Phenoxazine Functionalized, Exfoliated Graphite Based Electrodes for NADH Oxidation and Ethanol Biosensing (original) (raw)
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Ethanol Biosensors and Electrochemical Oxidation of NADH
Analytical Biochemistry, 1998
Comparative studies of the electrochemical oxidation of reduced nicotinamide coenzyme (NADH) at the surfaces of chemically modified graphite paste electrodes (CMEs) are reported. Three different electroactive materials, tetracyanoquinodimethane (TCNQ), tetrathiafulvalene (TTF), and dimethyl ferrocene (dmFc), were used to construct three different chemically modified paste electrodes. The oxidation of NADH was examined on the basis of cyclic voltammetric measurements. The results show that all three mediators (TCNQ, TTF, and dmFc) behave as efficient mediators of the oxidation of NADH. The typical response curves of NADH at the CMEs surfaces are reported. Incorporating alcohol dehydrogenase and electroactive materials (TCNQ, TTF, and dmFc) within the graphite paste electrodes has led to the development of ethanol biosensors. Typical response curves for the ethanol analysis are reported. Comparative studies on the mediated electrochemical responses of the biosensors to ethanol are discussed. © 1998 Academic Press 1
Analytica Chimica Acta, 2003
The present work deals with the use of the porous texture of expanded natural graphite (ENG) as transducer in order to design electrochemical biosensors. The sensing element is a NAD + -dependent dehydrogenase. An electrochemical pretreatment of the ENG is favorable because it allows on one hand generating functional surface groups that may act as mediators for NADH oxidation and, on the other hand, eliminating enzyme-toxic compounds. The electrocatalytic oxidation of NADH on the pretreated material leads to the formation of enzymatically active NAD + . However, some persistent problems, mainly related to enzyme instability, still hamper the development of the biosensors.
Electrocatalytic Oxidation of NADH at Polyadenylic Acid Modified Graphite Electrodes
Electroanalysis, 2002
The electrochemical oxidation of 5'-polyadenylic acid (poly-A) on graphite electrodes has been studied by cyclic voltammetry. The oxidation of poly-A in neutral and alkaline solutions gives rise to redox-active products strongly adsorbed on the electrode surface, which exhibit catalytic activity toward NADH oxidation. The amount and properties of the catalyst are remarkably influenced by the pH of the oxidation medium. Depending on the conditions of catalyst formation, it is possible to reduce the overpotential for NADH oxidation by 300 mV. Amperometric detection of NADH using electrodes modified from different media were evaluated and compared. Electrodes modified from 0.1 M NaOH solutions containing the polynucleotide allow carrying out the amperometric detection of NADH at 50 mV (vs. Ag/AgCl), at pH 9, within a wide concentration range, 2.5 Â 10 À8 À 1 Â 10 À4 M, and with a detection limit of 1.1 Â 10 À8 M. These electrodes also exhibit very good stability and reproducibility.
Electroanalysis, 1998
The preparation of a 2,6-dichlorophenolindophenol (DCPI) modified graphite electrode is described. DCPI was successfully immobilized by physical adsorption onto a plain graphite electrode (DCPI-CME) and onto graphite electrodes pretreated with lanthanum nitrate (DCPI-La-CME) or thorium nitrate (DCPI-Th-CME). The electrochemical behavior of DCPI-CME was extensively studied using cyclic voltammetry. The electrochemical redox reaction of DCPI was found to be fairly reversible at low coverage with E o 0 = þ55 mV (vs. Ag/AgCl/3M KCl) at pH 6.5. A pK a value of 5.8 Ϯ 0.1 for immobilized form of DCPI is determined from the intersection of the lines in the plot E o 0 vs. pH. The current I p has a linear relationship with the scan rate up to 1200 mV s ¹1 , which is indicative for very fast electron transfer kinetics. The calculated value of the standard rate constant is k o = 18 Ϯ 4 s ¹1. No decrease of either the anodic or the cathodic current of the cyclic voltammogram was observed after 500 runs of successive sweeps. The influence of the morphology of the electrode surface on the electrochemical behavior of the DCPI-CME was studied and a mathematical model is proposed, which partly describes the dependence of the geometrical area of the electrode surface on the grid of the emery paper. The modified electrodes were mounted in a flow-injection manifold, poised at þ60 mV (vs. Ag/AgCl/3M KCl) and a catalytic current due to the oxidation of NADH was observed reducing thus the oxidation overpotential of NADH for about 400 mV. Interference from various reductive species present in real samples was investigated. The repeatability was 1.2 % RSD (n = 10 for 0.1 mM NADH). The sensor showed good operational and storage stability.
