A new triantennary galactose-targeted PEGylated gene carrier, characterization of its complex with DNA, and transfection of hepatoma cells.

Nonviral gene vectors remain inefficient in vivo largely because of their rapid clearance from the circulation and also their nonspecific association with the extracellular matrix. To overcome such drawbacks, cationic lipoplexes are now frequently coated with hydrophilic polymers such as PEGs to reduce nonspecific interactions, and ligands are also linked to their surface to obtain cell-specific gene transfer. In view of the development of vectors for systemic gene delivery, we have designed and studied lipoplexes that carry a triantennary galactosyl ligand attached to the distal end of a (PEG)45-conjugated lipid. We incorporated this targeted PEGylated lipid into lipoplexes using two strategies of formulation, i.e., using either preformed micelles or liposomes. We demonstrated that the incorporation of PEG chains stabilized lipoplexes and masked, but only partially, the positive charges exposed on the surface of the particles. We have also shown that incorporation into lipoplexes of a lipidated PEG chain, bearing a ligand at its distal end, yielded particles that exhibited an accessible ligand throughout the whole range of cationic lipid to DNA ratios. We obtained a targeted transfection in HepG2 cells with one of the formulations. Our results strengthen the validity of using a ligand carried by a long PEG spacer arm for targeted gene transfer.