Hyaluronic acid-bearing lipoplexes: physico-chemical characterization and in vitro targeting of the CD44 receptor

The mechanism by which hyaluronic acid (HA)-bearing lipoplexes target the A549 lung cancer cell line was evaluated. For this purpose, cationic liposomes targeting the CD44 receptor were designed thanks to the incorporation in their composition of a conjugate between high molecular weight HA and the lipid DOPE (HA-DOPE). Liposomes containing HA-DOPE were complexed at different lipids:DNA ratios with a reporter plasmid encoding the green fluorescent protein (GFP). Diameter, zeta potential, lipoplex stability and DNA protection from nucleases have been determined. Lipids:DNA ratios of 2, 4 and 6 provided a diameter around 250 nm with a zeta potential of −30 mV. The strength of lipids:DNA interaction and the fraction of DNA protected from enzymatic degradation increased with the lipids:DNA ratio. 2D-immunoelectrophoresis demonstrated the low capacity to activate the C3 fraction of the complement system of any of these three ratios, with and without HA-DOPE. Transfection efficiency in the presence of 0, 10 and 15% of HA-DOPE or unconjugated HA, was determined on the CD44-expressing A549 cells by flow cytometry. Lipoplexes at a lipids:DNA ratio of 2 containing 10% (w/w) of HA-DOPE were the most efficient for transfection. The maximal level of GFP expression was obtained after 6 h of incubation demonstrating a slow transfection kinetics of lipoplexes. Finally, lipoplex cellular uptake, measured indirectly by the level of transfection using flow cytometry and validated by fluorescence microscopy, was shown to be mediated by the CD44 receptor and caveolae. These results demonstrate the strong specificity of DNA targeting through the CD44 receptor using HA of high molecular weight as a ligand.