Branched oligoester microspheres fabricated by a rapid emulsion solvent extraction method

Methyl formate was used as the solvent of biodegradable oligoesters for the fabrication of microspheres with encapsulated bovine serum albumin (BSA). The procedure of dispersion of the double emulsion of the w/o/w type and its dilution and solvent extraction is very rapid, taking only several minutes. A higher yield and better encapsulation efficiency were obtained with copolymers of DL-lactic acid with mannitol than with pure linear poly DL-lactic acid. The procedure was accelerated, and yields and encapsulation efficacy were enhanced by the addition of 5% methyl formate to the external water phase. The microspheres were smaller than 100 microm. No benefits were obtained from the addition of wetting agents or other additives to the intermediate (oligoesteric) phase. Further development should concentrate particularly on hydrodynamic conditions and optimization of the composition of the external phase.