Highly Sensitive Metronidazole Sensor Based on AgNPs/MWCNTs-Modified Acupuncture Needle Electrode with Molecular Imprinting

In this study, a novel molecularly imprinted electrochemical sensor was constructed using an acupuncture needle as the work electrode, enabling highly sensitive quantification of metronidazole. Through electrodeposition, silver nanoparticles and carboxylated multi-walled carbon nanotubes were immobilized onto the acupuncture needle surface, which markedly improved both the electrical conductivity and the electroactive surface area. Subsequently, a molecularly imprinted polymer layer for metronidazole was prepared on the modified electrode surface by cyclic voltammetry electropolymerization using aniline as the functional monomer. The key parameters governing the sensor assembly were systematically tuned to maximize its analytical performance. Electrode morphology and properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical techniques. In optimal conditions, the sensor demonstrated a linear detection range of 0.05 to 1000 μM, showing a detection limit of 0.019 μM for metronidazole. The sensor exhibited satisfactory selectivity, successfully eliminating interference from routine inorganic ions and analogous compounds. Moreover, it delivered outstanding repeatability (RSD = 1.77%) and reproducibility (RSD = 3.58%). Practical applicability was validated by detecting MNZ in spiked milk and urine samples, achieving recoveries between 96.10% and 106.23% with RSD below 6.30%. This work presents a rapid and sensitive approach for MNZ monitoring, holding promise for food safety inspection and clinical analysis.