A bio-nano-engineered platform fabricated from cerium oxide-carbon nanoparticles stabilized with chitosan for label-free sensing of a lung cancer biomarker†

Herein, we report a label-free cancer biosensor designed for carcinoembryonic antigen (CEA) detection using a nanohybrid comprising CeO₂ nanoparticles, carbon nanoparticles (CNPs), and chitosan (Ch). CeO₂ nanoparticles were prepared using a simple green synthesis process. A thin film of the CeO₂-CNPs-Ch nanohybrid was formed on indium tin oxide (ITO)-coated glass plates that endowed a high surface area, excellent stability, and good adsorption for the efficient loading of CEA antibodies. Quantitative and selective determination of CEA antigen was achieved by immobilizing monoclonal CEA antibodies (anti-CEA) on the CeO₂-CNPs-Ch/ITO platform. The electrochemical response of the anti-CEA/CeO₂-CNPs-Ch/ITO immunoelectrode was evaluated in a label-free immunoassay format using differential pulse voltammetry (DPV). The response studies of immunoelectrodes indicated wider linearity with respect to the CEA concentration in the range of 0.05–100 ng mL⁻¹. The electrochemical cancer biosensor exhibited a higher sensitivity of 22.40 μA cm⁻² per decade change in concentration along with storage stability for up to 35 days. The limit of detection (LOD) was 0.037 ng mL⁻¹. Furthermore, this cancer biosensor exhibited good specificity and reproducibility. Thus, the proposed CeO₂-CNPs-Ch nanocomposite-based platform provides an efficient method for the analysis of other antigen–antibody interactions and biomolecule detection. The efficacy of the anti-CEA/CeO₂-CNPs-Ch/ITO immunoelectrode was further examined by measuring CEA levels in human serum.