A new gene delivery formulation of polyethylenimine/DNA complexes coated with PEG conjugated fusogenic peptide

A fusogenic peptide, KALA, was conjugated with poly(ethylene glycol) (PEG) for use as an endosome disruptive agent in the gene delivery formulation of polyethyleneimine (PEI). A maleimide terminated methoxy-PEG, a cysteine sp ecific derivative, was reacted with KALA to produce a PEG-KALA conjugate. T he conjugate was analyzed by matrix-assisted laser desorption ionization ti me-of-flight mass spectrometry, and its hemolytic activity was determined r elative to KALA. Positively charged PEG-KALA conjugate was coated onto the surface of negatively charged DNA/PEI complexes to form net positively char ged PEG-KALA/DNA/PEI complexes. They were 200-400 nm in diameter with incre asing amount of PEG-KALA, whereas DNA/PEI complexes coated with KALA aggreg ated to a great extent. This was because PEG chains surrounding the surface of the complexes suppressed the inter-particle interaction that was mediat ed by cationic KALA. Transfection efficiency progressively increased as the amount of PEG-KALA to be coated was increased, suggesting that fusogenic a ctivity of KALA contributes to enhancing the level of gene expression. (C) 2001 Elsevier Science B.V. All rights reserved.