Cost‐Effective and User‐Friendly Pencil Graphite Electrode Immunosensor for Label‐Free Detection of Carcinoembryonic Antigen

We present a novel, cost-effective sensor for carcinoembryonic antigen (CEA) detection utilizing a pencil graphite electrode (PGE) in combination with electrochemical impedance spectroscopy (EIS), which offers high sensitivity and selectivity. Anti-CEA/AuNPs/PGE was successfully illustrated as a label-free impedimetric immunosensor for the detection of CEA. Through EIS, we observed distinct impedance changes upon CEA binding, enabling real-time detection with high reproducibility and low interference from non-target molecules. Due to its satisfying impedimetric response, this new immunosensor demonstrated that it can be used for high-performance detection of CEA with a wide linear range extending from 13.2 to 1 × 10⁵ pg mL^-1, with correlation coefficients (R²) of 0.9923. The PGE's excellent conductive properties and surface stability allowed for the successful detection of CEA at low concentrations, demonstrating a detection limit of 4.4 pg mL^-1, which is competitive with existing, more costly alternatives. The sensor's robust performance in spiked artificial urine samples indicates its potential for practical application in point-of-care cancer diagnostics, especially in resource-limited environments. The developed electrochemical biosensor holds promise for accurately detecting CEA in urine samples, offering a precise technique that could find valuable application in clinical tumor detection.