Self-assembled micelles of N-phthaloylchitosan-g-polyvinylpyrrolidone for drug delivery

A novel amphiphilic graft copolymer N-phthaloylchitosan-g-polyvinylpyrrolidone (PHCS-g-PVP) was synthesized by grafting polyvinylpyrrolidone (PVP) onto a chitosan derivative whose amino groups were protected by phthaloyl groups. Polymeric micelles were prepared by the dialysis method, and showed a low critical micelle concentration (CIVIC) of 0.83 mg/L detected by fluorescence spectroscopy. Prednisone acetate was incorporated in the polymeric micelles. The loading capacity was found to be around 44.6 wt%. Morphological investigation by transmission electron micrograph (TEM) showed that the micelles were round in shape. The mean particle diameter of the drug-loaded micelles were about 143.3 nm, much bigger than the unloaded micelles; which had a unimodal size distribution with an average diameter of 89.8 nm as measured by dynamic light scattering (DLS). In vitro tests showed release of prednisone acetate from the micelles was continuous with no initial burst. All the results suggest that the nano-size core-shell micelles might be used in controlled drug delivery system. (C) 2008 Elsevier Ltd. All rights reserved.