Dual stimuli responsive poly(N-isopropylacrylamide-co-acrylic acid) hydrogels based on a β-cyclodextrin crosslinker: synthesis, properties, and controlled protein release

pH- and thermal-sensitive hydrogels were synthesized by copolymerization of acrylic acid and N-isopropylacrylamide with a modified β-CD crosslinker in aqueous solutions. The swelling behaviors of the hydrogels at different temperatures and pHs were examined. The hydrogels shrink in acidic conditions or at temperatures above their collapse temperature and swell in neutral or basic media or at lower temperatures. These processes can be reversed by changing the pH or temperature. Using bovine serum albumin as the model protein drug, in vitro drug release experiments were carried out at different pH values and temperatures. The pH- and temperature-dependent release behaviors indicate that these materials show much promise as stimuli-responsive drug delivery carriers.