A lysosome targetable versatile fluorescent probe for imaging viscosity and peroxynitrite with different fluorescence signals in living cells

The lysosome, which acts as the cellular recycling centre, is filled with numerous hydrolases that can degrade most cellular macromolecules. The abnormalities of the lysosome are closely associated with diseases, such as Heřmanský-Pudlák syndrome, Griscelli syndrome and Chédiak-Higashi syndrome. Studies have shown that abnormal viscosity and the accumulation of reactive oxygen species (ROS) in the lysosome will disorder the normal function of the lysosome. In this research, a versatile fluorescent probe Lyso-NA has been developed for the multi-channel imaging of lysosomal viscosity and peroxynitrite (ONOO^-). When excited at 550 nm, the Lyso-NA exhibited about a 50-fold increase in fluorescence at 610 nm and also with the increasing viscosity from 1.0 cP to 1410 cP, and about a 3.5-fold increase in fluorescence at 510 nm (excitation at 440 nm) together with the increasing ONOO^-. These satisfactory response properties make it possible to use Lyso-NA to monitor changes in both viscosity and ONOO^- inside the lysosome. To achieve its practical application, it was further demonstrated that Lyso-NA exhibits low cytotoxicity, and good cell permeability, and could be used to monitor lysosomal viscosity and ONOO^- in living cells.