Imaging of DNA hybridization on microscopic polypyrrole patterns using scanning electrochemical microscopy (SECM): the HRP bio-catalyzed oxidation of 4-chloro-1-naphthol

We illustrate in this paper the successful combination of the direct and feedback mode of scanning electrochemical microscopy (SECM) for the writing of oligonucleotide patterns on thin gold films alongside the imaging of DNA hybridization. The patterning process was achieved using the direct mode of SECM, where the electrical field established between the SECM tip and the gold interface was used to drive the local deposition of micrometre sized polypyrrole spots to which a 15mer oligonucleotide (ODN) strand was linked covalently. Imaging of the deposited polypyrrole-ODNs was achieved by means of the feedback mode of SECM using Ru(NH3)63+ as the mediator. The detection of the hybridization reaction of the ODN probes with their biotinylated complementary strands using SECM was possible after subsequent reactions with streptavidin and biotinylated horseradish peroxidase (HRP). The HRP-biocatalyzed oxidation of 4-chloro-1-naphthol (1) in the presence of H2O2, and the precipitation of the insoluble product 4-chloro-1-naphthon (2) on the hybridized areas on the gold film caused a local alteration of conductivity. Such a change in conductivity was sensitively detected by the SECM tip and allowed imaging of DNA arrays in a fast and straightforward way

Microscopie électrochimique pour l'élaboration et la caractérisation de bio-assemblages sur électrode : application aux biopuces

This work deals with : (i) the electrochemical detection of nucleosides on a new carbonelectrode material, Boron Doped Diamond (BDD), and (ii) the use of a recent apparatus,scanning electrochemical microscopy (SECM) to micropattern surfaces with oligonucleotidesand to detect the hybridization event.On the one hand, we illustrate the capacity of scanning electrochemical microscopy tomicropattern and characterize surfaces. By direct mode of SECM, using the microelectrodeas a counter electrode, polypyrrole-oligonucleotide spots with micrometric dimensions aredeposited on a gold surface. This patterning method is optimized studying the spotshybridization by fluorescence microscopy. By the difference in surface conductivity betweengold and polypyrrole-oligonucleotide, SECM can detect the spots on the gold surface usingthe feedback mode. Then, the hybridization event is detected using the feedback mode by theprecipitation of an insulating product on the surface generated by the reaction catalysed bythe peroxidase which is coupled by a biological assembly to the complementaryoligonucleotide. Finally, this electrochemical method is coupled to an optical one, SurfacePlasmon Resonance imaging (SPRi), to visualize in real time the patterning step of the goldsurface with oligonucleotide spots or surface oligonucleotide gradients.On the other hand, the oxidation reactions of both nucleosides, 2'-deoxyguanosineand 2'-deoxyadenosine, are performed on an oxygenated boron doped diamond electrode.This points out the interest of this new material thanks to its enlarged potential window inaqueous media and its little and stable background current. Then, we show the formation ofa continuous film of oxidized products on the BDD surface by a macroscopic study analysingcyclic voltametries of a redox mediator, and in a microscopic way with the use of scanningelectrochemical microscopy.L'objectif de ce travail est double : (i) la détection électrochimique des nucléosides surun nouveau matériau carboné d'électrode, le diamant dopé bore (BDD), et (ii) l'utilisationd'un nouvel outil, la microscopie électrochimique à balayage (SECM), afin de fonctionnaliserdes surfaces avec des sondes oligonucléotidiques et de détecter le phénomène d'hybridation.Dans un premier temps, nous montrerons la dualité d'utilisation de la microscopieélectrochimique en tant qu'outil de fonctionnalisation et de caractérisation de surfaces. Parmode direct de la SECM, en utilisant la microélectrode en tant que contre-électrode, desspots de polypyrrole-oligonucléotide de taille micrométrique sont déposés sur un substratd'or. Cette méthode d'élaboration est optimisée en étudiant l'hybridation des spots enmicroscopie de fluorescence. La présence de ces spots sur la surface est ensuite détectée enmode feedback de la SECM via la différence de conductivité entre le polypyrroleoligonucléotideet l'or. Puis, le phénomène d'hybridation est étudié par mode feedback par laprécipitation d'un produit isolant sur la surface formé par une réaction catalysée par laperoxydase couplée par l'intermédiaire d'un assemblage biologique à l'oligonucléotidecomplémentaire. Enfin, cette technique électrochimique est couplée à une méthode optique,l'imagerie de résonance plasmonique de surface (SPRi), afin de visualiser en temps réell'étape de structuration de la surface d'or par des spots d'oligonucléotides ou par desgradients de surface d'oligonucléotides.Dans un second temps, nous présenterons l'étude des réactions d'oxydation desnucléosides, la 2'-désoxyguanosine et la 2'-désoxyadénosine, sur une électrode de diamantdopée bore oxygéné. Nous montrerons ainsi l'intérêt de ce nouveau matériau carbonéd'électrode pour cette application en raison de sa large fenêtre d'électroinactivité en milieuaqueux et son faible et stable courant de fond. Puis, nous mettrons en évidence la formationd'un film continu constitué des produits de ces réactions d'oxydation sur l'électrode par uneétude macroscopique à l'aide de voltamétries cycliques d'une sonde redox, et une étude àl'échelle microscopique en utilisant le microscope électrochimique à balayage

