Preparation of poly(polyethylene glycol methacrylateco-acrylic acid) hydrogels by radiation and their physical properties

The pH-responsive copolymer hydrogels were prepared with the monomers of polyethylene glycol methacrylate and acrylic acid based on gamma-ray irradiation technique. The gel content of these copolymer hydrogels varied depending on both the composition of monomers and the radiation dose. Maximum gel percent and degree of crosslinking were obtained at the composition of equal amount of comonomers. These copolymer hydrogels did not show any noticeable change in swelling at lower pH range. However they showed an abrupt increase in swelling at higher pH range due to the ionization of carboxyl groups. This pH-responsive swelling behavior was applied for the insulin carrier via oral delivery. Insulin-loaded copolymer hydrogels released most of their insulin in the simulated intestinal fluid which had a pH of 6.8 but not in the simulated gastric fluid which had a pH of 1.2. (C) 2003 Elsevier Ltd. All rights reserved.