Electrochemical immunosensor based on sea urchin-like PdAg and Au NPs/N-C@CNTs for ultrasensitive detection of CEA

Carcinoembryonic antigen (CEA), a clinically critical tumor biomarker, enables early cancer screening and diagnosis. Here, we describe a sandwich-structured electrochemical immunosensing platform enabling supersensitive CEA quantification, leveraging synergistic signal amplification by sea urchin-like PdAg nanostructures and Au NPs/N-C@CNTs substrates. The urchin-like morphology of PdAg endows the material additional catalytic active sites for hydrogen peroxide reduction, which has remarkable electrochemical performance. Moreover, PdAg with superior biocompatibility can effectively immobilize the secondary antibody. Polydopamine-coated carbon nanotubes are carbonized to yield nitrogen-doped carbon nanotubes (N-C@CNTs), which are bound to gold nanoparticles (Au NPs) via stable AuN bonds, thereby facilitating the subsequent binding of primary antibodies to the Au NPs. Optimized assays demonstrated a broad dynamic range (50 fg mL⁻¹–100 ng mL⁻¹) with low detection limits (1.04 fg mL⁻¹, S/N = 3), coupled with exceptional reproducibility, selectivity, and stability. This platform holds significant promise for the screening of early-stage tumor biomarkers.