A New Triantennary Galactose-Targeted PEGylated Gene Carrier, Characterization of Its Complex with DNA, and Transfection of Hepatoma Cells

Abstract

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.

Biotin-directed assembly of targeted modular lipoplexes and their transfection of human hepatoma cells in vitro

“…A similar steric crowding effect has been observed with PEGylated liposomes displaying triantennary galactose units at the distal ends of the polyethyleneglycol chains (Frisch et al, 2004). Ternary assemblies that afforded the highest transfection activity viz.…”

Molecular Conjugates

“…Galactosylated PEI (Gal-PEI) was shown to give galactose-inhibitable gene expression in cultured murine hepatocytes and it achieved superior delivery to hepatocytes (vs. unmodified PEI) after injection in mice [43]. Frisch et al attached a triantennary galactosyl ligand to a PEG-modified lipid delivery system and demonstrated targeted transfection of cultured human hepatocytes [44]. These results are surprising and somewhat confusing, given that the complexes examined had a diameter of around 150 nm, more than twice as large as the reported 70 nm upper size limit for endocytosis via interaction with the ASGPR [45].…”

Ligand-based targeted therapy: a novel strategy for hepatocellular carcinoma

“…52 Galactosylated polymers were developed as a drug/gene carrier system for targeted delivery in HCC therapy. 53,54 Zhang et al 53 …”

“…Gal-decorated gene carrier was also developed to investigate the transfection efficiency, demonstrating that galactosyl ligand could enhance the validity of targeted gene transfer for HCC. 54 Lactobionic acid (LA), comprising gluconic acid and Gal moiety, is the common ligand for hepatoma-targeted delivery. [55][56][57] The Gal residues on drug delivery system can recognize and bind specifically to the ASGPR on the hepatoma cells, 58,59 thus they facilitate drug delivery into the cells, which are inhibited and killed by therapeutic agents in delivery vehicles.…”