Preparation And Characterization Of Degradable Polyethyleneimine Functionalized Magnetic Carbon Nanotube And The Study Of Gene Transfection

Gene therapy is the process of replacing defective genes with health ones,adding new genes to help the body fight or treat disease or deactivating problem genes.Thereby it has great advantages in the treatment of major diseases associated with genes,such as genetic diseases and cancers.In gene therapy,gene vectors are one of the key point.Therefore,it is very necessary to develop a non-viral vector with high transfection efficiency and low cytotoxicity.The research of this paper mainly focuses on carbon nanotube/Fe₃O₄/polyethylenimine gene carriers.In the first chapter,we briefly described the current research progress of gene vectors.The advantages of polyethyleneimine as a non-viral vector,the application of carbon nanotubes in gene delivery systems,and the application of Fe₃O₄ nanoparticles in targeted therapy and diagnosis were introduced.In the second chapter,CNTs-Fe₃O₄ magnetic nanoparticles were prepaed by coprecipitation method.Then disulfide-linked polyethyleneimine?SSPEI?was grafted to the surface of CNTs-Fe₃O₄ to obtain CNTs-Fe₃O₄-SSPEI.The particle size and zeta potential of the CNTs-Fe3O4-SSPEI/DNA complexes were measured.The cytotoxicity of CNTs-Fe₃O₄-SSPEI in COS-7 cells was examined as compared with that of 25 kDa PEI by MTT assay.The cytotoxicity of CNTs-Fe₃O₄-SSPEI was much lower than that of 25KDa PEI.The transfection efficiency mediated by 1.8 kDa PEI,25KDa PEI and CNTs-Fe₃O₄-SSPEI was assessed in COS-7 and HeLa cells,the results revealed that the transfection efficiency of CNTs-Fe3O4-SSPEI was much higher than that of 1.8kDa PEI and comparable to that of 25KDa PEI with optimal ratio?N/P=10?.Moreover,the transfection efficiency could further increased under the prescence of external magnetic field.In the third chapter,the magnetic nanopaticles of CNTs-Fe₃O₄-HDDAPEI were obtained by introducing Fe₃O₄ magnetic nanoparticles and grafted ester-linked polyethyleneimine?HDDAPEI?on the surface of carboxylated carbon nanotubes.The particle size and zeta potential of CNTs-Fe3O4-HDDAPEI/DNA nanoparticles were measured.The cell cytotoxity of CNTs-Fe₃O₄-HDDAPEI was assayed by MTT.The transfection efficiency of CNTs-Fe3O4-HDDAPEI/DNA nanoparticle mediated pGLuc-3 plasmid was tested on COS-7 and HeLa cells.The morphology of pEGFP-C1 transfected with COS-7 cells 48 h after transfection with different nanoparticles was observed by confocal microscopy.The results showed that compared with commercial 25 KDa PEI,CNTs-Fe₃O₄-HDDAPEI nanoparticles have lower cytotoxicity,and their gene transfection efficiency was basically equivalent to25 KDa PEI.Furthermore,the transfection efficiency of CNTs-Fe₃O₄-HDDAPEI nanoparticles under the applied magnetic field was higher than that without external magnetic field.