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The transfection efficiency of plasmid DNA was inspected using multi-cationic polymer, 5, 10, 25 and 50KD polyethylenimine (PEI). The optimal neutralization ratio of PEI/DNA complexes by agarose assay was 1.5-2.0 (nmol/nmol) without much difference in molecular weight of PEI.In vitro transfection assay, most of PEI-mediated plasmid delivery was better compared to the naked DNA. Especially, 25KD PEI at optimal condition gave higher transfection rather than the standard assay of DEAE-dextran or Lipofectin. To enhance the cell targeting delivery, the liposome formulations were introduced using phospholipids. As a result, PC/PE liposomes increased 2-2.5 times of the transfection efficiency of PEI single or PC/PE single delivery, but not the case of 25KD PEI. Moreover, the DOTAP/PE-introduced PEI delivery reduced the transfection of DOTAP/PE single delivery. All these results proved that the PEI can be used not only good transfectants and but also good DNA condensing agents in neutral/anionic liposome for cell targeting delivery.
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