Magnetic nanotechnology for targeted gene transfer in the heart

Objectives: Gene therapy in cardiovascular system is limited due to the low transfection efficiency of gene vectors in blood and tissue. Moreover, virus-mediated transfection possesses a risk of infectious complications. We have developed a novel transfection technique combining non-viral polymer-based gene vectors with magnetic bead nanotechnology.

Material and Methods: The non-viral gene vector poly-ethyleneimine (PEI) was convalently conjugated with magnetic nanobeads and the desired gene using a Sulfo-NHS-LC-Biotin linker. Luciferase and LacZ were used as reporter genes. Transfection efficiency was assessed in several cell lines in vitro and in mouse hearts in vivo.

Results: The magnetic bead/PEI/DNA complexes were found very stable even in serum-containing medium. Compared with PEI/DNA complexes alone, magnetic beads/PEI/DNA complexes conjugated with a luciferase reporter gene had an approximately 100-fold higher transfection efficiency in 4 different cell lines in vitro. By applying a restricted external magnetic field to 2D cell cultures, LacZ gene transfection could be selectively targeted to a specific and localized cell population. In vivo, magnetic beads/PEI/DNA complexes injected into myocardium also resulted in an approximately 50-fold increase of transfection efficiency compared to PEI/DNA complexes alone. By using confocal microscopy to track the magnetic bead/PEI/DNA complex, effective vector endocytosis and extranuclear localization in lysosomes was demonstrated.

Conclusions: Magnetic nanobeads conjugated with non-viral polymer vector provide superior transfection efficiency in vitro and in myocardium in vivo, which can be locally focussed by external magnetic fields. Circumventing virus-associated problems, this technique may greatly enhance the prospects of gene therapy in the cardiovascular system.