Physicochemical characterization and gene transfection efficiency of lipid emulsions with various co-emulsifiers

Transfection systems based on complexes of DNA and lipid emulsions were evaluated with respect to their effectiveness, toxicity, physicochemical characteristics, and cell-type dependence. The potential of a series of co-emulsifiers to serve as vectors was investigated. The co-emulsifiers examined included 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), Tween, cholesterol, stearylamine, and polyethylenimine (PEI). Squalane and 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP), respectively, were the main oil phase and cationic lipid added to the lipid emulsions. Cell viability was reduced after inclusion of either of the two cationic components of stearylamine and PEI. DOPE and cholesterol showed both higher transfection activity and cell viability as compared to the other co-emulsifiers. The incorporation of DOPE and cholesterol also prevented droplet aggregation of the emulsions after long-term storage. Results of the transfection of COS-1, A549, or HaCat cell lines with lipid emulsions indicated differences in transfection activities of each formulation for the different cell lines. It is concluded that DOPE and cholesterol as co-emulsifiers for DOTAP were preferable for stability and DNA transfection of emulsions.