Electrochemical aptamer sensor based on AgNPs@PDANSs and "sandwich" structure guidance for the detection of tobramycin in water samples.

In this study, an ultrasensitive detection platform for tobramycin (TOB) was developed, featuring a "sandwich" structure guided by AgNCs@PDANSs and Thi-AuNCs@ZnONSs. To address the issue of large background current peak signals in tagless sensors, Thi-AuNCs@ZnONSs composites were synthesized as signal tags. Zinc oxide nanosheets (ZnONSs) served as the loading agent, and AuNCs with the electroactive molecule Thi acted as carriers. Furthermore, AgNPs@PDANSs nanocomposites, possessing excellent electrical conductivity and large specific surface areas, were prepared as substrate materials for the modified electrodes. A "sandwich" structure strategy was also introduced to enhance the accuracy of the electrochemical aptasensor. This strategy, utilizing a dual sequence for target labeling and capture, yielded higher sensitivity and simplified the sensor construction compared to methods employing a single sequence. Under optimal conditions, the detection limit for TOB was established at 1.41 pM, with a detection range of 0.05-5000 nM. The aptasensor was effectively applied in the detection of TOB in tap and lake water, demonstrating outstanding reproducibility, selectivity, and stability. These results may serve as a reference for environmental TOB detection.