Recently, the oxidative behavior of methotrexate (MTX) anticancer drug is highly demanded, due to its side effects on healthy cells, despite being a very challenging task. In this study, we have prepared porous NiO material using sodium sulfate as an electronic disorder reagent by hydrothermal method and found it highly sensitive and selective for the oxidation of MTX. The synthesized NiO nanostructures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. These physical characterizations delineated the porous morphology and cubic crystalline phase of NiO. Different electrochemical approaches have been utilized to determine the MTX concentrations in 0.04 M Britton–Robinson buffer (BRB) at pH 2 using glassy carbon electrode (GCE)-modified with electronically disordered NiO nanostructures. The linear range for MTX using cyclic voltammetry (CV) was found to be from 5 to 30 nM, and the limit of detection (LOD) and limit of quantification (LOQ) were 1.46 nM and 4.86 nM, respectively, whereas the linear range obtained via linear sweep voltammetry (LSV) was estimated as 15–90 nM with LOD and LOQ of 0.819 nM and 2.713 nM, respectively. Additionally, amperometric studies revealed a linear range from 10 to70 nM with LOD and LOQ of 0.1 nM and 1.3 nM, respectively. Importantly, MTX was successfully monitored in pharmaceutical products using the standard recovery method. Thus, the proposed approach for the synthesis of active metal oxide materials could be sued for the determination of other anticancer drugs in real samples and other biomedical applications.

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The successful monitoring of the anticancer drugs using nanostructured materials is very important but very challenging task. Beside this, uniform and ultra-small size of metal oxide nanoparticles is highly needed in order to enhance the catalytic activity which could result into the development of sensitive and selective electrochemical sensors for methotrexate (MTX). For this purpose, we have used a simple approach involving the polyaniline (PANI) as a sacrificing template for the growth of uniform and ultra-small Co3O4 nanoparticles by hydrothermal method. The structure, shape, composition and phase purity were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform Infrared (FTIR) techniques. The average size of Co3O4 nanoparticles was below 50 nm. The cubic crystallography is confirmed for the Co3O4 nanoparticles. The electrochemical properties of PANI assisted Co3O4 nanoparticles for MTX drug was evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in Britton–Robinson buffer (BRB) of pH 3.5. The PANI assisted Co3O4 nanoparticles were found highly sensitive for the MTX drug and exhibited a linear range from 5-75µM of MTX and limit of detection for the modified electrode was estimated 1.98µM. The proposed electrochemical sensor is low cost, simple, highly sensitive and selective towards MTX detection. The synthetic methodology using the conducting polymer as a sacrificing template for the growth of controlled and ultra-small Co3O4 nanoparticles can be utilized for the wide range of electrochemical applications.