生物相容性嵌段型聚电解质胶束在水溶液中的酶降解行为

采用激光光散射仪和原子力显微镜研究了生物相容性嵌段型聚电解质聚左旋乳酸-b-聚甲基丙烯酸二甲氨基乙酯(PLLA-b-PDMAEMA)胶束在水溶液中2个温度(室温25.0℃和人体温度36.8℃)和2个pH值(肿瘤pH=4.9和正常组织pH=7.4)条件下的酶降解行为. 酶降解过程中存在一个失活时间, 在此之前, 胶束的酶降解遵循逐个降解机理. 失活时间之后, 出现裂纹或是通道的胶束核为降低其在溶剂中的表面积, 从而降低体系自由能, 胶束之间发生了聚集. 升高温度后, 酶的活性提高, 初始降解速率加快. 由于pH=4.9时胶束壳层因静电斥力作用而较为伸展, 使得胶束降解更快.

Enzymatic Degradation of Biocompatible Block Polyelectrolyte Micelles in Aqueous Solutions

Enzymatic degradation behavior of biocompatible block polyelectrolyte poly(L-lactide)-b-poly2-(dimethylamino)ethyl methacrylate](PLLA-b-PDMAEMA) micelles in aqueous solutions at two different temperatures(25.0 ℃,36.8 ℃) and two different pH values(pH=4.9,7.4) was investigated by laser light scattering(LLS) and atomic force microscopy(AFM).It is found that there is an enzyme inactivation time during the degradation process.Before this time,the degradation mechanism of PLLA-b-PDMAEMA micelles follows a one-by-one process.After this time,the degraded micelles with cracks or tunnels in their cores aggregate into large micelles to minimize their surface area exposed to the solvent,therefore minimize the free energy of the micelles.After increasing temperature,the activity of the enzyme increases,and the degradation rate of micelles is much faster.At pH=4.9,the coronas of the micelles are stretched due to the electrostatic repulsion,because of which the degradation rate of micelles is faster at pH=4.9 than that at pH=7.4.