Dual-mode detection of Ochratoxin A based on silver nanocluster and phosphate.

Ochratoxin A (OTA) is widely present in the environment and has great harm to human safety. Therefore, a simple and sensitive method for OTA detection is urgently needed. Herein, a fluorescence and colorimetric dual-mode immunoassay based on glutathione silver nanocluster (GSH-AgNCs) and phosphate colorimetry was established. For fluorescence mode, the pyrophosphate ion (PPi) can reduce the fluorescence of GSH-AgNCs@Al by chelating Al. Meanwhile, the fluorescence can be recovered when PPi is hydrolyzed to phosphate ion (Pi) by alkaline phosphatase (ALP.) For colorimetric mode, Pi can be quantitatively analyzed by MoSb colorimetric method. The linear range of fluorescence mode was 1.25-35 ng/mL with limit of detection (LOD) of 0.54 ng/mL. For colorimetric mode, the linear range and LOD was 6.25-250 ng/mL and 3.13 ng/mL. The detection limits are much lower than the European Union's regulations. And this dual-mode immunoassay showed a satisfactory recovery rate and specificity in detecting real samples.