Novel series of non-glycerol-based cationic transfection lipids for use inliposomal gene delivery

A novel series of nontoxic and non-glycerol-based simple monocationic trans fection lipids containing one or two hydroxyethyl groups directly linked to the positively charged nitrogen atom were synthesized. The in vitro transf ection efficiencies of these new liposomal gene delivery reagents were bett er than that of lipofectamine, a widely used transfection agent in cationic lipid-mediated gene transfer. The most efficient transfection formulation was observed to be a 1:1:0.3 mol ratio of DHDEAB (N,N-di-n-hexadecyl-N,N-di hydroxyethylammonium bromide): cholesterol:HDEAB (N-n-hexadecyl-N,N-dihydro xyethylammonium bromide) using a DHDEAB-to-DNA charge ratio (+/-) of 0.3:1. Observation of good transfection at charge ratios lower than 1 suggests th at the amphiphile-DNA complex may have net negative charge. Our results ree mphasize the important point that in cationic lipid-mediated gene delivery, the overall charge of the lipid-DNA complex need not always be positive. I n addition, our transfection results also imply that favorable hydrogen-bon ding interactions between the lipid headgroups and the cell surface of biol ogical membranes may have some role for improving the transfection efficien cy in cationic lipid-mediated gene delivery.