Ultrasensitive Electrochemical Immunosensor for Avian Leukosis Virus Detection Based on a Β-Cyclodextrin-nanogold-ferrocene Host-Guest Label for Signal Amplification.

A novel sandwich-type electrochemical immunosensor was fabricated for the ultrasensitive detection of avian leukosis virus subgroup J (ALV-J). The immunosensor used a β-cyclodextrin-nanogold-ferrocene (β-CD-AuNP-Fc) host-guest complex as the label and a perylene-3,4,9,10-tetracarboxylic acid functional graphene nanocomposite (GR-PTCA) as the sensor platform. The abundant polycarboxylic sites of GR-PTCA facilitated the binding of primary antibodies (Ab1), whilst the excellent electrical conductivity of GR-PTCA promoted electron transfer. Immobilization of β-CD directly onto secondary antibodies (Ab2) via covalent bonding allowed strong binding of ferrocene-decorated gold nanoparticles (Fc-Au NP), thereby amplifying the immunosensor signal. Under optimized testing conditions, the reduction current of ferrocene exhibited a linearly dependence on the ALV-J titer in the concentration range of 102.0-104.0 TCID50/mL, with a low detection limit of 101.93 TCID50/mL. Furthermore, the immunosensor demonstrated high sensitivity, good reproducibility, reusability and stability, suggesting excellent potential for the quantitative detection of ALV-J in clinical applications.