Ni-Metal–Organic Framework/β-Cyclodextrin/Functionalized Carbon Black Nanomaterials for Enhanced Electrochemical Sensing of Metronidazole in Environmental and Clinical Samples

Metronidazole (MAT) is a commonly used nitroimidazole antibiotic that is increasingly detected in water bodies due to extensive medical use and incomplete metabolic breakdown. Its persistence and bioactivity may contribute to antimicrobial resistance and potential neurological and reproductive side effects, making its monitoring in environmental and clinical samples essential. In this work, we developed an electrochemical sensor based on a composite of nickel metal–organic framework (Ni-MOF), β-cyclodextrin (β-CD), and functionalized carbon black (f-CB) for the sensitive detection of MAT. The Ni-MOF provides redox-active sites, β-CD improves molecular affinity toward MAT, and f-CB enhances conductivity and electron transfer. Structural analyses (XRD, FTIR, Raman, SEM, and XPS) confirmed the successful formation of the composite, while electrochemical studies (EIS, CV, and DPV) demonstrated an improved charge transfer and catalytic response. The modified electrode Ni-MOF/β-CD/f-CB exhibited a wide linear detection range (1–510 and 560–1210 μM) with a low detection limit of 13.6 nM. The sensor also performed effectively in real samples, achieving recovery values of ∼98.5% in tap water, river water, and human urine. The simplicity of fabrication, low cost, and strong analytical performance suggest that this sensing platform is suitable for routine monitoring of MAT in environmental- and healthcare-related settings.