A highly selective and sensitive in vivo fluorosensor for zinc(II) without cytotoxicity

A highly selective and sensitive fluorescent Zn2+ sensor, 2,6-bis(2-hydroxy-benzoic acid hydrazide)-4-methylphenol (1), was designed and synthesized. In aqueous THF (4 : 6 v/v) ligand 1 induces a 2 : 1 complex formation with respect to Zn2+ at physiological pH. This probe features visible light excitation(390 nm) and emission (490 nm) profiles, excellent selectivity responses for Zn2+ over other competing biological metal ions with K-d < 1 pM(2), LOD < 1 ng L-1 and about 680 fold enhancement in fluorescent intensity upon Zn2+ binding. It also exhibits cell permeability and intracellular Zn2+ sensing in A375 human melanoma cancer cell.