Abstract: Insulin-loaded microspheres were prepared by solid-in-oil-in-water(S/O/W) technique with a polymer alloy of poly(lactic acid-co-glycolic acid)(PLGA) and monomethoxy polyethylene glycol-b-polylactic acid(MPEG-PLA) as the carrier material. It was demonstrated that the microspheres prepared by the S/O/W technique contain more insulin than those prepared by water-in-oil-in-water(W/O/W). They had a spherical shape. Their mean size was in the range of 1—3 μm. Their cross-section had a core-shell structure and the insulin located in the core of the capsule as a crystal solid. The shell itself was layered due to the phase-separation of the polymer alloy during the course of solvent evaporation. The in vitro release behavior of the insulin mirospheres prepared by S/O/W and by W/O/W were compared. It was found that less initial burst release of insulin from the mirospheres prepared by S/O/W was observed than the other. This improvement in initial burst release was dependent on the ratio of the two components of the polymer alloy.

Key words: Biodegradable polymer, Controlled release of drugs, Polymer alloy, Insulin