Research for Localized High-Efficient Gene Transfer by the Magnetic Force Control Using High Temperature Superconducting Bulk Magnet

Nonviral vectors used as a carrier of plasmid DNAs in gene transfer have a problem that their transfer efficiency is low, in spite of their high safety. Magnetically enhanced transfection (hereafter called "magnetofection") is the gene transfer method using ferromagnetic nanoparticles as nonviral vectors. In magnetofection, the contact probability of plasmid DNAs to the cell is improved by the application of a magnetic field, which will largely affect the transfer efficiency. If the carrier diffusion from the target site can be controlled, gene transfer with more safety and higher efficiency will be realized. We investigated the optimum magnetic field for magnetofection. Ferromagnetic nanoparticles coated with polyethylene imine (100 nm in diameter) were used as plasmid DNAs carrier and were confirmed to be positively charged in pH value of 7.4. Plasmid DNAs were conjugated with ferromagnetic particles by the electrostatic interaction. The transfer efficiency using these complexes was evaluated by the expression of the luciferase reporter gene with COS-7 cells, varying the distance from the surface of the high temperature superconducting (HTS) bulk magnet. In addition, diffusion suppression by applying the magnetic field was investigated in vivo experiment. As a result, transfer efficiency was strongly correlated with the magnetic field strength.