Formation and Imaging of Microscopic Enzymatically Active Spots on an Alkanethiolate-Covered Gold Electrode by Scanning Electrochemical Microscopy

Wittstock, Günther; Schuhmann, Wolfgang

doi:10.1021/ac970504o

Cited by 181 publications

(133 citation statements)

References 45 publications

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“…In this study, the antigen binding sites were presaturated with an antigen-conjugate capable of catalytically converting a redox-inactive mediator (4-aminophenyl phosphate) to an electroactive form (4-aminophenol), which was subsequently detected at the tip UME. SECM has also been employed to image active enzyme spots on an alkanethiol-gold substrate [68]. In this application, it was necessary to use the TC mode to characterise the micropatterned structures in order to avoid unwanted feedback from uncovered gold areas, which would otherwise complicate the tip current response.…”

Section: Redox Processes On Biological Surfacesmentioning

confidence: 99%

Scanning electrochemical microscopy: beyond the solid/liquid interface

Barker

Gonsalves

Macpherson

et al. 1999

Analytica Chimica Acta

145

107

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Section: Redox Processes On Biological Surfacesmentioning

confidence: 99%

Scanning electrochemical microscopy: beyond the solid/liquid interface

Barker

Gonsalves

Macpherson

et al. 1999

Analytica Chimica Acta

145

107

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“…SECM has the unique ability to set the exact distance from a sensing tip [an ultramicroelectrode (UME) of size ∼10 to 25 μm diameter] to a substrate through a feedback approach curve (11) (tip current, i T , vs. distance above substrate, d) and thus is able to measure the local concentration over a biofilm. Several studies concerned with the electrochemical measurement of hydrogen peroxide concentration have been reported (12)(13)(14)(15)(16)(17), but none dealt with spatial mapping adjacent to a biofilm surface. In addition, SECM has the ability to scan over a substrate in the x-y direction and thus is able to record a unique spatial concentration profile over the surface.…”

mentioning

confidence: 99%

Real-time mapping of a hydrogen peroxide concentration profile across a polymicrobial bacterial biofilm using scanning electrochemical microscopy

Liu

Ramsey

Chen

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

144

118

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Quantitative detection of hydrogen peroxide in solution above a Streptococcus gordonii (Sg) bacterial biofilm was studied in real time by scanning electrochemical microscopy (SECM). The concentration of hydrogen peroxide was determined to be 0.7 mM to 1.6 mM in the presence of 10 mM glucose over a period of 2 to 8 h. The hydrogen peroxide production measured was higher near the biofilm surface in comparison to Sg grown planktonically. Differential hydrogen peroxide production was observed both by fluorometric as well as by SECM measurements. The interaction between two different species in a bacterial biofilm of Sg and Aggregatibacter actinomycetemcomitans (Aa) in terms of hydrogen peroxide production was also studied by SECM. One-directional y-scan SECM measurements showed the unique spatial mapping of hydrogen peroxide concentration across a mixed species biofilm and revealed that hydrogen peroxide concentration varies greatly dependent upon local species composition.real-time (detection) | metabolite efflux | local concentration | oral flora | Au UME S treptococcus gordonii (Sg) is a member of the viridans group streptococci-Gram-positive oral microbes that are known to ferment sugars into lactic acid and produce hydrogen peroxide in the presence of oxygen (1). The presence of these beneficial oral streptococci has been shown to improve oral health, by either competition with pathogens for nutrients in the oral cavity or by the production of inhibitory concentrations of hydrogen peroxide. Populations of viridans group streptococci negatively correlate with the presence of many notable oral pathogens (2, 3). However, recent work has demonstrated that in vitro Sg can grow in coculture with the opportunistic oral pathogen Aggregatibacter actinomycetemcomitans (Aa) (4). In co-culture Aa preferentially utilizes Sg-produced lactic acid (5) and detoxifies Sg-produced hydrogen peroxide using the KatA enzyme (6). Recent work has demonstrated that hydrogen peroxide induces katA expression as well as apiA, which encodes an immunoprotective factor that renders Aa more resistant to killing by host innate immunity (5). These studies demonstrated induction of gene expression in mixed species biofilms by Sg-produced hydrogen peroxide. Because hydrogen peroxide is rapidly degraded by catalase and can also react with other biological materials, we sought to quantify local hydrogen peroxide concentrations in real time to be utilized for future polymicrobial experiments between Sg, Aa, and other oral bacteria.Previous measurements of hydrogen peroxide have been performed using fluorescence, spectroscopy and other methods (1, 7-10). However, current techniques lack the ability to quantify local hydrogen peroxide concentrations at the surface of a biofilm. In this study, scanning electrochemical microscopy (SECM) was used to address this problem. SECM has the unique ability to set the exact distance from a sensing tip [an ultramicroelectrode (UME) of size ∼10 to 25 μm diameter] to a substrate through a feedback approach curve (11)...

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“…(2)- (4)) constitutes a background signal against which a small flux from the sample must be detected. In addition there are situations where FB experiments are principally not possible [106]. Very early, the use of the UME as a microscopic generator and the sample as a collector have been demonstrated (tip-generation.sample-collection (TG.SC) mode [80] (Figure 7c).…”

Section: Generation-collection Modementioning

confidence: 99%

“…Often H 2 O 2 is formed as one of the products in this reaction. The local activity of glucose oxidase could be monitored by detecting the H 2 O 2 formed during the enzymatic oxidation of glucose and the concomitant reduction of O 2 [106]. As in technical systems, byproducts of the ORR such as H 2 O 2 and O 2 -· are cytotoxic and nature has developed several strategies to deal with this problem.…”

Section: Oxygen Reduction At Immobilized Enzymesmentioning

confidence: 99%

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Pust¹,

Maier²,

Wittstock³

2008

Zeitschrift Für Physikalische Chemie

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Scanning Electrochemical Microscopy (SECM) . Catalytic Electrodes .Electrochemical Energy Conversion . Fuel Cells . Oxygen Reduction Reaction . CorrosionScanning electrochemical microscopy (SECM) has developed into a very versatile tool for the investigation of solid-liquid, liquid-liquid and liquid-gas interfaces. The arrangement of an ultramicroelectrode (UME) in close proximity to the interface under study allows the application of a large variety of different experimental schemes. The most important have been named feedback mode, generation-collection mode, redox competition mode and direct mode. Quantitative descriptions are available for the UME signal, depending on different sample properties and experimental variables. Therefore, SECM has been established as an indispensible tool in many areas of fundamental electrochemical research. Currently, it also spreads as an important new method to solve more applied problems, in which inhomogeneous current distributions are typically observed on different length scales. Prominent examples include devices for electrochemical energy conversion such as fuel cells and batteries as well as localized corrosion phenomena. However, the direct local investigation of such systems is often impossible. Instead, suitable reaction schemes, sample environments, model samples and even new operation modes have to be introduced in order to obtain results that are relevant to the practical application. This review outlines and compares the theoretical basis of the different SECM working modes and reviews the application in the area of electrochemical energy conversion and localized

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Formation and Imaging of Microscopic Enzymatically Active Spots on an Alkanethiolate-Covered Gold Electrode by Scanning Electrochemical Microscopy

Cited by 181 publications

References 45 publications

Scanning electrochemical microscopy: beyond the solid/liquid interface

Scanning electrochemical microscopy: beyond the solid/liquid interface

Real-time mapping of a hydrogen peroxide concentration profile across a polymicrobial bacterial biofilm using scanning electrochemical microscopy

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

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