Sandwich-type electrochemical immunosensor based on CuFe2O4-Pd for cardiac troponin I detection

A sandwich-type electrochemical immunosensor was designed by highly efficient catalytic cycle amplification strategy of CuFe 2 O 4 -Pd for sensitive detection of cardiac troponin I. CuFe 2 O 4 with coupled variable valence metal elements exhibited favorable catalytic performance through bidirectional cycling of Fe 2+ /Fe 3+ and Cu + /Cu 2+ redox pairs. More importantly, Cu + acted as the intermediate product of the catalytic reaction, promoted the regeneration of Fe 2+ 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 CuFe 2 O 4 (CuFe 2 O 4 -NH 2 ) served as electrochemical mediators to capture labeled antibodies (Ab 2 ), and also as co-catalysts of CuFe 2 O 4 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. Graphical abstract