Materials Science Forum Vols. 610-613

Abstract: Based on the basic theory of molecular recognition , we design a organic molecules model to induce the crystallization of hydroxyapatite to synthesized tooth-like calcium phosphate/hydroxyapatite under a controllable way in vitro. The cross-linking of collagen on the dentin surface and extraneous collagen was optimized by varying the molar ratio of N,N-(3-dimethylaminopropyl)- N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) at a constant EDC concentration. CaCl2 and Na3PO4-12H2O solutions were added after the crosslinking process. X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis of organic protein monolayer for samples. The obtained composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX). XPS and FTIR analysis showed the surface organic compositions in experimental group is higher than that of normal dentin and decalcified dentin surface. The results showed that the dentinal tubule were blocked by neonatal hydroxyapatite layer which has a continuous structure of columns crystal with size of 10-40nm. Furthermore, there were column crystal with parallel direction inside, similar to the crystal array in the top of enamel rod. This study showed that the specific organic molecule model can be used as a potential effective crystal growth modifier.

Abstract: The bioactive glass is used widely as bone-repairing material due to its excellent bioactivity, biocompatibility and the function for bone restoration, which depended, to a great extent, on the composition, microstructure of the glass and the process conditions. In this study, effect of process conditions (the melting temperature and time) on compositions, microstructure and the properties of bioactive glass was analyzed using EDS, Density measurement, XRD and FTIR techniques. The results indicated that compositions and microstructure changed because of the selective evaporation of constituent and the change in homogeneity of components.The bioactivities of the glasses prepared under different process conditions were characterized by immersing the glass particles in simulated body fluid (SBF) combined with FTIR technique. The results indicated that hydroxyl-carbonate-apatite (HCA) layer formed on the surface of the samples after 24 hours soaking in SBF. A quantitative method was used to compare the bioactivity of samples. It indicated the different preparation processes had influence on the bio-mineralization properties. Then the optimal preparation condition (1450°C, 30min) was obtained.

Abstract: As a typical biological material, bone possesses high fracture strength and fracture toughness, which are closely related to its exquisite microstructure. SEM observation of a cannon bone shows that the bone is a kind of layered bioceramic composite consisting of hydroxyapatite sheets and collagen matrix. The hydroxyapatite sheets are of long and thin shape, distributing in parallel. The fracture toughness of the bone is analyzed with the representative model of the hydroxyapatite sheets and the concept of maximum pullout energy. It is shown that the lathy shape as well as the parallel distribution of the hydroxyapatite sheets increases the pullout energy and endows the bone with high fracture toughness.

Abstract: Objective：To observe the effect of human platelet extracts on proliferation and differentiation of rabbit growth-plate chondrocytes in monolayer and fabrication of tissue engineering cartilage in vitro. Method: To determine the effects of platelet extracts at different concentrations on proliferation and differentiation of rabbit growth-plate chondrocytes using 3H-TdR、PNP and HE staining. Results: Platelet extracts had very strong stimulative effects on proliferation and differentiation of chondrocytes, especially the hypertropization (termination) of chondrocytes.

Abstract: Aim In this study, the adaptability of an ELISA kit for quantification the residual BSA in TEMPs, the influence of rinsing protocol on reducing the residual BSA in TEMPs and the effectiveness of ultra-filtration on reducing the matrix effects of TEMPs immersion on BSA quantitative by ELISA were discussed. Methods Three kinds of TEMPs used in this study were: tissue engineered skin (TES), recombination human acellular dermal matrix (rhADM) and combination chitosan tissue engineered skin (cC-TES). The devices were rinsed according to the Directions for Use firstly. To investigating the influence of rinsing protocol on reducing the residual BSA in TEMPs, TES were rinsed by two different protocols separately. Then TEMPs immersions were prepared according to ISO10993.12, physiological saline (NS) was used as immersion medium. BSA concentration in immersions and filtrate were determined by using the “Quantitative measure of residual BSA ELISA kit” (detection range was 12.5-200ng/mL, manufactured by WUXI BOSHENG MEDICAL BIO-TEC DEVELOPMENT CO., LTD. As suspected to have some matrix effect on BSA quantification by ELISA kit, rhADM immersion was ultra-filtrated before detection. Results The results showed good correlation between dilution factors and the A450nm of TES and cC-TES immersions, correlation coefficient (r) was 0.9943±0.0007 and -0.9835±0.0037, respectively. No significant effect on BSA detection was found when NS was used as immersion medium. Comparing the results of protocol 1 and 2, the A450nm of TES immersion was significantly decreased after rising by protocol 2. After ultra-filtration, the correlations between absorption and dilution factors of rhADM immersion were improved significantly; the correlation coefficient (r) was raised from -0.7264±0.0089 to -0.9606±0.0039. Conclusions The quantitative ELISA kit was considered to be adaptability for detect the BSA in TEMPs. Different rinsing protocol may obviously affect on reducing the residual BSA in TEMPs. The matrix effects of rhADM immersion can be reduced obviously by using ultrafiltration.

