Reactive oxygen species-triggered off-on fluorescence donor for imaging hydrogen sulfide delivery in living cells

Hydrogen sulfide (H₂S), an important gasotransmitter, can mediate a variety of pathophysiological processes, and H₂S-based donors have been intensively explored for the therapy of cardiovascular injury, nerve damage and intestinal disorders. However, most of the H₂S donors are not capable of simultaneously real-time tracking intracellular H₂S delivery, which limits their biological application for elucidating the specific function of H₂S. Herein we develop the first reactive oxygen species (ROS)-triggered off-on fluorescence H₂S donor (NAB) by incorporating ROS-responsive arylboronate into a fluorophore through thiocarbamate. The donor NAB can release carbonyl sulfide (COS) and the fluorophore with a fluorescence off-on response via a ROS-triggered self-immolative reaction, and then COS is quickly converted to H₂S by the ubiquitous carbonic anhydrase. This dual function makes NAB suitable for not only in situ and real-time monitoring of the intracellular H₂S release but also rescuing RAW264.7 cells from the hazardous oxidative environment under the stimulation of phorbol-12-myristate-13-acetate, revealing the possible potential of NAB as a therapeutic prodrug with the fluorescence imaging capacity.