Sandwich-type electrochemical immunosensor based on CuFeO-Pd for cardiac troponin I detection.

A sandwich-type electrochemical immunosensor was designed by highly efficient catalytic cycle amplification strategy of CuFeO-Pd for sensitive detection of cardiac troponin I. CuFeO with coupled variable valence metal elements exhibited favorable catalytic performance through bidirectional cycling of Fe/Fe and Cu/Cu redox pairs. More importantly, Cu acted as the intermediate product of the catalytic reaction, promoted the regeneration of Fe and ensured the continuous recycling occurrence of the double redox pairs, and significantly amplified the current signal response. Pd nanoparticles (Pd NPs) loaded on the surface of amino-functionalized CuFeO (CuFeO-NH) served as electrochemical mediators to capture labeled antibodies (Ab), and also as co-catalysts of CuFeO to further enhance the catalytic efficiency, thus improving the sensitivity of the electrochemical immunosensor. Under the optimal experimental conditions, the linear range was 0.001 ~ 100 ng/mL, and the detection limit was 1.91 fg/mL. The electrochemical immunosensor has excellent analytical performance, giving a new impetus for the sensitive detection of cTnI.