A novel iridium(III) complex-based ratiometric luminescence probe for monitoring hydrogen sulfide in living cells and zebrafish.

Hydrogen sulfide exhibits crucial functions in many biological and physiological processes. The abnormal levels of HS have been revealed to be associated with numerous human diseases. The majority of existing fluorescent probes toward HS may still need to be improved in terms of single output signal, water solubility, biotoxicity and photostability. The construction of a ratiometric fluorescent probe based on metal complex is one effective strategy for avoiding the mentioned problems for precisely detecting HS. Herein, we report an iridium(III) complex-based ratiometric luminescence probe (Ir-PNBD), which is designed by coupling the 7-nitro-2,1,3-benzoxadiazoles (NBD) to one of the bipyridine ligands of Ir (III) complex luminophore through a piperazition moiety. Ir-PNBD owns high selectivity and sensitivity toward HS, and an excellent ability to target mitochondria. Moreover, Ir-PNBD was further successfully utilized to visualize exogenous and endogenous HS in HeLa cells and zebrafish. Our work offers new opportunities to gain deeper insights into the construction of transition metal complex-based ratiometric luminescent probes and expands their applications in biomedical imaging and disease diagnosis.