HIGH WATER-CONTENT BSA-PEG HYDROGEL FOR CONTROLLED-RELEASE DEVICE - EVALUATION OF THE DRUG-RELEASE PROPERTIES

The use as a controlled release system of high water content (> 96%) h ydrogels, obtained from the copolymerization of bovine serum albumin a nd poly( ethylene glycol), has been investigated. Such hydrogels allow ed the release of hydrophilic and hydrophobic substances, and even of small proteins. It was demonstrated using sever. different drugs and o ne protein that the mechanism of release by the hydrogel matrix was a Fickian diffusion-controlled process. The half-lives of release for th eophylline and lysozyme were 0.8 and 4.2 h, respectively. The effect o f the porosity of the hydrogel on the diffusive properties of theophyl line and hydrocortisone was evaluated by varying the molecular mass of the poly(ethylene glycol) and the OH/NH2 molar ratio used for the syn thesis of the hydrogel. High molecular masses of poly(ethylene glycol) and low OH/NH2 molar ratios of reagents led to hydrogels becoming mor e porous, allowing faster rates of diffusion. The control of diffusion was also studied by tailoring the thickness of the hydrogel. For theo phylline, an increase in the half-life of release from 0.26 to 1.98 h was observed when the thickness of the slab was increased from 0.1 to 0.3 cm. Also, as expected, the rate of diffusion was independent of th e concentration of the drug in the hydrogel. We believe that this fami ly of BSA-PEG hydrogels could be useful fur the preparation of control led release devices in the field of wound dressing.