Makino K, Ohshima H, Kondo T
Faculty of Pharmaceutical Sciences, Science University of Tokyo, Japan.
J Microencapsul. 1987 Jan-Mar;4(1):47-56. doi: 10.3109/02652048709031583.
The degree of degradation of poly(L-lactide) microcapsules was measured as a function of the time elapsed in solutions of different pH values. To determine how the distribution of poly(L-lactide) molecules in the microcapsule membrane changes during degradation, poly(L-lactide) microcapsules, at various stages of the degradation process in various solutions, were sampled and redispersed in pH 7.6 buffer solutions of different ionic strengths and their zeta potentials determined. In the early stages of the process, the zeta potential became more negative as time elapsed. Analysis of the ionic strength dependence of the surface potential on the basis of a simple model shows that hydrolytic scission of ester bonds in the polymer chains takes place preferentially at the microcapsule membrane surface creating negative charges localized at the membrane/solution interface. In the later stages of the degradation process, the zeta potential again became less negative. This suggests that liberation of degraded segments takes place in the later stages.
聚（L-丙交酯）微胶囊的降解程度是作为在不同pH值溶液中经过的时间的函数来测量的。为了确定在降解过程中聚（L-丙交酯）分子在微胶囊膜中的分布如何变化，在不同溶液中处于降解过程不同阶段的聚（L-丙交酯）微胶囊被取样，并重新分散在不同离子强度的pH 7.6缓冲溶液中，并测定其zeta电位。在该过程的早期阶段，随着时间的推移，zeta电位变得更负。基于一个简单模型对表面电位的离子强度依赖性进行分析表明，聚合物链中酯键的水解断裂优先发生在微胶囊膜表面，在膜/溶液界面产生局部负电荷。在降解过程的后期阶段，zeta电位再次变得不那么负。这表明在后期阶段发生了降解片段的释放。
