Size Reduction of Galactosylated PEI/DNA Complexes Improves Lectin-Mediated Gene Transfer into Hepatocytes

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Abstract
Hepatocytes are interesting targets for gene therapy applications. Several hepatocyte-directed gene delivery vectors have been described. For example, simple galactosyl residues coupled to polyethylenimine (PEI) gave an efficient vector which selectively transfected hepatocytes via the asialoglycoprotein receptor-mediated endocytosis [Zanta, M. A., et al. (1997) Bioconjugate Chem.8, 839−844]. However, the large size of these galactosylated PEI/DNA complexes prevented their use in vivo. We have investigated the role of the saccharide length on the size of glycosylated-PEI/DNA particles. When 5% of the PEI nitrogens were grafted with a linear tetragalactose structure (lGal4), small and stable particles were formed upon complexation with plasmid DNA. These particles were essentially toroids having a size of 50−80 nm and a ζ-potential close to neutrality. Moreover, these slightly charged PEI−lGal4/DNA complexes were as selective as the previously described galactosylated−PEI vector to transfect hepatocytes, but in addition, they were more efficient. It is expected that the properties of the PEI−lGal4/DNA complexes may increase their diffusion into the liver and their efficiency to transfect hepatocytes.