Thermo and pH Dual-Responsive Micelles of N-phthaloylchitosan-g-Poly(N-isopropylacrylamide) and Poly(acrylic acid-co-tert-butyl acrylate) for Drug Delivery

A novel amphiphilic copolymer N-phthaloylchitosan graft poly(N-isopropylacrylamide) and poly(acrylic acid-co-tert-butyl acrylate) (PHCS-g-PNIPAAm&P(AA-co-tBA)) was synthesized. The graft copolymer could form micelles in aqueous medium, and the critical micelle concentration (CMC) of the copolymer was 7.5 × 10^{? 3}mg/mL. The lower critical solution temperature (LCST) of the micelles was measured to be 30°C. Transmission electron microscopy (TEM) image showed that the micelles exhibited a regular spherical shape, and the mean diameter of the micelles was 94.1 ± 0.8 nm as determined by dynamic light scattering (DLS). The potential usefulness of the micelles as drug delivery systems was investigated using anti-inflammation drug prednisone acetate as the model. The drug loading capacity of the micelles was measured to be 22.86 wt%, and the DLS results showed that the mean diameter of the drug-loaded micelles was 133.3 ± 2.4 nm. In vitro drug release studies indicated that the micelles exhibited thermo and pH dual-responsive release profiles.