Hybrid vector including polyethylenimine and cationic lipid, DOTMA, for gene delivery.

We developed polyethylenimine (PEI) lipopolyplexes with N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethlylammonium chloride (DOTMA) and pDNA to investigate their usefulness for in vitro and in vivo gene delivery. The charge ratio of the complex to pDNA was calculated with molar values of nitrogen of PEI, and nitrogen of DOTMA to phosphate of pDNA. The polyplexes were prepared at charge ratio 2 (polyplex 2P) and 8 (polyplex 8P). DOTMA solution was added to polyplex 2P to prepare lipopolyplexes at charge ratio 1 (lipopolyplex 2P-1D), 2 (lipopolyplex 2P-2D), and 4 (lipopolyplex 2P-4D). The particle size of the complex was significantly reduced by the addition of DOTMA and settled to 74-114nm, indicating pDNA compaction. The addition of DOTMA to polyplex 2P decreased pDNA dissociation from the complex and degradation in serum. The addition of DOTMA to polyplex 2P remarkably increased gene expression in HepG2 cells in the absence or presence of FBS. These lipopolyplexes showed little cytotoxicity in the presence of FBS. After intravenous injection of the lipopolyplexes into mice, high-gene expression in the liver, spleen, and lung was observed with lipopolyplex 2P-2D, lipopolyplex 2P-4D, and polyplex 8P. In particular, lipopolyplex 2P-4D showed the highest gene expression.