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. 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. To circumvent this, it has proved effective to neutralize the negative charge of the nucleic acid with a positively charged substance. The most effective chemicals employed to date are those based on cationic lipids. The positive charge on the lipid neutralizes the charge and transfer across the membrane is achieved as a result of the lipid’s ability to fuse with the lipid-based membrane structure that surrounds the cell.