The inside walls of a nanopipette tip are decorated by a Pt deposit that is used as an open bipolar electrochemiluminescence (ECL) device to achieve intracellular wireless electroanalysis. The ...synergetic actions of nanopipette and of bipolar ECL lead to the spatial confinement of the voltage drop at the level of the Pt deposit, which generates ECL emission from luminol. The porous structure of Pt deposit permits the electrochemical transport of intracellular molecules into the nanopipette that is coupled with enzymatic reactions. Thus, the intracellular concentrations of hydrogen peroxide or glucose are measured in vivo as well as the intracellular sphingomyelinase activity. In comparison with the classic bipolar ECL, the remarkably low potential applied in our approach is restricted inside the nanopipette and it minimizes the potential bias of the voltage on the cellular activity. Accordingly, this wireless ECL approach provides a new direction for analysis of single living cells.
A nanopipette tip decorated with a Pt deposit is used as an open bipolar electrochemiluminescence device to achieve intracellular wireless electroanalysis. The porous structure of the Pt deposit permits electrochemical transport of intracellular molecules into the nanopipette. Intracellular concentrations of H2O2 or glucose are measured in vivo as well as the intracellular sphingomyelinase activity.
Electrochemiluminescence (ECL)-based capacitance microscopy using a square-wave voltage is established unprecedentedly to realize the label-free visualization of species on electrode surfaces and ...cellular plasma membranes. The drop in the local capacitance upon the binding of species to the surface or to a cellular membrane is derived to induce a relatively larger potential drop (V dl) across the double layer on the local electrode surface, which is utilized to prompt enhanced ECL at the binding position. The square-wave voltage with a frequency of as high as 1.5 kHz is proven to be favorable for the discrimination of the local ECL from the surrounding signal. Using this new detection principle and resultant capacitance microscopy, carcinoembryonic antigens (CEA) at amounts of as low as 1 pg can be visualized. Further application of this approach permits the direct imaging of CEA antigens on single MCF-7 cells through the capacitance change after the formation of the antigen–antibody complex. Successful visualization of the analyte without any ECL tag will allow not only special capacitance microscopy for label-free bioassays but also a novel ECL detection approach for the sensitive detection of biomolecules.
Electrochemiluminescence (ECL) is a widely used analytical technique with the advantages of high sensitivity and low background signal. The recent and rapid development of electrochemical materials, ...luminophores, and optical elements significantly increases the ECL signals and, thus, ECL imaging with enhanced spatial and temporal resolutions is realized. Currently, ECL imaging is successfully applied to high-throughput bioanalysis and to visualize the distribution of molecules at single cells. Compared with other optical bioassays, no optical excitation is involved in imaging, so the approach avoids a background signal from illumination and increases the detection sensitivity. This review highlights some of the most exciting developments in this field, including the mechanisms, electrode designs, and the applications of ECL imaging in bioanalysis and at single cells and particles.
Electrocatalysis is dominated by reaction at the solid–liquid–gas interface; surface properties of electrocatalysts determine the electrochemical behavior. The surface charge of active sites on ...catalysts modulate adsorption and desorption of intermediates. However, there is no direct evidence to bridge surface charge and catalytic activity of active sites. Defects (active sites) were created on a HOPG (highly oriented pyrolytic graphite) surface that broke the intrinsic sp2‐hybridization of graphite by plasma, inducing localization of surface charge onto defective active sites, as shown by scanning ion conductance microscopy (SICM) and Kelvin probe force microscopy (KPFM). An electrochemical test revealed enhanced intrinsic activity by the localized surface charge. DFT calculations confirmed the relationship between surface charge and catalytic activity. This work correlates surface charge and catalytic activity, providing insights into electrocatalytic behavior and guiding the design of advanced electrocatalysts.
Highly oriented pyrolytic graphite (HOPG) was employed as a model to analyze the promotion of surface charge for electrocatalytic reactions. Via plasma irradiation, numerous defects are generated, which would induce charge re‐distribution on the surface of HOPG. A direct relationship between surface charge and the electrocatalytic activity is proposed.
Electrochemiluminescence (ECL) microscopy is an emerging technique with a wide range of imaging applications and unique properties in terms of high spatial resolution, surface confinement and ...favourable signal-to-noise ratio. Despite its successful analytical applications, tuning the depth of field (
i.e.
, thickness of the ECL-emitting layer) is a crucial issue. Indeed, the control of the thickness of this ECL region, which can be considered as an "evanescent" reaction layer, limits the development of cell microscopy as well as bioassays. Here we report an original strategy based on chemical lens effects to tune the ECL-emitting layer in the model Ru(bpy)
3
2+
/tri-
n
-propylamine (TPrA) system. It consists of microbeads decorated with Ru(bpy)
3
2+
labels, classically used in bioassays, and TPrA as the sacrificial coreactant. In particular we exploit the buffer capacity of the solution to modify the rate of the reactions involved in the ECL generation. For the first time, a precise control of the ECL light distribution is demonstrated by mapping the luminescence reactivity at the level of single micrometric bead. The resulting ECL image is the luminescent signature of the concentration profiles of diffusing TPrA radicals, which define the ECL layer. Therefore, our findings provide insights into the ECL mechanism and open new avenues for ECL microscopy and bioassays. Indeed, the reported approach based on a chemical lens controls the spatial extension of the "evanescent" ECL-emitting layer and is conceptually similar to evanescent wave microscopy. Thus, it should allow the exploration and imaging of different heights in substrates or in cells.
