Electrochemical nanoprobe-based immunosensor for deoxynivalenol mycotoxin residues analysis in wheat samples

Deoxynivalenol (DON) is a toxic secondary metabolite produced by several species of Fusarium fungi, which can be predominantly found in agricultural crops such as wheat. In livestock, deoxynivalenol-contaminated grain can produce vomiting, feed refusal, weight loss, and diarrhea. This paper reports an electrochemical immunosensor for the detection of residual DON mycotoxin in food samples. The device uses electrochemical nanoprobes (CdSNP-AbDON) and antigen biofunctionalized magnetic μ-particles (DON-BSAMP) to detect the mycotoxin. CdSNP-AbDON are prepared by labelling the DON-specific antibodies with CdS nanoparticles (CdSNPs). Nanoparticle size and CdSNP-AbDON conjugation ratio are characterized using TEM images. The metal ions released by the CdSNP are reduced at the working electrode and read by anodic stripping voltammetry. DON can be detected in PBST buffer with an IC₅₀ of 6.74 ± 0.19 μg L^-1. The high detectability of the immunosensor developed allows detection of DON residues in 50-fold diluted wheat extracts. The limit of detection (LOD, IC₉₀) accomplished in wheat is of 342.4 μg kg^-1, which is below the maximum residue limit (MRL, 1750 μg kg^-1 for unprocessed durum wheat, 750 μg kg^-1 for cereals intended for direct human consumption) established by the EU for this mycotoxin. The working range is in the interval between 610 and 6210 μg kg^-1. The performance of the immunosensor was compared with the ELISA assay. DON naturally contaminated wheat samples were analyzed with the immunosensor, showing acceptable recoveries. Graphical abstract.