameter of the micropores was about 200nm. The HA coating appeared better uniformity than that on the modified titanium using phosphoric acid. BSA rapidly adsorbed onto the grafted titanium surface at first half an hour and then the adsorption quantity almost kept constant. These results indicate that TEP grafting is an effective approach to modify bioactivity of titanium.