Mitochondrion-targeting near-infrared fluorescent probe for detecting intracellular nanomolar level hydrogen sulfide with high recognition rate.

Hydrogen sulfide (HS) typically plays biphasic biological roles in living organisms with subnormal HS exerting cytoprotective effects such as participating in cardioprotective signaling pathways while HS with higher-than-normal concentrations in localized tissues acting the opposite way such as inhibiting mitochondrial respiration. Such concentration-dependent biological and pathological roles of HS with the wide involvement of mitochondria and the elusive feature of HS definitely highlight the vital significance of fast and precise estimation of the physiological level of HS in specific microenvironments, particularly within cellular mitochondria. In this work, we developed a new type of fluorescent probe (QcyCHO) featured with HS-triggered off-to-on near-infrared (NIR) fluorescence conversion within ~ 10 min, limit of detection (LOD) down to 8.3 nM, and high recognition specificity over other similarly interfering species. The ideal mitochondrion-targeting ability, high recognition specificity over typical interfering substances and other physiologically relevant species, and the ability for mapping intracellular HS in living cells of QcyCHO probe were also unequivocally confirmed, which imply its potential for shedding light on the biology of HS and therapeutic development in HS-associated diseases by identifying the specific physiological stimuli inducing HS production and determining the levels of HS at the location and time of stimulation.