A highly selective fluorescent probe for visualizing hazardous mercury ions in living cells and zebrafish

In recent years, notorious heavy metal mercury pollutants severely threaten both human health and ecological security. Therefore, the development of simple, effective, and reliable fluorescent sensing tools for accurately monitoring mercury ions (Hg²⁺) levels is of great significance. In this work, a coumarin-derived fluorescent probe, named PQT, was designed and synthesized for the highly sensitive and selective detection of Hg²⁺. Upon addition of Hg²⁺, the PQT solution changed from yellow to colorless, accompanied by nearly complete quenching of its intensive fluorescence. More significantly, the quenched fluorescence could be full restored upon subsequent addition of glutathione (GSH). Such fluorescence OFF-ON cycle could be repeated at least five times by alternately adding GSH and Hg²⁺ to the PQT solution. Confocal fluorescent imaging experiments demonstrated that PQT enables real-time visualization of intracellular reversible decomplexation processes between PQT and Hg²⁺ in various living cells. Furthermore, PQT proves to be a potentially powerful tool for investigating Hg²⁺-involved biological processes in zebrafish models. Collectively, these results indicate that PQT can serve as a reliable reversible fluorescent probe for Hg²⁺ in biological systems. This work provides a simple yet effective and reliable fluorescent probe for exploring diverse biological processes involving Hg²⁺ in living organisms.