聚乙烯亚胺-DNA复合物的形成和聚集行为研究

聚乙烯亚胺 (polyethyleneimine，PEI) 是一种优良的非病毒基因传输载体材料，本文对PEI/DNA复合物粒子的形成机制进行了初步探讨，电泳阻滞实验和紫外测定实验表明, 复合物的形成过程中存在着某种过渡状态即珠串样结构，透射电镜的结果提供了相应的例证。此外通过离子强度实验，作者认为在PEI与DNA的复合过程尽管以静电作用为主要作用力，同时也可能存在着其他类型的非静电作用力。PEI/DNA复合物粒子的表面电荷随着N/P的增加逐步增加，但由于DNA的分子质量较大，在N/P为8和12时表面电荷的绝对值较小,容易聚集成葡萄串样聚集体，离子强度实验表明该聚集过程的支配作用力可能是疏水作用力。EI/DNA复合物在N/P为12时的细胞转染效果与阳性对照组相当，表明聚集的PEI/DNA复合物也具有一定的细胞转染能力。

Formation and aggregation behavior of polyethyleneimine-DNA complexes

In vitro gene delivery, polyethyleneimine (PEI) has been described as one of the most efficient nonviral vector.  Herein the formation mechanism of PEI/DNA complexes is elucidated.  The transition phase of “bead-on-string” structure in the formation of complexes was supposed to exist through spectroscopy,    electrophoresis and transmission electron microscopy (TEM) technology.  The construction of PEI/DNA   complexes is related closely to the characteristics of PEI and DNA plasmid.  As well as the dominant electrostatic effects, the nonelectrostatic interactions were thought to be partially responsible for the presence of PEI/DNA comlexes even in the high ionic strength.  The surface charge of complexes particles increased with the N/P  ratio, but the absolute value of ζ potential was lower at the N/P ratio of 8 and 12, perhaps attributed to the use of larger DNA plasmid.  As a result, the repulsion between particles was decreased and prone to aggregate to the structure like a clustered grape-string in the solution.  Interestingly, contrast to the formation behavior of   complexes, the PEI/DNA complexes aggregated primarily due to hydrophobic interactions while electrostatic  attractions play a little role in the complexes particles aggregation in different concentrations of salt solutions.  Comparable transfection efficiency in HepG2 cells was observed for the Lipofectamine2000 and PEI/DNA  complexes at the N/P ratio of 12, and showed that larger or aggregatable complexes could transfect the cells in some different mechanisms.