Structural basis of DOTMA for its high intravenous transfection activity in mouse

Eleven structural analogues of two known cationic lipids, N-[1-(2,3-dioleyl oxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) and N-[1-(2,3-dioleoyl oxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP) were synthesized and u tilized to evaluate the structural characteristics of DOTMA for its high in travenous transfection activity Using a CMV-driven expression system and lu ciferase gene as a reporter, the transfection activity of these analogues w as evaluated in mice using fail vein injection. Results concerning the stru cture-activity relationship with regard to the influence of the backbone, r elative position between head group and the hydrophobic chains on the backb one, linkage bonds, as well as the composition of the aliphatic chains reve aled that cationic lipids which give a higher in vivo transfection activity share the following structural characteristics: (I) cationic head group an d its neighboring aliphatic chain being in a 1,2-relationship on the backbo ne; (2) ether bond for bridging the aliphatic chains to the backbone; and ( 3) paired oleyl chains as the hydrophobic anchor. Cationic lipids without t hese structural features had lower in vivo transfection activity. These str uctural characteristics, however, did not significantly influence their in vitro transfection activity. The contribution that cationic lipids make to the overall in vivo transfection activity is likely to be determined by the structure of DNA/lipid complexes and by the outcome of the interaction bet ween the DNA/lipid complexes and blood components upon intravenous administ ration.