Indeed, X-ray structural studies show that the rate of DNA release from lipoplexes as well as transfection activity well correlate with non-lamellar phase progressions observed in cationic PC mixtures with membrane lipids. Lipid phase behavior is known to depend strongly on the chain molecular structure and the above relationships thus substantiate a view that cationic PC phase propensities are an important determinant of their activity. Maximum transfection was observed for ethyl phosphate PCs (EPCs) with monounsaturated 14:1 chains (total of 2 double bonds and 30 chain carbon atoms). A summary of studies on a set of ∼30 cationic PCs reveals the existence of a strong, systematic dependence of their transfection efficiency on the lipid hydrocarbon chain structure: transfection activity increases with increase of chain unsaturation from 0 to 2 double bonds per lipid and decreases with increase of chain length in the range ∼30–50 total number of chain carbon atoms. Similarly to other cationic lipids, they form stable complexes (lipoplexes) with the polyanionic nucleic acids. Examined here is a particularly attractive cationic lipid class, triester phosphatidylcholines (PCs) exhibiting low toxicities and good transfection efficiency. Synthetic cationic lipids are presently the most widely used non-viral gene carriers.

Download phospholipid structure