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)₃ ²⁺) 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 significant ECL emission. In addition, the porous 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 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 advanced ECL emitters.