Quinoline-Based Fluorescent Probe for Ratiometric Detection of Lysosomal pH

A new pH-responsive fluorescent probe has been reported based on protonation-activable resonance charge transfer. In aqueous solution, probe PQ-Lyso exhibits ratiometric detection of pH changes with a large hypsochromic shift of 76 nm and remarkable changes in the fluorescence intensity ratio (R = F-494 (nm)/F-570 (nm), R/R-0 = 105). Furthermore, PQ-Lyso, which is localized to lysosomes in living cells, can calibrate lysosomal pH using fluorescence ratiometry.