A Rhodol-Based Fluorescent Probe With Spirocyclic Ring Open-Close Tunability for Sensitive Tracking of Lysosomal...

The polarity changes of subcellular organelles have a profound influence on numerous pathological and biological processes, thus the accurate sensing of polarity changes in lysosomes, an important subcellular organelle, is essential for investigating the role and mechanisms of polarity in pathophysiological processes. Herein, we present ROMO, a rhodol-based fluorescent probe designed to target lysosomes by incorporating a morpholine moiety and featuring a tunable spirocyclic ring that opens and closes in response to polarity variations. ROMO maintains its nonfluorescent spirocyclic form in low-polarity environments, whereas it undergoes a progressive conversion into the red-emitting zwitterionic form as the polarity rises, showing a good linear correlation between fluorescence intensity and solvent polarity. Notably, ROMO was effectively applied to monitor lysosomal polarity in living cells, encompassing young and senescent cells from diverse cell lines. The research findings revealed that the lysosomal polarity in healthy cells was notably higher than that in cancer cells, and it gradually elevated with the progression of cellular senescence.