Effects of material hydrophobicity on physical properties of polymeric microspheres formed by double emulsion process

Human serum albumin (HSA) was encapsulated as a model protein in microspheres of biodegradable and biocompatible polymers by the water-in-oil-in-water (w/o/w) emulsion solvent extraction/evaporation (double emulsion) technique for purpose of controlled release. To improve the properties and control the rate of drug release of the delivery vehicle, materials with different hydrophobicity from that of their conventional counterparts, such as poly(lactide-co-ethylene glycol) (PELA) in place of poly(lactide-co-glycolide) (PLGA) as the polymer matrix, ethyl acetate/acetone in place of dichloride methane (DCM) as the (co)solvent and d-alpha tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) as the additive, were used to prepare the microspheres. It has been found that PELA microspheres, compared with PLGA ones, were slightly smaller in size if prepared at identical emulsification strength. They had more porous surface and internal structure, higher encapsulation efficiency (EE) and more rapid in vitro release rate. Furthermore, the physical properties of the microspheres were also affected by the presence of solvents and additives and their properties. Our results suggest that these materials could have interesting potential applications in preparation of polymeric microspheres for controlled protein release.