Cation substitution in cationic phosphonolipids: A new concept to improve transfection activity and decrease cellular toxicity

Cationic lipids have been shown to be an-interesting alternative to viral v ector-mediated gene delivery into in vitro and in vivo model applications. Prior studies have demonstrated that even minor structural modifications of the lipid hydrophobic domain or of the lipid polar domain result in signif icant changes in gene delivery efficiency. Previously, we developed a novel class of cationic lipids called cationic phosphonolipids and described the ability of these vectors to transfer DNA into different cell lines and in vivo. Up until now, in all new cationic lipids, nitrogen atoms have always carried the cationic or polycationic charge. Recently we have developed a n ew series of cationic phosphonolipids characterized by a cationic charge ca rried by a phosphorus or arsenic atom. In a second step, we have also exami ned the effects of the linker length between the cation and the hydrophobic domain as regards transfection activity. Transfection activities of this l ibrary of new cationic phosphonolipids were studied in vitro in different c ell lines (HeLa, CFT1, K562) and in vivo using a luciferase reporter gene. A luminescent assay was carried out to assess luciferase expression. We dem onstrated that cation substitution on the polar domain of cationic phosphon olipids (N --> P or As) results in significant increase in transfection act ivity for both in vitro and in vivo assays and decrease of cellular toxicit y.