An inner filter effect-based near-infrared probe for the ultrasensitive detection of tetracyclines and quinolones

Antibiotics play important roles in the treatment and prevention of bacterial infections. However, the over-use of antibiotics can lead to a lot of adverse side-effects like nerve damage, anaphylaxis and drug tolerance. Herein, we report an inner filter effect (IFE)-based near-infrared (NIR) fluorescent probe for highly sensitive and selective detection of tetracyclines (TCs) and quinolones (QNs), of which being the most frequently applied antibiotics. NIR emissive carbon-dots (NIR-CDs) that displayed broad excitation range, stable and strong emission were selected as label-free fluorophores. In the presence of TCs or QNs, efficient IFE from CDs to the two types of antibiotics occurred because of the good spectrum overlap between the ultraviolet absorption of TCs/QNs and the excitation of NIR-CDs. As a result, fluorescence emission of the NIR-CDs was obviously quenched, and this builds the foundation of TCs and QNs quantification. The probe provides linear detection ranges, i.e. 1-80 nM and 0.01-0.2 mu M for oxytetracycline (OTC, an example for TCs) and norfloxacin (NOR, an example for QNs) with detection limits of 0.5 nM and 6.3 nM, respectively. To the best of our knowledge, this is the first report on NIR fluorescent probe for antibiotics assay. Moreover, the probe has been demonstrated to be very robust, and was successfully adopted for the determination of OTC and NOR in milk samples.