Interdigitated Array Electrode as an Alternative to the Rotated Ring−Disk Electrode for Determination of the Reaction Products of Dioxygen Reduction

Postlethwaite, Timothy A.; Hutchison, James E.; Murray, Royce W.; Fosset, Bruno; Amatore, Christian

doi:10.1021/ac960327b

Cited by 39 publications

(32 citation statements)

References 30 publications

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“…Cyclic voltammetry, performed at pH 7.4, showed sensor response to O 2 similar to that obtained by other research groups on glassy carbon electrodes 24,27 suggestive of a two-step O 2 reduction. 28 The in vivo drop in sensitivity (∼-18% after 7 days of implantation in the striatum) was higher than the in vitro decrease measured at the same time (∼-11%, data not shown), confirming a mild fouling process of the sensor surface despite the collodion coating. As detailed in the Experimental Section and Results sections, quiescent calibrations, performed using low and high O 2 concentrations at different times, were used to estimate oxygen concentration in vivo.…”

Section: Discussionmentioning

confidence: 75%

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

et al. 2009

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A miniaturized biotelemetric device for the amperometric detection of brain tissue oxygen is presented. The new system, derived from a previous design, has been coupled with a carbon microsensor for the real-time detection of dissolved O 2 in the striatum of freely moving rats. The implantable device consists of a single-supply sensor driver, a current-to-voltage converter, a microcontroller, and a miniaturized data transmitter. The oxygen current is converted to a digital value by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC). The digital data is sent to a personal computer using a six-byte packet protocol by means of a miniaturized 434 MHz amplitude modulation (AM) transmitter. The receiver unit is connected to a personal computer (PC) via a universal serial bus. Custom developed software allows the PC to store and plot received data. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption, and good linear response in the nanoampere current range. The in vivo results confirmed previously published observations on oxygen dynamics in the striatum of freely moving rats. The system serves as a rapid and reliable model for studying the effects of different drugs on brain oxygen and brain blood flow and it is suited to work with direct-reduction sensors or O 2 -consuming biosensors.Oxygen is the most important oxidative substrate for biochemical reactions and for the production of ATP in the brain. Tissue concentration of dissolved O 2 is regulated by the balance between blood supply and local utilization 1 and plays a key role in brain energy metabolism related to either glucose 2 or lactate 3 used as energy substrates.The electrochemical reduction of oxygen is a complex process which can occur on the sensor surface via two mechanisms. In the first, complete reduction occurs in a single step, without the formation of detectable intermediates: 4In the second mechanism, reduction of oxygen occurs in two steps with the formation of hydrogen peroxide as measurable intermediate: 4A wide variety of sensors have been used for direct-reduction of O 2 with the majority of measurements obtained using constant potential amperometry (CPA) at a noble metal microelectrode such gold 5 or platinum. 6 The use of carbon-based electrodes has been reported by several groups 7-9 and often they are preferred to Pt cathodes because of their in vivo stability and less surface poisoning. 9 Moreover, 10 µm Nafion-coated carbon fibers, coupled with fast scan voltammetry (FCV), have been used for the measurement of dissolved oxygen with a subsecond time resolution. 8 However, as previously discussed, 9 the ideal sensor size has to be greater than the dimension of blood capillaries (∼100 µm) for preventing direct blood sampling of dissolved oxygen. In this article we present a new oxygen sensor geometry (conical) particularly suited for in vivo applications, minimizing the tissue trauma related to the stereot...

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Section: Discussionmentioning

confidence: 75%

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

et al. 2009

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“…Unlike RRDEs, no rotation is required in IDAs, and the reaction with oxygen and the detection of PROS are diffusion-limited processes. IDAs have previously been used (11)(12)(13)(14) to assess the formation of PROS with reduction catalysts (13). The study presents here a report of the detection of PROS on IDAs as a function of eT through SAMs functionalized with hemoprotein models.…”

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confidence: 99%

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

Collman

Decréau

Lin

et al. 2009

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

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Five iron porphyrins with different superstructures were immobilized on self-assembled-monolayer (SAM)-coated interdigitatedarray (IDAs) gold-platinum electrodes. The selectivity of the catalysts i.e., limited formation of partially reduced oxygen species (PROS) in the electrocatalytic reduction of dioxygen, is a function of 2 rates: (i) the rate of electron transfer from the electrode to the catalyst, which is controlled by the length, and conjugation of the linker from the catalyst to the electrode and (ii) the rate of bound oxygen (superoxide) hydrolysis, which correlates with the presence of a water cluster in the gas-binding pocket influencing the rate of oxygen binding; these factors are controlled by the nature of the porphyrin superstructure. The structurally biomimetic Trisimidazole model is the most selective.electron transfer rate ͉ oxygen binding rates ͉ water cluster ͉ oxygen complex stabilization ͉ partially reduced oxygen species A recent report showed that water may inhibit oxygen binding in hemoprotein models (1). This echoes the ''water displacement model'' proposed for oxygen binding in myoglobin (2-4). This finding is relevant to cytochrome c oxidase (CcO) for 2 reasons: (i) CcO binds and reduces oxygen to form water (5) and (ii) the hydrolysis of the oxygen complex in CcO and in other enzymes is an issue and occurs when water, protons, and electrons are present (6, 7). This reaction releases partially reduced oxygen species (PROS) that are toxic to organisms (Fig. 1). The study herein examines the formation of PROS during the electrocatalytic reduction of oxygen by several site-isolated CcO models ( Fig. 2) as a function of (i) the oxygen association rate [k on (O 2 )] and the rate of hydrolysis, both associated with the presence of water in the gas binding pocket, and (ii) the availability of electrons at the oxygen reduction site associated with the rate of electron arrival from the electrode to the catalyst [k(eT)] and/or the presence of redox active species in the vicinity of the heme. The latter aspects were specifically addressed in previous studies by immobilizing the active-site models onto self-assembled-monolayer (SAM)-coated rotating ring disk gold electrodes (RRDE) (8-10): k(eT) was controlled by the length and conjugated character of the linker between the catalyst and the gold electrode, and immobilization allowed site isolation. To get better collection efficiencies for the detection of PROS and to prevent damage to the SAM associated with high rotation rates, the present study used Au-Pt interdigitated array electrodes (IDAs). The collection efficiency of these IDA electrodes is in the 65-90% range as compared with Ͻ20% in RRDE (8).IDAs have 2 sets of alternating arrays of electrodes. The electrode widths and spacing are on similar dimensions, and this distance is within diffusion layers for typical electroactive species in solution. This results in diffusion gradients of adjacent microband electrodes that overlap with each other. Redox products created at the Au generator ...

