A novel fluorescent probe based on dicyanoisophorone for the detection of tetracycline antibiotics and its application to water samples

Antibiotics play an irreplaceable role in controlling bacterial infections and safeguarding human health. However, the misuse of antibiotics in animal husbandry and aquaculture has caused widespread ecological contamination. Specifically, tetracycline antibiotics (Tetracyclines, TCs), as one of the most prevalent antibiotic residues, pose significant risks to environmental sustainability and food safety. To address this issue, we developed a novel dicyanoisophorone-based fluorescent probe, ( E )-2-(3-(2-(5-formyl-6-hydroxy-2-naphthalenyl)vinyl)-5,5-dimethylcyclohex-2-en-1-yl)malononitrile ( ZHP ), enabling rapid and selective detection of TCs. Notably, ZHP exhibited distinct fluorescence responses toward different TCs: fluorescence quenching upon binding to chlortetracycline (CTE) (detection limit: 9.6 µM) and fluorescence enhancement in the presence of doxycycline (DOX), oxytetracycline (OXY), and tetracycline (TET) (detection limits: 0.23 µM, 0.24 µM, and 0.39 µM). This differential response mechanism, potentially attributed to structural variations among TCs. The probe demonstrated excellent pH tolerance (pH 6 - 12) and high selectivity over 6 common interfering antibiotics. A paper-based colorimetric assay achieved visual TCs detection within 5 seconds, highlighting its field-deployable potential. Furthermore, the probe ZHP was successfully applied to quantify TCs in different water samples with recoveries of 96.33 - 103.00%. This work provides a sensing platform for TCs monitoring, offering critical insights into the design of multifunctional probes for environmental applications.