A Label-Free Fluorescence Aptasensor for the Detection of Ciprofloxacin in Actual Samples

Ciprofloxacin (CIP) is a third-generation fluoroquinolone antibiotic widely used in veterinary and clinical settings. However, overuse can result in the development of quinolone-resistant pathogens, posing risks to ecosystems and human health. In this work, we developed the fluorescence method for detecting CIP based on FRET (Förster Resonance Energy Transfer) between the fluorescein isothiocyanate (FITC) fluorescent dye and graphene oxide (GO). The aptamer was immobilized on the GO surface through π–π stacking interaction preventing effectively FITC from coming into contact GO to result in strong fluorescence. Upon the addition of CIP, the aptamer combined preferentially to the CIP and leaded to the release of GO, which made the FITC to be close to GO, leading to significant quenching of FITC due to FRET. The fluorescence intensity exhibited a consistent reduction in proportion to the CIP concentrations with 2.99–800 nM. Under the same conditions, the limit of detection was calculated to be 2.99 nM. The sensor can be used for the detection of CIP in serum, urine, and milk with spiked recoveries ranged from 99.65%–100.97% and relative standard deviations ranging from 0.17%–1.49%, which provided a detection tool for food safety and control standards.