A visualization and fluorimetric detection for sulfisoxazole based on selectively weakened peroxidase activity of gold nanoclusters.

In this study, a facile method for the sensitive and selective detection of sulfisoxazole (SFX) was developed using bovine serum albumin (BSA)-stabilized gold nanoclusters (BSA-AuNCs). These nanoclusters, which possess high intrinsic peroxidase-like activity, can catalyze the hydrogen peroxide (H2O2)-based oxidation of o-phenylenediamine (OPD) and rapidly generate bright yellow product: 2,3-diaminophenazine (DAP). We found that the antibiotic SFX strongly inhibits the catalytic activity of BSA-AuNCs, while other common sulfonamide compounds do not interfere. As the concentration of SFX increases, the yellow color produced by the system weakens, eventually fading to colorless, enabling visual detection of SFX colorimetrically. The detection limit of this method is as low as 7 nM using UV-vis spectroscopy and 10 nM by naked-eye observation. In addition, the decrease in intensity of BSA-AuNCs due to SFX is also detectable by fluorimetry, with a detection limit as low as 0.3 nM. The proposed method has been successfully applied for the detection of SFX in meat and blood samples from animals that have consumed the medicated food.