Dual-mode photothermal/chemiluminescence vertical flow assay for sensitive point-of-care detection of carcinoembryonic antigen using Cu2-xAgxS@liposome on a filter membrane

Conventional lateral flow assays based on colorimetry and fluorescence still have shortages in sensitivity and selectivity due to the severe background interference from complex human fluid sample matrices. In this work, Cu_2-xAg_xS nanocrystals with high photothermal conversion efficiency and good peroxidase-like activity were synthesized and applied in the construction of a dual-mode near-infrared-photothermal/chemiluminescence (CL) vertical flow assay of carcinoembryonic antigen (CEA). These two-mode principles showed nearly zero background and the synthesized Cu_2-xAg_xS exhibited a high photothermal conversion efficiency of 75.23%, enabling the luminol-H₂O₂ CL system to have over 4 min of chemiluminescence. By combining filter membrane enrichment, Cu_2-xAg_xS@liposome encapsulation amplification, and nanozyme catalysis, a dual-mode photothermal/CL portable assay was constructed for sensitive and accurate detection of CEA in serum, with linear ranges of 0.02–40 and 0.001–30 ng mL⁻¹, and detection limits of 0.0023 and 0.00029 ng mL⁻¹, respectively. Furthermore, a smartphone application and a 3D printing device were combined for point-of-care testing. This assay can be completed within 20 min, with simple operation and no need for large instruments. It exhibited good sensitivity, selectivity, and stability, and is expected to be used in early diagnosis and prevention of relevant diseases in resource-limited areas.