Rational Design of a Fluorogenic Probe for Sphingosine Based on Precisely Controlled Intramolecular Spirocyclization of Coumarin–Rhodamine Hybrid Dye

features fast response, high sensitivity, and high selectivity toward Sph, and has been applied to monitor Sph levels in senescent cells, mice, and their tissue slices, revealing a close correlation between aging and Sph levels in biological specimens. The present study provides a more generalizable design strategy for developing fluorogenic probes to study various pathological and biological processes.