Microscopie électrochimique pour l'élaboration et la caractérisation de bio-assemblages sur électrode : application aux biopuces

This work deals with : (i) the electrochemical detection of nucleosides on a new carbonelectrode material, Boron Doped Diamond (BDD), and (ii) the use of a recent apparatus,scanning electrochemical microscopy (SECM) to micropattern surfaces with oligonucleotidesand to detect the hybridization event.On the one hand, we illustrate the capacity of scanning electrochemical microscopy tomicropattern and characterize surfaces. By direct mode of SECM, using the microelectrodeas a counter electrode, polypyrrole-oligonucleotide spots with micrometric dimensions aredeposited on a gold surface. This patterning method is optimized studying the spotshybridization by fluorescence microscopy. By the difference in surface conductivity betweengold and polypyrrole-oligonucleotide, SECM can detect the spots on the gold surface usingthe feedback mode. Then, the hybridization event is detected using the feedback mode by theprecipitation of an insulating product on the surface generated by the reaction catalysed bythe peroxidase which is coupled by a biological assembly to the complementaryoligonucleotide. Finally, this electrochemical method is coupled to an optical one, SurfacePlasmon Resonance imaging (SPRi), to visualize in real time the patterning step of the goldsurface with oligonucleotide spots or surface oligonucleotide gradients.On the other hand, the oxidation reactions of both nucleosides, 2'-deoxyguanosineand 2'-deoxyadenosine, are performed on an oxygenated boron doped diamond electrode.This points out the interest of this new material thanks to its enlarged potential window inaqueous media and its little and stable background current. Then, we show the formation ofa continuous film of oxidized products on the BDD surface by a macroscopic study analysingcyclic voltametries of a redox mediator, and in a microscopic way with the use of scanningelectrochemical microscopy.L'objectif de ce travail est double : (i) la détection électrochimique des nucléosides surun nouveau matériau carboné d'électrode, le diamant dopé bore (BDD), et (ii) l'utilisationd'un nouvel outil, la microscopie électrochimique à balayage (SECM), afin de fonctionnaliserdes surfaces avec des sondes oligonucléotidiques et de détecter le phénomène d'hybridation.Dans un premier temps, nous montrerons la dualité d'utilisation de la microscopieélectrochimique en tant qu'outil de fonctionnalisation et de caractérisation de surfaces. Parmode direct de la SECM, en utilisant la microélectrode en tant que contre-électrode, desspots de polypyrrole-oligonucléotide de taille micrométrique sont déposés sur un substratd'or. Cette méthode d'élaboration est optimisée en étudiant l'hybridation des spots enmicroscopie de fluorescence. La présence de ces spots sur la surface est ensuite détectée enmode feedback de la SECM via la différence de conductivité entre le polypyrroleoligonucléotideet l'or. Puis, le phénomène d'hybridation est étudié par mode feedback par laprécipitation d'un produit isolant sur la surface formé par une réaction catalysée par laperoxydase couplée par l'intermédiaire d'un assemblage biologique à l'oligonucléotidecomplémentaire. Enfin, cette technique électrochimique est couplée à une méthode optique,l'imagerie de résonance plasmonique de surface (SPRi), afin de visualiser en temps réell'étape de structuration de la surface d'or par des spots d'oligonucléotides ou par desgradients de surface d'oligonucléotides.Dans un second temps, nous présenterons l'étude des réactions d'oxydation desnucléosides, la 2'-désoxyguanosine et la 2'-désoxyadénosine, sur une électrode de diamantdopée bore oxygéné. Nous montrerons ainsi l'intérêt de ce nouveau matériau carbonéd'électrode pour cette application en raison de sa large fenêtre d'électroinactivité en milieuaqueux et son faible et stable courant de fond. Puis, nous mettrons en évidence la formationd'un film continu constitué des produits de ces réactions d'oxydation sur l'électrode par uneétude macroscopique à l'aide de voltamétries cycliques d'une sonde redox, et une étude àl'échelle microscopique en utilisant le microscope électrochimique à balayage

