Herein is reported a near-field microscopy based on electrochemiluminescence (ECL) which allows to image the plasma membrane of single cells at the interface with an electrode. By analyzing photoluminescence (PL), ECL and AFM images of mammalian CHO cells, we demonstrate that, in contrast to the wide-field fluorescence, ECL emission is confined to the immediate vicinity of the electrode surface and only the basal membrane of the cell becomes luminescent. The resulting ECL microscopy reveals details which are not resolved by classic fluorescence microscopy, without any light irradiation and specific setup. The thickness of the ECL-emitting regions is ~ 500 nm due to the unique ECL mechanism which involves short-lifetime electrogenerated radicals. In addition, the reported ECL microscopy is a dynamic technique which reflects the transport properties through the cell membranes and not only the specific labeling of the membranes. Finally, disposable transparent carbon nanotube (CNT)-based electrodes inkjet-printed on classic microscope glass coverslips, were used to image cells in both reflection and transmission configurations. Therefore, our approach opens new avenues for ECL as a near-field microscopy to develop single cell assays and to image the dynamics of biological entities in cells or in membranes. ASSOCIATED CONTENTSupporting Information. ECL-potential curves. PL images of the CHO cells recorded at high magnifications in different focal planes. ECL microscopy with DBAE. DPV. Scheme and photograph of the inkjet-printed CNT electrodes on glass coverslips. Optical effects on the PET and glass coverslips.

We report here the development of coreactant-based electrogenerated chemiluminescence (ECL) as a surface-confined microscopy to image single cells and their membrane proteins. Labeling the entire cell membrane allows one to demonstrate that, by contrast with fluorescence, ECL emission is only detected from fluorophores located in the immediate vicinity of the electrode surface (i.e., 1-2 μm). Then, to present the potential diagnostic applications of our approach, we selected carbon nanotubes (CNT)-based inkjet-printed disposable electrodes for the direct ECL imaging of a labeled plasma receptor overexpressed on tumor cells. The ECL fluorophore was linked to an antibody and enabled to localize the ECL generation on the cancer cell membrane in close proximity to the electrode surface. Such a result is intrinsically associated with the unique ECL mechanism and is rationalized by considering the limited lifetimes of the electrogenerated coreactant radicals. The electrochemical stimulus used for luminescence generation does not suffer from background signals, such as the typical autofluorescence of biological samples. The presented surface-confined ECL microscopy should find promising applications in ultrasensitive single cell imaging assays.

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A low-cost, reliable and sensitive electrochemical method for free chlorine analysis in water using inkjet printed silver electrodes is presented. Free chlorine detection was based on linear sweep voltammetry (LSV) analysis of AgCl/Ag 2 O films formed over an inkjet printed silver electrode by the spontaneous reaction between silver and free chlorine species (i.e. HClO and ClO − ) present in solution. The formation of AgCl/Ag 2 O films was studied and characterized by high resolution scanning electron microscopy (HR SEM) and X-ray photoelectron spectroscopy (XPS) techniques. LSV characterization demonstrated a quantitative linear relationship between the amount of AgCl/Ag 2 O formed and the concentration of free chlorine in water within a range from 1 to 100 ppm. After optimization of several parameters (e.g. scan rate, reaction time, starting potential), lowest detectable free chlorine concentration was 0.4 ppm (by standard addition method), while the limit of detection (S/N = 3) was equal to 2 ppm, with a sensitivity of 30 μC/ppm. The validation of the proposed methodology was performed by comparison with the standard N,N-diethylparaphenylenediamine (DPD) method for analyzing swimming pool water samples. Finally, it was demonstrated that reproducible and disposable silver electrodes could be easily prepared by inkjet printing in a large scale and in any required geometry to fit on-line and onsite free chlorine analyses requirements.

TiO2-facilitated MALDI–TOF-MS was proposed to improve intact bacteria fingerprinting, allowing rapid and convenient antimicrobial resistance-associated protein detection during bacteria identification.

A combination of an immuno-affinity enrichment strategy and sensitive amperometric read-out was implemented in a point-of-care platform intended for bacterial infection analysis. Bacterial cells, selectively captured and enriched from complex matrices through immuno-affinity, were detected by amperometric monitoring of the redox state of metabolic activity indicators, providing species identification and viable-cell quantification. The method was successfully employed for the diagnosis of bacterial infections including antimicrobial susceptibility testing with only several hours of total working time.