Abstract
Ionizable hydrogels were prepared from new copolymers, poly(vinylalcohol-co-acrylic acid) indicated as P(VA-co-AA), by freezing-thawing processes. These materials are designed as potential controlled delivery devices with specific properties to respond to chemical environment stimuli. The swelling behavior of the P(VA-co-AA) hydrogels was evaluated in response to pH changes in release medium demonstrating a strong dependence with the environmental pH. The release of theophylline (THO) and bovine serum albumin (BSA) incorporated into the hydrogels before freezing-thawing cycles were examined by varying the pH. The release curves of the two different solutes showed a very similar trend depending on the hydrogel porosity and the medium pH. The dependence of THO and BSA release on their size and ionic nature was detected.