Effect of the combination of cationic lipid and phospholipid on gene-knockdown using siRNA lipoplexes in breast tumor cells and mouse lungs.

Previously, using three types of cationic lipids, the effect of phospholipids in liposomal formulations on gene-knockdown efficacy was determined after and transfection with small interfering RNA (siRNA)/cationic liposome complexes (siRNA lipoplexes) containing various cationic lipids and phospholipids. In the present study, six other types of cationic lipids, namely -dimethyl--tetradecyltetradecan-1-aminium bromide, -hexadecyl--dimethylhexadecan-1-aminium bromide (DC-1-16), 2-[bis{2-(tetradecanoyloxy)ethyl}amino]--trimethyl-2-oxoethan-1-aminium chloride (DC-6-14), 1,2-di--octadecenyl-3-trimethylammonium propane chloride (DOTMA), 1,2-distearoyl-3-trimethylammonium-propane chloride (DSTAP) and 1,2-dioleoyl-3-dimethylammonium-propane were selected, and the effect of phospholipids in liposomal formulations containing each cationic lipid on gene-knockdown was evaluated. A total of 30 types of cationic liposomes composed of each cationic lipid with phosphatidylethanolamine containing unsaturated or saturated diacyl chains (C14, C16 or C18) were prepared.