Fluorescence and colorimetric dual-mode immunoassay based on G-quadruplex/N-methylmesoporphyrin IX and p-nitrophenol for detection of zearalenone

In this work, a fluorescence and colorimetric dual-mode immunoassay for detecting zearalenone (ZEN) was established. This platform relied on the dephosphorylation of p-nitrophenyl phosphate (PNPP) by alkaline phosphatase (ALP) to produce yellow p-nitrophenol (PNP). And the internal filtration effect between G-quadruplex/N-methylmesoporphyrin IX (G4/NMM) and PNP led to fluorescence quenching of G4/NMM. Therefore, the color change of PNP and the fluorescence change of G4/NMM can be used as double signals to report the results of ALP mediated immunoassay. In this dual-mode immunoassay, the detection limit of fluorescence mode was 0.0072 ng/mL with a linear range 7.5-17.5 ng/mL. And the detection limit of colorimetric mode was 0.036 ng/mL with a linear range 7.5-20 ng/mL. In addition, the dual-mode immunoassay showed good selectivity for ZEN and satisfactory recovery in corn samples (fluorescence mode: 94.40-106.80%, colorimetric mode: 96.51-108.27%).