Sulfobetaine/Alginate/Chitosan Supported Hybrid N-Isopropylacrylamide Hydrogels: Composition-Dependent Diffusion/Compression Properties and Theophylline/Diclofenac Sodium/Ciprofloxacin Release Kinetics

Poly(N-isopropylacrylamide) (N), poly([3-(methacryloylamino)propyl] dimethyl(3-sulfopropyl) ammonium hydroxide) (SB) and SB/N hydrogels were prepared using N,N′-methylenebisacrylamide as crosslinker, while their hybrid semi-/full-IPNs N_1A, N_1C, N_1CA, SB/N_1A, SB/N_1C, and SB/N_1CA were synthesized in the presence of Alginate (A)/Chitosan (C). All the hydrogels were evaluated by taking into account their appearances, compression strengths and swelling behaviors in the ranges of pH 1.2–9.0 and temperature 4°C–40°C. The compressive moduli of N and SB/N hydrogels increased from ~10 to 80 kPa by changing composition (from N, SB/N to N_1CA, SB/N_1CA), swelling solution (from DDW to PBS) and temperature (from 25° to 37°C). The release profiles of diclofenac sodium (DFNa), theophylline (Thp), and ciprofloxacin (CIP) from N, SB/N, and their semi-/full-IPNs were investigated at pH 1.2 and pH 7.4, mimicking gastric and intestinal fluids. Higuchi, Peppas, and Weibull models were used, to describe the mechanisms of DFNa, Thp, and CIP releases from the hybrid IPNs of N and SB/N. The values of n (> 0.45) and β (> 0.75) at 37°C for Peppas and Weibull equations showed that DFNa and CIP releases from SB/N hybrids, which are more hydrophilic than IPNs of N, are mainly controlled by swelling/relaxation process.