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Single electrochemical impacts of Shewanella oneidensis MR‐1 Gram‐negative electroactive bacteria onto ultramicroelectrode surfaces are reported and in‐depth analysed. Chronoamperometry measurements recorded onto 10 μm‐diameter Pt and 7 μm‐diameter carbon fibre disk ultramicroelectrodes in a 20 mM potassium ferrocyanide aqueous solution in the presence of living bacteria show an electrostatic attraction of Shewanella cells onto the ultramicroelectrode surface polarized at +0.8 V vs Ag/AgCl. Single current step events analysis and atomic force microscopy experiments confirm the adsorption of living bacteria following the collision onto the ultramicroelectrode surface. The bacteria washing step before the chronoamperometry measurements leads to lower current step events related to the smaller size of the living cells. The electrostatic attraction of the negatively charged bacteria onto the positively charged ultramicroelectrode surface polarized at the oxidation potential of ferrocyanide is clearly demonstrated. [ABSTRACT FROM AUTHOR]

The detection of Rhamnolipid virulence factor produced by Pseudomonas aeruginosa involved in nosocomial infections is reported by using the redox liposome single impact electrochemistry. Redox liposomes based on 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine as a pure phospholipid and potassium ferrocyanide as an encapsulated redox content are designed for using the interaction of the target toxin with the lipid membrane as a sensing strategy. The electrochemical sensing principle is based on the weakening of the liposomes lipid membrane upon interaction with Rhamnolipid toxin which leads upon impact at an ultramicroelectrode to the breakdown of the liposomes and the release/electrolysis of its encapsulated redox probe. We present as a proof of concept the sensitive and fast sensing of a submicromolar concentration of Rhamnolipid which is detected after less than 30 minutes of incubation with the liposomes, by the appearing of current spikes in the chronoamperometry measurement. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical reduction of aqueous pyridinium and N‐methyl pyridinium ions is investigated in the absence and presence of CO2 and electrolysis reaction products on glassy carbon, Au, and Pt electrodes are studied. Unlike pyridinium, N‐methyl pyridinium is not electroactive at the Pt electrode. The electrochemical reduction of the two pyridine derivatives was found to be irreversible on glassy carbon. These results confirmed the essential role of the N−H bond of the pyridinium cation. In contrast, the electrochemical response of N‐methyl pyridinium ion at the glassy carbon electrode suggests that a specific interaction occurs between the glassy carbon surface and the aromatic ring of the pyridinium derivative. For all electrodes, an enhancement of current was observed in the presence of CO2. However, NMR spectroscopy of the solutions following electrolysis showed no formation of methanol or other possible byproducts of the reduction of CO2 in the presence of either pyridinium derivative ion. [ABSTRACT FROM AUTHOR]

Front Cover: Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface (ChemElectroChem 1/2023) Keywords: Single electrochemical impacts; Ultramicroelectrode; Electroactive bacteria; Chronoamperometry; Atomic force microscopy EN Single electrochemical impacts Ultramicroelectrode Electroactive bacteria Chronoamperometry Atomic force microscopy 1 1 1 01/06/23 20230102 NES 230102 B The Front Cover b illustrates the electrostatic attraction of the negatively-charged electroactive I Shewanella oneidensis i bacterium onto the positively-charged ultramicroelectrode surface polarized at the oxidation potential of ferrocyanide. Single electrochemical impacts, Ultramicroelectrode, Electroactive bacteria, Chronoamperometry, Atomic force microscopy. [Extracted from the article]