Lyso-H 2 S: A Mycophenolic Acid-Derived Probe for Ultra-Low Toxicity, Intracellular H 2 S Detection, and Zebrafish Model Validation.

In several biological processes, H 2 S is known to function as an endogenous gaseous agent. It is very necessary to monitor H 2 S and relevant physiological processes in vivo. Herein, a new type of fluorophore with a reliable leaving group allows for excited-state intramolecular transfer characteristics (ESIPT), inspired by mycophenolic acid. A morpholine ring was connected at the maleimide position of the probe to target the lysosome. Subsequently, the dinitrophenyl group known for a photoinduced electron transfer (PET) effect, was connected to allow for an effective "turn-on" probe Lyso-H 2 S. Lyso-H 2 S demonstrated strong selectivity towards H 2 S, a large Stokes shift (111 nm), and an incredibly low detection limit (41.8 nM). The imaging of endogenous and exogenous H 2 S in living cells (A549 cell line) was successfully achieved because of the specificity and ultra-low toxicity (100 % cell viability at 50 μM concentration of Lyso-H 2 S.) Additionally, Lyso-H 2 S was also employed to visualize the activity of H 2 S in the gallbladder and intestine in a living zebrafish model. This is the first report of a fluorescent probe to track H 2 S sensing in specific organ systems to our knowledge.