Highly sensitive colorimetric detection of glucose through glucose oxidase and Cu2+-catalyzed 3,3′,5,5′-tetramethylbenzidine oxidation.

Abstract 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)-H 2 O 2 reaction, as colorimetric readout. The sensing system involves two processes: generation of H 2 O 2 from GOx-catalyzed oxidation of glucose, and H 2 O 2 -induced the oxidization of TMB via the catalysis of Cu2+. The H 2 O 2 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 H 2 O 2 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. Graphical Abstract Unlabelled Image Highlights • A GOx-mediated strategy for detecting glucose based on oxTMB, which is generated from Cu2+-catalyzed TMB-H 2 O 2 reaction. • The enhancement in colorimetric signal relies directly on H 2 O 2 concentration. • The method exhibits an ultrasensitive detection of glucose with the detection limit down to 0.21 nM. • The method is universally applicable for detection of other H 2 O 2 -mediated substrates and enzymes. [ABSTRACT FROM AUTHOR]