Label-free electrochemical immunosensor based on AuNPs/Zn/Ni-ZIF-8-800@graphene composites for sensitive detection of monensin in milk

A facile, efficient and sensitive electrochemical immunosensor based on Au nanoparticles/Zn/Ni-ZIF-8-800@graphene composites was developed to detect the monensin in milk. Zn/Ni-ZIF-8-800 with high stability was obtained via pyrolysis of the Zn/Ni-bimetallic metal-organic frameworks (MOFs) precursor Zn/Ni-ZIF-8. Benefitting from the synergistic effects including the high porosity of the Zn/Ni-ZIF-8-800 and the excellent electrical conductivity of graphene, the electrochemical signal got greatly enhanced. The AuNPs were electro-deposited on the Zn/Ni-ZIF-8-800@graphene surface for antibody-antigen capture. Then the constructed hybrid materials not only possess high specific surface area, but also exhibit excellent biocompatibility and electron transfer ability. Morphology and elemental analyse of these composites were conducted via scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition, the crystal structure was analyzed by X-ray diffraction (XRD). Afterwards, the preparation process of the biosensor was investigated by cyclic voltammetry (CV), and the detection procedure was evaluated by differential pulse voltammetry (DPV). Under the optimal conditions, the achieved linear range was 0.25-100 ng mL(-1), and the calculated detection limit was 0.11 ng mL(-1). The as-prepared biosensor in this work offers an effective approach to measure monensin and may be a promising candidate for detecting other veterinary drugs in food products.