Dual-responsive polyacrylate copolymer micelles with PMAA and PNIPAAm graft brushes: Physicochemical properties and prednisone release

A thermo- and pH-stimuli-responsive brush-shaped graft copolymer based on macromonomers acrylate terminated PMAA-CH=CH2 and PNIPAAm-CH=CH2 was synthesized, which is composed of poly(methacrylic acid) (PMAA) and poly(N-ispropylacrylamide) (PNIPAAm) as graft brushes, named PMAA-b-PNIPAAm. The copolymers can self-assemble to form spherically-shaped core-shell nanostrucrued micelles in different media, with the critical micelle concentration (CMC) in aqueous solution from 9.24 to 32.81 mg L-1, and the hydrodynamic diameters varying with pH and temperature, from 120 to 195 nm. The resultant nanoscale copolymer micelles exhibited pH-triggered thermoresponsive behavior, with low critical solution temperature (LCST) about 38.2-47.5 degrees C. The polymer micelle nanoparticles were observed to be stable under simulated physiological conditions. The cytotoxicity studies by MTT assay and in vitro prednisone drug release demonstrated that the PMAA-b-PNIPAAm copolymer micelles were not directly toxic to L929 mouse embryonic fibroblasts and the in vitro release behavior under various physiological environments depended upon pH and temperature change. Therefore the as-prepared brush-shaped graft copolymer micelle nanoparticles may serve as a promising intelligent drug delivery carrier. (C) 2013 Elsevier B.V. All rights reserved.