A NIR fluorescent probe for the rapid detection of Hg 2+ in living cells and in vivo mice imaging.

A near-infrared fluorescent probe NIR-Hg, for the detection of Hg ²⁺ ion, has been synthesized directly by condensing Changsha dye with 4-Phenyl-3-thiosemicarbazide and the structure has fully characterized by ¹ HNMR, ¹³ CNMR, and ESI-MS. The probe has been designed on the basis of the reaction that Hg ²⁺ 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 Hg ²⁺ added, high selectivity over other related metal ions and a low detection limit of 5.8 × 10 ^-8 M in the phosphate buffer. The linear response range covers the concentration of Hg ²⁺ from 5 × 10 ^-7 to 5 × 10 ^-6 M. In addition, the probe has good cell-membrane permeability, which is suitable for fluorescence imaging for Hg ²⁺ in living cells and in vivo mice.