Study Of Sustained-release Insulin/PLGA Nanoparticles

After oral administration,insulin(INS)is easy to be degraded by these enzymes in thegastrointestinal tract,which decreases the bioactivity of INS.Therefore,INS is usually treated by subcutaneous injection on clinical.However,the long-term and frequent injection may cause serious side effects on the injection sites,such as: turgescence,pruritus,allergy,and infection,et al.The rapid development of Drug Delivery Systems(DDS)lays a foundation for the fabrication of INS controlled-release nanoparticles formulation.Encapsulating INS into PLGA copolymers to obtain a INS-loaded PLGA formulation not only can improve the stability of INS,but also may reduce dosing frequency.Such method increases patients' tolerance,and decreases the pains and injure of diabetes caused by the fluctuation of blood sugar.In this study,an INS-loaded PLGA nanoparticles(INS-PLGA NPs)was fabricated via a W/O/W composite solvent evaporation method.Many influence factors,such as: emulsifiers,PLGA concentrations,emulsifier concentrations,emulsification time,inner water volumes,oil/water ratios,and lyophilized agents,et al,on the morphology,particle size and encapsulation efficiency were studied.The optimal formula was shown below: inner water phase was 200 ?L of 10.0 % INS solution;oil phase was 2.0 mL of PLGA solution(37.5 mg/mL);outer water phase was 20.0 mL of 0.7 % PVA solution.The optimal fabrication conditions were shown below: the initial emulsion time was 60 s;the compound emulsion time was 10 min;the system was ultrasonic oscillated for 5 s every 3 s;the solvent volatile time was 4 h.Results obtained from scanning electric microscope showed that INS-PLGA NPs had spheric morphology with an average diameter of 419.5 nm,and the polydispersity of final NPs was 0.113.The encapsulation efficiency of INS-loaded NPs was up to 36.61 ± 2.31 %.The release profile of INS from INS-loaded NPs was also carried out with phosphate buffer solution(PBS)as releasing medium.The influence factors of particle size,drug-loading on the release profiles of INS were also studied.In vitro release profiles illustrated that the cumulated release amount of INS was up to 61.48 ± 1.55 % after 36 h releasing.Subsequently,the release tendency of INS began to flatten.After 72 h,INS release profile reached to the quilibrium state,and the maximum release amount was 83.99 ± 1.90 %.3 h later,the obvious hypoglycemic effects were observed after subcutaneous injection of released INS from INS-PLGA NPs(5 IU of INS)and original INS solution,respectively.The lowest blood glucose concentration was decreased to 30 % of the original levels.The results indicated that the insulin in PLGA nanoparticles still maintained its activity.Studies on hypoglycemic effect showed that the blood glucose concentration Wistar rats began to decrease after 2 h of administrating 37.5 IU/Kg of INS-PLGA NPs via subcutaneous injection.8 h later,the lowest blood glucose level was observed,which was decreased to 39.40 ± 3.65 % of the original level.Comparing with the commercially available INS solution,INS-PLGA NPs had a similar hypoglycemic effect.Though INS-PLGA NPs showed a slower glucose-lower effect,the effect could last for about 36 h.In short,the INS-PLGA NPs had a slow but effective hypoglycemic effect.