Preparation And Characterization Of Biodegradable Polyethylenimine Grafted Carbon Nanotubes As Gene Vector

Gene therapy is the therapeutic delivery of nucleic acid polymers into a patient's cells as a drug to treat disease which makes it possible to cure genetic diseases. Therefore, more and more researchers focus their study on gene therapy. There are three factors of gene therapy which are therapeutic gene, gene vector and targeted cell. Currently, the majority of gene vectors used for clinical gene therapy are viral vectors because of their high transfection efficiency. However, which also have the potential security problems. Non-viral vectors are known as high safety, while the transfection efficiency are much lower compared with viral vectors. The development of high transfection efficiency and safe vector is one of the most important factors on gene therapy. As we know, the carbon nanotubes(CNT) have the ability to pierce through the phospholipid bilayer of cells, which makes them great potential material as gene vector. Among various non-viral gene vectors, polyethyleneimine(PEI) is known as its high transfection efficiency and cytotoxicity, a serious of modifications were carried out to reduce it's cytotoxicity.In Chapter 1, the principle of gene therapy, the obstacles which need to overcome, and the recent progress of non-viral gene vectors along with their advantages and disadvantages are reviewed.In Chapter 2, N,N'-bis(acryloyl)cystamine(CBA) the crosslink agent which contains disulfide bond was prepared, then it was used to crosslink the low molecular weight PEI of 1800 Da to a high molecular weight PEI derivative(SS-PEI) which is biodegradable. The CNT was modified to obtain acyl chloride group on its surface. three different grafting ratio SS-PEI-CNT were prepared by CNT grafted with SS-PEI. Infrared spectroscopic analysis(IR), scanning electron microscope(SEM) and thermogravimetric analysis(TGA) were used to characterize it's structure. Water solubility, biodegrade ability as well as pH buffer capability were further tested. The result shows that SS-PEI-CNT has good water solubility, pH buffering capacity and it can also be degraded successfully under certain conditions. All the results indicate that SS-PEI-CNT has great potential in gene delivery.In Chapter 3, the low molecular weight polyethylenimine(1800Da) was crosslinked by 1,6-Hexanediol diacrylate(HDDA) to obtain HDDA-PEI which is ester bond-containing. A serious of different grafting ratio SS-PEI-CNT were prepared by CNT grafted with HDDA-PEI. The products were characterized by FT-IR, SEM, TGA, etc. Water solubility, biodegrade ability and pH buffering capacity were further tested. The experiment results show that products have good solubility in water, good pH buffering capacity, and they are also biodegradable. The results indicate that SS-PEI-CNT has great potential to be used as a novel biodegradable and efficient gene vector.