Oxygen vacancy-enhanced ZrO2/ERGO nanocomposite via one-step co-deposition for precision electrochemical detection of methotrexate

The usage of antineoplastic drugs and immunosuppressants, represented by methotrexate (MTX), has been increasing. However, their administration is characterized by significant inter-individual variability, often leading to ineffective treatment or severe adverse reactions, necessitating therapeutic drug monitoring (TDM). This study proposes a fabrication strategy for an electrochemical sensor, involving the electroreduction of graphene oxide (GO) followed by the deposition of zirconium dioxide nanoparticles (ZrO 2 NPs) to construct a ZrO 2 -decorated electrochemically reduced graphene oxide-modified glassy carbon electrode (ZrO 2 -ERGO/GCE). The developed electrochemical sensor was employed to detect MTX in phosphate-buffered saline (PBS) and diluted calf serum simulated samples. The ZrO 2 -ERGO/GCE sensor exhibited two segments of good linearity within a wide concentration range of 1 μmol/L - 600 μmol/L (with R 2 values of 0.9954 and 0.9936, respectively)， with a sensitivity of 7.09 μA/(μM·cm 2 ) and a low detection limit of 7.72 nmol/L. The platform achieved high sensitivity, a low detection limit, wide linear range, excellent reproducibility, long-term stability, and robust anti-interference capability against common biological species, demonstrating its promising potential for clinical TDM applications.