Portable Capillary-Microplasma Optical Emission Spectrometer: Gold-Labeled and Silver-Stained Signal Amplification for Carcinoembryonic Antigen Detection

Signal amplification techniques based on catalytic silver deposition on immunogold labels have been used for immunoassays. However, conventional instruments often suffer from limitations in point-of-care testing due to their bulky size, high cost, and complex operation. We herein designed an integrated, portable 3D-printed device by integrating capillary liquid electrode glow discharge (CLEGD) with optical emission spectrometer (OES) for the sensitive determination of carcinoembryonic antigen (CEA) in tiny samples. Without the need for additional devices, the sample solution is automatically drawn into the discharge chamber under the action of capillary force and applied high voltage; Ag(I) in the analyte is atomized and excited in the discharge plasma, resulting in Ag atomic emission lines at 328.1 nm. The system enables the detection of 10¹–10⁶ ng mL^–1 Ag(I) and further quantification of carcinoembryonic antigen concentration. Under optimized conditions, the compact equipment achieves CEA detection comparable to that of ICP-OES, with a linear range of 1–500 ng mL^–1 and a limit of detection as low as 0.9 ng mL^–1.