The influence of biodegradable microcapsule formulations on the controlled release of a protein

Biodegradable microcapsules were prepared from various polymer compositions such as poly-d,l-lactic acid or poly-l-lactic acid and poly-d,l-lactide-co-glycolide for the controlled release of a model protein Bovine Serum Albumin (BSA). ELISA data indicated that the binding activity of BSA toward anti-BSA antibody was not lost during the microencapsulation process and the release from microcapsules. The effect of different microcapsule formulations on release profiles of the protein was investigated. It was found that the polymer composition, total amount of polymers and protein loading were factors involved in the determination of release profiles of BSA. The degradation of various microcapsules was also investigated. Factors such as degrees of the hydrolytic chain scission of ester linkages, water content and internal structures were compared. The microcapsule formulation influenced the porosity and the degree of concentration gradient of BSA. These were related to the initial burst effects and release patterns. All these factors interplayed their roles on the release characteristics of BSA. Depending on the microcapsule formulation, controllable and predictable release profiles of BSA that could be described by either zero- or firstorder kinetics were observed.