A Novel Electrochemical Aptasensor for Sensitive and Selective Detection of Aflatoxin B1 Based on PDA/MXene/MWCNTs/NiCo <sub>2</sub>O <sub>4</sub> Nanocomposite

This work established a novel nucleic acid aptamer sensor for the sensitive and selective detection of AFB1 (Aflatoxin B1), which has important implication for food safety. In a word, we synthesized MXene/MWCNTs/NiCo2O4 composite nanomaterials to improve the sensitivity of the aptamer sensor. The surface of the composite nanomaterials was modified with PDA (Poly dopamine) in order to immobilize the NH2-cDNA-aptamer complex on the electrode surface by the Schiff base reaction. Characterization of MXene/MWCNTs/NiCo2O4 nanocomposites was carried by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Meanwhile, 4-carboxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (TEMPO-COOH) was used as an electrochemical signal to detect AFB1. Under optimal conditions, the electrochemical DPV signal decreased with increasing AFB1 concentration, ranging from 2.5 to 200 ng/mL, and the lowest limit of detection (LOD) at 1.890 ng/mL (S/N = 3). In addition, the ensemble sensor has possessed great reproducibility, stability and selectivity, which has been successfully applied to the determination of AFB1 in maize flour and maize residue samples with recoveries ranging from 92.2 ~ 109.8%. This work have comparable detection limits and detection ranges, and shorter detect time (within 5 min) of AFB1, compared to other detection methods for AFB1, which providing a new method for the rapid determination of AFB1 in food samples.