Aptamer-based tri-mode sensing for detecting oxytetracycline mediated by SYBR Green I and functionalized Au nanoparticles

Exploiting multi-mode aptamer sensing approaches for target pollutants is urgently required to meet the multi-scene detection requirements and improve the accuracy of detection. Herein, we developed a novel aptamer-based tri-mode sensing for detecting oxytetracycline (OTC). First, OTC can induce the conformational changes of the aptamer, which can promote the formation of duplex structures of the aptamer. Then SYBR Green I (SGI) can embed into the duplex structures of the aptamer to enhance the fluorescence signal. Meanwhile, it can also induce the aggregation of functionalized Au nanoparticles (AuNPs-4MBA) based on the charge neutralization strategy, producing stable colorimetric and Raman signals. Furthermore, we evaluated for the first time the advantage of SGI over salt induced nanoparticles from the perspective of Raman detection. The detection limit for the fluorescence, colorimetric, and Raman mode was 0.074, 5.019, and 0.036 nM, respectively. Moreover, the tri-mode sensing could provide broad detection range with five orders of magnitude (0.1–10000 nM). It also exhibited excellent analytical performance for tap water and honey samples with recoveries of 90.11–119.75% (n = 3). The false-positive results could be effectively avoided through the cross-validation. We expect that aptamer-based tri-mode sensing will provide a potential application for the different application scenarios.