A thiazolo[4,5-b]pyridine-based fluorescent probe for detection of zinc ions and application for in vitro and in vivo bioimaging.

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+ .