A ratiometric two-photon fluorescent probe for imaging hydrogen sulfide in lysosomes

Hydrogen sulfide (H₂S) is a kind of gaseous signalling molecule that plays pivotal role in various biological processes. So far, it is still a challenge to develop convenient and reliable methods for H₂S detection in lysosomes. Herein, we developed a novel ratiometric two-photon fluorescent probe LR-H₂S for imaging H₂S in lysosomes. Upon the addition of H₂S (using Na₂S as a donor) to LR-H₂S in buffer solution, the azide group is reduced to amino group and subsequently the carbamate ester is cleaved by 1,6-elimination, resulting in a fluorescence emission increase at 541nm and a concomitant emission decrease at 475nm. Under two-photon excitation of 840nm, an 80-fold fluorescence ratio (F₅₄₁/F₄₇₅) enhancement was observed with a wide linear range of 25-2500μM. The detection limit was calculated to be 0.70μM based on 3σ/k method, indicating that the probe can detect H₂S with a high sensitivity. The probe also shows excellent selectivity toward H₂S among other biological interference species and features with low cytotoxicity and favorable two-photon properties. Furthermore, LR-H₂S can easily localize in lysosomes and vividly illuminate endogenous/exogenous H₂S level and distribution in lysosomes of living SGC-7901 cells.