Materials Science Forum Vols. 610-613

Abstract: Chitosan membranes were prepared by solvent cast method. In order to increase cell adhesion of the chitosan membranes, oxygen plasma treatment was applied to improve the hydrophilicity of the surface of chitosan membranes. The surface properties were characterized by scanning electron microscopy (SEM), contact angle analyzer, X-ray photoelectron spectroscopy (XPS). The effects of exposure time, plasma generating power, and chamber pressure on water contact angle of the chitosan membranes were investigated. The water contact angle of chitosan membranes decreased from 94.1° to 49.2° after plasma treatment. Which suggested the surfaces became more hydrophilic. XPS analysis showed that the oxygen content and the ratio of O/C increased markedly after oxygen plasma treatment. Furthermore, it was found that C-H bonds were broken with oxygen plasma treatment. C-OH group had been increased after plasma irradiation.

Abstract: Ti3SiC2 is a bioinert material. The combination of high fracture toughness, excellent corrosion resistance and easy machinability make it a new class of potential biomaterials for orthopedic applications, dental implants, and fixation devices for the bone. In this paper, effect of Si concentration on the sintering of Ti3SiC2 bulk material was reported. Ti3SiC2 bulks were fabricated by pressureless reactive sintering of powder compacts made of Ti, Si and graphite powders. Nearly pure Ti3SiC2 bulk was obtained by reactive sintering of the powder compact, with a nominal composition of 3:1.1:2 in molar ratio of Ti:Si:C, at 1500 °C for 120 minutes. TiC, a non-preferable impurity was avoided by the appropriate addition of excess Si (relative to stoichiometric composition of 3:1:2 in Ti3SiC2). However, too much Si will result in the formation of significant amount of TiSi2 and SiC in the sintered Ti3SiC2. Microstructure of the prepared Ti3SiC2 bulks was analyzed by scanning electron microscope. Phase constituent analysis was carried out by x-ray diffraction. Effect of Si content on the density of sintered samples was also studied.

Abstract: Oxygen plasma was employed to treat a fluorosilicone acrylate RGP contact lens material (Boston EO) in order to improve surface hydrophilicity. X-ray photoelectron spectroscopy (XPS) was applied to characterize the surface chemical state. The surface morphology and hydrophilicity were investigated by scanning electron microscope (SEM) and contact angle measurement respectively. The surface contact angle measurement indicated an evident improvement of surface hydrophilicity after plasma treatment. XPS results indicated that the incorporation of oxygen and the transform of -Si-CH3 into hydrophilic -Si-O after plasma treatment were the main reasons for surface hydrophilicity improvement. SEM showed some decrease of surface roughness under moderate plasma condition. But plasma with higher power would etch the material surface.

Abstract: In order to improve the surface hydrophilicity and the resistance to protein deposition of fluorosilicone acrylate RGP (rigid gas permeable) contact lens, low temperature ammonia plasma treatment was used to modify the lens surface. The changes of surface structures and properties were characterized by contact angle analyzer, X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Effects of exposure time and plasma generating power on surface properties of the RGP contact lens were investigated. The surface contact angle measurements showed a great improvement of hydrophilicity after plasma treatment. XPS analysis indicated that the oxygen content and the nitrogen content increased remarkably after ammonia plasma treatment. Furthermore, the content of the hydrophilic group O-C=O/N-C=O on the surface increased and the content of the hydrophobic group CF2 decreased after plasma treatment. AFM results showed that ammonia plasma could lead to surface etching.

Abstract: In situ synthesis technique of β-tricalcium phosphate(β-TCP)/ Na-doped 58S bioglass composite powders were investigated. Firstly, the β-TCP ultra-micro powders are synthesized via wet chemical method. β-TCP/Na doped 58S bioglass composite powders were synthesized in situ by sol-gel technique, using tetraethyl orthosilicate(TEOS), triethyl phosphate(TEP), calcium nitrate tetrahydrate(Ca(NO3)2•4H2O), sodium nitrate(NaNO3) as starting materials. The composite powders were characterized by XRD, EDX　and SEM. The bioactivity of the synthesized powders was analyzed by immersion studies in simulated body fluid (SBF). The results show that the composite powders are made up of good crystalline β-TCP and amorphous bioglass, and it was conformed that the material had good osteoproduction and bioactivities, that is an indication of bioactive potential in vivo. It is believed that the β-TCP/ Na-doped 58S bioglass (58SN) composite by sol-gel technique in situ could be a desirable biomaterial for preparing scaffold of bone tissue engineering.

