▎ 摘　　要

An ultrasensitive electrochemiluminescence (ECL) immunosensor for the detection of tetrodotoxin (TTX) is proposed, which are composed of the branched poly-(ethylenimine) (BPEI) functionalized graphene (BGNs)/Fe3O4-Au magnetic capture probes and luminol-capped gold nanocomposites (luminol-AuNPs) as the signal tag. Herein, a typical sandwich immunecomplex was constructed on the glassy carbon electrode. The BGNs/Fe3O4-Au hybrids could efficiently conjugate primary antibody via the Au-S chemical bonds or Au-N chemical bonds and rapidly separate under external magnetic field. The introduction of BPEI to GO could enhance the luminol-ECL intensity. Meanwhile, the multifunctional nanocomposites have been proved with good water-solubility, excellent electron transfer, outstanding stability, etc. The luminescent luminol-AuNPs, a high efficient electrochemiluminescence marker, can be assembled on the second antibody, which can produce the ECL signal to achieve the determination of TTX. This proposed ECL immunosensor with a linear range from 0.01-100ng/mL can be applied in the detection of TTX in real samples with satisfactory results.