Construction Of Melittin Sustained Release Preparation And Its Toxicity Reduction And Effect Enhancement Study

Background and Purpose:Type 2 diabetes(T2D)is a metabolic disease of global concern.Medical workers around the world are striving to find more safe and effective drugs to treat type 2 diabetes and achieve better drug compliance.As a kind of pure natural bioactive peptide,how to develop and utilize this kind of polypeptide has always been a concern of researchers in China and even in the world.Melittin,a typical bioactive peptide,is a polypeptide isolated from bee venom and has been shown to reduce blood sugar levels in animals.However,the clinical application of Melittin has been seriously hindered by its strong hemolytic activity,toxicity to normal cells,easy degradation in vivo,and extremely short half-life.The unique physical and chemical properties of nanoparticles can effectively enhance the therapeutic effect of drugs,reduce hemolytic and cytotoxicity,and increase the accumulation of drugs at the target site.Therefore,we believe that modification of Melittin by nanometer drug carrier system can effectively reduce its toxicity,which will contribute to the application of Melittin in type 2 diabetes.Research Contents:This study is divided into three parts.The first part mainly focused on the toxic effect of Melittin peptide in ICR mice.The acute toxicity test was used to determine the toxicity range of Melittin in mice through LD50.The toxic target organs of Melittin in mice were determined by pathological observation and biochemical indexes.In the second part,a new method,termed flash nanocomplexation(FNC)was used to conduct the research on polyelectrolyte encapsulating of melittin.Melittin and dextran sulfate were turbulent mixed in a small impact aircraft(CIJ)to form nanoparticles within a few tens of milliseconds.The optimization of bee venom peptide/dextran sulfate nanoparticles(Melittin/DS nanoparticles)was carried out through a series of characterization work.The third part mainly discusses the efficacy,toxicity and safety of modified Melittin/DS nanoparticles.Continuous monitoring of blood glucose levels,body weight and mortality in mice was carried out.Results:In this research,the following results were mainly obtained:the LD50 of peptide melittin intraperitoneally injected into normal ICR mice was 6.05mg/kg,and the 95%confidence limit was 5.40-6.79mg/kg.The polypeptide melittin caused acute toxicity to the liver of healthy ICR mice,causing obvious acute liver injury.The polypeptide melittin had no obvious toxicity to other tissues and organs of healthy ICR mice.Melittin/DS nanoparticles can reduce blood glucose level of db/db mice,indicating that the blood glucose control of type 2 diabetes by Melittin/DS nanoparticles is long-term and stable.Melittin/DS nanoparticles can effectively control the body weight of db/db mice with a single recessive mutation,indicating that Melittin/DS nanoparticles have medicinal value for obesity-related metabolic syndrome.The death rate of db/db mice injected with Melittin/DS nanoparticles was greatly reduced,indicating that Melittin/DS nanoparticles could effectively reduce the toxicity of polypeptide melittin in mice.Conclusion and significance:Studies on the pharmacodynamics of polypeptides from animal and plant sources have been in a bottleneck state.This study innovatively modified Melittin by using FNC nano sustained release system,and successfully constructed the melittin/dextran sulfate nano-drug delivery system.Melittin was polymerized with dextran sulfate to make nano-drug,which not only effectively solved the toxicity problem of melittin,but also regulated the blood glucose level of db/db mice and reduced the weight of db/db mice.This study provides a new idea and method for the development and application of Melittin as a drug for the treatment of type 2 diabetes,and also lays a foundation for the discovery of other bioactive peptides and further research.