中文摘要：

用邻位苄基溴与双胺进行门舒特金反应,合成了2种线性的季铵盐阳离子聚合物.其中,含有酚基酯键的阳离子聚合物,一旦进入细胞后,可以在细胞内的酯酶催化下快速水解,使得聚合物自降解断裂为不带电的非季铵盐小分子,从而快速释放DNA,最终达到提高转染效率的目的.通过对复合物纳米颗粒的粒径和电势测定,证明了这2种阳离子聚合物都能够有效地结合DNA形成表面带正电的复合物纳米颗粒.凝胶阻滞电泳实验表明,所合成的阳离子聚合物都能稳定地包裹DNA.而在酯酶条件下,含有酚基酯键的阳离子聚合物可以发生降解,使得纳米复合物释放出DNA.同时,含有酚基酯键的阳离子聚合物由于其独特的可降解性,相比于PEI,降低了细胞毒性.在体外细胞转染实验中,2种阳离子聚合物都有较好的转染效果.其中酯酶响应的载体在高N/P下依然表现出较高的转染效率,说明该阳离子载体能够在细胞内有效降解并释放出DNA.

英文摘要：

Cationic polymers have been widely explored as non-viral gene delivery vectors. The high density of cationic charges and high molecular weight of cationic polymers enable them efficiently condense DNA into nanosized polyplexes, which protect DNA from degradation and facilitate DNA cellular internalization. However, these characters also make the polyplexes hardly dissociate to release DNA, hindering its access to the DNA transcription process for gene expression. In this study, we synthesized two kinds of linear quaternized ammonium-based cationic polymers from 2,6-dibromomethylphenolic esters using Menschutkin Reaction. The esterases in cytosol could hydrolyze the phenolic ester and trigger a self-immolative chain fragmentation, leading to the quick release of the packed DNA for efficient transcription. The DLS measurements of the size and zeta potential of the resulting polyplexes showed that these cationic polymers could pack DNA molecules efficiently into positively-charged nanoparticles. Agarose-gel electrophoresis experiment revealed that anionic DNA molecules were condensed stably and compactly with cationic polymers. Furthermore, self-immolative elimination was successfully monitored by high performance liquid chromatography（HPLC）, which confirmed the esterase-responsiveness and compatibility of this well-designed cationic polymers. Gel retardation assay showed that the packed DNA could be quickly released after incubation with esterase solution, indicating that the polyplexes would become incompact and disassemble once in the cytosol. Meanwhile, compared with commercially available PEI, the polycation had a lower cytotoxicity in cancer cells, which might contribute to the fragmentation and the removal of the quaternary amine cationic charges. In A549 and Hela cancer cells, these two kinds of polyplexes achieved excellent gene transfection efficiency. But complex 1 was better than complex 2 at high N/P ratios, thanks to the activation of self-immolative elimination by intracellular esterases.