A reflective microfiber biosensor for monitoring of trace flumequine residues enhanced by europium-incorporated covalent organic framework

A reflective microfiber biosensor with fiber Bragg grating (FBG) is presented for detecting flumequine (Flu) concentration through successive surface modification with polydopamine (PDA) and europium-incorporated covalent organic framework (Eu@COF). The detection mechanism relies on refractive index (RI) changes induced by Flu adsorption, which are monitored by tracking of interference wavelength shifts. Experimental results demonstrate that the sensor exhibits a significant response within a concentration range of 0.1–100 μM, achieving a sensitivity of 0.732 nm/μM in the 0.1–1 μM range with a limit of detection (LOD) of 0.1 μM. Furthermore, the biosensor demonstrates the exceptional specificity for Flu detection among various quinolone antibiotics, while delivering reliable detection in real samples. With the integrated advantages of high sensitivity, superior selectivity, and long-term stability, this sensing platform shows the promising potential for on-site monitoring applications in food safety supervision and veterinary drug residue analysis.