A powerful cooperative interaction between a fusogenic peptide and lipofectamine for the enhancement of receptor-targeted, non-viral gene delivery via integrin receptors.

Background Following receptor-mediated endocytosis, vector/DNA complexes require assistance to exit endocytic vesicles in order to avoid degradation in the lysosomes. Overcoming this barrier is a major challenge for the development of receptor-targeted, non-viral gene delivery. Methods The fusogenic peptide of influenza virus haemagglutinin, lipofectamine and chloroquine were tested singly and in combination in various doses for promoting in vitro gene transfer by an integrin-targeted, non-viral DNA vector (polylysine-molossin). Results The fusogenic peptide and lipofectamine both individually promoted integrin-targeted gene delivery. However, the combined use of these agents was particularly effective, even at concentrations where neither agent singly had any effect on promoting gene delivery by polylysine-molossin. This optimal combination was effective on several cell lines and primary cell cultures. On the HuH7 cell line, it was ∼five-fold more effective than optimal chloroquine concentrations for integrin-targeted gene delivery and four to five times more effective than commercially available polyethylenimine. With the β-galactosidase reporter gene, 60–65% of HepG2 cells and 75–80% of HuH7 cells were positive. The surface charge of polylysine-molossin/DNA/lipofectamine/fusogenic peptide complexes was approximately the same as that of polylysine-molossin/DNA complexes. The size distribution of the complexes suggested that competitive binding of polylysine-molossin and lipofectamine to DNA influenced the overall efficacy of this approach. Conclusions Although the mechanisms are not clear, the combined use of very low doses of two membrane-destabilizing agents results in high levels of receptor-targeted gene delivery. Copyright © 2001 John Wiley & Sons, Ltd.