Microscopie électrochimique pour l'élaboration et la caractérisation de bio-assemblages sur électrode (application aux biopuces)

L'objectif de ce travail est double : (i) la détection électrochimique des nucléosides sur un nouveau matériau carboné d'électrode, le diamant dopé bore (BDD), et (ii) l'utilisation d'un nouvel outil, la microscopie électrochimique à balayage (SECM), afin de fonctionnaliser des surfaces avec des sondes oligonucléotidiques et de détecter le phénomène d'hybridation. Dans un premier temps, nous montrerons la dualité d'utilisation de la microscopie électrochimique en tant qu'outil de fonctionnalisation et de caractérisation de surfaces. Par mode direct de la SECM, en utilisant la microélectrode en tant que contre-électrode, des spots de polypyrrole-oligonucléotide de taille micrométrique sont déposés sur un substrat d'or. Cette méthode d'élaboration est optimisée en étudiant l'hybridation des spots en microscopie de fluorescence. La présence de ces spots sur la surface est ensuite détectée en mode feedback de la SECM via la différence de conductivité entre le polypyrroleoligonucléotide et l'or. Puis, le phénomène d'hybridation est étudié par mode feedback par la précipitation d'un produit isolant sur la surface formé par une réaction catalysée par la peroxydase couplée par l'intermédiaire d'un assemblage biologique à l'oligonucléotide complémentaire. Enfin, cette technique électrochimique est couplée à une méthode optique, l'imagerie de résonance plasmonique de surface (SPRi), afin de visualiser en temps réel l'étape de structuration de la surface d'or par des spots d'oligonucléotides ou par des gradients de surface d'oligonucléotides. Dans un second temps, nous présenterons l'étude des réactions d'oxydation des nucléosides, la 2'-désoxyguanosine et la 2'-désoxyadénosine, sur une électrode de diamant dopée bore oxygéné. Nous montrerons ainsi l'intérêt de ce nouveau matériau carboné d'électrode pour cette application en raison de sa large fenêtre d'électroinactivité en milieu aqueux et son faible et stable courant de fond. Puis, nous mettrons en évidence la formation d'un film continu constitué des produits de ces réactions d'oxydation sur l'électrode par une étude macroscopique à l'aide de voltamétries cycliques d'une sonde redox, et une étude à l'échelle microscopique en utilisant le microscope électrochimique à balayage.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Experimental and Theoretical Investigations on the Adsorption of 2'-deoxyguanosine Oxidation Products at Oxidized Boron-Doped Diamond Electrodes

International audienceElectrochemical oxidation of 2'-deoxyguanosine has been performed on boron-doped diamond (BDD) electrodes, resulting in a strong adsorption of the formed oxidized products onto the BDD surface. The adsorption behavior has been investigated by studying the electrochemical behavior of a redox probe ([IrCl6]3-) using cyclic voltammetry. The most probable situations are the formation of (A) an insulating adsorbed film resulting in a partially blocked electrode behavior, (B) a porous film, or (C) an overall conductive film. Different parameters such as the standard rate constant, the charge-transfer coefficient, the electrode/adsorbed products/solution interface resistance, and the formal potential of the redox couple were determined. Through comparison of theoretical current-potential curves obtained by analytical calculations with experimental cyclic voltammograms, we found that the oxidized products of 2'-deoxyguanosine form a continuous conductive film on BDD

Intermittent operation of a 55kw proton exchange membrane electrolyzer : test protocols and experimental insights on system flexibility, efficiency and durability

International audienceWith its ability to decarbonize industrial activities and mitigate intermittency issues linked to the integration of renewable energies in the grids, green hydrogen holds very strong assets for accelerating the energy transition. This process can be achieved through electrolysis allowing the production of a clean and renewable hydrogen when the electrical source comes from a renewable energy, intermittent by nature, whilst most systems are currently designed to operate at nominal capacity and constant load. Current literature has shown that the intermittent operation of an electrolyzer necessarily implies losses on different performance aspects [1] [2] [3] [4].Even though these issues have gained interest over the last decade, the behavior of electrolyzers subjected to such conditions has not been sufficiently investigated within the scientific community and few quantitative assessment of the associated impacts, especially at pilot/large scale, have been reported from current literature. This study aims at experimentally evaluating the ability of a commercial 55kW PEM electrolyzer to withstand harsh dynamic on/off and fluctuating load conditions and the impacts on the key performance indicators identifiedas the most sensitive to intermittency. Harmonized test protocols from [5] were used as a guideline and adapted to the specific needs of this case study

