Electrochemical sensor based on α-Fe₂O₃/rGO core-enhanced carbon interfaces for ultra-sensitive metronidazole detection

In this work, we describe the creation of a new magneto-electrochemical biosensor that detects metronidazole (MTZ), an antibiotic that is frequently used to treat anaerobic bacterial and protozoal infections, with extreme sensitivity. The sensor platform is engineered by integrating α-Fe₂O₃ magnetic core nanoparticles with reduced graphene oxide (rGO) to fabricate a core-enhanced carbon electrode (α-Fe₂O₃/rGO@CE). The synergistic combination of α-Fe₂O₃ and rGO significantly enhances the electrocatalytic activity, electron transfer rate, and surface area of the sensing interface. Using X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM), structural and morphological characterizations were carried out to verify the uniform distribution of spherical α-Fe₂O₃ nanoparticles (~ 25 nm) anchored on rGO nanosheets. Electrochemical performance was systematically investigated through cyclic voltammetry (CV) and Differential Pulse voltammetry (DPV). When compared to the unmodified Counter Electrode (CE) (-0.65 V against Ag/AgCl), the suggested biosensor showed a notable change in the metronidazole reduction peak to a higher positive potential (-0.4 V vs. Ag/AgCl), suggesting superior catalytic efficiency. With a remarkable limit of identification (LOD) of 2.80 × 10⁻⁶ M and a limit of quantization (LOQ) of 8.0 × 10⁻⁶ M, a broad linear detection range of 8.0 × 10⁻⁶ to 1.0 × 10⁻⁵ M was attained. The sensor was effectively used for the quantitative measurement of metronidazole in medication and in human urine samples (collected from Mangalore Medical Centre with informed consent obtained from the respective patients, ensuring ethical compliance for clinical analysis) due to its exceptional sensitivity, stability, and reproducibility. This study demonstrates how α-FeO₃/rGO hybrid nanomaterials can be used to create effective magneto-electrochemical biosensors for use in clinical and pharmaceutical diagnostic settings.