A water-soluble NIR fluorescent probe capable of rapid response and selective detection of hydrogen sulfide in food samples and living cells.

DDAO (1,3-Dichloro-7-hydroxy-9,9-dimethyl-2(9H)-acridone) is a near-infrared (NIR) fluorophore that has received increasing attention in recent years, exhibiting near-infrared emission at 658 nm, low pKa (∼5.0), good water solubility and high quantum yield (Φ = 0.39). The reported DDAO-based fluorescent probes can be applied to biological imaging ofenzymes and other substances in vivo with high sensitivity and selectivity. Herein, using -OCN as the detection group, a novel NIR HS fluorescent probe DDAO-CN based on DDAO was designed and synthesized. In PBS buffer (10 mM, pH 7.4), probe DDAO-CN displayed specific selection, short response time (within 10 s) and low detection limit (4.3 nM) towards to HS under the catalysis of CTAB. At the same time, the probe is able to sense HS gas produced by food spoilage via the fluorescent test strip loaded with DDAO-CN. Moreover, since the probe has optimal pH range (6.0-9.0), it has been successfully used for bioimaging HS in the HeLa cells with low cytotoxicity.