Novel microparticulate system made of poly(methylidene malonate 2.1.2)

Formulation of PMM 2.1.2 microparticles entrapping ovalbumin as a model protein was achieved by using a double emulsion solvent evaporation method. Parameters such as the nature of the solvent, polymer concentration and polymer molecular weight were investigated. Preparation process led to the formation of spherical and smooth particles with a mean diameter of 5 μm, and an encapsulation efficiency and protein loading level of up to 16 and 2.9% w/w, respectively. After an initial burst of approximately 10%, the protein was released at a rate of less than 1% per day. This slow release kinetics of encapsulated ovalbumin in phosphate buffer indicates that most of the protein was encapsulated within the polymer matrix. Degradation of PMM 2.1.2 microparticles in the presence of esterases indicated that side chain hydrolysis of the polymer was the rate-determining step in bioerosion; cleavage of the ester side chain, which was further hydrolyzed to glycolic acid and ethanol, led to an acrylic acid and subsequent solubilization of the polymer. However, slow polymer backbone solubilization after degradation was observed.