Oligonucleotide delivery by a cationic derivative of the polyene antibiotic amphotericin B - I: Interaction oligonucleotide/vector as studied by optical spectroscopy and electron microscopy

Antisense strategy requires efficient systems for the delivery of oligodeox yribonucleotides (ODN) into target cells. Cationic amphiphiles have shown g ood efficiency in vitro and a lot of attention is currently paid to their i nteraction with nucleic acids. In the present study, this interaction was, for the first time, analysed at the molecular level, taking advantage of th e spectroscopic properties of the positively charged chiral polyene molecul e amphotericin B 3-dimethylaminopropyl amide (AMA), the efficiency of which , as delivery system, has been demonstrated [Garcia et al., Pharmacol. Ther . (2000), in press]. By UV-visible absorption and circular dichroism (CD) w e studied its self-association properties in pure water, saline and RPMI me dium. Drastic changes were observed upon ODN addition, stronger in pure wat er than in media of high ionic strength. At low AMA concentration (< 10(-6) M), the strong increase of the CD signal, characteristic of self-associati on, indicated condensation of AMA on the ODN molecules. At a higher concent ration (10(-6) M), and for a nucleic acid negative charge/AMA positive char ge ratio higher than 1, spectra were interpreted as a reorganisation of fre e self-associated AMA species into smaller ones 'decorating' the nucleic ac id molecule. Electron microscopy data were interpreted according to this sc heme. (C) 2000 Elsevier Science B.V. All rights reserved.