Low-temperature electrolysis under intermittent operation: modeling of the impacts and experimental validation

International audienceGreen hydrogen has progressively emerged as a viable option for energy transition, addressing two key issues: offer flexibility and storage services to unlock the massive integration of renewable energies into electrical grids while decarbonizing a wide range of sectors in industry and mobility. For that purpose, the dynamic operation of electrolysis is the missing link. Indeed, the intermittent nature of renewable energy sources induces fluctuating events in the load profile, which inevitably lead to performance losses during the system operation. The main impacts reported from the current literature can be outlined as follows: higher specific consumption, lower hydrogen purity, performance degradation over lifetime [1] [2]. Assessing and understanding the hurdles related to the intermittent operation of low-temperature electrolyzers is crucial to improve green hydrogen competitiveness. Even though conventional technologies have proven their ability to be dynamically operated, the quantitative characterization of the above-mentioned impacts remains limited to date. This work focuses on the development of tools and methodologies based on experiments and models aiming at exhaustively assessing key performance indicators of alkaline and PEM electrolyzers operating under intermittent conditions. A dynamic lumped 0D performance model of a 100 MW pressurized alkaline electrolyzer has been developed on Dymola software and validated based on real experimental data. The characterization ofthese impacts may lead to the development of mitigation strategies on the design or the operation

Nucleosides and ODN electrochemical detection onto boron doped diamond electrodes

International audienceBoron doped diamond (BDD) is a promising material for electroanalytical chemistry due mainly to its chemical stability, its high electrical conductivity and to the large amplitude of its electroactive window in aqueous media. The latter feature allowed us to study the direct oxidation of the two electroactive nucleosides, guanosine and adenosine. The BDD electrode was first activated by applying high oxidizing potentials, allowing to increase anodically its working potential window through the oxidation of CH surface groups into hydroxyl and carbonyl terminations. Guanosine (1.2 V vs. Ag/AgCl) and adenosine (1.5 V vs. Ag/AgCl) could then be detected electrochemically with an acceptable signal to noise ratio. The electrochemical signature of each oxidizable base was assessed using differential pulse voltammetry (DPV), in solutions containing one or both nucleosides. These experiments pointed out the existence of adsorption phenomena of the oxidized products onto the diamond surface. Scanning electrochemical microscopy (SECM) was used to investigate these adsorption effects at the microscopic scale. The usefulness of BDD electrodes for the direct electrochemical detection of synthetic oligonucleotides is also evidenced

The 2008 food price crisis negatively affected household food security and dietary diversity in urban Burkina Faso

Although the 2008 food price crisis presumably plunged millions of households into poverty and food insecurity, the real impact of the crisis has rarely been documented using field data. Our objective was to assess the consequences of this crisis for household food insecurity and dietary diversity in urban Burkina Faso. Two cross-sectional surveys were conducted among randomly selected households in Ouagadougou in July 2007 (n = 3017) and July 2008 (n = 3002). At each round, food insecurity assessed by the Household Food Insecurity Access Scale (HFIAS), the Dietary Diversity Score of an index-member of the household (IDDS = number of food groups consumed in the last 24 h), and food expenditure were collected. Food prices of the 17 most frequently consumed food items were recorded throughout the study area. Food prices at local markets increased considerably between 2007 and 2008, especially those of fish (113%), cereals (53%), and vegetable oil (44%), increasing the household monthly food expenditure by 18%. Thirty-three percent of households were food secure in 2007 and 22% in 2008 (P = 0.02). Individuals consumed fewer fruits and vegetables, dairy products, and meat/poultry in 2008 than in 2007 (mean IDDS = 5.7 +/- 1.7 food groups in 2007 vs. 5.2 +/- 1.5 in 2008; P < 0.0001). Differences in IDDS and HFIAS between the 2 y were even more marked after adjustment for confounding factors and food expenditure. Food security and dietary diversity significantly decreased between 2007 and 2008, whereas food prices increased. Households increased their food expenditure, but this was not sufficient to compensate the effects of the crisis. J. Nutr. 142: 1748-1755, 2012