Combination of Luminescence Imaging and Amperometry to Analyze Molecular Fluxes Induced by Membrane Permeabilization of Single Giant Liposomes in Microfluidic Channels.

The content release of single giant liposomes (40-100 μm diameter) confined in a microfluidic device was investigated by combining amperometric, fluorescence, and electrochemiluminescence (ECL) monitoring techniques. Accordingly, a microfluidic device was designed to guide, isolate, and immobilize without altering a single liposome in contact with a semitransparent platinum electrode, in a micrometric channel compatible with luminescence microscopy observations. Sealed giant asymmetrical liposomes were made from DOPG/DOPC phospholipids (i.e., 1,2-dioleoyl-sn-glycerol-3-phospho-(1'-rac-glycerol) sodium salt/1,2-dioleolyl-sn-glycero-3-phosphocholine) trapping ECL reagents ([Ru(bpy)3]2+ luminophore and tri-n-propylamine coreactant). The liposome membrane permeation/rupture was triggered by polarization of the platinum electrode. Under these conditions, the liposomes content releases were simultaneously imaged and analyzed by ECL, photoluminescence, and amperometry. It was shown that ECL generation following liposome electroporation is governed not only by membrane permeabilization but critically by the convective transport of ECL reagents above the electrode interface. Emission was observed only upon rapid membrane rupture, which generates sufficient lateral convection to displace released reagents beyond phospholipid-blocked electrode regions. ECL imaging further reveals localized suppression of electrochemical activity due to phospholipid adsorption after rupture. Together, these findings establish convective transport as a key determinant of ECL detection at the single-liposome level in confined environments, with important implications for the electrochemical analysis of biological and artificial vesicles.