Improving protein delivery from microparticles using blends of poly(DL lactide co-glycolide) and poly(ethylene oxide)-poly(propylene oxide) copolymers

Purpose. Microparticles containing ovalbumin as a model for protein drags were formulated from blends of poly(DL lactide-co-glycolide) and poly(ethylene oxide)-poly(propylene oxide) copolymers (Pluronic). The objectives were to achieve uniform release characteristics and improved protein delivery capacity. Methods. The water- in oil -in oil emulsion/solvent extraction technique was used for microparticle production. Results. A protein loading level of over 40% (w/w) was attained in microparticles having a mean diameter of approximately 5 mu m. Linear protein release profiles over 25 days in vitro were exhibited by certain blend formulations incorporating hydrophilic Pluronic F127. The release profile tended to plateau after IO days when the more hydrophobic Pluronic L121 copolymer was used to prepare microparticles. A delivery capacity of 3 mu g OVP/mg particles/ day was achieved by formulation of microparticles using a 1:2 blend of PLG:Pluronic Flu. Conclusions. The w/o/o formulation approach in combination with PLG:Pluronic blends shows potential for improving the delivery of therapeutic proteins and peptides from microparticulate systems. Novel vaccine formulations are also feasible by incorporation of Pluronic L121 in the microparticles as a co-adjuvant.