NIR-Thiol dinitrobenzenesulfonate has both absorption and emission in the NIR region. It is capable of imaging endogenously produced thiol in living cells and mice.

NIR-Thiol dinitrobenzenesulfonate is highly selective to typical small molecular weight biological thiols (Cys, Hcy, and GSH) over other biorelevant species, such as Phe, Gly, Arg, Lys, Tyr, Leu, glucose, Ser, and Val. The sensor NIR-Thiol dinitrobenzenesulfonate is incubated with living HeLa or Bel 7702 cells, and bright fluorescence is observed. NIR-Thiol dinitrobenzenesulfonate has some prominent features, including NIR absorption and emission, rapid response, high sensitivity, excellent selectivity, good cell membrane permeability, and low cytotoxicity.

A different amount (0, 20, 40, or 160 nmol) of NIR-Thiol dinitrobenzenesulfonate is injected into the i.p cavity of mice. Strong fluorescence is noted for the mice injected with 20 nmol of NIR-Thiol dinitrobenzenesulfonate, whereas almost no fluorescence is observed in the control mice. In addition, the mice injected with a higher amount (40 or 160 nmol) of NIR-Thiol dinitrobenzenesulfonate provides brighter fluorescence. A very large signal-to-noise contrast ratio (ca. 700-fold enhancement) is observed for the mice injected with 20 nmol of NIR-Thiol dinitrobenzenesulfonate. In addition, the signal-to-noise contrast ratio jumped to ca. 2900- or 7400-fold enhancement when the mice are injected with 40 or 160 nmol of NIR-Thiol dinitrobenzenesulfonate, respectively.