Ti₃C₂T_X MXene/Ag@Fe₃O₄ core-shell nanocomposite-based electrochemical immunosensor for sensitive detection of CA242 in colorectal cancer

In this study, a novel and sensitive electrochemical immunosensor platform was developed for the detection of CA242 cancer biomarker. For optimal biosensor performance, the glassy carbon electrode (GCE) was modified with Ti₃C₂TX MXene/Ag@Fe₃O₄ core-shell nanocomposite. MXene provided an efficient substrate for immobilization of the bioreceptor due to its high surface area, efficient electron transfer, active functional groups, and suitable electrocatalytic activity, while Ag@Fe₃O₄ nanoparticles enhanced the electrochemical performance due to their high conductivity and surface energy. The synergy between these two components led to a significant improvement in the electrochemical response of the platform. By immobilizing a CA242-specific antibody on the surface of the modified electrode, the detection of the CA242 antigen was achieved through the formation of an antigen-antibody complex and the disruption of electron transfer involving the standard redox couple [Fe(CN)₆]^3-/4-. The synthesis and structure of the nanocomposite were confirmed by a set of characterization methods, including FE-SEM, EDS, XRD, and FTIR. The proposed immunosensor enabled the detection of CA242 over a wide range of 1 × 10^-6 U/mL to 100 U/mL with high linearity (R² = 0.9987), and LOD and LOQ values were obtained as 0.368 × 10^-6 U/mL and 1.228 × 10^-6 U/mL, respectively. In addition, this platform demonstrated good selectivity against interfering proteins, good reproducibility, and operational sensitivity (28.08 μA/cm²·dec) in complex human plasma samples, and its results were compared and confirmed with the ELISA method. The findings of this study indicate that the developed immunosensor can be used as an efficient tool for the early clinical diagnosis of CA242 and the assessment of cancer prognosis.