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 it s dilution and solvent extraction is very rapid, taking only several minute s. A higher yield and better encapsulation efficiency were obtained with co polymers of DL-lactic acid with mannitol than with pure linear poly DL-lact ic acid. The procedure was accelerated, and yields and encapsulation effica cy were enhanced by the addition of 5% methyl formate to the external water phase. The microspheres were smaller than 100 mu m. No benefits were obtai ned from the addition of wetting agents or other additives to the intermedi ate (oligoesteric) phase. Further development should concentrate particular ly on hydrodynamic conditions and optimization of the composition of the ex ternal phase.