Electrochemiluminescence immunosensors based on ECL-RET triggering between Au/g-C₃N₄@Co MOF and PtCu@GO for ultrasensitive detection of nectin-4

This study presents a novel quenching-type electrochemiluminescence (ECL) immunosensor for the ultrasensitive detection of nectin-4 based on ECL resonance energy transfer (ECL-RET). In this protocol, gold nanoparticle-modified graphitic carbon nitride/cobalt metal-organic framework (Au/g-C 3 N 4 @Co MOF) was prepared as the signal amplification unit, exhibiting highly enhanced ECL emission in the presence of K 2 S 2 O 8 as a co-reactant to generate the “signal on” state. Specifically, the Co MOF component, with its abundant active sites, served as an efficient co-reaction accelerator by catalyzing the generation of reactive oxygen species. Moreover, Au nanoparticles facilitated electron transfer while providing abundant binding sites for antibody immobilization. Platinum-copper alloy-decorated graphene oxide (PtCu@GO) was used as the energy acceptor, achieving efficient ECL-RET quenching via spectral overlap and producing a remarkable reduction in ECL for the “signal off” state. Based on the sandwich immunoassay format, the target nectin-4 formed a luminophore-antigen-quencher complex, leading to a concentration-dependent ECL drop. The proposed immunosensor exhibited excellent analytical performance with a wide linear range from 1 × 10⁻ 5 to 100 ng/mL and a low detection limit of 3.2 × 10 − 4 pg mL −1 (S/ N = 3), along with outstanding stability, reproducibility, and resistance to interference. This strategy might provide a promising alternative for early screening and dynamic monitoring of bladder cancer in clinical diagnostics.