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.