Abstract: TiO2, ZrO2 and titanium oxide in deficiency oxygen environment were used to modify the surface of biomedical NiTi stents. The coatings were prepared by vacuum deposition. The surface microstructures and characteristics, blood compatibility of the modified stents in simulated body fluids were assessed using scanning electron microscopy (SEM), hemolysis test, coagulation test and blood platelet adhesion test. The hemocompatiblity of the modified stents were all improved by layer coating. Enhancement of blood compatibility was believed to stem from the improved surface water affinity and hemolysis resistance of the layer, and titanium oxide in deficiency oxygen environment displayed better. This study indicated that layer coating was a promising effective modification method for improving the surface properties of biomedical NiTi alloy intravascular stents. As a coating materials，titanium oxide in deficiency oxygen environment was better than TiO2 and ZrO2.

Abstract: Organic polymer–hydroxyapatite (HA) hybrid was expected as a promising bone substitute. In this work, poly(vinyl alcohol) (PVA) was used as a polymer substrate and the PVA-HA hybrid was prepared by a biomimetic process. The resultant PVA-HA composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. It was found that HA could deposite on PVA surface when PVA soaked in water for a little swelling and then was carried out CaP treatment previously. The formed HA showed bone-like structure and had a good interaction with PVA substrate. The resultant hybrid might exhibit good osteoconductivity and biocompatibility, and could be expected as a useful scaffold for bone tissue regeneration.

Abstract: PPy film with micro-antennal morphology was prepared by potentio-static method without any templates directly onto the surfaces of iron, platinum and gold-plated plastic sheets, respectively. Morphology of PPy film was observed with scanning electron microscopy, and its electrochemical properties were determined by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Attention was paid to the influence of reaction time, potential value, types of substrates, types and conconcentrations of electrolyte on the morphology and electrochemical properties of PPy film. Stable PPy film with thriftily long antennae was obtained on different substrates with good electrochemical properties. The film was applied for a prototype of biosensor, in which bioactive substance of glucose oxidase was immobilized.

Abstract: Hydroxyapatite/TiO2 composite material was coated onto Ti25Nb3Mo2Sn3Zr (TLM) alloy substrate. To study the effects of hydroxyapatite/TiO2 composite coatings on bone-related protein expression, the osteoblast were cultured with composite coatings for different times. The phase transformation and compound formation of the HA/TiO2 coatings were investigated using XRD (X-ray diffraction). The mRNA expression of Type I collagen, alkaline phosphatase (ALP) and osteocalcin were studied by RT-PCR (reverse transcriptional polymerase chain reaction). The titania delayed the crystallization of HA. The mRNA expressions of Type I collagen are decreased as the increasing of TiO2 percentage. The mRNA expressions of osteocalcin are approached. The ALP expression on H4 coating (HA/TiO2 mol ration is 5) after the osteoblast cultured with composite coating for 6 days is the highest. The increasing of TiO2 amount decreases the bioactivity of the composite coatings.

Abstract: The aim of this paper is to present a synthesis method of biodegradable aliphatic polyesters by the ring opening polymerization of lactones catalyzed with nontoxic magnesium compound. Poly(DL-lactide-co-ε-caprolactone) copolymers were prepared by the copolymerization of DL-lactide and ε-caprolactone using magnesium octoate as a catalyst. Microstructure and crystallization and thermal properties of the obtained polymers were investigated by NMR, XRD and DSC.