pH- and thermo-sensitive semi-IPN hydrogels composed of chitosan, N-isopropylacrylamide, and poly(ethylene glycol)-co-poly(ε-caprolactone) macromer for drug delivery

In this study, semi-IPN chitosan/poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been prepared via in situ UV-photo-crosslinking of N-isopropylacrylamide monomer using poly(ethylene glycol)-co-poly(ε-caprolactone) (PEG-co-PCL) macromer as a crosslinker in the presence of chitosan. Swelling properties of the resultant hydrogels were studied by investigating pH- and temperature dependence of equilibrium swelling ratio and oscillatory swelling–deswelling kinetics. It was found that semi-IPN hydrogels responded to both temperature and pH changes, and such stimuli-responsiveness was rapidly reversible. The rheological measurements demonstrated that the incorporation of chitosan greatly improved the mechanical strength of the hydrogels prepared. The release profiles of bovine serum albumin (BSA) from the hydrogels were also evaluated. The results showed that the release rate of BSA was higher in pH 2.0 buffer solution than in pH 7.4 buffer solution at 37 °C. Such double-sensitive hydrogels have the potential to use as smart carriers for drug delivery systems.