Preparation and properties of monodispersed rifampicin-loaded poly(lactide-co-glycolide) microspheres

Monodispersed rifampicin (RFP)-loaded poly(lactide-co-glycolide) (PLGA) microspheres were prepared by a solvent evaporation method. In order to control the sizes of the microspheres, a membrane emulsification technique using Shirasu porous glass (SPG) membranes was applied. RFP/PLGA microspheres with the average diameters of 1.3, 2.2, 5.2, and 9.0 microm were obtained. They were relatively monodisperse and the values of the coefficient of variation (CV) for the size distributions of the microspheres were in the range between 7.0 and 16.0%. The loading efficiency of RFP was in the range between 50.3 and 67.4% independent of the microsphere size. The release ratio of RFP from RFP/PLGA microspheres was measured in pH 7.4 PBS at 37 degrees C. From RFP/PLGA microspheres with average diameters of 1.3 and 2.2 microm, almost 60% of RFP loaded in the microspheres was released in the initial day and the release was terminated almost within 10 days. On the other hand, from those with average diameters of 5.2, and 9.0 microm, the release of RFP was observed even 20 days after the release started.