Optimizing the formulation of procationic liposomes-protamine-DNA complexes by response surface methodology.

The procationic liposomes-protamine-DNA (PLPD) vectors we described here are non-viral vehicles for gene delivery comprised of polycation-condensed plasmid DNA and procationic liposomes made of phospholipids, cholesterol, and CHETA (Cholest-5-en-3beta-yl[2-[[4-[(carboxymethyl)dithio]-1-iminobutyl]amino]ethyl] carbamate, C36H61N3O4S2). Response surface methodology (RSM) was employed to optimize the formulation of PLPD. A three-factor, five-level RSM design was used for the optimization procedure, with the weight ratio of protamine/DNA (X1), the molar percent of CHETA (X2), and the weight ratio of CHETA/DNA (X3) in the procationic liposomes as the independent variables.