Electrochemical quenching of the fluorescence produced by NBD-labelled cell penetrating peptides: A contribution to the study of their internalization in large unilamellar vesicles

International audience; This work investigates the implementation of a simple and versatile electrochemical setup aimed at achieving a fast and complete fluorescence extinction of NBD-labelled (NBD = 7-nitrobenz-2-oxa-1,3-diazole) cell penetrating peptides contained in 2-5 cm 3 samples containing phosphate buffer + Large Unilamellar Vesicles. The quenching is obtained through a reductive electrolysis in a 2-compartment cell homebuilt from disposable plastic labware, which remains inert towards the adsorption of both peptides and lipid vesicles. Considering the micromolar concentration of NBD-tagged peptides, the main electrochemical reaction observed is hydrogen evolution, NBD reduction representing a small fraction of the cathodic current/charge engaged. The electrolysis conditions are discussed with respect to the nature of the reduction products formed, the integrity of Large Unilamellar Vesicles and phosphate buffering properties. This electrochemical method is compared to the traditional chemical dithionite quenching of NBD and tested to monitor the internalization of Cell Penetrating Peptides in Large Unilamellar Vesicles.