CPOS Seminar: "Single-entity electrochemistry for investigating electroactive bacteria and redox liposomes"

Speaker: Estelle Lebegue, Associate Professor, Nantes Université, CNRS, CEISAM, UMR 6230, F-44000 Nantes, France 
Electroanalytical chemistry greatly evolved with the continuous improvement of instrumentation sensitivity and especially with the development of the electrochemical detection of individual entities. In this context, single-entity electrochemistry, namely discrete collisions technique or nano-impacts method based on stochastic events, is a useful tool for the detection via single impacts of various micro- and nano-entities such as nanoparticles, cells, bacteria, vesicles, viruses, proteins in solution at a polarized ultramicroelectrode (UME). Single-entity electrochemistry method can provide unique information on various individual entities through the detection of discrete events in contrast to ensemble (bulk) measurements. For each impact event, the chronoamperometry measurement (i‒t curve) shows a specific signal corresponding to an “impact” of the entity onto the UME surface. Subsequent analysis of electrochemical impact events in the i‒t curve can provide useful data, such as the concentration and the size of the colliding entities. In our work, we focus on single-entity electrochemistry applied to bacteria and liposomes, particularly electroactive bacteria such as Shewanella oneidensis and phospholipid redox liposomes with ferrocyanide species encapsulated. These soft targets have interesting properties in term of release mechanism, membrane permeability and electron transfer at a polarized ultramicroelectrode, that we investigate by single-entity electrochemistry and more recently, coupled to microscopy.