Smartphone-enabled colorimetric immunoassay for deoxynivalenol based on Mn²⁺-mediated aggregation of AuNPs

Deoxynivalenol (DON) is a common mycotoxin in food that mainly pollutes grain crops and feeds, such as barley, wheat and corn. DON has caused widespread concern in the field of food and feed safety. In this study, a colorimetric immunoassay was proposed based on the aggregation of gold nanoparticles (AuNPs) due to the decomposition of Mn²⁺ from gold-coated manganese dioxide (AuNP@MnO₂) nanosheets. In this study, 2-(dihydrogen phosphate)-l-ascorbic acid (AAP) was hydrolyzed by alkaline phosphatase (ALP) and converted to ascorbic acid (AA). Then, AuNP@MnO₂ was reduced to Mn²⁺ and AuNPs aggregation occurred. Using the unique optical characteristics of AuNPs and AuNP@MnO₂, visible color changes realized simple detection of DON with high sensitivity and portability. With increasing DON content, the color changed more obviously. To quantitatively detect DON, pictures can be taken and the blue value can be read by a smartphone. The detection limit (Ic10) of this method was 0.098 ng mL^-1, which was 326 times higher than that of traditional competitive ELISA, and the detection range was 0.177-6.073 ng mL^-1. This method exhibited high specificity with no cross-reaction in other structural analogs. The average recovery rate of DON in corn flour samples was 89.1 %-110.2 %, demonstrating the high accuracy and stability of this assay in actual sample detection. Therefore, the colorimetric immunoassay can be used for DON-related food safety monitoring.