SYNTHESIS AND CHARACTERIZATION OF PNIPAM-b-POLYCARBONATE COPOLYMERS AS SELF-ASSEMBLED THERMOSENSITIVE MICELLES FOR DRUG DELIVERY

A series of poly(N-isopropylacrylamide) (PNIPAM) -blocked polycarbonates, P(MAC-co-DTC)-b-PNIPAM, were designed as thermosensitive micelles for drug delivery. The amphiphilic block copolymers were synthesized by enzymatic ring-opening copolymerization of HO-PNIPAM, 5-methyl-5-allyloxycarbonyltrimethylene carbonate (MAC) and 5,5-dimethyltrimethylene carbonate (DTC). The novel block copolymers were characterized by (1)H-NMR and GPC-MALLS analyses. All the amphiphilic copolymers were able to self-assemble into nano-sized micelles in aqueous solutions with hydrophilic PNIPAM shells and hydrophobic polycarbonates cores. The critical micelle concentration (CMC) determined by fluorescence spectroscopy using pyrene as a probe was around 20 similar to 60 mg/L. Transmission electron microscopy (TEM) measurements showed that the micelles presented even spherical shape and the diameters of them were about 20 similar to 70 nm. The micelles exhibited thermosensitivity at lower critical solution temperature (LCST) of around 38 similar to 43 degrees C, which was related to the hydrophilic PNIPAM blocks. In vitro experiments demonstrated that the P(MAC-co-DTC)-b-PNIPAM showed low cytotoxicity. Furthermore, the micelles were loaded with hydrophobic drug of prednisone acetate (PA) and in vitro drug release investigation also displayed thermosensitivity. The results suggested that P(MAC-co-DTC)-b-PNIPAM copolymers would be a promising thermosensitive carrier for drug delivery.