Highly sensitive fluorometric determination of oxytetracycline based on carbon dots and Fe3O4 MNPs

In this paper, a novel, selective and eco-friendly biosensor has been fabricated and applied for sensitive detection of antibiotic oxytetracycline (OTC). This fluorescent biosensor was based on carbon quantum dots (CDs), H 2 O 2 and Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 MNPs). Herein, we firstly demonstrated that the fluorescence of CDs decreased apparently in the presence of OTC, H 2 O 2 and Fe 3 O 4 MNPs. The fluorescence quenching of CDs not only is caused by the hydroxyl radical produced from the Fenton reaction and complexation of Fe 3 O 4 MNPs with OTC, but also might be related to the inner filter effect (IFE) between CDs and OTC, which improved the selectivity and sensitivity of the fabricated biosensor. Under the optimal experiment conditions, the relative fluorescence intensity of the CDs decreased linearly with the increasing concentration of OTC from 25   nM to 1.75   μM. The detection limit of the fabricated biosensor on OTC was 9.5   nM at a signal-to-noise ratio of 3. Compared with other current protocols, the method described here displayed a few advantages including simplicity, low cost and rapid detection. The precision and reproducibility of the proposed sensor were also acceptable Significantly, the practicality of this sensitive sensor for OTC detection in drugs was further validated, revealing the advantages of high simplicity, sensitivity and selectivity. Hence, the developed biosensor might provide a useful and practical tool for OTC determination and related food safety analysis and clinical diagnosis.