Synergistic coordination-driven ratiometric fluorescence detection of the anthrax biomarker dipicolinic acid

2,6-Dipicolinic acid (DPA) is a unique biomarker of <i>Bacillus anthracis</i>, and the development of a simple, rapid, sensitive, and timely detection method for DPA plays a crucial role in preventing anthrax infection. In this study, a novel ratiometric fluorescent nanoprobe was developed for the stable detection of DPA. This design is based on synergistic coordination of a tribipyridine derivative and ZIF-8 with Zn²⁺ to generate a strong and stable reference fluorescence signal. Subsequently, the carboxyl-functionalized terpyridine moiety acts as a molecular pincer, tightly chelating rare-earth ions to complete the construction of the sophisticated Tpy@ZIF-8/Eu³⁺ probe. The Tpy@ZIF-8/Eu³⁺ nanoprobe serves as a multicolor ratiometric fluorescence sensing platform capable of detecting trace amounts of DPA in both aqueous media and complex environments. The sensing system displayed a linear response to DPA over a broad range of 0-60 μM with a low detection limit of 37.55 nM. Importantly, the integration of Tpy@ZIF-8/Eu³⁺-based test strips with a smartphone facilitates sensitive, real-time, and visually accessible detection of DPA.