Photo-cross-linked biodegradable thermo- and pH-responsive hydrogels for controlled drug release

A new strategy was developed to prepare thermo- and pH-sensitive hydrogels by the crosslinking of poly(N-isopropylacrylamide) with a biodegradable crosslinker derived from poly(L-glutamic acid). Hydrogels were fabricated by exposing aqueous solutions of precursor containing photoinitiator to UV light irradiation. The swelling behaviors of hydrogels at different temperatures, pHs, and ionic strengths were examined. The hydrogels shrank under acidic condition or at temperature above their collapse temperature and would swell in neutral or basic media or at lower temperature. These processes were reversible as the pH or temperature changed. All hydrogels exhibited no weight loss in the simulated gastric fluid but degraded rapidly in the simulated intestinal condition. Bovine serum albumin were used as a model protein drug and loaded into the hydrogels. The in vitro drug release experiment was carried out at different pH values and temperatures. The pH and temperature dependent release behaviors indicated the promising application of these materials as stimuli-responsive drug delivery vehicles. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012