Photostable rhodamine 6G-based fluorescent probe for selective and sensitive visualization of dynamic lysosomal pH

RGB probe monitors lysosomal pH in real time. • Biocompatible design suits live-cell imaging. • High sensitivity tracks subtle pH fluctuations. • Enables visualization of lysosome-related pathological processes. Lysosomal pH is tightly linked to diverse cellular physiological and pathological processes, and real-time monitoring of its dynamic shifts is critical for uncovering underlying disease mechanisms. Herein, we developed a new lysosome-targeted pH fluorescent probe RGB with facile synthesis, low cytotoxicity, favorable biocompatibility and efficient cell membrane permeability. Its fluorescence emission intensity exhibits a well-defined linear correlation with environmental pH, enabling rapid, sensitive and quantitative detection of subtle pH changes at the single-lysosome level. RGB functions via a pH-triggered spirolactam ring-opening ICT fluorescence turn-on mechanism, with a measured pKa value of 4.12. Confocal fluorescence imaging results verify that RGB can evaluate oxidative stress-induced cellular damage and dynamically visualize autophagy in live tumor cells. As a robust molecular imaging reagent, RGB holds great promise for subcellular pH detection and basic mechanistic exploration of lysosome-associated disorders. The RGB fluorescent probe provides a simple, biocompatible tool for sensitive real-time monitoring of lysosomal pH. It allows visualization of key cellular events and offers valuable insights for biomedical research on lysosome-related processes. Download: Download high-res image (154KB) Download: Download full-size image