PLA/PEG/PLA三嵌段共聚物载药纳米胶囊的制备及表征

用于药物控释体系的微胶束具有实心微球结构，药物分子主要吸附于微球表面，极易脱落，在释药初期有明显的突释效应；而微胶囊的药物主要集中于囊心部分，药物通过扩散作用以及高分子膜的降解而逐渐释放到环境中，因而更有利于药物分子平稳、缓慢地释放．对于自然界中能够自发形成微胶囊的小分子材料，其分子中往往具有一个较小的亲水部分和一个相对较大的憎水部分，

Preparation and Characterization of Drug-loaded PLA/PEG/PLA Triblock Copolymer Nanocapsules

Biodegradable triblock copolymer PLA/PEG/PLA was synthesized by ring-opening bulk polymerization of D,L-lactide in the presence of poly(ethylene glycol) (PEG), in the molecular structure of which, the length of PEG and PLA chain segments was made to be quite different. Nanoparticles were prepared by using the copolymer via a double emulsion-evaporation technique. The paticles tended to form the configuration like capsules, i.e., the nanocapsules, because of the great size difference in PEG and PLA segments of the copolymer. Insulin, chosen as a model drug, was encapsulated into nanocapsules. The effect of preparation conditions on the size, insulin encapsulation efficiency, and in vitro drug release behavour of the nanoparticles were investigated. The experimental results show that the nanocapsules had a smooth spherical surface and the mean diameter was in the range from 180 nm to 350 nm, and the entrapment of insulin achieved up to 78.4. The drug-loaded nanocapsules released their content continuously, remarkably different from the corresponding micelles which gave a significant initial burst release followed by a slow release.