Nafion-glucose oxidase electrode

Electrode and Nafion film Platinum disk electrode (area = 0.28 cm2) was fabricated as previously described (27). A solution of Nafion (EW = 1100) 5% w/v in a mixture of lower aliphatic alcohols and 10% water was obtained from Aldrich and diluted with methanol to give a stock solution of 0.35% w/v. Films of Nafion-glucose oxidase were formed by syringing aliquot (20 pi) of the mixed solution (86.7 pi of Nafion stock solution and 13.3 pi of glucose oxidase solution) at the surface of the platinum electrode. The solvents were left to evaporate at room temperature for at least 30 min. The extra amount of GOD was... 

Qiu B, Lin Z, Wang J, Chen Z, Chen J, Chen G (2009) An electrochemiluminescent biosensor for glucose based on the electrochemiluminescence of luminol on the nafion/ glucose oxidase/poly(nickel(ll)tetrasulfophthalocyanine)/multi-walled carbon nanotubes modified electrode. Talanta 78(l) 76-80. doi 10.1016/j.talanta.2008.10.067... 

Ricci et al. [13] Beverages Glucose oxidase (GOx)/ with glutaraldehyde and Nafion Prussian Blue (PB)-modified glassy carbon (PB-GC) particles screen-printed electrodes/-0.05 V vs. Ag/AgCl Prussian Blue... 

Luiz de Mattos et al. [41] Coffee Glucose oxidase/covered with a Nafion layer Glassy carbon electrode/-50 mV vs. Ag/ AgCl Prussian Blue electrodeposited on the electrode... 

Liu et al., 1998 [106] Milk Glucose oxidase (GOD)/ cross-linked with fi-cyclodextrin polymer. Coated with Nafion film Glassy carbon electrode/ +0.35 V vs. Ag/AgCl Ferrocene (also included in the polymer)... 

Previously, Nafion was used in electroanalysis as electrode covering membrane to immobilize cationic species (7,8) and as a barrier to anionic species (9,10). In biosensor field, the main limitation in the use of Nafion for enzyme entrapment is related to the solubility of the Nafion in lower aliphatic alcohols which are not compatible with the enzyme activity (11). Until now, only glucose oxidase was successfully immobilized in Nafion. 

Film Fabrication. The platinum electrode (0.28 cm area) was fabricated and cleaned as previously described (19). Thin films of AQ-enzyme were prepared by dissolving an amount of the enzyme, as indicated below, in 10 il of 1.5% AQ polymers solution at room temperature. Two aliquots of 5 il were deposited atop the platinum electrode and the first aliquot was allowed to dry before the second addition. This procedure corresponds to the first protocol. In addition, for the second protocol, 10 il of the 0.5% Nafion solution was casted atop the dried AQ-enzyme film and the methanol was allowed to evaporate at room temperature. The third protocol consisted in the deposition of 10 il of a 1% of AQ solution containing the enzyme, atop the platinum electrode followed by heating in an oven at 50°C during 30 min. In each case, 2 U of glucose oxidase were used. 

Figure 1. Current-time curves of glucose biosensors prepared A) in depositing the mixture of glucose oxidase and AQ atop the platinum electrode and allowing the solvent to evaporate at room temperature, B) in covering this AQ-glucose oxidase film with a Nafion layer or C) in heating the AQ-glucose oxidase film at 50°C in an oven for 30 min. The assays were done with 20 mM of glucose at pH 7.

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. 

Application of transition metal hexacyanoferrates for development of biosensors was first announced by our group in 1994 [118]. The goal was to substitute platinum as the most commonly used hydrogen peroxide transducer for Prussian blue-modified electrode. The enzyme glucose oxidase was immobilized on the top of the transducer in the polymer (Nafion) membrane. The resulting biosensor showed advantageous characteristics of both sensitivity and selectivity in the presence of commonly tested reductants, such as ascorbate and paracetamol. 

S. H. Lim, J. Wei, J. Lin, Q. Li, and J. K. You, A glucose biosensor based on electrodeposition of Palladium nanoparticles and glucose oxidase onto Nafion-solubilized carbon nanotube electrode. Biosens. Bioelectron. 2341-2346 (2005). 

In this article, we describe the preparation and use of amperometric electrodes for sensing the analytically significant substrate glucose based on a PEG-modified glucose oxidase (GOD) (4,5) and on a lipid-modified GOD (6). The PEG-modified GOD has been incorporated into a carbon paste (CP) electrode the modified enzyme exhibits higher activity in a hydrophobic CP matrix than hydrophilic, native GOD (7-10). The lipid-modified GOD has been immobilized on a glassy carbon (GC) electrode with a thin Nafion overcoat. The water-insoluble modified enzyme is far more stable between the electrode surface and the polymer layer than native GOD (77). 

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