Electrochemiluminescence immunoassay of cTnI with ruthenium‐based metal covalent organic framework and dual DNAzymes cascade amplification strategy

Currently, metal‐organic frameworks (MOFs) with tunability and covalent organic frameworks (COFs) with high stability are promising nanomaterials for electrochemiluminescence (ECL), while Ru‐based metal covalent organic frameworks (Ru‐MCOFs) have rarely been reported. Herein, an ECL immunosensor based on a strong ECL‐emitting Ru‐MCOF was proposed for the sensitive detection of the cardiac troponin‐I (cTnI). Imine‐linked Ru‐MCOF was prepared as an ECL emitter via solvothermal method using tris(4,4' ‐diamino‐2,2' ‐bipyridine)ruthenium(II) (Ru(dbpy)32+) as a precursor. Compared with monomers, the imine‐linked Ru‐MCOF achieved structural extension through covalent bonds, which not only effectively facilitated the electrochemical activation of the luminophores but also shortened the transmission distance between electrons and co‐reactants, generating dense ECL emission. In addition, the porous framework of Ru‐MCOF provided a microreactor with nanoconfinement effect, which could accelerate the diffusion of co‐reactants into the framework and promote the excitation of internal and external ECL emitters, significantly enhancing the ECL intensity. Considering the excellent ECL performance of Ru‐MCOF, combined with dual DNAzymes‐driven catalytic hairpin cycle amplification, the ECL immunosensor achieved sensitive detection of cTnI with a detection limit as low as 0.42 fg/mL. The proposed highly stable Ru‐MCOF raises a new approach for exploring MCOF‐based luminophores, highlighting the potential of MCOFs in advancing ECL emitters.