Construction Of SiRNA Delivery System Based On The Modified Polyethyleneimine

Cancer is one of the largest global public health problems which has become a serious threat to human health.Radiotherapy and chemotherapy as the main means of cancer treatment have brought irreversible physical damage to cancer patients,and gene therapy may become a good choice for cancer therapy.The application of genetic engineering technology will be introduced into the cancer treatment to correct the defects of pathogenic genes and the eradication of genetic diseases.PEI is a very effective cationic carrier for nucleic acid drugs,and it has been widely used in drug delivery system.But it contains a large number of amino groups,which lead to serious cell toxicity,and a large number of positive charge may lead PEI to be cleared by RES system in blood easily.PEG has the ability to shield the charge and prolong the blood circulation time,so PEI modified by PEG can theoretically reduce the toxicity and prolong the blood circulation time.Meanwhile,TAT has high efficiency of trans-membrane and can be the molecule vector to carry macromolecules into cells.So essentially,the TAT-modified PEI-PEG could increase the transfection efficiency theoretically.In this study,cationic carrier PEI was modified by PEG and TAT,and a novel cationic carrier was synthesized.The properties of the cationic carrier and the effect of siRNA delivery were evaluated.The main contents of this paper include the aspects as following:1.The characteristics of PEI-PEG-TAT polymerPEI-PEG-TAT polymer was designed on the basis of PEI,and its buffer capacity and cytotoxicity were investigated.The buffer capacity of PEI determined the capacity to enter cells,as a result of the proton sponge effect,so if the modified carrier,still had a proton sponge effect,it would be conducive to release nucleic acid drugs in the cells.The buffer capacity of PEI-PEG-TAT was similar to that of PEI,so it still had the proton sponge effect,which could release the drug into the cytoplasm effectively.The cell viability of PEI-PEG-TAT was 76% but the cell viability of PEI was only 53% when the concentration reached 8 ?g / ml.Therefore,the cytotoxicity of the modified PEI-PEG-TAT polymer was significantly lower than that of PEI.PEI-PEG-TAT polymer was less toxic and more favorable to be nucleic acid drug carriers.2.The preparation of PEI-PEG-TAT/si RNA nanoparticlesThe siRNA targeting survivin gene was selected as the model drug,and then the optimal condition of PEI-PEG-TAT loading siRNA was screened,and the stability of nanoparticles was tested.When the N/P ratio was 6:1,the aqueous medium was 5%glucose solution,PEI-PEG-TAT/si RNA nanoparticles have smallest average particle size,appropriate zeta potential and the largest combination degree.The nanocomposites prepared by these conditions can maintain the stability of particle size,potential and binding degree within 15 days.3.Study on the siRNA delivery by PEI-PEG-TAT nanocarrierThe effect of siRNA delivery by PEI-PEG-TAT nanocarrier was evaluated.The inhibition of tumor cells,cellular uptake,inhibition of gene expression were all detected.PEI-PEG-TAT complex with siRNA at 6:1 N/P ratio could form form a stable cystic structure,and maintain stable particle size and zeta potential.The cellular experiments showed that PEI-PEG-TAT could successfully delivery siRNA into tumor cells and decreased the expression of survivin mRNA and protein,which lead to the inhibition of tumor cell growth.In summary,the modified PEI-PEG-TAT polymer is a potential nucleic acid drug carrier,which is less toxic than PEI and more effective in delivering siRNA into cells.The PEI-PEG-TAT polymer designed and evaluated in this paper can lay a solid foundation for further research on multifunctional drug delivery systems.