Label-free baseline-calibrated electrochemical immunosensor for carcinoembryonic antigen detection using...

Early cancer diagnosis is vital for improving patient survival. The present work uses a novel and label-free baseline calibrated electrochemical immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The sensor platform was constructed on a glassy carbon electrode (GCE) modified with electro-synthesized silver nanoparticles (e-AgNPs) and carboxyl-functionalized NiFe₂O₄ nanoparticles (cit-NFO-COOH). This nanocomposite enhanced the electrode surface area, conductivity, and antibody immobilization stability. Comprehensive material characterization was performed using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-Ray diffraction analysis (XRD), and dynamic light scattering (DLS), and zeta potential analysis, while electrochemical performance was evaluated via cyclic and differential pulse voltammetry. Optimization studies disclosed that the optimal concentrations for AgNO₃, cit-NFO-COOH, and antibody were 0.05 mM, 1000 mg/L, and 20 µg/mL, respectively. The fabricated immunosensor exhibited a wide linear detection range (0.1 pg/mL to 10 ng/mL) with a linear regression equation of y = 0.2306ln [CEA] + 3.0227 (R² = 0.999) and an exceptionally low detection limit of 0.09 pg/mL. The precision and accuracy of the probe for intraday and interday tests were assessed as mean relative standard deviation (RSD%) and relative error (RE%) with values of 4.1%, 3.0%, 10.2%, and 10.9%, respectively. Also, specificity was tested in the presence of various biologically available biomarkers and biomolecules with absolute mean change of 8.2%. The validation results were confirmed following the Food and Drug Administration (FDA) guidelines for developing sensing platforms in biological media. The high sensitivity and stability of this biosensor highlight its significant potential as a powerful tool for clinical application in cancer biomarker monitoring.