阳离子基因载体的pH敏感遮蔽体系的制备及表征

合成了一种pH敏感的遮蔽体系-谷氨酸苄酯/谷氨酸共聚物(PBLG-co-PGA), 用于对DNA/阳离子基因载体复合物颗粒表面正电荷的遮蔽, 以提高其在体内的稳定性. 研究表明, PBLG-co-PGA (PGA(x), x为PGA占共聚物中摩尔百分数)具有pH敏感性. 并以pH敏感点接近生理pH值的PGA(60)为遮蔽体系进行研究. PGA(60)能够对DNA/PEI(1:1)复合物颗粒表面正电荷进行有效遮蔽. 凝胶阻滞电泳显示, 用PGA(60)对DNA/PEI复合物进行不同比例遮蔽, 没有发生与DNA的链交换作用. MTT细胞毒性测试表明, PGA(60)和三元复合物DNA/PEI/PGA(60) 在测试范围内几乎没有细胞毒性. 荧光素酶转染实验表明, 部分遮蔽后转染效率有所提高; 用PGA(60)对DNA/PEI复合物完全遮蔽为负电后, 由于同细胞表面的电荷排斥作用, 三元复合物不易被细胞内吞, 导致不发生细胞转染. 因其合适的pH响应性, PGA(60)将可能成为一种能随pH值的变化, 实现对聚阳离子基因载体进行电荷遮蔽/智能释放的遮蔽材料.

Synthesis and characterization of a pH-sensitive shielding system for polycation gene carriers

To increase the in vivo stability of polycation gene carriers, a pH-sensitive shielding system, γ-benzyl l-glutamate-co-glutamate acid polymer (PGA(60) (60 means the mol ratio of glutamate acid in the polymer)), was synthesized and characterized. PGA(60) shows pH sensitivity at about pH 6.0. PGA(60) could efficiently shield the positive charge of DNA/PEI (1:1) complexes. Gel retardation assay showed that no DNA-strand exchange with PGA(60) occurred after adding PGA(60) to DNA/PEI complexes in different proportions. MTT cytotoxicity test demonstrated that both PGA(60) and DNA/PEI/PGA(60) ternary complexes had no cytotoxicity within the test concentration. The transfection efficiency was improved when the positive charge was partly shielded by PGA(60). Because of the charge repulsion between the surface of cells and ternary complex particles, there was almost no transfection efficiency when the zeta potential of ternary complexes turned to negative. Because of the suitable pH sensitive range, PGA(60) may be a potential shielding system for polycation gene carriers to be used in vivo.