Nucleic Acids, Protein Synthesis, and Molecular Genetics
Folate-targeted, Anionic Liposome-entrapped Polylysine-condensed DNA for Tumor Cell-specific Gene Transfer (*)

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We have developed a lipidic gene transfer vector, LPDII, where DNA was first complexed to polylysine at a ratio of 1:0.75 (w/w) and then entrapped into folate-targeted pH-sensitive anionic liposomes composed of dioleoyl phosphatidylethanolamine (DOPE)/cholesteryl hemisuccinate/folate-polyethlene glycol-DOPE (6:4:0.01 mol/mol) via charge interaction. LPDII transfection of KB cells, a cell line overexpressing the tumor marker folate receptor, was affected by both the lipid to DNA ratio and the lipid composition. At low lipid to DNA ratios (e.g. 4 and 6), LPDII particles were positively charged; transfection and cellular uptake levels were independent of the folate receptor and did not require a pH-sensitive lipid composition. Meanwhile, transfection and uptake of negatively charged LPDII particles, i.e. those with high lipid to DNA ratios (e.g. 10 and 12), were folate receptor-dependent and required a pH-sensitive lipid composition. The transfection activity of LPDII was lost when the inverted cone-shaped DOPE was replaced by dioleoyl phosphatidylcholine. LPDII particles with lipid to DNA ratios of 4, 6, 10, and 12 were ~20-30 times more active than DNA•3-β-[N-(N′,N′-dimethylethane)carbamoyl]cholesterol cationic liposome complexes in KB cells and were much less cytotoxic. On the sucrose gradient, LPDII particles had a migration rate in between those of the free DNA and the DNA•polylysine complex. An electron micrograph of LPDII showed a structure of spherical particles with a positively stained core enclosed in a lipidic envelope with a mean diameter of 74 ± 14 nm. This novel gene transfer vector may potentially be useful in gene therapy for tumor-specific delivery.

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*

This work was supported by National Institutes of Health Grants CA59327, HL50256, DK44935, and CA64654. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked #x0201C;advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.