The effects of infiltration on protein release from multi-phase microspheres fabricated via solvent removal

Multi-phase polymer microspheres for drug encapsulation have been fabricated via solvent removal using poly(L-lactic) acid (PLLA) and poly(fumaric-co-sebacic) anhydride (P(FA:SA)20:80). A process of protein infiltration by the polymer solution was studied to determine the effect on protein release. Additionally, multiple variations of the infiltration process were investigated. The mechanisms involved in the different infiltration methods were looked at to determine if polymer degradation was occurring or if the protein was aggregating as a result of the infiltration process. Multiple drugs were used in these studies: FITC-labelled bovine serum albumin (BSA), a model drug and antide (a GnRH antagonist), which is a therapeutic agent. Characterization and comparison of the various microsphere batches was performed via scanning-electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), gel-permeation chromatography (GPC) and differential-scanning calorimetry (DSC). Protein infiltration by the polymer solution was successful in decreasing the initial burst of drug with insignificant differences between the various methods of infiltration. Furthermore, there were minimal differences in polymer degradation due to the different methods of infiltration and there were no significant differences in the degree of crystallinity of the polymers in the various batches fabricated with and without infiltration.