中文摘要：

通过琥珀酸酐将低分子量支化聚乙烯亚胺（PEI，分子量1000）偶联到普鲁兰多糖（Pullulan）上，合成了新型基因载体P—PEI．利用。HNMR、FTIR、粒度仪、Zeta电位仪、透射电镜和凝胶电泳对聚阳离子载体及其与质粒pDNA的复合物进行了表征．凝胶阻滞实验结果证明，载体P—PEI在体外可以通过静电相互作用稳定结合pDNA，并能有效抑制DNA水解酶及血清成分对pDNA的降解．噻唑蓝（MTT）细胞毒性测试、绿色荧光蛋白表达质粒（pGFP）及荧光素酶表达质粒（pGL3）转染实验结果表明，载体P—PEI在N／P高达12．5时对细胞MCF-7，HeLa和COS-7的毒性低于PEI；当N／P为6．25时能有效将pGFP和pGL3带入Hela细胞并表达，最佳转染效率及荧光素酶活分别为[（36．67±0．25）％和（28．73±7．19）×10^8RLU／mg蛋白，RLU为光强度]，比Lipo2000[（49．13±0．61）％，（58．47±7．62）×10^8 RLU／mg蛋白）略低．因此以Pullulan为骨架材料的P—PEI是一种新的有潜在应用价值的非病毒基因载体．

英文摘要：

A novel non-virus gene delivery vector（P-PEI） was synthesized by grafting low-molecular branched PEI（molecular weight： 1000） onto the backbone of pullulan with succinic acid as a spacer. 1H NMR, FTIR, particle size analysis and zeta-potential measurements, TEM and gel electrophoresis were performed to characterize P-PEI and P-PEI/pDNA complexes. Gel electrophoresis retardation assay demonstrated that P-PEI can wrap pDNA with electrostatic interaction excellently even in the presence of heparin, and protect pDNA from the degradation by DNase I and serum. Compared with PEI/pDNA complexes, the P-PEI/pDNA complexes show relative lower cytotoxicity against MCF-7, HeLa and COS-7 cells, even at high N/P（ up to 12. 5 ） demonstrated by MTT assay. Flowcytometry revealed that the highest transfection efficiency[ （36.67±0. 25 ）% ] for P-PEI as a delivery agent was obtained at N/P ratio of 6.25, which was comparable with that of Lipofectamine 2000[ （49. 13±0.61 ）% ], and consistent with the results of luciferase expression. These results suggest that the pullulan-grafted branched polyethylenimine polymer（P-PEI） might be an excellent biocompatible candidate for gene delivery systems.