Controlled release from a composite silicone/hydrogel membrane

To enhance the drug uptake and release capacity of silicone rubber (SR), N- isopropylacrylamide (NIPA) hydrogel particles have been incorporated into a SR membrane. The NIPA particles were thoroughly blended with uncured SR wi th a certain ratio at room temperature. The mixture was then cast in a Petr i dish to 1 mm thickness and cured 10 hours at 90 degreesC. The SR/NIPA com posite gel can absorb water approximately equal to its dry weight. Brillian t blue, used as a mock drug, was loaded into the composite gel. Drug releas e increased exponentially to a final value that is temperature dependent: l ow at T> =34 degreesC, and high at T< 34<degrees>C. This finding is because the hydrophobicity of NIPA changes with temperature. Pulsed release in res ponse to temperature switching between 20 and 39 degreesC has been achieved . Drug uptake and release capability strongly depends upon the structure of the composite gel. The optimal range of NIPA composition is between 75 and 87% by volume. In the cited range, the NIPA particles form an interconnect ed network that provides a channel for diffusion of drug solution. The SR/N IPA composite gel has promising attributes as a wound dressing and other us es.