Preparation Of Amphoteric Polymers Based On Curdlan As Carriers For Nucleic Acid Delivery

RNA interference(RNAi)is a regulation mechanism of gene expression at post-transcriptional level caused by double-stranded RNA.It has great potential in the clinical treatment of various diseases.One of the important issues of RNAi clinical application is to construct gene delivery vector with safety and efficiency.In this thesis,taking the natural polysaccharide Curdlan as a starting reactant,the fully oxidized ?-(1,3)-polyglucuronic acid has been prepared by oxidizing the C5 position of its structural unit followed by acidifying.Then,the synthesis of polymer TEPAC-m(m = 1,-2,-3)were carried out with tetraethyllenepentamine(TEPA)by the tetrahedral reaction.The structures of obtained compounds were confirmed by 1HNMR and 13CNMR,and the particle size distribution and Zeta potential were determined by laser particle size analyzer.The bufferring capacity on H +was determined by the acid base titration method.Subsequently,the cytotoxicity test,the GFP plasmid and siRNA transfection test in vitro were used to study the safety and nucleic acid delivery efficiency of TEPAC gene vectors.The results showed that all of the novel amphoteric polymers have good water solubility,proton sponge effect and positive Zeta surface potential.They were able to deliver GFP plasmids into HepG2 and 293T cell lines efficiently.They showed low cytotoxicity in A549 and HeLa cell lines,and were able to efficiently delivery siRNA to down regulate the expression level of target mRNA significantly.Therefore,the novel amphoteric polymers have potential for further research and development as nucleic acid carriers.In conclusion,we successfully synthesized water-soluble amphoteric polymers TEPAC-m(m=1,-2,-3)and used as carriers for in vitro delivery of nucleic acid,of which the safety and delivery efficiency had been studied systematically.The results not only provide us novel amphoteric polysaccharide carriers in gene therapy field,but also layed the foundation for further development of subsequent nucleic acid carriers.