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BACKGROUND: Chitosan is one of the most significant non-viral vector materials with the advantages of outstanding biocompatibility. Quarternary chitosan derivatives can improve transfection efficiency and solubility of chitosan in a broader range of pH values. OBJECTIVE: To synthesize a new vector of quarternary chitosan and to study its complex conditions with plasmid and transfection efficiency compared with chitosan. DESIGN, TIME AND SETTING: A contrast observational study was performed in Second Affiliated Hospital of School of Medicine of Zhejiang University between August and October 2008. MATERIALS: Quarternary chitosan was synthesized in Polymer Materials Lab of Beijing Institute of Technology. Plasmid pEGFP-C1 was presented friendly by Mr. Zheng of School of Medicine of Zhejiang University. Hela cells were provided by Miss. Cheng of School of Medicine of Zhejiang University. METHODS: Quarternary chitosan was prepared according to mass concentration of 0.2 g/L, pH value 5.5 (or 6.9, 7.6) and sodium acetate concentration of 50 mmol/L, and rapidly mixed with pEGFP-C1. The mixture was swirled for 15-30 second and stood at room temperature for 30 minutes at least. MAIN OUTCOME MEASURES: The impacts of pH values and time on complex ability of quarternary chitosan and plasmid were studied by gel retardation test. Transfection efficiency of quarternary chitosan on Hela cells was observed by inversed fluorescence microscope and also compared with chitosan. RESULTS: Quarternaty chitosan could form complex with plasmid in acidic, neutral and basic conditions. It could be used in a broader range of pH values. In an acidic condition, the combination of quarternary chitosan with plasmid was superior to chitosan. A stable complex was formed via a combination of quarternary chitosan or chitosan with plasmid within 30 minutes, and the stability lasted for 12 hours. Transfection efficiency of quarternary chitosan on Hela cells demonstrated that transfection efficiency of quarternary chitosan was superior to chitosan. CONCLUSION: Quarternary chitosan has a broader range in use and higher transfection efficiency than chitosan; however, there is no significant difference in stability between quarternary chitosan and chitosan. Additionally, transfection efficiency of quarternary chitosan on Hela cells is superior to chitosan, which needs a further research.
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BACKGROUND: Cellulose is natural material, which has good chemical stability and biocompatibility. The modified material from cellulose has new properties besides its inherent properties.OBJECTIVE: Based on cytocompatibility evaluation tests, this study is designed to evaluate the cytocompatibiUty of materials synthesized from cellulose to make sure its reliability.DESIGN: Contrast study.SETTING: Department of High Polymer, Material Science and Engineering College, Beijing University of Technology.MATERIALS: This study was performed in the Material Science and Engineering College, Beijing University of Technology between March 2003 and June 2004. The material from cellulose prepared by Beijing University of Technology was white, granules, no taste, and no volatilization (density: 1.2 g/cm3, pH: 6-7). L-929 vigorous cells were provided by Chinese Military Academy of Medical Science. Ten male New Zealand rabbits were provided by Animal Center of Chinese Military Academy of Medical Science.METHODS: Based on GB/T16175-1996 standard, cytotoxicity of the materials from cellulose on L-929 cells was evaluated by growth suppression technique (MTr chromatometry). In addition, based on GB-T14233.2-1993 standard, hemolysis in vitro was evaluated through measuring erythrocyte lysis and ferrohemoglobin freeing degree with indirect contact method.MAIN OUTCOME MEASURES: Cytotoxicity test and hemolysis test.RESULTS: Cytotoxicity test showed that the materials from cellulose did not have obvious toxicity on L-929 cells, and the cytotoxicity graduation of the materials from cellulose was 1 or 0. Hemolysis test suggested that the materials from cellulose did not have obvious hemolysis reaction, and the hemolysis rate in vitro was 1.5 %, which was less than the national standard (5%).CONCLUSION: The materials from cellulose do not have obvious cytotoxicity but have great cytocompatibility.
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The thermooxidative degradtion of ethylene oxide and tetra-hydrofuran (EO-THF) co-polyether has been studied by electron spin resonance(ESR),Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The initial degradation site was found to be at the α-carbon of the ether bond. Two free radicals which derived from dehydrogenation and oxygen addition were successfully detected by spin-trapping technique which used α-phenyl-N-tert-butyl nitrone (PBN) as spin trap. Both FT-IR and NMR have been used tofollow structural changes of the copolyether during degradation. Nearly 20 product frngnents including formate,carbonate,methyl,alcohol,methylene-dioxy,hydroperoxide and semiformal have been characterized by 1 D and 2 D NMR.The thermooxidtion of co-polyether preferred to occur on the THF units especially at the alternating linkage of EO and THF.Antioxidant (BHT) not only retarded the thermooxidation but also modified the degradation products with less ester and methylene-dioxy groups but more hydroxyl and methyl groups.