A chiral electrochemical sensor based on β-CD/Ce-doped Cu-MOF/MWCNTs-COOH for enantioselective recognition and detection of levofloxacin.

BACKGROUND

Chirality plays a critical role in drug efficacy and environmental safety. The antibacterial activity of ofloxacin resides almost exclusively in its S-enantiomer (levofloxacin, LEV), while the R-enantiomer contributes little to therapeutic effects but may pose unnecessary risks. Rapid and reliable methods for enantioselective determination of ofloxacin enantiomers are therefore essential for pharmaceutical quality control, food safety monitoring, and environmental analysis. However, existing electrochemical sensors often suffer from limited enantioselectivity and insufficient sensitivity. To address this challenge, a novel enantioselective electrochemical platform is developed.

RESULTS

A β-cyclodextrin/cerium-doped copper metal-organic framework/carboxylated multi-walled carbon nanotube composite (β-CD/Ce-doped Cu-MOF/MWCNTs-COOH) was fabricated on a glassy carbon electrode. The sensor achieves discrimination of ofloxacin enantiomers with an IL/ID ratio of 3.39. DFT calculations at pH 4.0 reveal that β-CD binds LEV with higher adsorption energy (-63.8 kJ/mol) than DEX (-58.3 kJ/mol), confirming the superior response for LEV originates from stereospecific inclusion. Quantitative analysis of LEV shows two linear ranges (0.03-1 μM and 1-10 μM) with a low detection limit of 0.01 μM. The sensor also enables accurate determination of LEV percentage in enantiomer mixtures across 0-100%. Excellent selectivity against common interferents, good reproducibility (RSD = 0.98%), repeatability (RSD = 1.26%), and long-term stability (95.2% retention after 21 days) are demonstrated. Practical applicability is validated by detecting LEV in commercial eye drops, honey, and tap water with satisfactory recoveries (96.0-108.0%).

SIGNIFICANCE AND NOVELTY: This work presents the first application of Ce-doped Cu-MOF/β-CD/MWCNTs-COOH composites for the enantioselective electrochemical sensing of ofloxacin, a chiral fluoroquinolone antibiotic. The synergistic combination of high conductivity, abundant catalytic sites, and stereospecific host-guest recognition provides a generalizable strategy for high-performance enantioselective sensing, with promising applications in pharmaceutical, food, and environmental analysis.