Preparation And In Vitro Release Properties Of PH-responsive Insulin-loaded Mesoporous Silicon Nanorods

At present,the treatment of type I diabetes is mainly through intravenous injection to balance the blood glucose level in the body.However,the injection of drugs usually causes injection site infection,subcutaneous fat atrophy and other problems.Therefore,it is necessary to develop a new insulin delivery system.Compared with insulin injection,oral insulin directly enters the liver through portal vein after absorption through gastrointestinal tract,which simulates the normal physiological pathway of human body to a certain extent,improves the compliance of patients,and has obvious advantages in clinical application.However,direct oral administration of insulin will be degraded and inactivated in the gastrointestinal tract.Insulin is a kind of macromolecular polypeptide drugs,which will be inactivated at extreme p H,because its molecular weight reaches 5800,membrane permeability is poor,so the absorption rate is low.Silicon nanorod particles can open tight junctions temporarily through receptor-mediated,promote insulin by-pass absorption,and have good biocompatibility.Ordered mesoporous silicon also has the advantages of controllable morphology and high drug loading.In this paper,we combined the advantages of coating materials and inorganic nanorods to prepare p H responsive silicon nanorods for oral administration of insulin.At the same time,we studied the biological toxicity of the carrier,the structure,morphology,and in vitro release properties of the drug loaded nanorods.The main research contents are as follows:（1）SBA-15 is widely used in drug carrier research because of its excellent structure and properties.However,after it enters the clinic,it is more directly exposed to the human body,and its biological toxicity cannot be ignored.The up regulation or down regulation of NO-e NOS-KLF signaling pathway may lead to inflammatory reaction.First,five kinds of SBA-15 with different morphologies were synthesized by sol-gel method.The appearance and morphology characteristics were characterized by TEM and SEM.They were five kinds of irregular particles,spherical,aggregated spheres,rod like and fibrous,respectively.The pore size was analyzed by N₂ adsorption desorption curve,and the pore size was 6-14 nm,and the space dimension of insulin was（1.3×three point four×3 nm）,so SBA-15 can be used as insulin carrier.CCK-8method was used to determine the toxicity of five kinds of particles to HUVECS,and the cell viability was slightly decreased,but still more than 80%.Western blot was used to determine the protein expression levels of nitric oxide synthase（e NOS）and KLF like factor.The results showed that only rod-shaped SBA-15 had the least interference on no signal pathway and had good biocompatibility.It was suitable for oral insulin carrier.（2）The drug loaded mesoporous silica nanorods SBA-15/INS were prepared by impregnation method with SBA-15 as insulin carrier.The pore size of the nanorods was analyzed by N₂ adsorption desorption curve.The results showed that the specific surface area,pore size and pore volume of the drug loaded nanorods were decreased,indicating that insulin could enter the SBA-15 pore channel or attach to its surface through electrostatic action.At the same time,a series of experiments were carried out to optimize the drug loading process.The drug loading was 24.45%.In simulated gastric juice,the cumulative release was 60.6%in 12 h,and in intestinal fluid,the cumulative release was 49.3%in 12 h.Finally,the release mechanism of SBA-15/Ins nanorods in different environments was explored through different release kinetics models.It was found that the Korsmeyer-Peppas formula had the highest fitting degree with the drug release process,with R²=0.951 and n<0.45.The fitting results showed that the drug release process followed the Fick diffusion principle.（3）In order to solve the problem of sudden release of SBA-15/Ins nanorods in gastric juice,an enteric coating material HP55 was coated on the surface of the nanorods,which was stable in gastric juice and rapidly dissolved in intestinal juice.Different amounts of HP55 were coated on the surface of SBA-15/Ins nanorods by double emulsion solvent evaporation method to obtain HP55/SBA-15/Ins nanorods.The cumulative release of 15%coated HP55/SBA-15/Ins nanorods in simulated gastric juice was 28.8%in 12 h,and 57.8%in intestinal juice in 12 h,showing obvious p H response.The cytotoxicity of HP55/SBA-15/Ins nanorods was determined by CCK-8 method,and the cell survival rate was 100%,which indicated that the drug loading system had good biocompatibility.The results show that HP55/SBA-15/Ins has high drug loading capacity,p H responsive release performance and good biocompatibility,which is a potential oral insulin delivery system.