MODELING MONOMER RELEASE FROM BIOERODIBLE POLYMERS

A theoretical model was developed that describes the erosion of biodegradable polymers and the resulting release of monomers. Erosion is simulated using a Monte Carlo Model that describes the morphological changes during erosion. It allows the calculation of porosity distributions that are needed for modeling drug and monomer release using a modified diffusion equation. This equation takes into account the diffusion of monomers, the concentration dependence of diffusivities, the porosity along the diffusion pathway, as well as the presence of suspended monomers and their pH dependent dissolution. The model was used to describe the release of monomers from polyanhydride copolymers, which show a pH dependent release behavior that cannot be explained by existing models. After the determination of model parameters by fitting the model to release profiles, it was possible to predict other system properties like the amount of accumulated crystallized monomer or the total polymer matrix weight during erosion. With some modifications such models might become useful for predicting drug release from the investigated polymers.