A comparative study of carbon fiber-based microelectrodes for the measurement of nitric oxide in brain tissue (original) (raw)
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Analytica Chimica Acta, 2005
The role of nitric oxide ( • NO) as a regulatory diffusible molecule in the brain requires the evaluation of its concentration dynamics. In this work, we have developed microelectrodes suitable for real time electrochemical measurements of • NO in vitro. Nafion and o-phenylenediamine were used to modify the surface of carbon fiber microelectrodes (8 m diameter; ≈100 m tip length). Coating with Nafion was done at 170 • C and the o-phenylenediamine solution was electropolimerized on the carbon surface. • NO peak potential (+0.78 ± 0.03 V versus Ag/AgCl) was determined by square wave voltammetry with • NO solutions prepared from the-generating compound diethylenetriamine/nitric oxide (DETA/NO). Microelectrodes were calibrated by amperometry at a potential of +0.90 V versus Ag/AgCl. They showed good sensitivity (954 ± 217 pA/M; n = 6) and linearity to • NO in the concentration range of 100-1000 nM. They were also characterized in terms of detection limit (6 ± 2 nM, n = 4), response time at 50% (1 s), and selectivity against interferents, such as nitrite (780 ± 84:1, n = 6), ascorbic acid (750 ± 187:1, n = 6) or dopamine (18 ± 2:1, n = 6). Injections of 1 mM l-glutamate, 1 mM l-arginine, and 0.1 mM N-methyl-d-aspartate did not produce changes in background current. Finally, the microelectrodes were used to measure • NO concentration dynamics in rat hippocampal brain slices stimulated with l-glutamate and N-methyl-d-aspartate. Taken together, the data indicate that the microelectrodes exhibit the proper sensitivity and selectivity for studies of • NO dynamics in brain slices (in vitro) and possibly in whole brain (in vivo) recordings.
In vivo nitric oxide sensor using non-conducting polymer-modified carbon fiber
Biosensors and Bioelectronics, 1998
Nitric oxide (NO) is emerging as a very important and ubiquitous gaseous messenger in the body. The response characteristics of NO sensors made of non-conducting polymer modified carbon fiber electrodes are investigated to determine their selectivity, sensitivity, and stability for in vivo use. A composite polymer, comprising Nafion, m-phenylenediamine, and resorcinol, showed the best selectivity and stability to amperometric NO detection. The non-conducting, self-limiting polymer film protects the electrode from interference and fouling by other biochemicals. Although the relative sensitivity to NO of the modified sensor is lower than that of the unmodified carbon fiber electrodes (less than 6%), the composite polymer electrode showed high selectivity against ascorbic acid (> 2000:1), nitrite (> 600:1), and dopamine (> 200:1). The stability of the NO sensor was maintained for at least 1 week. The NO sensitivity after in vivo experiments (n ϭ 8) is 88.1 Ϯ 5.6% of initial sensitivity data obtained before in vivo experiments. Preliminary in vivo experiments done with this electrode are shown to capture elevated NO levels in brain following an ischemic injury.
Journal of Electroanalytical Chemistry, 1997
An NO sensor based on a carbon fibre microelectrode modified by a poly(N-methylpyrrole) incorporating [(H20)FeUlpwt iO39 ]4sublayer and coated by a Nation ® external layer is described. It is based on the NO oxidation current measured by differential normal pulse voltammetry. In solution, a linear response is obtained between this oxidation current and the NO concentration in the range 10-7 to 10-3 M with a sensitivity of 2.65 + 0.15 nA lzM-i. A comparative study has been carried out with poly(N-methylpyrrole) doped with 004, polypyrrole doped with sulfonated nickel porphyrin, polypyrrole and poly(N-methylpyrrole) doped with Nation ®. This sensor implanted in the rat brain is efficient to detect in real time the NO released. The validation of in vivo measurements is made by injecting the rat with an NO-synthase inhibitor.
Biosensors and Bioelectronics, 2013
A novel biomimetic microsensor for measuring nitric oxide (NO) in the brain in vivo was developed. The sensor consists of hemin and functionalized multi-wall carbon nanotubes covalently attached to chitosan via the carbodiimide crosslinker EDC followed by chitosan electrodeposition on the surface of carbon fiber microelectrodes. Cyclic voltammetry supported direct electron transfer from the Fe III /Fe II couple of hemin to the carbon surface at À 0.370 V and À 0.305 V vs. Ag/AgCl for cathodic and anodic peaks, respectively. Square wave voltammetry revealed a NO reduction peak at À 0.762 V vs. Ag/AgCl that increased linearly with NO concentration between 0.25 and 1 mM. The average sensitivity of the microsensors was 1.72 nA/mM and the limit of detection was 25 nM. Oxygen and hydrogen peroxide reduction peaks were observed at À 0.269 V and À 0.332 V vs. Ag/AgCl, respectively and no response was observed for other relevant interferents, namely ascorbate, nitrite and dopamine. The microsensor was successfully applied to the measurement of exogenously applied NO in the rat brain in vivo.
