Graphene oxide-integrated hydrogel upconversion sensor for ciprofloxacin detection in aquatic products

A GO integrated hydrogel UCNP sensor for ciprofloxacin detection. • Aptamer-functionalized UCNPs provide specific recognition for CIP. • UCNP-GO FRET disruption enables sensitive fluorescence response. • Ciprofloxacin detected at 1.34 × 10 −2  ng mL −1 , lower than most sensors. Ciprofloxacin residues in aquatic products pose significant threats to food safety and public health, yet sensitive and reliable detection in complex matrices remains challenging. Herein, a fluorescence “off-on” hydrogel sensing platform integrating graphene oxide (GO) and aptamer-functionalized upconversion nanoparticles (UCNPs) was developed for the sensitive detection of ciprofloxacin. Aptamer-functionalized UCNPs were embedded into a GO-incorporated hydrogel matrix, wherein GO acted as an efficient fluorescence quencher via fluorescence resonance energy transfer (FRET). In the absence of the target, the upconversion fluorescence was effectively quenched by GO, establishing a low-background “off” state. Upon specific recognition of ciprofloxacin by the aptamer, the resulting conformational change disrupted the FRET process, yielding pronounced fluorescence recovery (“on” state). Under optimized conditions, this target-triggered “off-on” switching strategy exhibited a good linear relationship over 0.1–100 ng mL −1 , with a detection limit of 1.34 × 10 −2  ng mL −1 . The integrated design combines aptamer-based target recognition, GO-mediated fluorescence quenching, and hydrogel-assisted probe confinement within a single sensing platform. The platform also demonstrated good selectivity toward ciprofloxacin. Satisfactory recoveries of 88.85%–97.72% were obtained in spiked aquatic product samples, showing good agreement with high-performance liquid chromatography (HPLC) analysis. This work provides a sensitive and practical strategy for antibiotic residue monitoring and holds great promise for food safety assurance in complex matrices. Download: Download high-res image (133KB) Download: Download full-size image