The term transfection is commonly used to describe the process of adding DNA into cells with a view to mediating protein expression of the transgene of interest. Although DNA transfection is the most commonly adopted technique, the term can also be applied to RNA transfection, where the purpose may also be to mediate protein expression or to achieve knockdown of the transcription of a specific gene, either by RNAi, ribozyme or antisense methodologies.
Non-viral gene transfer is arguably the safest way in which to introduce exogenous nucleic acid into living cells. However, in general this is also a very inefficient means of introducing DNA or RNA into cells. In order for a gene to be expressed it must find its way into the cell’s nucleus, this means it has to pass two lipid barriers; the extracellular membrane and the nuclear membrane. Given that nucleic acid and the lipids that comprise a cell’s membrane are both negatively charged, electrostatic forces would result in the repulsion of any nucleic acid that approached a cell.