Delivery of oligonucleotides into mammalian cells by anionic peptides: comparison between monomeric and dimeric peptides

The use of antisense oligonucleotides as putative therapeutic agents is lim ited by their poor delivery into the cytosol and/or the nucleus because the y are nut able to efficiently cross lipid bilayers. To circumvent this pitf all, anionic amphipathic peptides derived from the influenza virus fusogeni c peptide have been used to destabilize membranes in an acidic environment. In this paper, we compare the ability of a monomeric and a dimeric peptide to introduce oligonucleotides into the cytosol and nuclei of several types of cultured cells. Cells incubated at pH 6.2 or at a slightly lower pH in the presence of the monomeric peptide but not the dimeric peptide were effi ciently permeabilized. The location of fluorescent derivatives of peptides and of oligonucleotides was assessed by confocal microscopy. Both the pepti des and oligonucleotides remained entrapped in vesicular compartments at ne utral pH, at acidic pH, oligonucleotides in the presence of the monomeric p eptide were mainly in the nucleus, while in the presence of the dimeric pep tide they co-localized with the peptide into vesicles. The data are interpr eted on the basis of the spectroscopic behaviour of monomeric and dimeric p eptides in relation to the environmental pH.