Multifunctional Fe3O4 core/Ni–Al layered double hydroxides shell nanospheres as labels for ultrasensitive electrochemical immunoassay of subgroup J of avian leukosis virus

A novel electrochemical immunosensor for ultrasensitive detection of subgroup J of avian leukosis virus (ALVs-J) was designed by using graphene sheets (GS)-layered double hydroxides (LDHs) composites modified electrode with multifunctional Fe 3 O 4 core/Ni–Al LDHs shell (LDHs@Fe 3 O 4 ) nanospheres as labels. At first, the GS-LDHs were used for the immunosensor platform for improving the electronic transmission rate as well as increasing the surface area to capture a large amount of primary antibodies (Ab 1 ). After that, ferrocene (Fc), secondary antibodies (Ab 2 ) and horseradish peroxidase (HRP) multifunctional LDHs@Fe 3 O 4 nanospheres were used as labels with high load amount and good biological activity. Subsequently, in presence of H 2 O 2 , amplified signals were obtained by an electrochemical sandwich immunoassay protocol. To embody the signal amplification property of the protocol, the analytical properties of various immunosensor platform and labels were compared in detail. Under optimal conditions, the reduction peak currents of the electrochemical immunosensor were proportional to the ALVs-J concentration over the range from 10 2.32 to 10 5.50 TCID 50 /mL with a low detection limit (180 TCID 50 /mL, S/N=3). The resulting immunosensor also displayed a good selectivity, reproducibility and stability.