Temperature-responsive porous polycaprolactone-based films via surface-initiated ATRP for protein delivery

Abstract

The inherent hydroxyl groups on the porous polycaprolactone (PPCL) films (prepared by using poly(ethylene glycol) as the pore-forming agent) could be reacted with 2-bromoisobutyrate bromide to produce a sufficient concentration of surface-coupled atom transfer radical polymerization (ATRP) initiators for the subsequent surface-initiated ATRP of thermo-responsive N-isopropylacrylamide (NIPAAm) at room temperature. A kinetics study revealed that the chain growth of the grafted NIPAAm polymer (P(NIPAAm)) was very fast and consistent with a ‘controlled’ process. The graft copolymerization not only occurred on the porous film surface, but also took place into the film bulk. The resultant P(NIPAAm)-grafted PPCL (PPCL-g-P(NIPAAm)) films assumed a uniform and interconnected porous structure and exhibited a temperature-sensitive property with a lower critical solution temperature (LCST) of about 32 °C, not unlike pure P(NIPAAm). The release of bovine serum albumin (BSA as a model protein) from the PPCL-g-P(NIPAAm) films was characterized by an initial burst, followed by a sustained release. These thermo-responsive PPCL-g-P(NIPAAm) porous films are potentially useful in biomedical fields.