L-Lysine was used to modify 4. OC polyamidoaminec (PAMAM ) , and a new polyamidoamine derivative named PAMAM-Lys was synthesized via the liquid-phase synthesis. The structures of PAMAM-Lys were characterized by IR, lH NMR, elementary analysis and granularmetric analysis. For PAMAM-Lys, the elemental analysis results of C, H and N were 53.43% , 9. 58% and 24.29% , respectively, the end amino measured value was 2.18, close to the theoretical value. The mean grain size of PAMAM-Lys was about 6. 35 nm and its particle size polydispersity was about 0. 09. Microstructures of the composites were observed by TEM. The cytotoxicity tests in vitro transfected with PAMAM and PAMAM-Lys dendrimers were evaluated by Thiazolyl Blue Tetrazolium Bromide(MTT) assay. According to the observed results with TEM, the composite of PAMAM-Lys and plasmid DNA made the DNA structure shrink, the average grain diameter of plasmids ranged from 50 nm to 100 nm, plasmids had the even distribution and the regular morphology. On the basis of the MTT assay results, when acting on 293T in vitro, PAMAM-Lys and PAMAM-Lys/DNA had the lower cytotoxicity and the better biocotnpatibility than 5.0C PAMAM. It showed that PAMAM-Lys dendrimer had been synthesized successfully, the modification by lysine could reduce the cytotoxicity of PAMAM dendrimer significantly. PAMAM-Lys had the better biocompatibility in vitro and could improve the transfection efficiency for DNA, thus PAMAM-Lys would be a promising DNA vector in future.%通过液相合成法,用L-赖氨酸(L-Lys)对4代聚酰胺-胺(4.0G PAMAM)进行表面修饰,制备了新型的PAMAM-Lys树枝状高分子.采用FHR、1 H NMR、元素分析和粒径分析等手段进行了结构表征.PAMAM-Lys的C,H,N元素含量分别为53.43％,9.58％和24.29％,端氨基测定值为2.18,接近于理论计算值；平均粒径约6.35 nm,多分散系数约0.09.应用透射电子显微镜和噻唑蓝四氮唑溴化物(MTT)比色法,探讨了PAMAM和PAMAM-Lys树枝状高分子载体/质粒DNA复合物的形态及体外细胞毒性.当最佳电荷比R+/-=4时,PAMAM-Lys与DNA形成复合物,通过静电作用,使DNA结构收缩,质粒粒径介于50～ 100nm之间,分布较均匀,形态规则；作用于体外293T细胞时,PAMAM-Lys及其与DNA复合物的细胞毒性明显低于5代聚酰胺-胺(5.0G PAMAM).研究结果表明,制备的新型PAMAM-Lys树枝状高分子显著降低了高代数PAMAM树枝状高分子载体的细胞毒性,具有良好的体外细胞相容性,有望成为一种DNA疫苗的优良载体.
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