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AIM: To develop a novel non-viral gene delivery system,which has a small particle size and a high transfection efficiency to hepatocyte and hepatoma cells.METHODS: Lipid-polycation-DNA lipopolyplex (LPD) was prepared by mixing plasmid DNA and polylysine. The resulted polyplex was incubated for 10 min at room temperature,following the 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 the transfection efficiency was performed by galactosidase assay in Chang cells and SMMC-7721 cells.RESULTS: LPD had a regular spherical surface. The average diameter and the zeta potential of LPD were 132.1 nm and 26.8 mV respectively. LPD could protect plasmid DNA from nuclease degradation after 2 hours incubation at 37°C while the naked DNA degraded rapidly. The average transfection efficiencies were 86.2±8.9% and 72.4±6.5% in Chang cells and SMMC-7721 cells respectively.CONCLUSION: LPD has a rather small particle size and a high transfection activity. LPD may be a good non-viral vector for application in some gene delivery.