Upconversion fluorescence resonance energy transfer-a novel approach for sensitive detection of fluoroquinolones in water samples

A novel homogeneous assay method was put forth for simultaneous sensing of fluoroquinolone derivatives (FQs) in water utilizing the upconversion fluorescence resonance energy transfer (FRET) process based on the competitive reaction between dissolved FQs and labeled AuNPs for FQs Mab connected UCPs. The prepared size-tunable β-NaLuF4:Yb,Er,Gd upconversion phosphors (UCPs) were functionalized with carboxylic acid (COOH-) and monoclonal antibody (Mab, C2F3C2) to act as a donor. The gold nanoparticles (AuNPs) labeled with the corresponding antigen (ciprofloxacin-BSA) take the role of an acceptor. Under optimized conditions, the limit of detections (LODs) for three common FQs, enrofloxacin (ENR), ciprofloxaxin (CIP), and norfloxacin (NOR), were 0.19-0.32 ng/mL based on 3σ. The recoveries were found to be in the range of 73.5-114.5% (normalized value according to the cross-reactivity of Mab) for water samples (tap water, pond water and river water). The proposed approach possesses significant advantages as follows: (i) simple procedure (only one step) without washing and separation steps, and no sample pretreatment other than filtration; (ii) fast liquid-phase kinetics with shortened incubation time; and (iii) high tolerance to various interfering substances. All of which indicated its potentiality as an efficient biosensor towards the monitoring of FQs in aquatic environments.