New Fluorescent Dye for the Detection of Zn in Living Cells and Fixed Sections of the Rat Pancreas.

We report the synthesis and characterization of a new 4-methoxyphenyl-2,2'-bipyridine-based ligand, such as 12, bearing dipicolylaminomethyl core as a receptor unit, as a probe for the fluorescence "turn-on" detection of Zn. Thus, in the presence of Zn the probe 12 exhibited a fluorescence enhancement with a Stokes shift of ~ 180 nm and photoluminescence quantum yields value of ~ 1.0. In addition, 12 exhibited higher binding constant for Zn (~ 2 × 10 M) with the LOD reaching the nanomolar level (~ 0.1 × 10 M) compare to the previously reported probe 1. The stoichiometry and structure of the [Zn(12)] and [Zn(1)] complexes were supported by XRD analysis, DFT calculations and H NMR experiments. It was postulated that, as a result of binding of Zn, the sample exhibited a bright "on" state via the PET-ICT processes. Molecular docking studies and confocal fluorescence microscopy experiments demonstrated that the probe 12 could be used for the fluorescence detection of Zn not only in artificially enriched with zinc salts live cells, but also in fixed tissues with cations are in a bound state. The high binding constant of compound 12 to Zn cation allows it to be used for the accurate localization of pancreatic beta cells (islets of Langerhans).