Targeting of plasmid DNA-lipoplexes to cells with molecules anchored via a metal chelator lipid.

Background: The ability to deliver plasmid DNA (pDNA) to specific cells in vivo is crucial for achieving efficient targeted transfection with nonviral vectors. We previously used stealth liposomes containing the chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA(3)-DTDA) to target delivery of antigen and cytokines to immune cells in vivo. In the present study, we utilized liposomes containing NTA(3)-DTDA and the ionizable aminolipid 1,2-dioleoyl-3-dimethyl-ammonium-propane (DODAP) to incorporate pDNA into complexes for targeting to cells.

Methods: Liposomes containing DODAP, NTA(3)-DTDA and helper lipids were acidified (pH 5.5) and mixed with pDNA to form complexes. These lipoplexes were neutralized and engrafted with His-tagged molecules for targeting to extracellular receptors. Targeted transfection efficiency was assessed using the enhanced green fluorescent protein reporter gene.

Results: Initial transfections of HEK-293 cells using a His-tagged peptide (T2) related to the Arg-rich motif of HIV-1 TAT protein resulted in a low transfection efficiency (<2.5%). Optimization of the lipid formulation and use of an endosome-destabilizing peptide and inhibitor of DNase II, increased transfection approximately 20-fold. These lipoplexes are approximately 250 nm in diameter, and transfection efficiencies were: approximately 50% for HEK-293 cells targeted with lipoplexes containing pEGFP-N1 and engrafted with T2, and 30-40% for HepG2 cells targeted with lipoplexes engrafted with a peptide specific for the VEGF receptor Flt-1.

Conclusions: The results show that DODAP-containing lipoplexes incorporating NTA(3)-DTDA enable the engraftment of targeting molecules and the effective targeting of pDNA to cells in serum-containing media, resulting in efficient transgene expression. The strategy may provide a convenient approach for targeting pDNA to cells in vivo in therapeutic applications.