An "on-off" electrochemiluminescence immunosensor for PIVKA-II detection based on the dual quenching of CeO2-Au-g-C3N4 hybrids by Ag nanocubes-VB2

Herein, we report a novel dual-quenching electrochemiluminescence (ECL) immunosensor for detecting protein induced by vitamin K absence or antagonist-II (PIVKA-II) based on ECL resonance energy transfer (ECL-RET). In this protocol, self-accelerated ECL hybrids of CeO2 and Au nanoparticles functionalized g-C3N4 nanosheets (CeO2-Au-g-C3N4) were prepared, which exhibited high ECL emission in the presence of S2O82- as a coreactant for "signal on" state. Concretely, CeO2 with a reproducible redox couple of Ce3+ and Ce4+ could act as an efficient co-reaction accelerator to generate more oxidizing intermediate (SO4 center dot-) to significantly self-promote the ECL emission of g-C3N4 NSs/S2O82- ECL system. Besides, Au nanoparticles not only accelerated electron transfer in the ECL process, but also provided massive active sites for biomolecules immobilization. The dual quenching labels of Ag nanocubes modified with vitamin B-2 (AgNCs-VB2) were firstly proposed towards g-C3N4 NSs/S2O82- ECL system by ECL-RET, resulting in the remarkable ECL decrease for "signal off" state. Based on the sandwich immunoreaction, the "on-off' PIVKA-II ECL immunosensor gratifyingly possessed excellent detection sensitivity with the linear range of 0.4 pg mL(-1) -10 ng mL(-1) and the low detection limit of 28.46 fg mL(-1) (S/N = 3). This presented strategy might provide a potential alternative tool for PIVKA-II detection in medical research and early clinical diagnostics of hepatocellular carcinoma.