Self-assembly of polylactic acid and cholesterol-modified dextran into hollow nanocapsules

A study of the direct preparation of hollow polymer nanocapsules which composed of the biocompatible and biodegradable polymers, polysaccharide and polylactic acid (PLA), was presented. By the dialysis of a DMSO solution of cholesterol-modified dextran (Chol-Dex) and poly(d,l-lactic acid) against water, hollow polymer nanocapsules with a highly stable structure and relatively narrow size distribution were obtained. The formation mechanism and the effects of various factors such as PLA molecular weight and the weight ratio of Chol-Dex to PLA on the formation of hollow polymer nanocapsules were investigated by SEM, TEM and ¹H NMR analysis. The results showed that hollow capsules were obtained when the weight ratio of Chol-Dex to PLA was between 3:1 and 1:1, and when PLA of molecular weights greater than 360 Da were used. The hollow capsules with a sandwich shell structure derived from deposition of PLA and some amphiphilic polysaccharide on the internal interface of the polysaccharide-coated aggregates, which were formed through phase separation during the initial phase of the dialysis. This novel approach to hollow polymer nanocapsule formation represents a rare example of the self-assembly of two biocompatible polymers into nanometer-scale objects with interesting structures, shapes and morphology through a simple assembly process.