STUDY ON PREPARATION AND PHARMACODYNAMICS OF INSULIN-LOADED POLYESTER MICROPARTICLES

AIM　To investigate the possibility of using poly (ε-caprolactone-block-D,L-lactide) (PLCA) as a kind of materials to prepare the microparticles drug carrier. METHODS　PCLA-MP (microparticle, MP) was prepared by double-emulsification solvent evaporation method. Its morphology was examined by scanning electron microscope. Its size diameter was examined by particle analyser. Insulin (INS), as a model drug, was then encapsulated into PCLA-MP (INS-PCLA-MP). HPLC method was established for determining INS in INS-PCLA-MP. An “antibody-capture” procedure was devised for investigating encapsulation mechanism. The in vitro release behaviour of INS-PCLA-MP was determined in phosphatic buffer solution (pH 7.4). The diabetic rat model was established and blood glucose levels were measured using glucose oxidase (GOD-PAP) method to evaluate the hypoglycaemic effects after subcutaneous administration of INS-PCLA-MP. The pharmacological bioavailability (PBA) of INS-PCLA-MP was calculated from the area above the curve (AAC) in contrast with INS-solution. RESULTS　The mean diameter of INS-PCLA-MP was 1.9 μm, while the encapsulation ratio of INS reached to 76.46%. Only 18.25% encapsulated INS was on the surface of the microparticles, it could be measured by “antibody-capture” experiment. The in vitro release curve of INS-PCLA-MP consists of initial rapid release stage followed by slower exponential stage. In pharmacodynamic studies, after subcutaneous administration of INS-PCLA-MP 12 u.kg^-1, the hypoglycaemic effect was significant. The PBA of INS-PCLA-MP was 123.08%. CONCLUSION　PCLA might become a new drug carrier material in the future.