Preparation Of Insulin-loaded Chitosan/Alginate Microspheres And Study On Oral Drug Delivery System With Insulin-loaded Microspheres

At present, injection is the only means of administration of insulin in clinic. The problem is the short half-life and repeated injection administration, resulting physical and spiritual burdens for long-term or life-long insulin-dependent patients. Therefore, the development of non-injection administration of insulin is very important. Oral delivery is the perfect administration of the non-injection because of security and higher advantage of the compliance of patients. However, insulin, must first be broken down by digestive enzyme and loss of efficacy. Meanwhile, as amphoteric element, insulin with hydrophilic properties are not absorbed by intestinal epithelial barrier.In order to sovle problems of oral insulin delivery, impulsive electrostatic technique was used with chitosan and sodium alginate as microsphere material, studies on preparation of insulin microspheres.The pharmacodynamic, pharmacokinetic and the relative pharmacological bioavailability of oral freeze-drying insulin-loaded Alginate/ chitosan microspheres, were mainly studied in this article.The research were made as follow:1. Insulin-loaded alginate/chitosan microspheres were preparede by impulsive electrostatic technique. The interrelated factors influencing the diameter and sphericity were studied through orthogonal experiments,and finally the statistic analysis made sure the optimum conditions to prepare microspheres. The scanning electron microscope and biological inverted microscope were used to observe diameter, the surface morphology and internal structure of microspheres. The encapsulation efficiency of insulin-loaded microspheres were determined by CBBG.The results showed that the diameter of needle was the most significant factor to the diameter of microspheres. The optimum conditions for the least diameter of microspheres were 450μm diameter of needle, 2cm from needle tips to the gelation surface, 10mg/mL alginate concentration,8mL/h speed of flowing-liquid and metal containers.2. Microspheres were prepared by Vacuum freeze-drying, then inspected the diameter of microsphere before freeze-drying, and changes in the relative activity of insulin. The results showed that the freeze-dried microspheres were slight effect on the drug activity, but the diameter of the microspheres were greatly reduced. The average diameter of microspheres decreased from 123 urn to 48 urn , the rate of decreasing is 61%.3. Diabetic animal model provided stable and reliable animal model for following oral pharmacokinetic and pharmacodynamic. In this paper, the weight of 18～22g Kunming-rats were subcutaneous injected 200mg/kg alloxan-saline solution, to establish a similar animal model of human type 1 diabetes.4. Studies of pharmacodynamic on insulin-loaded microspheres showed that microspheres had hypoglycemic effect not only on the normal rats, but also on alloxan-induced diabetic rats, Also there was a certain relationship between dose and hypoglycemic effect. Hypoglycemic effect showed the maximum rate at 6h, and maintained within 10h after oral 48μm microspheres on normal rats. Blood glucose level decreased to 27.2% , 40% respectively after 6h with oral 3.2IU/kg, 6IU/kg on normal rats. For diabetic rats, the hypoglycemic effect became more apparent, and blood glucose level maintained lower during 6～10h after oral 4.8IU/kg microspheres.The lowest level was at 6h, then cameback to 46.01% of original level .The whole process showed a steady and effective hepoglycemic effect after oral. Compared to the administration of subcutaneous injection method, the relative pharmacological bioavailability of oral insulin-loaded microspheres reached 41.20%.The hypoglycemic effect of the high dose (4.8IU/kg)was better than lower dose after oral different dose of insulin-loaded microspheres to diabetic rats,, the largest of hypoglycemic effect reached was 57.31%, 40.16%, 23.87%.5. Study of pharmacokinetic showed : With diabetic rats as animal model, the serum insulin level were determined by Radioimmunoassay(RIA) after oral insulin-loaded microspheres. the serum insulin level showed a slow and steady increase after oral 4.8IU/kg insulin-loaded microspheres, and the serum insulin level was the highest value at 4h. Compared to the administration of subcutaneous injection method, the relative pharmacological bioavailability of oral insulin-loaded microsphere reached 41.22%. It was a good dose-response relationship after oral different doses of insulin-loaded microspheres in diabetic rats, the relative pharmacological bioavailability were 41.22% , 37.32% and 35.37% respectively.