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) pr epared by a multiple emulsion potentiometric dispersion technique. Wat er-soluble compounds were dissolved in the aqueous phase (W) and emuls ified in soybean oil(O) to form a stable emulsion. This primary emulsi on 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 s olution of light mineral oil (O) using a potentiometric dispersion tec hnique to produce microspheres of the W/O/O/O type with a very narrow and selective size distribution. The size of the microspheres was cont rolled by varying the internal diameter of the conductive infusion tub e or by the variation of voltage applied to the conductive tube. Parti cle size analysis revealed a particle size distribution of 1-50 mu m f or microspheres made by this method as compared to a distribution of 5 0-500 mu m for microspheres made by conventional agitation methods. Ch lorpheniramine maleate was encapsulated with a loading efficiency of 8 8.9% with the potentiometric method as compared with a loading efficie ncy of 74.3% for the agitation method.