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“…2). The proximity of the collector electrode enables collection efficiencies Ͼ55% providing superior sensitivity for PROS detection (41,42).In the past, we have reported several functional synthetic model complexes of CcO (32,39). These functional FeCu CcO models provided insights into important issues such as reversible inhibition by NO and CN Ϫ poisoning (43).…”

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confidence: 99%

“…2). The proximity of the collector electrode enables collection efficiencies Ͼ55% providing superior sensitivity for PROS detection (41,42).…”

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confidence: 99%

O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex

Collman

Dey

Yang

et al. 2009

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

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O2 reactivity of a functional NOR model is investigated by using electrochemistry and spectroscopy. The electrochemical measurements using interdigitated electrodes show very high selectivity for 4e O2 reduction with minimal production of partially reduced oxygen species (PROS) under both fast and slow electron flux. Intermediates trapped at cryogenic temperatures and characterized by using resonance Raman spectroscopy under single-turnover conditions indicate that an initial bridging peroxide intermediate undergoes homolytic OOO bond cleavage generating a trans heme/nonheme bis-ferryl intermediate. This bis ferryl species can oxygenate 2 equivalents of a reactive substrate.C ytochrome c oxidase (CcO) and nitric oxide reductase (NOR) belong to the heme copper oxidase superfamily of enzymes (1, 2). CcO is the terminal enzyme in the respiratory chain of higher organisms, located in their mitochondrial membrane, that reduces O 2 to H 2 O as source of energy. The O 2 reduction process in CcO generates a pH gradient across the bilayer membrane, which provides the driving force for ATP synthesis. The bimetallic active site of CcO has a heme ligated to the protein by a proximal histidine ligand and a distal Cu B site coordinated by 3 histidine ligands ( Fig. 1) (3). In addition to the bimetallic site, there is a conserved tyrosine ligand covalently attached to one of the histidines coordinated to Cu B (4, 5). The NORs are the older member of the family and are found in bacteria using NO 3 Ϫ as source of energy instead of O 2 (2, 6, 7). Although there are no high-resolution crystal structures of NOR, biochemical studies and computer modeling indicate that these enzymes have a histidine-ligated heme, quite like the CcOs, and a distal Fe B , unlike Cu B in CcO, coordinated by 3 histidines ( Fig. 1) (8-10). NORs do not have the conserved tyrosine residue of CcO but have a few conserved key glutamate residues (11,12). Although the NOR enzymes are proposed to have specific proton channels, they are probably not involved in generating proton gradients (13-16).These 2 enzymes exhibit complementary reactivity toward 2 very significant diatomic molecules in nature; O 2 and NO. In eukaryotes CcO (aa 3 type) reduces O 2 to H 2 O and is reversibly but strongly inhibited by [17][18][19][20]. Several other CcOs (ba 3 , caa 3 , cbb 3 ) are reported to exhibit limited (Ͻ1%) NOR activity, i.e., reduce NO to N 2 O (7, 21). On the other hand, NORs that reduce NO to N 2 O are reversibly but strongly inhibited by O 2 , and some of them show modest (Ϸ10%) O 2 reduction activity (12). The parallels in their reactivities toward O 2 and NO and similarities in their secondary structures have led to a hypotheses regarding NOR's and CcO's similar evolutionary origins (6,22).Electrochemistry is a very powerful technique that can provide fundamental insights into reaction mechanisms of redox catalysts (23-27). Conventionally, a catalyst is deposited on a conducting electrode material (e.g., graphite); however, this approach does not allow site isola...

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Interdigitated Array Electrode as an Alternative to the Rotated Ring−Disk Electrode for Determination of the Reaction Products of Dioxygen Reduction

Cited by 39 publications

References 30 publications

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex

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Interdigitated Array Electrode as an Alternative to the Rotated Ring−Disk Electrode for Determination of the Reaction Products of Dioxygen Reduction

Cited by 39 publications

References 30 publications

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

Role of a distal pocket in the catalytic O 2 reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

O 2 reduction by a functional heme/nonheme bis-iron NOR model complex

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Role of a distal pocket in the catalytic O ₂ reduction by cytochrome c oxidase models immobilized on interdigitated array electrodes

O ₂ reduction by a functional heme/nonheme bis-iron NOR model complex