A Fluorescent Probe with Large Stokes Shift Based on Benzothiadiazole Scaffolds for Selective Detection of Hg²⁺ in Lysosomes and Its Application in Biological Imaging

Mercury is highly toxic, and appropriate amounts of the mercury-selenium complex can protect plasma. However, when excessive mercury (II) ions (Hg²⁺) are exposed to human skin or ingested directly, it can lead to irreversible accumulation in the body. Therefore, detecting the presence of Hg²⁺ in cells is important. A novel fluorescent probe BTD-Hg-Lyso was designed and constructed based on the intramolecular charge transfer mechanism. Thiotaldehyde could specifically recognize Hg²⁺ so that the probe could produce a fluorescence enhancement effect. In addition, the fluorescent probe BTD-Hg-Lyso exhibited the advantages of large Stokes shift (210 nm) and good selectivity. More importantly, the probe BTD-Hg-Lyso could be used for the determination of Hg²⁺ in cellular lysosomes. BTD-Hg-Lyso was able to image Hg²⁺ in HeLa cells, zebrafish, and tobacco seedlings (rhizome and stem) successfully.