Alkaline phosphatase-triggered dual-signal immunoassay for colorimetric and electrochemical detection of zearalenone in cornmeal

Zearalenone (ZEN), as one of the most important foods and feeds pollutant mycotoxins, is threatening human and animal health. Here, we have developed a dual-signal immunoassay triggered by alkaline phosphatase (ALP) for detecting ZEN in cornmeal. The immobilized ZEN-bovine serum albumin and free ZEN in the sample were competitively bound to an anti-ZEN monoclonal antibody (McAb). Then, the ALP labeled goat anti-mouse IgG (ALP-IgG) combined with the McAb. ALP catalyzed ascorbic acid 2-phosphate to produce L-ascorbic acid (AA). AA converted potassium ferricyanide (K3[Fe(CN)6]) to potassium ferrocyanide (K4[Fe(CN)6]), which reacted with ferric ion (III) to promote the formation of Prussian blue nanoparticles (PB NPs). Consequently, the solution appeared multicolor changes. Meanwhile, PB NPs had a maximum absorption peak at 700 nm. It could be monitored by an UV–vis spectrometer. As an electron transfer medium, K3[Fe(CN)6] was consumed gradually along with PB NPs formation. Therefore, electrochemical detection was also used for detecting ZEN. Under the optimum conditions, the logarithm of ZEN concentration showed a good linear relationship with the absorbance from 0.2 to 0.8 ng/mL (R2 = 0.987) and the differential pulse voltammetry peak current from 0.125 to 0.5 ng/mL (R2 = 0.993). The limits of detection of colorimetric and electrochemical methods were 0.04 and 0.08 ng/mL, respectively. The recovery rates of ZEN from cornmeal samples were in the range of 80–120%, and relative standard deviations were lower than 10%. The results demonstrated that the dual-signal immunoassay has a high sensitivity for ZEN detection in corn samples.