Sensors and Actuators B: Chemical, 2020
Microelectrodes coupled to fast electrochemical techniques are an attractive approach towards real time in vivo monitoring with minimal damage to living tissue. Here, carbon fiber microelectrodes (CFM) were modified by electrodeposition of ruthenium purple (RP) for monitoring of H2O2 concentration dynamics in brain tissue preparations. The RP-modified CFM (CFM-RP) showed catalytic activity for the reduction of H2O2 at-0.1 V vs. Ag/AgCl in aqueous electrolyte at neutral pH and in the presence of physiological concentration of sodium cation (154 mM). The CFM-RP displayed a linear response in the concentration range of 2-500 µM, with a sensitivity of 0.98 ± 0.37 µA cm-2 µM-1 and a limit of detection of 70 ± 40 nM. Coating the CFM-RP with a Nafion® layer greatly extended the operational stability of the RP film to 3 hours in a medium containing a high sodium concentration at physiological pH 7.4. Validation of the CFM-RP-Nafion® sensor suitability for monitoring H2O2 concentration dynamics was achieved by measuring exogenously and locally applied H2O2 in rodent striatal slices. Together, these results support the excellent analytical performance of this new CFM-RP-Nafion® sensor design for sensitive and selective monitoring of H2O2 concentration dynamics in brain tissue.
Biosensors and Bioelectronics, 2008
A nitric oxide (NO) microbiosensor based on cytochrome c (cyt c), a heme protein, immobilized onto a functionalized-conducting polymer (poly-TTCA) layer has been fabricated for the in vivo measurement of NO release stimulated by an abuse drug cocaine. Based on the direct electron transfer of cyt c, determination of NO with the cyt c-bonded poly-TTCA electrode was studied using cyclic voltammetry and chronoamperometry. Interferences for the sensory of NO by foreign species such as oxygen and hydrogen peroxide were minimized by covering a Nafion film on the modified electrode surface. Cyclic voltammograms taken using the cyt c/poly-TTCA electrode with NO solutions show a reduction peak at −0.7 V. The calibration plot showed the hydrodynamic range of 2.4-55.0 M. The detection limit was determined to be 13 ± 3 nM based on S/N = 3. The microbiosensor was applied into the rat brain to test fluctuation of NO evoked by the abuse drug cocaine. The concentrations of NO levels by acute and repeated injections of cocaine were determined to be 1.13 ± 0.03 and 2.13 ± 0.05 M, respectively, showing high sensitivity of the microbiosensor in monitoring NO concentrations in the in vivo intact brain.
Electrochemical nitric oxide microsensors: sensitivity and selectivity characterisation
Analytica Chimica Acta, 2000
In this study, we have prepared two nitric oxide (NO) microsensors using two combinations of nickel tetrasulfonated phthalocyanine (NiTSPc), o-phenylenediamine (o-PD) and Nafion ® based layers to modify the surface of 8 m diameter carbon fiber electrodes. We have compared the performances of the obtained composite microsensors (carbon/NiTSPc/Nafion ® , and carbon/Nafion ® /o-PD, respectively) in our home made operating conditions. We have developed the sessile drop contact angle measurement technique as well as the use of the electrochemical quartz crystal microbalance (EQCM), differential normal pulse voltammetry (DNPV) and differential normal pulse amperometry (DNPA) to correlate the hydrophobicity, mass deposit of the polymer coatings and the sensitivity of the examined microsensors. By comparing the permeability of the microsensors to various interfering analytes, such as L-arginine, ascorbate, nitrite, serotonine, dopamine, acetamidophenol, 4-met-catechol, epinephrine, norepinephrine, dopac and 5-hydroxyindol, we have discussed the molecular sieving exclusion of the deposited membranes in term of molecular weight cutoff (MWCO).
Biosensors, 2021
The impaired blood flow to the brain causes a decrease in the supply of oxygen that can result in cerebral ischemia; if the blood flow is not restored quickly, neuronal injury or death will occur. Under hypoxic conditions, the production of nitric oxide (●NO), via the classical L-arginine–●NO synthase pathway, is reduced, which can compromise ●NO-dependent vasodilation. However, the alternative nitrite (NO2−) reduction to ●NO, under neuronal hypoxia and ischemia conditions, has been viewed as an in vivo storage pool of ●NO, complementing its enzymatic synthesis. Brain research is thus demanding suitable tools to probe nitrite’s temporal and spatial dynamics in vivo. In this work, we propose a new method for the real-time measurement of nitrite concentration in the brain extracellular space, using fast-scan cyclic voltammetry (FSCV) and carbon microfiber electrodes as sensing probes. In this way, nitrite was detected anodically and in vitro, in the 5–500 µM range, in the presence of ...
Overoxidation of carbon-fiber microelectrodes enhances dopamine adsorption and increases sensitivity
The Analyst, 2003
The voltammetric responses of carbon-fiber microelectrodes with a 1.0 V and a 1.4 V anodic limit were compared in this study. Fast-scan cyclic voltammetry was used to characterize the response to dopamine and several other neurochemicals. An increase in the adsorption properties of the carbon fiber leads to an increase in sensitivity of 9 fold in vivo. However the temporal response of the sensor is slower with the more positive anodic limit. Increased electron transfer kinetics also causes a decrease in the relative sensitivity for dopamine vs. other neurochemicals, and a change in their cyclic voltammograms. Stimulated release in the caudate-putamen was pharmacologically characterized in vivo using Ro-04-1284 and pargyline, and was consistent with that expected for dopamine. † Electronic supplementary information (ESI) available: National Instruments Data Acquisition System. See http://www.rsc.org/suppdata/an/b3/ b307024g/ This journal is