| Summary: | 碩士 === 高雄醫學大學 === 醫藥暨應用化學研究所碩士班 === 94 === Polyelectrolyte complexes have been widely studied as gene carriers in recent years. Polyethylene imines (PEI, MW=600) was grafted onto chitosan (PEI-g-CHI) as a non-viral gene carrier in order to improve the inherent transfection efficiency of chitosan (CHI, MW=330K). In this study, we demonstrated a novel method to conjugate the amine groups between CHI and PEI through the epoxide rings of ethylene glycol diglycidyl ether (EX-810). We characterize the degree of substitution of PEI onto CHI by NMR. The cytotoxicity determined by MTT assay showed that the cell viability of PEI-g-CHI is compatible to CHI at the low concentrations using human kidney 293T cells, but a lower cytotoxicity at the high concentration of 1 mg/ml. However, the cytotoxicity of CHI and PEI-g-CHI was much lower than that of PEI (MW=25K) and LipofectamineTM2000. After the formation of polyplexes between PEI-g-CHI and plasmid DNA, we measured the particle size, zeta potential, and stability of the polyplexes at different N/P ratios. The mean particle sizes of PEI/DNA, PEI-g-CHI/DNA, and CHI/DNA were from 154 to 229, 197 to 265, and 185 to 294 nm, varying with N/P ratios, respectively. The mean particle size of the PEI/DNA polyplexes was smaller than that of other two polyplexes. Though the mean particle size of the PEI-g-CHI/DNA polyplexes was smaller than that of the CHI/DNA polyplexes, the zeta potential did not increase in the PEI-g-CHI/DNA polyplexes at different N/P ratios. When compared the transfection efficacy using the same weight ratios of polymers to plasmid DNA, PEI-g-CHI showed a better transfection efficacy than CHI (330K).
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