Temperature-triggered gelation and controlled drug release via NIPAAm/NVP-based hydrogels

Novel physically crosslinked hydrogels based on N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone were synthesised using photopolymerisation. The gelation behaviour of the copolymers was investigated using modulated differential scanning calorimetry, oscillatory rheological analysis and the test tube inversion method. A number of the samples gelled spontaneously under physiological conditions and importantly did not undergo syneresis within the desired temperature window. Two active pharmaceutical ingredients (APIs), diclofenac sodium and procaine hydrochloride, were entrapped within the thermogelling materials by increasing external test temperature. The temperature-triggered gelation of the copolymer gels was used as a means of controlling the release of the APIs, and was found to retard the dissolution rate significantly.