Abstract
In this paper, we first report the construction of Nafion/glucose oxidase (GOD)/xylose dehydrogenase displayed bacteria (XDH-bacteria)/multiwalled carbon nanotubes (MWNTs) modified electrode for simultaneous voltammetric determination of d-glucose and d-xylose. The optimal conditions for the immobilized enzymes were established. Both enzymes retained their good stability and activities. In the mixture solution of d-glucose and d-xylose containing coenzyme NAD+ (the oxidized form of nicotinamide adenine dinucleotide), the Nafion/GOD/XDH-bacteria/MWNTs modified electrode exhibited quasi-reversible oxidation-reduction peak at −0.5V (vs. saturated calomel electrode, SCE) originating from the catalytic oxidation of d-glucose, and oxidation peak at +0.55V(vs. SCE) responding to the oxidation of NADH (the reduced form of nicotinamide adenine dinucleotide) by the carbon nanotubes, where NADH is the resultant product of coenzyme NAD+ involved in the catalysis of d-xylose by XDH-displayed bacteria. For the proposed biosensor, cathodic peak current at −0.5V was linear with the concentration of d-glucose within the range of 0.25–6mM with a low detection limit of 0.1mM d-glucose (S/N=3), and the anodic peak current at +0.55V was linear with the concentration of d-xylose in the range of 0.25∼4mM with a low detection limit of 0.1mM d-xylose (S/N=3). Further, d-xylose and d-glucose did not interfere with each other. 300-fold excess saccharides including d-maltose, d-galactose, d-mannose, d-sucrose, d-fructose, d-cellobiose, and 60-fold excess l-arabinose, and common interfering substances (100-fold excess ascorbic acid, dopamine, uric acid) as well as 300-fold excess d-xylitol did not affect the detection of d-glucose and d-xylose (both 1mM). Therefore, the proposed biosensor is stable, specific, reproducible, simple, rapid and cost-effective, which holds great potential in real applications.
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