Pluronic P85/poly(lactic acid) vesicles as novel carrier for oral insulin delivery

Poly(lactic acid)-b-Pluronic-b-poly(lactic acid) (PLA-P85-PLA) vesicles were developed as novel carrier for oral insulin delivery. PLA-P85-PLA block copolymer was synthesized by ring opening polymerization of the monomer l-lactide using Pluronic copolymer P85 as the initiator. Insulin-loaded PLA-P85-PLA vesicles were prepared by dialysis method and the mean diameter of insulin-loaded PLA-P85-PLA vesicles was determined to be 178 nm. The cytotoxicity studies using human ovarian cancer cells OVCAR-3 indicate that PLA-P85-PLA block copolymer has good biocompatibility. Both in vitro and in vivo release behavior of insulin loaded in PLA-P85-PLA vesicles were studied. It was observed that insulin was released out gradually from PLA-P85-PLA vesicles and almost all insulin was released out 7.5 h later. More importantly, for the oral administration of insulin-loaded PLA-P85-PLA vesicles at insulin doses of 200 IU/kg, the minimum blood glucose concentration was observed in the diabetic mice test after 2.5 h, which was 15% of initial glucose level. Furthermore, the blood glucose concentration increased slowly to 31.8% of initial blood glucose concentration after 10.5 h and was maintained at this level for at least an additional 14 h (32.5% of initial blood glucose concentration at 24.5 h). These results proved that PLA-P85-PLA vesicles could be promising polymeric carriers for oral insulin delivery application due to their sustained and enhanced hypoglycemic effect.