Benzothiazole-Based Fluorescent Sensor for Ratiometric Detection of Zn(II) Ions and Secondary Sensing PPi and Its Applications for Biological Imaging and PPase Catalysis Assays

In this paper, we designed and synthesized three benzothiazole-based fluorescent probes L₁, L₂, and L₃ for zinc ion detection. Among various metal ions, only the zinc ion exhibited fluorescence enhancement at 475 nm accompanied by the blue-shift emission wavelength in HEPES buffer solution containing probes. Through titration experiment, the detection limit of L₁ for zinc ion sensing was calculated to be as low as 7 nM, which showed a high sensitivity. Furthermore, the confocal laser scanning micrographs of HeLa cells demonstrate good cell permeability of probe L₁ and selective detection of zinc ion in living cells. The L₁-Zn²⁺ complex was further used for pyrophosphate (PPi) sensing in HEPES buffer solution, the limit of detection was calculated to be as low as 60 nM. L₁-Zn²⁺ can monitor the enzyme catalyzed degradation process of PPi, thus providing a meaningful way for tracking of zinc ion and pyrophosphate in biological systems.