New Thermo-responsive Hydrogels Based on Poly (N-isopropylacrylamide)/Hyaluronic Acid Semi-interpenetrated Polymer Networks: Swelling Properties and Drug Release Studies

New pH and temperature sensitive semi-interpenetrated polymer networks (semi-IPNs) were developed by combining cross-linked PNIPAAm with hyaluronic acid (HA). At pH 7.4, the PNIPAAm/HA semi-IPN hydrogels had significantly greater and faster swelling at 25 degrees C and a more complete deswelling at 37 degrees C than PNIPAAm hydrogels. The temperature-dependent reversibility behavior was analyzed for biomaterial applications. Gentamicin was incorporated as a model drug, and the release profile from the hydrogels was followed under physiological conditions. The presence of HA, even in small quantities, allowed a more complete release of the gentamicin from the hydrogel. The PNIPAAm/HA semi-IPN hydrogels respond to both changes in temperature and pH making it suitable as a delivery system for therapeutics.