Magnetofection is a simple and highly efficient transfection

Transfection

Transfection is the process of deliberately introducing nucleic acids into cells. The term is used notably for non-viral methods in eukaryotic cells...

 method that uses magnetic fields to concentrate particles containing nucleic acid

Nucleic acid

Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...

 into the target cells. This method attempts to unite the advantages of the popular biochemical (cationic lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s or polymers) and physical (electroporation

Electroporation

Electroporation, or electropermeabilization, is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an externally applied electrical field...

, gene gun

Gene gun

A gene gun or a biolistic particle delivery system, originally designed for plant transformation, is a device for injecting cells with genetic information. The payload is an elemental particle of a heavy metal coated with plasmid DNA...

) transfection methods in one system while excluding their inconveniences (low efficiency, toxicity). Magnetofection was invented by Christian Plank and Christian Bergemann 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

Endocytosis

Endocytosis is a process by which cells absorb molecules by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane...

 and pinocytosis

Pinocytosis

In cellular biology, pinocytosis is a form of endocytosis in which small particles are brought into the cell—forming an invagination, and then suspended within small vesicles that subsequently fuse with lysosomes to hydrolyze, or to break down, the particles...

, 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

Endosome

In biology, an endosome is a membrane-bound compartment inside eukaryotic cells. It is a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for...

 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 charge neutralization and 3) is 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

Cell nucleus

In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

 without cell division

Cell division

Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

. 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.