An integrated magnetic/photothermal capillary immunochromatographic assay based on rambutan-like Fe₃O₄@Cu_2-xS@PDA-Au...

Highly sensitive and quantitative detection of tumor markers is critically important for the early diagnosis and treatment of cancers. In this study, we propose a novel magnetic/photothermal dual-sensing capillary immunochromatographic assay (CICA) strategy for the sensitive detection of carcinoembryonic antigen (CEA). To achieve this, we developed a rambutan-like Fe₃O₄@Cu_2-xS@PDA-Au core-shell heterostructure with a high photothermal conversion efficiency of 59.1 % and stable magnetic characteristics through a shell-by-shell method. Under optimal conditions, the dual-mode CICA platform exhibited good linearity within the ranges of 0.5-10 ng mL^-1 and 0.005-2.5 ng mL^-1 for photothermal and magnetic modes, respectively. Notably, leveraging the biosensing system based on the atomic spin-exchange relaxation-free (SERF) effect, the magnetic mode achieved an enhanced sensitivity with a limit of detection as low as 0.0021 ng mL^-1, two orders of magnitude higher than that of the photothermal mode. The complementary detection of dual signals effectively overcomes the limitations of the single-signal mode. These findings provide new insights into the sensitive and quantitative detection of low-abundance CEA analytes, exhibiting enormous potential for the detection of other biomarkers.