Transfection

Transfection is when foreign nucleic acid molecules are introduced into cultured eukaryotic cells by non-viral means. This method allows scientists to study gene expression, RNAi silencing, and to generate stable cell lines. They also have a wide range of applications in cancer research, drug development, and genetics.

Transfections can be transient or permanent. In transient transfections, the foreign genetic information will be expressed only temporarily without replicating nucleic acids. Hence their effect lasts only a short period. For permanent transfection, the nucleic acids will be integrated into the cellular genome and thus can be studied for a long time. Various chemical and physical methods can be employed for transfection. The choice of what method to use depends on the cell type and the objective of the experiment.

Chemical methods to achieve transfection rely on electrostatic interactions in the cells. One of the main challenges in this process is to overcome the issue of introducing negatively charged nucleic acid molecules into cells with negatively charged membranes. Calcium phosphate, diethylamino (DEAE) dextran, and cationic lipid-based reagents are used to coat the DNA. They can neutralize or, at times, impart a positive charge to the molecule, hence making it easier for the nucleic acids to cross the membrane. The nucleic acids, along with the molecules that coat them, make up the transfection complex, and the cells uptake this complex via endocytosis.

In physical methods, direct microinjection of the foreign genetic material into the cells using a fine needle is used. However, the delivery via this process is inefficient. Another method is electroporation, where an electric pulse is used to rupture the cell membrane to create pores that allow the entry of nucleic acids into the cell. This technique can be tuned for optimization by adjusting the pulse duration. However, in this method, there is a significant death of cells. Yet another method of physical transfection is biolistic particle delivery, where high-velocity microprojectiles containing nucleic acids are introduced into recipient cells via penetration. This technique can be used both in-vitro and in vivo. With the recent emergence of nanotechnology, nanoparticles are increasingly utilized for this procedure.

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