Design of a Ratiometric Two-Photon Fluorescent Probe for Dual-Response of Mitochondrial SO2 Derivatives and Viscosity in Cells and in Vivo

The content of sulfur dioxide (SO2) in mitochondria is related to various physiological and pathological processes. The irregular viscosity in mitochondria would result in mitochondria disorders. In this research, a novel ratiometric two-photon fluorescent probe (MBCB) based on carbazole framework has been strategically designed and synthesized for dual-detection of mitochondrial SO2 derivatives and viscosity. The results show that probe MBCB is capable of responding to SO2 derivatives and viscosity using dual-color imaging. MBCB can not only recognize SO2 derivatives utilizing a ratiometric change of fluorescent intensity (I-434( nm)/I-600 (nm)), but also shows a high sensitivity and selectivity for monitoring SO2. On the other hand, the fluorescent intensity ratio (I-567 nm/I-415 (nm)) of MBCB increased with the increment of viscosity and exhibited a good logarithmic linear relationship between the ratio and viscosity (R-2 = 0.99). Satisfactorily, probe MBCB has a good targeting ability to mitochondria and a low cell cytotoxicity, and can be successfully applied to detect HSO3- in living cells and in vivo. Furthermore, the probe can visualize the change of mitochondrial viscosity induced by nystatin.