Oxidation- and thermo-responsive poly(N-isopropylacrylamide-co-2-hydroxyethyl acrylate) hydrogels cross-linked via diselenides for controlled drug delivery

A novel diselenide crosslinked poly(N-isopropylacrylamide-co-2-hydroxyethyl acrylate) hydrogel was successfully synthesized and characterized. The resultant hydrogel showed a swelling–shrinkage behavior as a function of external temperature because of the unique hydrophilic–hydrophobic transition of poly(N-isopropylacrylamide) (PNIPAM) segments. In addition to the temperature-dependent response, the oxidation-induced gel-to-sol transition of the hydrogel was also observed. The salicylic acid (SA) loaded hydrogels were prepared in order to investigate their stimuli-responsive release behaviors. The cumulative release profile of the SA-loaded hydrogels showed a thermo-induced slow sustained drug release and an oxidation-induced quick burst release, exhibiting temperature/oxidation dual-stimuli-responsive drug release. This novel type of hydrogels may hold great promise for controlled drug delivery systems.