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%) hydrogels, obtained from the copolymerization of bovine serum albumin and poly( ethylene glycol), has been investigated. Such hydrogels allowed the release of hydrophilic and hydrophobic substances, and even of small proteins. It was demonstrated using sever. different drugs and one protein that the mechanism of release by the hydrogel matrix was a Fickian diffusion-controlled process. The half-lives of release for theophylline and lysozyme were 0.8 and 4.2 h, respectively. The effect of the porosity of the hydrogel on the diffusive properties of theophylline and hydrocortisone was evaluated by varying the molecular mass of the poly(ethylene glycol) and the OH/NH2 molar ratio used for the synthesis of the hydrogel. High molecular masses of poly(ethylene glycol) and low OH/NH2 molar ratios of reagents led to hydrogels becoming more porous, allowing faster rates of diffusion. The control of diffusion was also studied by tailoring the thickness of the hydrogel. For theophylline, 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 the concentration of the drug in the hydrogel. We believe that this family of BSA-PEG hydrogels could be useful fur the preparation of controlled release devices in the field of wound dressing.