RESUMO
The use of high water content (> 96%) hydrogels obtained from copolymerisation of bovine serum albumin and poly(ethylene glycol) as a controlled release system has been investigated. Such hydrogels allowed release of soluble and hydrophobic substances, even proteins. Release is shown to occur by a diffusion controlled mechanism, leading to half-life times of release ranging between 0.8 hour for theophylline and 4.2 hours for lysozyme, when a 2.4 mm thick disc of BSA-PEG (MW of 10000) was used. The effect of the porosity of the hydrogel on the diffusive properties of theophylline and hydrocortisone has been evaluated by varying the molecular weight of the poly(ethylene glycol). It was shown that poly(ethylene glycol) of high molecular weight leads to more porous hydrogels in which the diffusion is faster.
