Cationic lipid colipids

Since the introduction of the transfection reagent Lipofectin , a cationic liposome composed of 1 1 (w/w) mixture of the quaternary ammonium cationic lipid jV[1-(2, 3-dioleyloxy)propyl]-Ar, N, N-trimethylammonium chloride (DOTMA) and a colipid dioleoylphosphatidylethanolamine (DOPE) (Feigner et al., 1987), an increasing number of cationic lipids have been developed. To date, cationic lipids can be grouped into seven different categories ... 

Cationic lipids are often combined with neutral and zwitterionic lipids in formulations for gene therapy. The most frequent colipids are cholesterol, DOPE and dioleoylphosphatidylcholine (DOPC) (or other PCs) (Fig. 28). These neutral lipids may play a role in transfection by increasing the level of DNA protection against DNases or facilitating the destabilization of the endosomes [35,103]. The optimum cationic lipid/helper lipid stoichiometry varies for the different cationic lipids, nucleic acids, and cells. 

Figure 14.3 Chemical structures of colipid DOPE and some cationic lipids commonly used for gene transfer...

Ferrari M E, Rusalov D, Enas J, et al. (2002). Synergy between cationic lipid and colipid determines the macroscopic structure and transfection activity of lipoplexes. Nucleic Acids Res. 30 1808-1816. 

Including a second lipid component obviously introduces a new variable in the preparation of cationic lipid DNA complexes namely, the colipid cationic lipid... 

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