Optimized aptamer-based impedimetric assay for sensitive and selective determination of moxifloxacin

Moxifloxacin (MOX) is a broad-spectrum fluoroquinolone antibiotic used in the treatment of various bacterial infections, including acute exacerbation of chronic bronchitis, community-acquired pneumonia, skin and soft tissue infections, complicated intraabdominal infections, and conjunctivitis. Due to the growing global concern over antibiotic resistance, it is essential to monitor MOX levels in critical cases to ensure therapeutic efficacy and minimize toxicity. Personalized treatment strategies and rapid point-of-care drug monitoring are critical for preventing resistance and optimizing patient outcomes. In this study, an electrochemical aptasensor based on an optimized MOX-specific aptamer (MOX-Opt) was developed for the ultrasensitive and selective detection of MOX. The biosensor was electrochemically characterized using cyclic voltammetry and electrochemical impedance spectroscopy. Under optimized conditions, a linear response was observed between 10¹ and 10⁶ fM, with a limit of detection (LOD) of 3.92 fM. The selectivity of the aptasensor was assessed against structurally related antibiotics, Levofloxacin and Ciprofloxacin, demonstrating high specificity for MOX. To evaluate real-world applicability, MOX was successfully detected in artificial urine, artificial serum, and pharmaceutical formulations (Moxidexa® and Avelox®), achieving LODs of 0.047 fM, 0.50 fM, 6.15 fM, and 0.11 fM, respectively. Relative error studies further confirmed the reliability of the biosensor in complex matrices. To the best of our knowledge, this is the first report on an aptasensor employing an aptamer for MOX detection, achieving femtomolar sensitivity and superior selectivity over related fluoroquinolones. This work underscores the potential of aptamer-based electrochemical sensors in therapeutic drug monitoring and supports their application in clinical diagnostics and point-of-care settings.