Establishment of magnetofection - a novel method using superparamagnetic nanoparticles and magnetic force to enhance and to target nucleic acid delivery

Among the physical methods of drug localization, especially
magnetic drug targeting promises great potential. In this method,
an anti-cancer drug is bound to magnetic particles and an external
magnetic field can guide the administered magnetic particle-drug
complex to the desired site. The objective of this thesis was to
apply the principle of magnetic drug targeting to the delivery of
nucleic acids in cell culture and in vivo. To establish the method
of magnetic nucleic acid targeting (magnetofection), the
characteristics (sizes and organization) of different
superparamagnetic iron oxide nanoparticles coated with cationic or
anionic polymers (termed “trMAGs”, synthesized by Chemicell GmbH
Berlin), the binding of DNA to the magnetic beads, transfections
with the different types of magnetic particles, the mechanism of
magnetofection, optimization of magnetofection, the gene transfer
efficiency of magnetofections compared to standard (conventional)
transfections, magnetic field-guided localization of gene transfer,
magnetofection of a variety of cells and the applicability of
magnetofection in vivo, were examined. In binding studies, it
turned out that efficient binding of charged DNA vectors to charged
magnetic particles could be achieved by salt-induced colloid
aggregation. Incubation of cells with magnetic particle/DNA
associates (magnetofectins) resulted in gene transfer and
application of a magnetic field significantly increased gene
expression. Additionally, polyethylenimine (PEI) had an enhancing
effect on magnetofection efficiency. Mechanistic studies revealed
that the paramagnetic vectors are concentrated efficiently by
magnetic force on the cell surface within minutes and the
predominant uptake mechanism is endocytosis. Comparison of
magnetofections and the corresponding standard transfections (same
vectors but without magnetic particles and no applied magnetic
field) showed that with magnetofection the gene transfer efficiency
was usually significantly enhanced (up to 971-fold), the nucleic
acid dose-response profile could be improved and the incubation
times (of cells with vectors) could be reduced from hours to
minutes. Finally, in animal experiments (injection into ear veins
of pigs, into ear arteries of rabbits and into ilea of rats) it was
demonstrated that magnetofection enables targeted and efficient
gene transfer in vivo.