Synergistic Multieffect Catalytic Amplified Cathodic Electrochemiluminescence Biosensor via Target Binding-Induced Aptamer Conformational Changes for the Ultrasensitive Detection of Synthetic Cathinone

Signal amplification is a powerful approach to increasing the detection sensitivity of electrochemiluminescence (ECL). Here, we developed synergistic multieffect catalytic strategies based on CuCo₂O₄ nanorod combination of Ag NPs as coreaction accelerators to fabricate an efficient covalent organic framework (PTCA-COF)-based ternary ECL biosensor. Concretely, the high redox reversibility of Co³⁺/Co²⁺ and Cu²⁺/Cu⁺ would constantly promote the decomposition of S₂O₈^2- for ECL emission. Meanwhile, the introduction of Ag NPs with excellent electrocatalytic activity further realized multiple amplification of the ECL signal. Furthermore, the good hydrogen evolution reaction (HER) ability of Ag@CuCo₂O₄ nanorods could accelerate the proton transmission rate of the system to amplify ECL behavior. In the presence of the target synthetic cathinone 4-chloroethcathinone (4-CEC) as the quenching ECL signal-response probe, the Ferrocene (Fc)-labeled aptamer folded into the conformationally limited stem-loop structure, bringing Fc near the ECL luminophore and resulting in quenched ECL emission. The quenching effect was connected with target-induced aptamer conformational changes and consequently reflected the target concentration. Under optimum conditions, the proposed biosensor realized a highly sensitive assay for 4-CEC with a large dynamic range from 1.0 × 10^-12 to 1.0 × 10^-6 g/L and a detection limit as low as 2.5 × 10^-13 g/L. This study integrated multiple amplification strategies for efficient ECL enhancement, which provided a novel approach to constructing highly bioactive and sensitive sensors.