A Smart Ru‐Locked Chemiluminescence Probe via Bioorthogonal Activation for Highly Selective, Real‐Time and Noninvasive In Vivo Imaging of Thiol Dysregulation

ABSTRACT Bioorthogonal cleavage chemistry (BCC) has been extensively applied to fluorescence‐based imaging in cancer diagnostics. Its potential in chemiluminescence imaging is to be explored. In this study, a smart ruthenium (Ru)‐catalyzed bioorthogonal activation chemiluminescence (BAC) probe is developed by integrating BCC with a phenoxy‐adamantyl‐1,2‐dioxetane (PAD) for real‐time in vivo imaging of thiol‐containing metabolites, particularly hydrogen sulfide (H₂S), associated with thiol dysregulation in the tumor microenvironment. The BAC probe overcomes many limitations that existed in other chemiluminescence probes via a highly selective “Ru‐locked” mechanism to achieve light‐independent, thiol‐triggered activation in the complex tumor microenvironment. This mechanism enables rapid activation (1 min), high sensitivity (LOD = 0.243 µM), and stable luminescence with a half‐life of 18.5 h, as determined in vitro, across a broad emission range (400–800 nm). The probe also demonstrates enhanced selectivity for thiol‐containing metabolites, particularly H₂S, and exhibits low toxicity both in vitro and in vivo. In a breast cancer mouse model, the probe successfully visualizes endogenous H₂S with high spatial precision, supporting its utility in tumor localization and image‐guided surgery. In addition, the PAD scaffolds are developed via an efficient synthetic route, significantly lowering production costs (300‐ to 400‐fold) and increasing yields from 40% to 95%. Furthermore, our BAC probe holds a broad potential for noninvasive diagnosis and real‐time monitoring of thiol dysregulation and pathophysiological processes.