Oxidase electrodes

W. Sung and Y. Bae, A glucose oxidase electrode based on electropolymerized conducting polymer with polyanion-enzyme conjugated dopant. Anal. Chem. 72, 2177-2181 (2000). 

FIGURE 5.25. Avidin-biotin construction of a monolayer glucose oxidase electrode with an attached ferrocenium cosubstrate and cyclic voltammetric response in a phosphate buffer (pH 8) at 25°C and a scan rate of 0.04 V/s. a attached ferrocene alone, h In the presence of 0.5 M glucose, c Variation of the inverse of the plateau current with the inverse of substrate concentration. Adapted from Figure 1 in reference 24, with permission from the American Chemical Society. 

Fructose ethanol multibiosensor (modified with mediator or oxidase electrodes... 

Aspartame has been assayed by a flow injection analysis biosensor employing an immobilized enzyme (pronase) which cleaves the peptide bond. The resulting phenylalanine methyl ester is then detected by an L-amino acid oxidase electrode. This method was applied to analysis of aspartame in foods [82]. 

Figure 3. Calibration curve for AQ-choline oxidase electrode, prepared by casting 25 il of 1% AQ solution and 3 U of enzyme. The film was dried at 50°C during 30 min in an oven.

Electrochemical Characterization of Ferrocene Derivatives in a Perfluoropolymer Glucose Oxidase Electrode... 

Figured Effect of Stabilizers on Alcohol Oxidase Electrode Stability.

Acetylcholineesterase and choline oxidase Electrode was developed by co-immobilization of AChE with ChO H202. Disposable sensors constructed by co-immobilization in a gelatin membrane on Pt electrode or by immobilizing AChE in polyurethane on a thick-film metallized Pt electrode. A kinetically controlled bioenzyme sensor was also used at a low activity of ChE for determining inhibitors. [75]... 

LDH enzyme electrodes follow electrochemically NADH consumption or NAD" " formation (211). Electrochemically activated microcarbon electrodes can be utilized in conjunction with immobilized LDH to determine pyruvate in small volumes (50 pL) of cerebrospinal fluid within the concentration range 10 pM to 2 mM (234). The construction of pymvate oxidase electrodes operating either at positive potentials (H2O2 detection) or at negative potentials (oxygen depletion) (92) is described by... 

Figure 3-7. Assembly of an electrically-contacted polyaniUne-reconstituted glucose oxidase electrode. Reproduced with permission from ref. 34. Copyright 2002 American Chemical Society.

Figure 3-8. Cyclic voltammograms corresponding to the bioelectrocatalyzed oxidation of variable concentrations of glucose by the integrated, electrically-contacted polyaniline-reconstituted glucose oxidase electrode. Glucose concentrations correspond to (a) 0 mM, (b) 5 rnM. (c) 10 mM, (d) 20 mM, (e) 35 inM. (1) 50 mM. Reproduced with permission from ref. 34. Copyright 2002 American Chemical Society.

Figure 3-10. The assembly of an Au-nanoparticle (1.4 nm) electrically contacted glucose oxidase electrode by (a) the primary reconstitution of apo-GOx on the FAD-functionalized Au-nanoparticle, and the immobilization of the enzyme-nanoparticle hybrid on an electrode surface (b) the primary immobilization of the FAD-modified Au-nanoparticle on tire electrode surface and the surface reconstitution of apo-GOx on the functionalized electrode. Reproduced with permission from ref. 41. Copyright 2003, AAAS.

Figure 3-30. Organization of a photoswitchable glucose oxidase electrode for the bioelectrocatalyzed oxidation of glucose (A) The synthesis of the photoisomerizable nitrospiropyran-FAD cofactor. (B) The reconstitution of apo-glucose oxidase, apo-GOx, with the photoisomerizable FAD-cofactor (20a). (C) The assembly of the reconstituted photoisomerizable GOx on an electrode surface and the photoswitching of the bioelectrocatalytic function of the enzyme electrode in the presence of ferrocene carboxylic acid (21) as mediator.

Figure 3-32. (A) The assembly of an electro switchable, electrically-contacted, glucose oxidase electrode by the reconstitution of apo-glucose oxidase, apo-GOx, on PQQ-FAD units linked to a polyacrylic acid fihn that includes Cu -ion attached to the fihn. The conductivity of the film and the electrical contacting of the enzyme is accomplished by applying a potential of -0.5 V vs. SCE and the generation of Cu-clusters in the film. Reproduced with permission from ref. 89. Copyright 2003 American Chemical Society.

Similarly, the conversion of a homologous substrate has been demonstrated by using lactate oxidase. 2-Hydroxybutyric acid was measured with a lactate oxidase electrode with a sensitivity comparable with that for the normal substrate, lactate. 

Yao and Wasa (1988a) assembled modified electrodes for amino acids by crosslinking L- or D-amino acid oxidase with glutaraldehyde on silanized platinum probes. The sensors were employed as detectors in high pressure liquid chromatography. Whereas the L-amino acid oxidase electrode responded to L-tyrosine, L-leucine, L-methionine, and L-phenylalanine in amounts as low as 2 pmoles, the D-amino acid electrode measured only D-methionine and D-tyrosine. The response time in steady state measurements was only 5-10 s. 

During application of the choline oxidase electrode to serum samples, Mascini and Moscone (1986) observed that the sensor also indicated ACh due to adsorption of AChE from the sample on the enzyme membrane. This finding can be explained by the high surface activity of AChE and its high concentration in normal serum, and has been confirmed by Gruss (1989), who investigated the adsorption of serum on carbon electrodes. 

A glucose sensor system consisting of an oxygen electrode and a glucose oxidase electrode was recently implanted into the vena cava of a dog (McKean and Gough, 1988). The sensors operated in the potentio-static mode and were connected to an implantable telemetry system. Both the enzyme stability and the power consumption allowed operation of the system for three months. 

A sensor system involving an alcohol oxidase electrode and an enzyme-free oxygen probe has been used for continuous assay of ethanol in alcoholic fermentation (Verduyn et al., 1984). The bare O2 electrode served to compensate for pC>2 variations in the fermenter. The measuring range was rather narrow so that only the initial phase of ethanol formation could be followed. 

M. B. Assoumani, et. al.. Use of a lysine oxidase electrode for lysine determination in soybean meal hydrolyzates, Lebens.-Wiss.Technol. 23 (4), 322-27 (1990). 

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