Stabilization of recombinant human growth hormone against emulsification-induced aggregation by Pluronic surfactants during microencapsulation

Protein aggregation upon exposing to the water/organic solvent interface is one of the most significant obstacles in developing poly(lactic-co-glycolic acid) (PLGA) microspheres with double emulsion process. The aim of present study is to devise a formulation strategy to prevent recombinant human growth hormone (rhGH) from aggregation during microencapsulation. The excipients used for stabilizing rhGH were selected from sugars, nonionic surfactants, polyol, and protein. Among the candidates, surfactants exhibited potentialities in protecting rhGH against emulsification-induced aggregation. It was also found that Pluronic F127 showed an outstanding as well as concentration-dependent stabilizing effect on rhGH, which was different to Pluronic F68 and Tween 20. After the rhGH solution comprising F127 and sucrose was emulsified with methylene chloride, the recovery of monomeric protein achieved 99.0%, principally attributed to the presence of F127. This solution was subsequently encapsulated as inner aqueous phase in the PLGA microspheres by a conventional double emulsion process, with the encapsulation efficiency higher than 98%. Improvement in the release of rhGH was observed for the microspheres co-encapsulating Pluronic F127 regardless in the presence or absence of sucrose, compared to the microspheres containing rhGH alone. The result further implied that co-encapsulation of Pluronic F127 in the microspheres played an important role in the stabilization of rhGH.