Preparation And Properties Of PH-Responsive Insulin-loaded Micelles

At present,diabetes mellitus has become one of the major threats to human health,and the incidence in young people is increasing.Insulin is one of the most effective drugs to treat diabetes and it can only be absorbed by parenteral administration.Subcutaneous insulin injection is the common treatment for patients with type?diabetes.However,parenteral administration not only brings inconvenience to the patients,but also have a variety of complications,such as hypoglycemia,atrophy of subcutaneous fat,hypertrophic malnutrition and so on.Oral administration can avoid these problems and side effects and become an ideal method for insulin treatment,However,because it is a kind of protein which can be degraded by many gastrointestinal digestive enzymes like pepsin,also due to its large molecular weight and poor membrane permeability,which severely restricts the research and exploit of insulin oral preparations.In view of the oral insulin barrier and the different pH of human stomach/intestinal environment,this paper designed pH-sensitive amphiphilic polymer materials and insulin-loaded micelle systems.Polymer P(MMA-co-MAA)-b-P(PEGMA)has clear structure,good biocompatibility,controlled insulin release and good stability.The structure of the target polymer was characterized by GPC,~1H NMR and FT-IR The CMC values of a series of polymers with different molar ratios in the pro/hydrophobic section were tested by hydrazine as a fluorescent probe;the lower CMC value indicated that the polymer has good micelle ability.When preparing micelles by dialysis,the factors such as hydrophilic/hydrophobic block of polymer,soluble polymer solvent,mass ratio of polymer to insulin were optimized.It was characterized by DLS,SEM and TEM to obtain drug-loaded micelles with uniform particle size distribution about 200 nm.The optimal drug loading(14.9%)and encapsulation efficiency(89.8%)of insulin-loaded micelles were obtained by optimizing the factors such as hydrophobic/hydrophobic block of polymer,soluble polymer solvent and mass ratio of polymer to insulin.In the gastric juice environment,the cumulative release in 10 hours did not exceed 25%,the cumulative release of insulin in the intestinal fluid for 4 hours reached82%,and the acid-base sensitivity was obvious.Cytotoxicity experiments showed that the micelles were less toxic.In order to make insulin absorbed more effectively orally,the mixed micelles containing insulin were prepared by mixing the polymer P(MMA-co-MAA)-b-P(PEGMA)and the membrane adhesion polymer P(MMA-co-MAA)-b-P(AEMA),which have the dual functions of pH sensitivity and membrane adhesion.By changing the mass ratio of the two polymers,P(MMA-co-MAA)-b-P(PEGMA)/P(MMA-co-MAA)-b-P(AEMA)is equal to 3/7 mixed micelles,and the encapsulation efficiency is obtained(12.4%)and drug loading(74.5%),the strongest film adhesion(+18.5mV).The cytotoxicity test showed minimal toxicity to the cell.The release rate in gastric juice is less than 40%but reaches 78%in the intestinal environment.