Thermoresponsive copolymer-grafted SBA-15 porous silica particles for temperature-triggered topical delivery systems

A series of poly(N-isopropylacrylamide-co-acrylamide) thermoresponsive random copolymers with different mo- lecular weights and composition were synthesized and characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance (NMR) spectroscopy. The lower critical solution temperatures (LCST) of the copolymers were tuned by changing the mole ratios of monomers. Copolymer with highest molecular weight and LCST (41.2 °C) was grafted on SBA-15 type mesoporous silica particles by a two-step polymer grafting procedure. Bare SBA-15 and the thermoresponsive copolymer- grafted (hybrid) SBA-15 particles were fully characterized by scanning electron microscope (SEM), ATR-FTIR, thermo- gravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) analyses. The hybrid particles were tested for their efficiency as temperature-sensitive systems for dermal delivery of the antioxidant rutin (quercetin-3-O-rutinoside). Improved control over rutin release by hybrid particles was obtained which makes them attractive hybrid materials for drug delivery.