A Modular (1,3-Oxathiolan-2-yl)ethoxy Trigger Unlocks Activatable Probes for In Vivo Imaging of Hypobromous Acid

Hypobromous acid (HOBr) is a critical reactive oxygen species in inflammatory pathology; however, tracking its dynamics in vivo remains a formidable challenge. Herein, we report a convenient, sensitive and selective (1,3-oxathiolan-2-yl)ethoxy (OTE) recognition moiety for the development of activatable HOBr probes that respond via a sequential oxidative/β-elimination cascade. By connecting this OTE moiety to a fluorophore or chemiluminophore bearing a hydroxyl or amino group, turn-on probes can be conveniently prepared. The versatility of the OTE recognition moiety is demonstrated by the rational construction of a diverse "palette" of fluorescent probes (HBAP380, 390, 520, and 550), spanning the blue-to-red spectral range (450-586 nm). Each probe exhibited high sensitivity and preserved the optimal photophysical properties of their parent fluorophores. Building upon this success, we further engineered a high-performance 1,2-dioxetane-based chemiluminescent probe, CL-2. CL-2 exhibits outstanding performance including high sensitivity (detection limit of 0.64 nM), a remarkable turn-on response exceeding 5200-fold, and excellent selectivity over competing species such as HOCl. Crucially, CL-2 enabled real-time in vivo chemiluminescent imaging of endogenous HOBr fluctuations in a murine model of acute inflammation. This work demonstrates the utility of the OTE recognition moiety for constructing HOBr-activatable probes and establishes a foundation for chemiluminescent HOBr bioimaging.