Magnetofection

Magnetofection is a simple and highly efficient transfection method that uses magnetic fields to concentrate particles containing nucleic acid into the target cells. This method attempts to unite the advantages of the popular biochemical (cationic lipids or polymers) and physical (electroporation, gene gun) transfection methods in one system while excluding their inconveniences (low efficiency, toxicity). Magnetofection was invented by Christian Plank and Christian Bergmann and is registered as a trademark.

Principle
The magnetofection principle is to associate nucleic acids with cationic magnetic nanoparticles: these molecular complexes are then concentrated and transported into cells supported by an appropriate magnetic field. In this way, the magnetic force allows a very rapid concentration of the entire applied vector dose onto cells, so that 100% of the cells get in contact with a significant vector dose.

Applications
Magnetofection has been adapted to all types of nucleic acids (DNA, siRNA, dsRNA, shRNA, mRNA, ODN…), non viral transfection systems (transfection reagents) and viruses. It has been successfully tested on a broad range of cell lines, hard-to-transfect and primary cells.

Mechanism
The magnetic nanoparticles are made of iron oxide, which is fully biodegradable, coated with specific cationic proprietary molecules varying upon the applications. Their association with the gene vectors (DNA, siRNA, ODN, virus, etc.) is achieved by salt-induced colloidal aggregation and electrostatic interaction. The magnetic particles are then concentrated on the target cells by the influence of an external magnetic field generated by magnets. The cellular uptake of the genetic material is accomplished by endocytosis and pinocytosis, two natural biological processes. Consequently, membrane architecture & structure stays intact, in contrast to other physical transfection methods that damage the cell membrane.

The nucleic acids are then released into the cytoplasm by different mechanisms depending upon the formulation used: 1) is the proton sponge effect caused by cationic polymers coated on the nanoparticles that promote endosome osmotic swelling, disruption of the endosome membrane and intracellular release of DNA form, 2) is the destabilization of endosome by cationic lipids coated on the particles that release the nucleic acid into cells by flip-flop of cell negative lipids and charged neutralization and 3) the usual viral infection mechanism when virus is used. Magnetofection works for primary cells and hard to transfect cells that are not dividing or slowly dividing, meaning that the genetic materials can go to the cell nucleus without cell division. Coupling magnetic nanoparticles to gene vectors of any kind results in a dramatic increase of the uptake of these vectors and consequently high transfection efficiency.

Biodistribution of magnetic nanoparticles
The biodegradable cationic magnetic nanoparticles are not toxic at the recommended doses and even higher doses. Gene vectors / magnetic nanoparticles complexes are seen into cells after 10-15 minutes that is much faster than any other transfection method. After 24, 48 or 72 hours, most of the particles are localized in the cytoplasm, in vacuoles (membranes surrounded structure into cells) and occasionally in the nucleus.