A highly sensitive electrochemical sensor based on poly(alizarin red)/gold nanoflowers/molybdenum disulfide composite for the detection of methotrexate.

A sensitive electrochemical sensor for the detection of methotrexate (MTX), a widely used anticancer and anti‑autoimmune drug, was constructed. MTX monitoring is of great significance for reducing toxic side effects and guaranteeing clinical medication safety. The sensor was based on a glassy carbon electrode (GCE) modified with a nanocomposite of molybdenum disulfide (MoS2) nanosheets loaded with gold gold nanoflowers (AuNFs), followed by the electrochemical polymerization of alizarin red (AR) to form a stable polymeric film (PAR) on its surface. The MoS2 nanosheets were prepared via liquid-phase exfoliation, and the AuNPs were deposited onto them via electrodeposition. The morphology of the modified electrode (PAR/Au@MoS2/GCE) was characterized by scanning electron microscopy (SEM), and its electrochemical properties were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The synergistic effect of the nanocomposite and the conductive polymer significantly enhanced the electrocatalytic activity towards MTX oxidation. Under optimized conditions, the oxidation peak current of MTX at the modified electrode was nearly six times higher than that at a bare GCE. The sensor exhibited a linear response to MTX concentrations ranging from 0.4 to 38.6 µM, with a low detection limit of 0.027µM (S/N = 3). The sensor demonstrated excellent reproducibility, stability, and selectivity. Its practical applicability was successfully validated by determining MTX content in commercial tablet formulations with satisfactory recoveries.