“On-off” regulation of drug release in response to temperature changes as a command from the exterior of body has been achieved using temperature-responsive copolymer geis of N-isopropylacrylamide(IPAAm). In the design of the “on-off” regulating system using these thermosensitive gels, the phase transition must be maintained within temperature values which meet external temperature changes. Design of the gel structures with phase transition temperatures greater than that of poly (IPAAm) (32°C) are required for application in the human body. In this study, both phase transition and thermosensitivity of poly (IPAAm) gels have been controlled by introduction of comonomers into the gel. Hydrophobic alkyl methacrylate, hydrophilic acrylamide and N, N'-dimethylacrylamide have been used as comonomers. Effects of these comonomers on the phase transition temperature, the thermosensitivity and the skin formation process with increasing temperature have been investigated. By controlling these gel properties, the switching temperature of drug release has been controlled to achieve “on-off” regulation in response to small temperature changes around body temperature. Actually, complete “on-off” drug release for the temperature changes between 36 °C and 38 °C was achieved.
