Eco-friendly synthesis of a porous reduced graphene oxide–polypyrrole–gold nanoparticle hybrid nanocomposite for electrochemical detection of methotrexate using a strip sensor

Chemotherapy is a crucial cancer treatment, but its effectiveness requires precise monitoring of drug concentrations in patients. This study introduces an innovative electrochemical strip sensor design to detect and continuously monitor methotrexate (MTX), a key chemotherapeutic drug. The sensor is crafted through an eco-friendly synthesis process that produces porous reduced graphene oxide (PrGO), which is then integrated with gold nanocomposites and polypyrrole (PPy) to boost the performance of a screen-printed carbon electrode (SPCE). Advanced techniques were employed for detailed characterization of the nanocomposites such as X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and BET analysis. The enhanced sensor exhibited a notable increase in the electrochemical oxidation signals of MTX, attributed to the improved electron transfer at the SPCE/PrGO-PPy-Au electrode interface. Superior electrochemical interfacial properties were well characterized with the techniques of cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry. The sensor demonstrates an efficient electrochemical response toward the detection of MTX with a broad detection range from 130 nM to 1 μM, an impressively low detection limit of 0.4 nM in human serum, and a sensitivity of 24.1 μA μM^-1. This combination highlights its exceptional performance in detecting analytes with high precision and sensitivity. The sensor exhibited a long-term continuous monitoring stability response to monitor the MTX drug in human serum for 4 hours. The sensor's high sensitivity, selectivity, reproducibility, and stability over time emphasize its potential as a valuable tool for the swift on-site testing of anticancer drugs in clinical and environmental settings.