Abstract: AimTo develop a novel non-viral gene delivery systems lipid-polycation-DNA complexes (LPD) and investigate their transfection efficiencies in vitro. MethodsLPD were prepared as follows by first mixing the plasmid DNA and protamine together, then the resulted polyplexes were incubated for 10 min at room temperature, followed by addition of preformed cationic liposomes. The morphology of LPD was observed by transmission electron microscopy. The diameter and surface charge of LPD were measured by photon correlation spectroscopy (PCS). The nuclease protection ability of LPD was evaluated by agarose gel electrophoresis. Estimation of transfection efficiency was performed by galactosidase assay in Chang, HepG2 and SMMC-7721 cells. ResultsThe average diameter and the zeta potential of LPD were 143.5 nm and 32.6 mV, respectively. LPD could protect the plasmid DNA from nuclease degradation after 2 hours incubation at 37 ℃ while the naked DNA degraded rapidly. The average transfection efficiencies were (69±6)%, (43±7)% and (96.2±1.8)% in Chang cells, HepG2 cells and SMMC-7721 cells respectively. ConclusionLPD could be prepared easily with small particle sizes and high transfection activities. LPD may be good non-viral vectors for applications in gene delivery.