A fluorescent aptasensor based on ZIF-8 @PdNCs and DNA-AgNCs for tobramycin detection in milk

A novel ratiometric fluorescent aptasensor was constructed utilizing ZIF-8-encapsulated palladium nanoclusters (ZIF-8 @PdNCs) as reference signals that emit blue fluorescence, and DNA-templated silver nanoclusters (DNA-AgNCs) containing aptamer fragments as response signals that emit yellow fluorescence. In the absence of tobramycin (TOB), the aptamers of DNA-AgNCs bind to ZIF-8 @PdNCs via π-π stacking, resulting in the quenching of the fluorescent signals of DNA-AgNCs. The presence of TOB can weaken the π-π stacking interaction between ZIF-8 @PdNCs and single-stranded DNA (ssDNA) aptamers, which can lead to the desorption of DNA-AgNCs from the surface of ZIF-8 @PdNCs. As a result, the fluorescence signals of DNA-AgNCs are restored. The developed fluorescent sensor exhibits a linear range between 50 nM and 500 nM, with a limit of detection determined to be 15.3 nM. Exposure to UV light triggers a visible change in fluorescent color from blue to yellow as the concentration of TOB increases. To build a miniaturized and portable device for detecting TOB concentration, we employed 3D printing technology to create an RGB (Red Green Blue) instrument recognition framework with ultraviolet lamp beads and RGB recognition components. The RGB standard curve and programming in Python can be used to directly read the TOB concentration.