| Gene therapy has been an exciting and promising area of study, which is expected to become an alternative to the existing chemotherapy, radiation and operation. Efficient gene delivery and expression of delivered exogenous gene are important determinant of gene therapy. There are different gene delivery approaches available including cationic liposomes, polymeric DNA-binding cations and recombinant viral vectors. Almost two-thirds of all gene therapy trials undertaken, to date, have been for cancer, mostly based on recombinant viral vectors to carry the gene of interest. But, recombinant viral vectors are associated with immunogenicity, toxicity, lack of tissue specificity, difficulty in large-scale production, potential risk of inducing tumorigenic mutations, unknown long-term effects, generating active viral particles through recombination and the bloodstream's rapid clearance. Non-viral vectors have become an attractive alternative, most of which can be classified as polycationic polymers and liposomal preparations. But most non-viral vectors are limited in low efficiency of transfection, especially in vivo. Lack of efficient, non-cytotoxic, targeting gene vectors has become the major barrier to the routine application of gene therapy. The recent topic has been focused on the new non-viral vectors. The study of non-viral gene vectors has not been limited in the polymeric cations. Other materials have been described as a carrier that condenses DNA and enables its efficient deliveryinto cells, such as inorganic compound. The chemical synthesis of these carriers can be easily scaled up and produced at relatively low costs. Based on such carriers, these molecules can be used as a type of " work bench " to add additional components to the system.In this study, the newly nanotechnology and molecular biology were combined to develope a self-assembled non-viral gene carrier, Poly-L-Lysine modified Iron Oxide Nanoparticles (IONP-PLL). The feasibility of using IONP-PLL as gene vector was analysed by in vitro and in vivo assay. The system was optimized to enhance the gene delivery efficiency. Furthermore, according to the distribution of IONP-PLL especially the characteristic of penetrating cross the blood brain barrier, IONP-PLL was used to the gene therapy research of gliomas.IONP was prepared by alkaline precipitation of divalent and trivalent iron chloride in the presence of high concentration of dextran. In this system, iron oxide nanoparticles was equably dispersed in surfactant in suspend state. The electron microscopy showed that the diameter of IONP is about 20nm?4.8nm. As the gene vector, the DNA binding ability is essential requirement. DNA binding ability of IONP-PLL can be determined by observing whether DNA mobility was retarded on gel analysis and co-sedimentation assay. The DNA binding assay showed that at acid pH, IONP can bind DNA, but at pH 7 and 9, IONP has no the potential to bind DNA. The binding is achieved byinteraction between the negatively charged DNA phosphate groups and positively charged gene vectors. The surface charge of IONP was determined by measuring the zeta potential. At pH 7 and 9, IONP respectively possessed zeta potentials of 2.1 1.0 and -9.6 0.91. When titrated to pH 3, the IONP showed an increase in zeta potential to 6.3 0.36. A zeta potential of at least +6 was sufficient to predict binding of plasmid DNA by this type of particle. The electronstatistic interaction can also protect DNA against the digestion of nuclease at acid pH.So, in order to bind DNA at physiological conditions (pH 7.35-7.45), Poly-L-Lysine was grafted on the surface of IONP, called IONP-PLL, which is characteristic of small size and positive surface charge (6.7 0.36). DNA binding assay and co-sedimentation assay showed high affinity of IONP-PLL for nucleic acids under physiological conditions. Increasing amounts of IONP-PLL incubated with constant amounts of plasmid DNA resulted in a concomitant DNA mobility reduction on an agarose gel, implying DNA binding to the particl...
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