A novel selective and sensitive multinanozyme colorimetric method for glutathione detection by using an indamine polymer.

A sensitive and selective novel multinanozyme colorimetric method for glutathione (GSH) detection was developed. MnO2-nanozymes can catalyze the oxidation reaction of 3, 3՛-diaminobenzidine (DAB) and produce a brown indamine polymer. In the presence of GSH, this reaction slowly proceeds. When Au-nanozymes was used as peroxidase mimic along with MnO2-nanozymes, the analytical signal and selectivity (particularly, over Cys and AA) were significantly improved for GSH detection. Therefore, this novel multinanozyme system was further developed through optimization for the colorimetric detection of GSH. The calibration curve presented two wide linear range from 0.05 to 0.19 and 0.19-11.35 mg L̶ 1 with a very low detection limit of 0.02 mg L̶ 1 (5 nM) for GSH. The developed method was employed for human serum analysis without any dilution and any deproteinization.

A field-applicable colorimetric assay for notorious explosive triacetone triperoxide through nanozyme-catalyzed irreversible oxidation of 3, 3'-diaminobenzidine.

A field-applicable colorimetric assay for fast detection of notorious explosive triacetone triperoxide (TATP) has been developed through the selective irreversible oxidation of 3, 3'-diaminobenzidine by hydrogen peroxide (HP) liberated during the acidic hydrolysis/degradation of TATP in the presence of MnO2 nanozymes. The generated HP was detected by probing the absorbance of the product (indamine polymer) of the 3, 3'-diaminobenzidine (DAB) oxidation reaction at 460.0 nm. The UV-Vis measurements provided a linear range from 1.57 to 10.50 mg L-1 TATP with a detection limit of 0.34 mg L-1. The oxidation of DAB cannot proceed by molecular oxygen, thus it is selectively oxidized by H2O2; this prevents false-positive results from laundry detergents (containing O2-releasing substances). Moreover, a naked-eye field test was developed, and a fast spot test analyzing time of 5 s was achieved. The selectivity of the assay was checked by analyzing some synthetic samples prepared with a laundry detergent as camouflage. The results of the developed assay revealed quantitative recoveries for TATP whereas the standard nanozyme-based method showed significant false-positive results. Graphical abstract.