Preparation of poly(D,L-lactide) and copoly(lactide-glycolide) microspheres of uniform size.

In an attempt to prepare monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres, a novel emulsification technique (membrane emulsification) was employed and the preparation conditions which might affect the monodispersity were evaluated. With this technique nearly monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres were successfully prepared and their sizes were controllable only by making use of microporous glass membranes of different pore sizes. However, in the present system of emulsion (methylene chloride/water) the surfactant used was limited to ionic ones and the amount of polymers available for the formation of microspheres was inevitably too small in concentration to entrap sufficient amounts of drug. As for the drug release, the effect of particle size was not appreciable but the method of solvent removal gave a great influence; the solvent extraction method showed a more drug-sustaining effect than did the solvent evaporation method. The present results suggest the possibility of making drug-loaded and biodegradable monodisperse microspheres.