Atomically Fe‐anchored MOF‐on‐MOF nanozyme with differential signal amplification for ultrasensitive cathodic electrochemiluminescence immunoassay

The successful application of electrochemiluminescence (ECL) in immunoassays for clinical diagnosis requires stable electrodes and high‐efficient ECL signal amplification strategies. Herein, the authors discovered a new class of atomically dispersed peroxidase‐like nanozymes with multiple active sites (CoNi‐MOF@PCN‐224/Fe), which significantly improved the catalytic performance and uncovered the underlying mechanism. Experimental studies and theoretical calculation results revealed that the nanozyme introduced a Fenton‐like reaction into the catalytic system and the crucial synergistic effects of definite active moieties endow CoNi‐MOF@PCN‐224/Fe strong electron‐withdrawing effect and low thermodynamic activation energy toward H(2)O(2). Benefiting from the high peroxidase‐like activity of the hybrid system, the resultant ECL electrode exhibited superior catalytic activity in the luminol‐H(2)O(2) system and resulted in an ≈17‐fold increase in the ECL intensity. In addition, plasmonic Ag/Au core‐satellite nanocubes (Ag/AuNCs) were designed as high‐efficient co‐reactant quenchers to improve the performance of the ECL immunoassay. On the basis of the differential signal amplification strategy (DSAS) proposed, the immunoassay displayed superior detection ability, with a low limit of detection (LOD) of 0.13 pg mL(−1) for prostate‐specific antigen (PSA). The designed atomically anchored MOF‐on‐MOF nanozyme and DSAS strategy provides more possibilities for the ultrasensitive detection of disease markers in clinical diagnosis.