Point-of-Care Detection of Carcinoembryonic Antigen (CEA) Using a Smartphone-Based, Label-Free Electrochemical Immunosensor with Multilayer CuONPs/CNTs/GO on a Disposable Screen-Printed Electrode

In order to identify carcinoembryonic antigen (CEA) in serum samples, an innovative smartphone-based, label-free electrochemical immunosensor was created without the need for additional labels or markers. This technology presents a viable method for on-site cancer diagnostics. The novel smartphone-integrated, label-free immunosensing platform was constructed by nanostructured materials that utilize the layer-by-layer (LBL) assembly technique, allowing for meticulous control over the interface. Detection relies on direct interactions without extra tagging agents, where ordered graphene oxide (GO), carbon nanotubes (CNTs), and copper oxide nanoparticles (CuONPs) were sequentially deposited onto a screen-printed carbon electrode (SPCE), designated as CuONPs/CNTs/GO/SPCE. This significantly amplifies the electrochemical signal, allowing for the detection of low concentrations of target molecules of CEA. The LBL approach enables the precise construction of multi-layered structures on the sensor surface, enhancing their activity and optimizing the electrochemical performance for CEA detection. These nanostructured materials serve as efficient carriers to significantly increase the surface area, conductivity, and structural support for antibody loading, thus improving the sensitivity of detection. The detection of carcinoembryonic antigen (CEA) in this electrochemical immunosensing transducer is based on a decrease in the current response of the [Fe(CN)₆]^3-/4- redox probes, which occurs in proportion to the amount of the immunocomplex formed on the sensor surface. Under the optimized conditions, the immunosensor exhibited good detection of CEA with a linear range of 0.1-5.0 ng mL^-1 and a low detection limit of 0.08 ng mL^-1. This label-free detection approach, based on signal suppression due to immunocomplex formation, is highly sensitive and efficient for measuring CEA levels in serum samples, with higher recovery ranges of 101% to 112%, enabling early cancer diagnosis. The immunosensor was successfully applied to determine CEA in serum samples. This immunosensor has several advantages, including simple fabrication, portability, rapid analysis, high selectivity and sensitivity, and good reproducibility with long-term stability over 21 days. Therefore, it has the potential for point-of-care diagnosis of lung cancer.