β-cyclodextrin-ferrocene host–guest complex multifunctional labeling triple amplification strategy for electrochemical immunoassay of subgroup J of avian leukosis viruses

A novel sandwich-type electrochemical immunosensor was fabricated for ultrasensitive detection of subgroup J of avian leukosis virus (ALVs-J) by employing β -cyclodextrin-ferrocene (CD-Fc) host–guest complex multifunctional Fe 3 O 4 nanospheres as labels and β -cyclodextrin functional graphene sheets (CD-GS) nanocomposite as sensor platform. The sensitivity was greatly improved based on the triple amplification strategy. Firstly, the CD-GS improved the electron transfer rate as well as increasing the surface area to capture a large amount of primary antibodies (Ab 1 ). Secondly, the CD on the Fe 3 O 4 surface with strong recognition capability could form stable CD-Fc host–guest inclusion complex and provided larger free room for the conjugation of secondary antibodies (Ab 2 ) and glucose oxidase (GOD). Finally, the conjugated GOD exhibited extraordinary electrochemical biocatalysis towards the reduction reaction of Fc + by glucose. Under the optimized conditions, the electrochemical immunosensor exhibited a wide working range from 10 2.27 –10 3.50 TCID 50 /mL (TCID 50 : 50% tissue culture infective dose) with a low detection limit of 10 2.19 TCID 50 /mL ( S / N =3). The selectivity, reproducibility, and stability are acceptable. The assay was evaluated for real avian serum sample, receiving satisfactory results. This new type of triple amplification strategy may provide potential applications for the clinic application.