A versatile mechanism based on a chemical lens to control the electrochemiluminescence (ECL) spatial distribution is presented. Changing the buffer capacity modifies the rate of ECL reactions, and therefore the thickness of the ECL-active layer.
Here, luminol electrochemiluminescence was first applied to analyze intracellular molecules, such as glucose, at single cells. The individual cells were retained in cell-sized microwells on a gold ...coated indium tin oxide (ITO) slide, which were treated with luminol, triton X-100, and glucose oxidase simultaneously. The broken cellular membrane in the presence of triton X-100 released intracellular glucose into the microwell and reacted with glucose oxidase to generate hydrogen peroxide, which induced luminol luminescence under positive potential. To achieve fast analysis, the luminescences from 64 individual cells on one ITO slide were imaged in 60 s using a charge-coupled device (CCD). More luminescence was observed at all the microwells after the introduction of triton X-100 and glucose oxidase suggested that intracellular glucose was detected at single cells. The starvation of cells to decrease intracellular glucose produced less luminescence, which confirmed that our luminescence intensity was correlated with the concentration of intracellular glucose. Large deviations in glucose concentration at observed single cells revealed high cellular heterogeneity in intracellular glucose for the first time. This developed electrochemiluminescence assay will be potentially applied for fast analysis of more intracellular molecules in single cells to elucidate cellular heterogeneity.
Electrochemiluminescence Loss in Photobleaching Han, Dongni; Goudeau, Bertrand; Manojlovic, Dragan ...
Angewandte Chemie International Edition,
March 29, 2021, Letnik:
60, Številka:
14
Journal Article
Recenzirano
The effects of photobleaching on electrochemiluminescence (ECL) was investigated for the first time. The plasma membrane of Chinese Hamster Ovary (CHO) cells was labeled with a Ru(bpy)32+ derivative. ...Selected regions of the fixed cells were photobleached using the confocal mode with sequential stepwise illumination or cumulatively and they were imaged by both ECL and photoluminescence (PL). ECL was generated with a model sacrificial coreactant, tri‐n‐propylamine. ECL microscopy of the photobleached regions shows lower ECL emission. We demonstrate a linear correlation between the ECL decrease and the PL loss due to the photobleaching of the labels immobilized on the CHO membranes. The presented strategy provides valuable information on the fundamentals of the ECL excited state and opens new opportunities for exploring cellular membranes by combining ECL microscopy with photobleaching techniques such as fluorescence recovery after photobleaching (FRAP) or fluorescence loss in photobleaching (FLIP) methods.
Light versus light! The impact of photobleaching on the electrochemiluminescence was investigated at the level of single cells. Specific regions of the labeled membranes were photobleached confocally and then visualized by multimodal imaging. This study demonstrates the crucial role of the photobleaching process on the electrochemiluminescence signal.
•Spatially resolved electrochemical imaging of the charge injection yield on the surface of hematite is achieved using SECCM.•Hydrogen peroxide eliminates the holes in hematite to separate the charge ...injection and separation processes in PEC oxidation.•Charge injection yield increases with a thin film, indicating the control of photocurrent by the charge injection process.
In-depth studies of charge injection and separation processes are important in characterizing the photoelectrochemical (PEC) properties of semiconductor materials, but high spatial resolution observations of the charge injection yield of such materials have not yet been reported. Here, scanning electrochemical cell microscopy (SECCM) is used for spatially resolved electrochemical imaging of the charge injection yield for a model material (hematite). Hydrogen peroxide is introduced as a hole scavenger to reduce the recombination of electrons and holes in the material, thereby achieving a division between charge injection and separation processes during PEC oxidation. Then, by calculating the ratio between the photocurrents before and after the addition of hydrogen peroxide, the distribution of the charge injection yield in the hematite film can be obtained at the nanoscale. The co-imaging of the morphology and the charge injection yield of hematite using SECCM makes it possible to observe the inverse dependence of the charge injection yield on the film thickness, which indicates that the main influence on the photocurrent is the charge injection process. The successful development of this nanoscale imaging method could provide more information to help elucidate the mechanism of the PEC process and, eventually, to aid in the design of more effective PEC materials.
•Local ECL imaging is realized by the incorporation of SECCM and PMT modules.•Local ECL emission in a micro-sized droplet is recorded at the electrode surface.•Local ECL emission exhibits a high ...heterogeneity that might be caused by the different local environment at the electrode surface.
In this communication, local electrochemiluminescence (ECL) imaging is achieved using scanning electrochemical cell microscopy (SECCM) to create a localized region for the occurrence of ECL reaction. The system is demonstrated using a droplet at the micropipette that is contact with the prepared Ru-Silica@Au particles at indium tin oxide (ITO) slide. Tri-n-propylamine (TPrA) in the droplet reacts with ruthenium complex in a 10 μm-diameter-region to produce ECL emission, which is recorded by photo multiplier tube (PMT) underneath the ITO slide. By contacting each local region consecutively, the distribution of steady-state current and the related ECL emission at the ITO surface is imaged. The local ECL intensity show an approximately linear dependence with the current, but obvious deviation from the linear curve is observed at some regions. This result suggests that the ECL emission is not only determined by the transferred electron number in the electrochemical reaction, and also affected by local environments at ITO surface. As compared with the traditionally used ECL imaging in the bulk solution, this strategy avoids the cross-talking of ECL emission from nearby regions, and could offer a new way to unveil more molecular mechanism in the ECL reaction.
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