Dynamic Electrochemiluminescence Imaging of Single Giant Liposome Opening at Polarized Electrodes

In this work, the characterization of release events from liposomes has been addressed quantitatively by an electrochemiluminescence (ECL) imaging strategy. First, ECL reagents ([Ru(bpy)3]2+ and tripropylamine) were encapsulated in sealed giant asymmetrical liposomes (100 μm in diameter) made of DOPG/DOPC phospholipids. After sedimentation on an indium tin oxide electrode material, the opening of liposomes was triggered by polarization of the surface. Under these conditions, amperometry, epifluorescence imaging, and ECL imaging were combined and synchronized to monitor and image the rupture of giant liposomes during the release and subsequent ECL emission of their redox content. Amperometry allowed the quantification of the content released from single liposomes. The location and status of liposomes (closed or opened) were assessed by epifluorescence imaging. ECL provided the image of the efflux of matter after liposome opening. This original ECL imaging approach favorably compares with strictly photoluminescent or electrochemical techniques and appears to be adapted for the investigation of membrane rupture/permeation events.