Galactose functionalized injectable thermoresponsive microgels for sustained protein release

Abstract

Novel galactose functionalized thermoresponsive injectable microgels, poly(N-isopropylacrylamide-co-6-O-vinyladipoyl-d-galactose) P(NIPAAm-co-VAGA), have been fabricated using a combination of enzymatic transesterification and emulsion copolymerization. The microgels exhibit reversible temperature-responsive behavior, which can be tuned by varying the monomer feed ratio. The lower critical solution temperatures (LCSTs) of the materials are close to body temperature and can result in a rapid thermal gelation at 37°C. Field emission scanning electron microscopy showed the resultant microgels to have porous structures, and dynamic light scattering experiments indicated a dramatic reduction in particle size as solutions of the polymers are heated through the LCST. The polymers can be loaded with protein (bovine serum albumin; BSA), and in vitro studies showed that the BSA release kinetics depend upon the temperature and copolymer composition. Microgels based on P(NIPAAm-co-VAGA) could hence serve as candidates for site-specific sustained release drug delivery systems.