Mitochondria-targeted and FRET-based fluorescent probe for the imaging of endogenous SO2 in living cells.

[Display omitted] • Using benzopyridine-naphthalimide as a fluorescent platform. • FRET-based response mechanism to pH. • Ratiometric imaging of SO 2 in living cells. • in situ Detection of Cys-induced SO 2 dynamic changes in living cells. Sulfur dioxide (SO 2) is an important signal molecule in living systems, and plays a wide range of physiological functions. Real-time and in situ detection of the dynamic balance of SO 2 in mitochondria is of great significance to in-depth study its biological roles. Herein, we have developed a mitochondria-targeted fluorescent probe Nap-L based on the FRET mechanism to detect SO 2 in living cells. The probe Nap-L employed naphthalimide and positively charged benzopyridine as the donor and acceptor in the FRET system, and emitted green and red fluorescence under excitation. In respond to SO 2 , the nucleophilic addition of bisulfite to benzopyridine and then interrupted the FRET process from naphthalimide to benzopyridine fluorophore, thereby triggering an obvious change in the fluorescence ratio. The probe Nap-L showed high selectivity to SO 2 over the biothiols (Hcy, GSH, Cys) and other biologically related species. Biological experiments suggested that the probe Nap-L mainly distributed in mitochondria, and can be successfully used to detect mitochondrial endogenous SO 2 in living cells. [ABSTRACT FROM AUTHOR]