A NIR fluorescent probe for the rapid detection of Hg2+ in living cells and in vivo mice imaging

A near-infrared fluorescent probe NIR-Hg, for the detection of Hg2+ ion, has been synthesized directly by condensing Changsha dye with 4-Phenyl-3-thiosemicarbazide and the structure has fully characterized by (HNMR)-H-1, (CNMR)-C-13, and ESI-MS. The probe has been designed on the basis of the reaction that Hg2+ ion promotes thiosemicarbazide to oxazole in aqueous media and had been induced to produce turn-on fluorescence via an irreversible spirolactam ring-opening process. The probe NIR-Hg has exhibited fast response (1 min), high sensitivity with 44-fold fluorescence intensity enhancement under six equivalent amounts of Hg2+ added, high selectivity over other related metal ions and a low detection limit of 5.8 x 10(-8) M in the phosphate buffer. The linear response range covers the concentration of Hg2+ from 5 x 10(-7) to 5 x 10(-6) M. In addition, the probe has good cell-membrane permeability, which is suitable for fluorescence imaging for Hg2+ in living cells and in vivo mice.