Glucose sensing based on an effective conversion of O2 and H2O2 into superoxide anion radical with clay minerals

An effective promotion for the generation of superoxide anion radical from H2O2 and O-2 was accomplished with montmorillonite K10 clay mineral (denoted Mont. K10). This catalytic event was characterized by a fluorescence assay using amplex red and superoxide dismutase (SOD) as probes. The iron species (Fell and Fell) contained in Mont. K10 are thought to contribute to this catalytic event. Due to this property, a glucose sensor was fabricated on the basis of Mont. K10, amplex red, and glucose oxidase (GO(x)). When glucose is injected with amplex red over the clay vertical bar GO(x) electrode, H2O2 is produced in the enzyme zone, transduced to superoxide anion radical by the clay, and quenched by amplex red. Since the resulting product, resorufin, is emission-active under the irradiation of visible light (lambda(ex): 563 nm; lambda(em): 583 nm, pH 8), the analyte can thus be recognized and reported as optical signals with a luminescence spectrometer via a Y-type optical fiber atop of the electrode. The optical signal showed a linear response to glucose up to 150 mu M at pH 8. The lower and upper limits were estimated to be 1.0 and 150 mu M, respectively, at this pH. These results suggest that Mont. K10 is a promising O-2(-center dot) transducer. (c) 2005 Elsevier B.V. All rights reserved.