2-HPTP, a novel thiazolo [4, 5-b] pyridine-based Zn2+ selective fluorescent probe has been synthesized and investigated. This probe exhibited a high selectivity towards Zn2+ over other biologically essential cations such as Na+, K+, Ca2+, or Mg2+. 2-HPTP formed a 1:1 complex with Zn2+ and showed a fluorescent enhancement with a long emission wavelength red-shift (85 nm) upon complex formation with Zn2+. The detection limit and association constant were calculated as 3.48 × 10-7 M and 2.40 × 106 M-1 by a fluorescence titration experiment. Furthermore, the live cell imaging experiment showed that 2-HPTP was membrane permeable and photostable, and hence, could be used to monitor the concentration changes of intracellular Zn2+. The co-staining experiments in the cells demonstrated that 2-HPTP possessed high lysosomal selectivity in living cells. Finally, using the nematode C. elegans as an experimental model, we established that 2-HPTP could be successful in imaging Zn2+ concentration changes in living tissues. Therefore, this molecule should be useful for studies on the biological functions of Zn2+.
Keywords: Fluorescent probe; Lysosomal selectivity; Membrane permeable; Thiazolo[4,5-b]pyridine; Zinc ions.
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