A cationic lipid emulsion/DNA complex as a physically stable and serum-resistant gene delivery system

Purpose. To develop a non-viral gene delivery system in the form of an oil- in-water (o/w) lipid emulsion. Method. Cationic lipid emulsions were formulated with soybean oil, 1,2-diol eoyl-sn-glycero-3-trimethylammonium-propane (DOTAP) as a cationic emulsifie r and other co-emulsifiers. The physical characteristics of the lipid emuls ion and the emulsion/DNA complex were determined. The in vitro transfection efficiency of the emulsion/DNA complex was determined in the presence of u p to 90% serum. Results. The average droplet size and zeta potential of emulsions were cn. 180 nm and ca. +50 mV, respectively. Among the emulsions, a stable formulat ion was selected to form a complex with a plasmid DNA encoding chlorampheni col acetyltransferase. By increasing the ratio of emulsion to DNA, zeta-pot ential of the emulsion/DNA complex increased monotonously from negative to positive without any changes in the complex size. The complex was stable ag ainst DNase I digestion and an anionic poly-L-aspartic acid (PLAA). The com plex delivered DNA into the cells successfully, and the transfection effici ency was not affected by complex formation time from 20 min to 2 h. More im portantly, the cationic lipid emulsion facilitated the transfer of DNA in t he presence of up to 90% serum. Conclusions. The cationic lipid emulsion/DNA complex has physical stability and serum resistant properties for gene transfer.