Development of a ratiometric fluorescent probe for selective detection and bioimaging of hydrogen peroxide in HeLa cells and zebrafish.

Because intracellular H2O2 levels vary dynamically and are involved in both redox signaling and oxidative stress linked to human health and disease, quantitative fluorescent detection of H2O2 is essential in living systems. In this work, a carbazole-based ratiometric fluorescent probe, KD-H2O2, was designed and synthesized for the selective detection of H2O2. Performance evaluation demonstrated that KD-H2O2 exhibited excellent sensing properties, including a broad pH tolerance range (pH 3.0-11.0), high detection sensitivity with a low limit of detection (LOD) of 2.74 μM, and favorable biocompatibility and low cytotoxicity. Notably, upon reaction with H2O2, the probe solution exhibited a distinct colour change that could be readily observed with the naked eye. Furthermore, bioimaging experiments demonstrated that KD-H2O2 enabled visualization of endogenous and exogenous H2O2 in HeLa cells, and it could detect exogenous H2O2 in zebrafish. Overall, the probe is a reliable tool for monitoring dynamic H2O2 changes in biological systems and has potential biomedical applications.