Abstract: A nano-carbon and iron composite--carbon coated iron nanoparticles produced by carbon arc method can be used as a new kind of magnetic targeting and heating drug carrier for cancer therapy. It presents an special nanostructure of iron nanoparticles in inner core and nano-carbon shells outside. The nano-carbon shells have a high drug adsorption ability because of its high surface area and its inner core has great effect of targeting magnetic heating. Magnetic induction heating effect of pig liver injected mixed liquids with different concentration carbon coated iron particles in physiological saline indicates that the more quantity of nanoparticles used, the higher temperature it is. Magnetic induction heating effect of the pig liver was compared in the case of filling method and injection method (both were containing 0.3g carbon coated iron nanoparticles). The iron nanoparticle in its inner core has good effect of magnetic induction heating, the temperature can go up to 51 °C in the case that carbon coated iron nanoparticles mixed with physiological saline were distributed uniformly in pig liver. And the temperature can go up to 46°C in the case that carbon-coated iron nanoparticles was injected in a certain section of pig liver. It is obvious that injected one is much better than that of filled, but they are all enough to kill the cancer cells.

Abstract: To further improve the bioactivity of Ti6Al4V alloy and to accelerate bone growth, the porous TiO2 coating containing calcium and phosphate prepared on Ti6Al4V alloy substrate using micro-arc oxidation (MAO) technique was treated in 5M NaOH aqueous solution at 60 °C for 24 h and followed by a heat treatment at 400 °C for 1 hour (termed as MAONH). The experimental results showed that Ca2+ and P5+ easily precipitated on the MAONH coating and formed a thicker apatite film. The reason could be ascribed to hydrolysis of CaTiO3, which resulted in appearance of large numbers of Ca2+ and OH- ions within coating.

Abstract: Fluor-hydroxyapatite (FHA) films were deposited on titanium and laser gas nitrided titanium substrates using sol-gel technique respectively. Typical apatite structures were obtained for all coatings after dipping and subsequent heat treatment from 600°C to 800°C. The obtained films were uniform and dense, with a thickness of 5 μm. The 3-D TiN dendritic structure fabricated on the surface of Ti plate using laser gas nitriding technique in advance should be help anchor the HA/FHA coating and improved the interfacial adherence significantly compared with the naked titanium surface.

Abstract: The development of skin tissue engineering provides a noninvasive method for skin restoration. Unfortunately, the lack of a vascular plexus leads to greater time for vascularization compared with native skin autografts and contributes to graft failure. Our purpose was to construct tissue-engineered skin with VEGF- modified human bone marrow mesenchymal stem cells (hMSCs) as well as acellular dermal matrix(ADM) in vitro , Thus by increased vascular endothelial growth factor expression, which could prospectively improve vascularization of tissue-engineered skin for wound healing applications. To reach this aim, hMSCs were isolated and cultured with density gradient centrifugation combined with attachment culture method in vitro. Liposome- mediated gene transfer was used to generate a population of hMSCs overexpressing the gene encoding VEGF165. Then VEGF- modified hMSCs were seeded onto the surface of ADM. The experimental results showed that ADM we prepared has good compatibility with MSCs, the cells in ADM grew and proliferated well in vitro and the tissue - engineered skin with VEGF- modified hMSCs and ADM has been successfully constructed.

Abstract: Objective: To investigate effects of bFGF and collagen on tissue-engineered cartilage in pellet culture. Methods: Rabbit rib growth-plate chondrocytes were incubated in pellet culture. bFGF and Collagen was applied alone and in combination based on the results of previous search . The histological structure of neocartilage was observed by species stained with H＆E and Immunohistochemical analysis. The DNA content of neocartilage was measured by hoechst33258 dye. The production of matrix was estimated from the determination of hydroxyproline content and Alcian Blue method. Results: Chondrocytes formed cartilage-like tissue with distinct differentiated zones and regions. The DNA content of neocartilage was enhanced by bFGF and collagen. The production of collagen and PG was promoted by collagen. bFGF and collagen could suppress the expression of collagenⅠwhile they could decelerate the decrease of collagenⅡ. The combination of bFGF and collagen had synergistic effects. Conclusion: Pellet culture could maintain chondrocytes phenotype and enhance matrix production; bFGF could stimulate the proliferation of chondrocytes, collagen could stimulate the proliferation and the matrix production of chondrocytes, it also had a positive effect on the maintenance of cell phenotype, the combination of bFGF and collagen had synergistic effects on the maintenance of chondrocytes phenotype and the regeneration of cartilage.