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 specific derivative, was reacted with KALA to produce a PEG-KALA conjugate. The conjugate was analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry, and its hemolytic activity was determined relative to KALA. Positively charged PEG-KALA conjugate was coated onto the surface of negatively charged DNA/PEI complexes to form net positively charged PEG-KALA/DNA/PEI complexes. They were 200-400 nm in diameter with increasing amount of PEG-KALA, whereas DNA/PEI complexes coated with KALA aggregated to a great extent. This was because PEG chains surrounding the surface of the complexes suppressed the inter-particle interaction that was mediated by cationic KALA. Transfection efficiency progressively increased as the amount of PEG-KALA to be coated was increased, suggesting that fusogenic activity of KALA contributes to enhancing the level of gene expression.