Thermally controlled protein release from gelatin-dextran hydrogels

Biodegradable hydrogels in which drug release was controlled by sol-gel tra nsition were prepared. Gelatin was used as a component because it exhibits sol-gel transition in response to temperature changes. Glycidyl methacrylat ed (GMA) dextran was crosslinked by low dose gamma-irradiation in the prese nce of gelatin and the model drugs, beta-galactosidase (beta-GA), bovine se rum albumin (BSA) or 5-fluorouracil (5-FU). The enzyme activity of beta-GA remained greater than 95% after irradiation. Temperature-responsive release of beta-GA and BSA resulted from the sol-gel transition of gelatin. Sol-ge l transition was confirmed by the temperature dependence of the spin-spin r elaxation time of the gel polymer protons. The protein release rate was aff ected by both the degree of GMA substitution and the gelatin concentration. Desired release rate could be achieved by adjusting these factors. The rel ease rate of 5-FU was not affected by the sol-gel transition of gelatin. (C ) 1999 Elsevier Science Ltd. All rights reserved.