Highly sensitive colorimetric detection of glucose through glucose oxidase and Cu²⁺-catalyzed...

We develop a glucose oxidase (GOx)-mediated strategy for detecting glucose based on oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB), which is generated from Cu²⁺-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ reaction, as colorimetric readout. The sensing system involves two processes: generation of H₂O₂ from GOx-catalyzed oxidation of glucose, and H₂O₂-induced the oxidization of TMB via the catalysis of Cu²⁺. The H₂O₂ formed by GOx-catalyzed oxidation of glucose oxidizes colorless TMB to blue oxTMB, thus enhancing the absorbance intensity at 670 nm. Therefore, we draw a conclusion that the enhancement in colorimetric signal relies directly on H₂O₂ concentration, which, in turn, depends on glucose concentration. This color change can be used not only for visual detection of glucose by naked eyes but for reliable glucose quantification in the range from 1 to 100 nM with a detection limit of 0.21 nM. The method possesses the following advantages: simple design, low experimental cost, and no any additional experimental equipment for heating, illuminating, or bubbling.