Preparation and in-vitro evaluation of poly[N-vinyl-2-pyrrolidone-polyethylene glycol diacrylate]-chitosan interpolymeric pH-responsive hydrogels for oral drug delivery.

Biocompatible and biodegradable pH-responsive hydrogels based on N-vinyl pyrrolidone (NVP), polyethylene glycol diacrylate (PAC) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a free radical polymerization technique using azobisisobutyronitrile (AIBN) as initiator and N,N'-methylenebisacrylamide (BIS) as crosslinker. These hydrogels were subjected to equilibrium swelling studies in enzyme-free simulated gastric and intestinal fluids (SGF and SIF). These swelling studies clearly indicated that these hydrogels were swollen more in SGF when compared to SIF. Theophylline and 5-fluorouracil (5-FU) were entrapped into these hydrogels and equilibrium-swelling studies were carried out for the drug-entrapped gels in enzyme-free SGF and SIF. The in-vitro release profiles of the drugs were established in enzyme-free SGF. More than 50% of the entrapped drugs were released in the first 2 h at gastric pH and the rest of the drug release was slower.