Electrochemical determination of NADH and ethanol based on ionic liquid-functionalized graphene
Biosensors & Bioelectronics, 2010
It is firstly reported that low-potential NADH detection and biosensing for ethanol are achieved at an ionic liquid-functionalized graphene (IL-graphene) modified electrode. A substantial decrease (440 mV) in the overvoltage of the NADH oxidation was observed using IL-graphene/chitosan coating, with oxidation starting at ca. 0 V (vs. Ag|AgCl). And the NADH amperometric response at such a modified electrode is more stable (95.4% and 90% of the initial activity remaining after 10 min and 30 min at 1 mM NADH solution) than that at bare electrode (68% and 46%). Furthermore, the IL-graphene/chitosan-modified electrode exhibited a good linearity from 0.25 to 2 mM and high sensitivity of 37.43 μA mM−1 cm−2. The ability of IL-graphene to promote the electron transfer between NADH and the electrode exhibited a novel and promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. With alcohol dehydrogenase (ADH) as a model, the ADH/IL-graphene/chitosan-modified electrode was constructed through a simple casting method. The resulting biosensor showed rapid and highly sensitive amperometric response to ethanol with a low detection limit (5 μM). Moreover, the proposed biosensor has been used to determine ethanol in real samples and the results were in good agreement with those certified by the supplier.
Journal of Sensors, 2018
Different carbon-based materials have been compared for the development of NADH sensors: glassy carbon electrodes (GCE), multiwalled carbon nanotubes (MWCNT), and carbon black (CB). The GCE and MWCNT has been subjected to oxidative pretreatment to study the influence of oxidative groups for NADH oxidation. The materials had been characterized by FT-IR to identify the surface composition. The response of bare (GC) and GC/modified electrodes toward potassium ferricyanide have been employed to obtain information about the electroactive area and electron transfer rate. Studies of NAD+/NADH redox behavior showed that MWCNT and GCE exhibit high degree of passivation while CB shows no fouling effects. Catalytic effect of surface-oxygenated groups was also proved for GCE and MWCNT, and both, O-GCE and O-MWCNT, exhibited a lower oxidation overpotential compared to the respective untreated materials. Chronoamperometric quantification showed a linear dependence between 2–18 μmol·L−1 and a dete...
The electrochemical behavior of a modified electrode obtained by immobilization of single-walled carbon nanotubes onto a graphite electrode modified with a new phenothiazine derivative, bis-phenothiazin-3-yl methane (BPhM), G/BPhM-CNT, has been evaluated and compared with BPhM adsorbed on graphite electrode (G/BPhM). The G/BPhM-CNT electrode presents improved performances for NADH electrocatalytic oxidation in comparison with G/BPhM electrode, expressed by: (i) a significant increase of electrocatalytic rate constant (kobs,[NADH] 0) for NADH oxidation (856.32 L mol–1 s–1 for G/BPhM-CNT and 51.63 L mol–1 s–1 for G/BPhM, in phosphate buffer, pH 7); (ii) the obtained amperometric sensors for NADH detection present increase sensitivity (S = 6.9 mA L mol–1 for G/BPhM-CNT and S = 0.55 mA L mol–1 for G/BPhM, pH 7).
Analytica Chimica Acta, 1994
Chemically modified electrodes with Methylene Green adsorbed on the graphite surface and incorporated into carbon paste exhibit excellent electrocatalytic ability for oxidation of NADH. Alcohol dehydrogenase, nicotinamide adenine dinucleotide (NAB+) and mediator were incorporated into a carbon paste matrix to yield an alcohol sensor. The enxyme and cofactor retain their bioactivity within the matrix. The surface of the sensor is protected by coverage with a poly(ester sulphonic acid) cation exchanger to form a membrane, which effectively prevents the aqueous soluble species from dissohing out from the enxyme electrode and reduces or eliminates the interference from electroactive anions. The oxidation current of the NADH formed by enxymatic reaction serves as the response for target analytes. The reagentless sensor shows steady-state signals within 50 s, owing to the intimate contact between the biocatalytic and sensing sites. The influence of various experimental conditions was explored for optimum analytical performance. The sensor remained relatively stable for about 15 days.
Electroanalysis, 2009
A new approach for photoelectrocatalytic oxidation of NADH is described, based on a graphite electrode (G) modified with a new phenothiazine derivative, polyphenothiazine formaldehyde (PPF). Electrochemical measurements reveal that G/PPF presents a quasireversible voltammetric response, corresponding to a 2e À /2H þ transfer and that G/PPF modified electrodes show electrocatalytic activity for NADH oxidation. When the surface of the G/PPF modified electrode was irradiated with a light source (250 W Halogen lamp), a significant increase in the electrocatalytic current was observed. The second order electrocatalytic rate constant (k obs, [NADH]¼0 ¼ 3.9 Â 10 3 M À1 s À1 , pH 7.0) was calculated from rotating disk electrode experiments, performed at various NADH concentrations. From amperometric measurements, it was noticed that, in the presence of light irradiation, the sensitivity of NADH detection (calculated as I max /K M ratio) increased ca. 3 times.
Biosensors and Bioelectronics, 1993
A new kind of chemically modified electrode for electrocatalytic oxidation of NADH is described. Carbon paste (graphite : paraffin oil) electrodes are chemically modified with the addition of an aqueous insoluble polymer containing a covalently bound phenothiazine dye, Toluidine Blue 0, through an amide linkage between a primary amine group of the Toluidine Blue 0 moiety and the polymer backbone. Some basic properties of this chemically modified carbon paste electrode for the electrocatalytic oxidation of NADH are described, using cyclic voltammetry, as are the properties when the electrode is used as an amperometric sensor for NADH in a flow injection system. At an applied potential of +lOO mV vs. Ag/AgCl, the detection limit for NADH was O-4 PM.