An ultra-fast, NIR, mitochondria-targeted fluorescent probe for sulfur dioxide based on benzopyrylium and its imaging of in living cells

Near-infrared emission, is a significant influencing contributor to the detection and visualization of biomolecules and their associated target analytes by fluorescent probes in vivo. SO2 is a critical component of reactive sulfur species (RSS), playing an irreplaceable influence towards various physiological activities. Excessive inhalation of SO2 can cause irreparable respiratory damage, which also is associated with cardiovascular disease, lung cancer and neurological disorders. In this work, we have rationally developed a NIR (690 nm) fluorescence probe 1 based on benzopyrylium towards SO2. The probe 1 can ratiometricly detect SO2 in ultra-fast time (10 s) and overcome physiological interferences from long-term exposure of biothiols. The probe 1 displayed a large blue-shift of 210 nm along with the obvious fluorescence transition from red to blue. The sensing mechanism was proved to be the p-conjugated system of benzopyrylium unit in probe 1 was broken duo to the active C=C double bond attacked by SO2. Fortunately, the probe 1 can serve as an effective cell-permeable molecular tool to detect and visualize dynamic equilibrium of SO2 in mitochondria of living cells.