In the past few years, several novel analytical methods with high sensitivity and spatial-temporal resolution that enable qualitative and quantitative analysis at single-cell and subcellular levels have emerged. *
The four major areas of analytical methods usually reported are electrochemical analysis, super-resolution microscopy, mass spectrometry imaging, and microfluidics. *
Electrochemistry offers a distinctive and essential advantage in its ability to combine high sensitivity and easy handling with a light and portable instrumentation, thereby enabling miniaturized devices for micro-biosensor applications. *
In this way, the electrochemistry of discrete impacts onto ultramicroelectrode (UME) offers the opportunity for electrochemical analysis at the single-cell level with high sensitivity. *
Fast and easy handling instruments for detection of bacteria at the single cell scale, with maximal sensitivity, have become reachable with the promising electrochemistry of single impacts onto a microelectrode surface. *
Although this method is not efficient for selective bacterial detection yet, the observation of these single events can provide information on various individual nanoparticles in contrast to ensemble (bulk) measurements. *
The main advantage of studying collisions of single entities is the low limit of detection (in principle, one single species) inherent to this electroanalytical method and the ability to study various single entities (e. g. cells, viruses, nanoparticles) in real time (dynamic measurement). *
This approach is advantageous because it allows the direct characterization of the electrical interaction between a single bacterium and an UME under controlled conditions, in the absence of a biofilm (UME surface biofouling), and also minimizes the effect of secreted materials on the sensitivity of the electrochemical signal. *
In the article “Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface” Hassiba Smida, François-Xavier Lefèvre, Christine Thobie-Gautier, Mohammed Boujtita, Catarina M. Paquete and Estelle Lebègue report single electrochemical impacts of Shewanella oneidensis MR-1 Gram-negative electroactive bacteria onto ultramicroelectrode surfaces and analyse them. *
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. *
NANOSENSORS uniqprobe qp-SCONT AFM probes (typical tip radius 10 nm, typical spring constant of 0.1 N/m, typical resonant frequency of 14 kHz) were used for the quantitative Atomic Force Microscopy (AFM) imaging. *
All AFM experiments were performed in water (droplet deposited on the UME surface after single bacteria impact experiment) with an applied force of 0.12 nN. Sensibility and spring constant of the AFM cantilever were determined by thermal noise method. All the AFM experiments were performed immediately within in maximum 1 hour after the chronoamperometry measurement and the UME surface was gently washed with distilled water to remove the electrochemical solution. *
Figure 5 from “Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface” by Hassiba Smida et al.
AFM images recorded in water of (A and C) CF and (B and D) Pt UME surfaces (A and B) before and (C and D) after a chronoamperometry measurement at +0.8 V vs Ag/AgCl in 2 mL of 20 mM K4Fe(CN)6 0.1 M PBS at pH 7.4 as aqueous solution under inert atmosphere (N2) in the presence of 109 cells of living SOMR1 bacteria sample. The circle in white dashed line is added for showing the UME disk on the AFM images.
*Hassiba Smida, François-Xavier Lefèvre, Christine Thobie-Gautier, Mohammed Boujtita, Catarina M. Paquete and Estelle Lebègue
Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface
ChemElectroChem, Volume 10, Issue 1, January 2, 2023, e202200906
DOI: https://doi.org/10.1002/celc.202200906
Open Access: The article “Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface” by Hassiba Smida, François-Xavier Lefèvre, Christine Thobie-Gautier, Mohammed Boujtita, Catarina M. Paquete and Estelle Lebègue is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.