Dual-mode immunosensor based on Cu-doped Mo₂C nanosheets as signal labels

A method for detecting of Carcinoembryonic antigen(CEA) with improved accuracy is urgently needed. In this work, a dual-mode immunosensor for accurate detection of CEA was fabricated, which used a Cu-doped Mo₂C co-catalyst as an enhancer. Especially, Cu-doped Mo₂C presents a strong different pulse voltammetry (DPV) signal for the electron transfer between Cu²⁺ and Cu⁺, without the addition of K₃[Fe(CN₆)] and other electron transfer mediators, but also shows high electrocatalytic activity towards H₂O₂ redox reactions. So that detection sensitivity of the chronoamperometry (CA) was enhanced. Furthermore, characterized by excellent conductivity, highly ordered pore distribution and great surface area, Ti₃C₂ Mxenes can be effective in promoting electron transfer and loading a large number of AuNPs. In the meantime, AuNPs can also immobilize CEA-Ab₁ through Au-N bonds. Based on a Cu-Mo₂C-Au dual-signal indicator, Ti₃C₂ Mxene-Au as the matrix, the immunsosensor was developed to achieve dual-signal detection of CEA. Satisfactory detection ranges (1 fg.mL^-1 to 40 ng.mL^-1) were obtained with limits of detection of 0.33 fg.ml^-1 (DPV) and 1.67 fg.ml^-1 (CA), respectively. Therefore, the prepared electrochemical immunosensor has good application prospects for the detection of CEA.