AND logic-gate-based Au@MnO2 sensing platform for tetracyclines with fluorescent and colorimetric dual-signal readouts

Tetracyclines (TCs) are the most common antibiotic drugs in the world. However, due to the overuse and difficulty of degradation, TCs pollution is becoming a global threat to aquatic and terrestrial biodiversity. Current methods for detecting TCs mainly rely on fluorescent probes or nanomaterials with enzyme-mimicking catalytic activities, which only provide a single signaling mode and are vulnerable to experimental factors. Herein, this study reports the development of an AND logic-gate-based sensing platform for TCs with fluorescent and colorimetric dual-signal readouts using Au@MnO2 nanoparticles that could be mutually verified for the selective sensing of TCs. It was found that Au@MnO2 nanoparticles could oxidize TC into its oxidation state (oxTC), resulting in significant green fluorescence emission. Meanwhile, the MnO2 shell was etched away, and the released Au core nanoparticles gradually aggregated, with a color change from brown to light blue. As such, we established the fluorescence "turn-on" and colorimetric quantitative relationships towards TC with detection limits of 21.9 and 83.3 nM, respectively. Furthermore, Au@MnO2-based analytical paper devices were prepared and demonstrated successfully for the fluorescent and colorimetric dual-signal readout detection of TC in real samples. This paper sheds light on the on-site detection of tetracycline using paper-based analytical devices and smartphones.