Effects of the surface charge on the stability of PEG-b-PCL micelles: simulation of the interactions between charged micelles and plasma components

Abstract

Poly(ethylene oxide)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymers with three kinds of terminal functional groups (amino, carboxyl and methoxyl) at the hydrophilic block end were synthesized via sequential ring-opening polymerization (ROP). Their structures were characterized by GPC and 1H NMR. Micelles prepared from these copolymers showed different surface charge properties. The enzymatic degradation behaviour of these charged micelles in PBS (pH 7.0) was investigated using DLS, UV and TEM. BSA was used as a model protein to simulate the interactions between charged micelles and plasma components. It was found that micelles with different surface charges showed distinct degradation behaviour using lipase PS as the enzyme and different stability in the presence of BSA. Micelles with a neutral surface group showed a slow and partial degradation, while charged micelles showed a quick and complete degradation. We found that the nature of interactions between charged micelles and proteins was critical to the stability of polymeric micelles in vitro.