Thermo-responsive hydrogels of poly(N-isopropylacrylamide-co-butyl methacrylate) (poly-(IPAAm-co-BMA)) are capable of swelling-deswelling changes in response to external temperature. As poly(IPAAm-co-BMA) gels swell larger at a lower temperature, the degree and rate of the swelling
could be controlled by temperature without altering the chemical structure. Therefore, drug release profiles were remarkably changed by alternation of temperature. The release profiles of indomethacin from poly(IPAAm-co-BMA) were observed to be zero-order at 20°C. This release profile
was explained in terms of a Case-II diffusion mechanism; which indicates relaxation of polymer chains with swelling was rate-determining. In the case of 10°C, release demonstrated a sigmoidal profile. The acceleration of drug release was due to a rapid increase in swelling with disappearance
of the glassy core which had constrained swelling. The regulation of the water-uptake process by changing external temperature remarkably affected drug release and resulted in several different release profiles.
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Document Type: Research Article
Department of Chemical Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku-ku, Tokyo 169, Japan
Institute of Biomedical Engineering, Tokyo Women's Medical College, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162, Japan
Publication date: 1993-01-01