Graphite-glucose oxidase electrodes

Figure 14-8. Response of a graphite-glucose oxidase electrode in an automatic flow-injection system.

Pishko MV, Katakis I, Lindquist SE, Ye L, Gregg BA, Heller A. 1990. Direct electron exchange between graphite electrodes and an adsorbed complex of glucose oxidase and an osmium-containing redox polymer. Angew Chem 102 109-111. 

A. Salimi, R.G. Compton, and R. Hallaj, Glucose biosensor prepared by glucose oxidase encapsulated sol-gel and carbon-nanotube-modified basal plane pyrolytic graphite electrode. Anal. Biochem. 333, 49— 56 (2004). 

P.C. Pandey, S. Upadhyay, N.K. Shukla, and S. Sharma, Studies on the electrochemical performance of glucose biosensor based on ferrocene encapsulated ORMOSIL and glucose oxidase modified graphite paste electrode. Biosens. Bioelectron. 18,1257—1268 (2003). 

J. Gun and O. Lev, Sol-gel derived, ferrocenyl-modified silicate-graphite composite electrode wiring of glucose oxidase. Anal. Chim. Acta 336, 95-106 (1996). 

R.M. Ianniello, T.J. Lindsay, and A.M. Yacynych, Differential pulse voltammetric study of direct electron transfer in glucose oxidase chemically modified graphite electrodes. Anal. Chem. 54, 1098-1101 (1982). 

Figure 34 Cyclic voltammograms recorded at a pyrolitic graphite electrode in an aqueous solution (pH 7) containing (a) [(r -CsHs)Fe(rf-C5H4COOH)] (0.5 mM) and D-glucose (50 mM) (b) after the addition of glucose oxidase (10.9 nM). Scan rate 0.001 Vs 1...

Llopis et al. [37] Cola beverage Glucose oxidase (GOD)/ entrapped together with the mediator in the bulk of the biocomposite material Graphite and nonconducting epoxy resin composite electrode/ +0.3 V vs. Ag/AgCl Tetrathiafulvalene-tetracyanoquino-dimethane (TTF - TCNQ)... 

Ivekovic et al. [42] Fruit juice, yoghurt drink Glucose oxidase (GOx)/ into palladium hexacyanoferrate (PdHCF) hydrogel Nickel hexacyanoferrate (NiHCF) electrodeposited onto graphite electrode/-0.075V vs. SCE Nickel hexacyanoferrate... 

Guzman-Vazquez de Prada et al. [96] Methanol Ethanol Glucose Lactate (in the same assay) Wine Glucose oxidase (GOx), lactate oxidase (LOx), alcohol oxidase (AOx) and peroxidase (HRP)/ physically entrapped in the graphite-Teflon composite matrix Ferrocene-graphite-Teflon Ferrocene composite electrode/O V vs. Ag/AgCl... 

A recent successful approach uses mediators like ferrocene, which reoxidizes the FADH 2 in the glucose oxidase molecule without forming hydrogen peroxide (85). Using ferrocene results in a more stable electrode system and a larger dynamic concentration range. The ferrocene molecule is immobilized by adsorption to graphite or other carbon electrodes onto which the enzyme can be deposited. 

Carbonaceous substrates (graphite and glassy carbon) are generally preferred because of their mechanical, chemical, and electrochemical properties. Excellent results are also obtained by chemically modified platinum (154,156,179) and tin(IV) oxide electrodes (155). For example, glucose oxidase has been successfully immobilized by cross-linking the enzyme with BSA and GA onto an electrochemically oxidized platinum surface, with silanization using 3-amino-propyltriethoxysilane ... 

Although enzymes with deeply embedded active centers do not normally allow significant non-mediated electron transfer [44], under carefully chosen conditions direct electron transfer is possible, and has been reported for glucose oxidase (GOx) at a bare Ag electrode [45] and in graphite paste electrodes [46]. These systems are unusual and the nonmediated mechanism of such long-range electron transfer is not fully understood. 

CCEs have also been used in conjunction with enzymes. Glucose oxidase was encapsulated within the methyl silicate (or silica)-graphite composite [216, 220]. Reduced oxygen from the enzymatic reaction results in the production of H2O2, which is oxidized at the electrode. Palladium and rhodium catalysts have been added to the electrode to help lower the over voltage required for hydrogen peroxide oxidation [219, 221]. Glucose oxidase and horseradish peroxidase have been simultaneously entrapped within a CCE for a biosensor that does not require a... 

This enzyme-based biosensor uses glucose oxidase (GO) as a chemical recognition element, and an amperometric graphite foil electrode as the transducer. It differs from the first reported glucose biosensor discussed in the introduction to this chapter in that a mediator, 1,1 -dimethylferricinium, replaces molecular oxygen as the oxidant that regenerates active enzyme. The enzymatic reaction is given in Eq. 7.15, and the electrochemical reaction that provides the measured current is shown in Eq. 7.16. 

Fu, C.L, Yang, W.S., Chen, X., and Evans, D.G. (2009) Direct electrochemistry of glucose oxidase on a graphite nanosheet-Nafion composite film modified electrode. Electrochemistry Communications, 11 (5), 997-1000. 

The presence of various functional surface groups and the high conductivity and porosity of carbon material permit effective enzyme adsorption. Glucose oxidase has been irreversibly adsorbed to a graphite electrode by drying a concentrated enzyme solution on the surface (Ikeda et al., 1984). In the presence of p-benzoquinone an electrocatalytic current was observed at 500 mV vs SCE. The measuring signal was... 

Glucose oxidase MWCNT/ZnO NP/PDDA modified pyrolytic graphite electrode Glucose biosensor [134]... 

---