Properties of multiphase microspheres of poly(D,L-lactic-co-glycolic acid) prepared by a potentiometric dispersion technique.

Multiphase microspheres of poly(D,L-lactic-co-glycolic acid) (PLGA) were prepared by a multiple emulsion potentiometric dispersion technique. Water-soluble compounds were dissolved in the aqueous phase (W) and emulsified in soybean oil (O) to form a stable emulsion. This primary emulsion was dispersed in a solution of PLGA and acetonitrile (O) to form a W/O/O emulsion. The W/O/O emulsion was then dispersed in a hardening solution of light mineral oil (O) using a potentiometric dispersion technique to produce microspheres of the W/O/O/O type with a very narrow and selective size distribution. The size of the microspheres was controlled by varying the internal diameter of the conductive infusion tube or by the variation of voltage applied to the conductive tube. Particle size analysis revealed a particle size distribution of 1-50 microns for microspheres made by this method as compared to a distribution of 50-500 microns for microspheres made by conventional agitation methods. Chlorpheniramine maleate was encapsulated with a loading efficiency of 88.9% with the potentiometric method as compared with a loading efficiency of 74.3% for the agitation method.