A novel sandwich-type electrochemical immunosensor for avian leukosis virus subgroup J (ALV-J) is described. The immunosensor was prepared by first modifying a glassy carbon electrode (GCE) with reduced graphene oxide that was functionalized with tannic acid and magnetite nanoparticles (rGO-TA-Fe3O4). Primary antibodies (Ab1) were then deposited on the modified GCE. Hollow zeolitic imidazolate framework (eZIF) crystals functionalized with tannic acid and carrying secondary antibodies (Ab2) and horseradish peroxidase (HRP) were used for signal amplification. The hollow eZIF crystals were found to be an excellent carrier for both Ab2 and HRP, prompting the wider use of metal organic frameworks in electrochemical sensing. Under optimal conditions, the immunoassay afforded a detection range from 152 to 10,000 TCID50 mL-1 (where TCID50 is the 50% tissue culture infective dose) and a low detection limit of 140 TCID50 mL-1 (at S/N = 3). The immunoassay is highly selective for ALV-J, and it demonstrates excellent reproducibility and operational stability. The practicability of the immunoassay for the fast detection of ALV-J was confirmed in experiments with spiked avian serum samples. Graphical abstract Schematic of a sandwich-type electrochemical immunosensor for avian leukosis virus subgroup J (ALV-J). It consists of reduced graphene oxide, tannic acid and magnetite as the sensing platform, and an etched zeolitic imidazolate framework carrying horseradish peroxidase for signal amplification.
Keywords: ALV-J; Electrochemical immunosensor; Signal amplification; eZIF.