Preparation And Pharmacodynamic Evaluation Of Long Acting Insulin Delivery System

Sucrose acetate isobutyrate(SAIB)can be dissolved in small amount of biocompatible organic solvent,and the viscosity of the SAIB solution can be reduced to a range suitable for injection.The solvent and water exchanged in the injection site,the SAIB phase transitions to an in situ depot which can release drug slowly for long period of time.The polylactic acid(PLA)is a polymer which is chemically polymerized by lactic acid,and the lactic acid can be prepared by fermentation of starch.PLA can be degraded into lactic acid in the human body,the final metabolites are water and carbon dioxide.PLA has good biocompatibility,the United States FDA has approved the use of PLA as materials for medical gentle controlled release drug.Insulin(INS)therapy is essential in the treatment of patients with type ? diabetes,partial type ? diabetes,gestational diabetes,and various secondary diabetes.But there are many limitations for the oral administration of INS,the approach of subcutaneous injection is the traditional treatment method for patients.Diabetic patients have to receive frequent subcutaneous insulin injections that are associated with poor patient compliance,including pain and local tissue necrosis.A controlled and prolonged release system is needed to reduce the injection frequency and enhance patient compliance.In this study,in order to prolong the action time of insulin,reduce blood sugar fluctuation and improve patient compliance,we select the PLA and SAIB as drug-loading matrix,built two new insulin delivery system: INS-SAIB in situ depot and INSPLA implants.In this study,the high performance liquid chromatography(HPLC)methods for INS-SAIB depot and PLA implants were established for in vitro analysis,respectively.The specificity,reproducibility and accuracy of the method were good.The rheological properties of the SAIB/anhydrous ethanol solution system was researched and the viscosity of the 20%(w/w)anhydrous ethanol SAIB solution was 0.14 Pa?s.The results obtained support the 20% ethanol in SAIB in situ depot is easy to inject.The homogeneous insulin powders were prepared by high pressure homogeneous method and freeze-drying method,INS-PLA microspheres were fabricated via solvent evaporation technique.The prepared microspheres were characterized by scanning electron microscopy,fourier transform infrared spectroscopy,differential scanning calorimetry and X-ray powder diffractometer.The encapsulation efficiency and drug loading of the microspheres were measured.The results showed that the surface of the microspheres was smooth,the sphericity was good,and the insulin was evenly distributed in the polylactic acid microspheres.The INSSAIB in situ depot was prepared by using freeze-dried insulin and INS-PLA microspheres as the main drug,SAIB as the matrix and absolute ethanol as the solvent.The cumulative release amount of insulin in the INS-PLA SAIB depot was 34.5 ± 2.5% after 12 hours,and then the release rate was slowed down.After 96 hours,the cumulative release amount of insulin reached 72.1 ± 2.9%.Two kinds of hydrophilic excipients were selected by in vitro dispersion experiment and subcutaneous implantation experiment: poloxamer 188 and poloxamer 407.In vitro release studies showed that the ratio of poloxamer and the different types of poloxamer in the implant resulted in differences in the release rate of the implants.After 12 hours,the insulin cumulative release amount of the implanted tablets reached 70.6±1.8% ? 84.8±1.6%.The SEM images showed the pore structure of the subcutaneous implant after implantation,which was due to the good water solubility of poloxamer 188 and poloxamer 407,they could be continuously dissolved and could form a concentration gradient between inside and outside of the implants.During the release process,tiny pores would be generated.The insulin presented on the surface of the implant and superficial layer was diffused into the release medium.The internal insulin spread out through the pores dissipated by poloxamer in the PLA matrix.The type ? diabetes rat model was prepared by using streptozotocin as an inducer and Wistar male rats as experimental animals.In vivo pharmacodynamics of INS-SAIB depot and INSPLA implants were studied.The experimental data showed that INS-SAIB depots and INSPLA implants had a good hypoglycemic effect.At the same dose(10 IU/Kg),the SAIB depot system containing INS-PLA microspheres and the INS-PLA implant had a burst phenomenon in the first 4 hours,then the blood sugar were stable in a platform period.The effective time of INS-PLA SAIB depot system was about 120 hours,and the INS-PLA implants were continuously hypoglycemic for 84 hours.Muscle irritation test showed that the INS-SAIB depots had little muscle irritation and good biocompatibility.