A near-infrared ratiometric fluorescence probe for mitochondrial H2O2 imaging in biosystems and water samples.

Hydrogen peroxide (H2O2) is a crucial signaling molecule involved in various physiological and pathological processes. Mitochondria are the primary site of endogenous H2O2 generation, and its dysregulation is closely linked to diseases such as cancer and neurodegenerative disorders. Therefore, developing robust tools for real-time, accurate, and in-situ H2O2 detection is of great significance. Herein, we report a novel near-infrared (NIR) ratiometric fluorescent probe, NIR1, designed for the selective imaging of mitochondrial H2O2. The probe utilizes a hemicyanine scaffold and a boronate ester as the specific H2O2 recognition group. Upon reaction with H2O2, NIR1 exhibits a distinct ratiometric fluorescence signal change (F715 nm/F675 nm) in the NIR region, accompanied by a visible color shift from blue to light green. This probe demonstrates high sensitivity (detection limit: 15.8 nM), excellent selectivity, and a fast response time (40 min). Crucially, NIR1 shows outstanding mitochondrial targeting capability (Pearson coefficient: 0.9792) and good biocompatibility. It has been successfully applied to monitor both exogenous and endogenous H2O2 fluctuations in living cells via confocal microscopy. Furthermore, NIR1 is effective for the quantitative determination of H2O2 in various real water samples with satisfactory recoveries. This work provides a promising NIR ratiometric tool for investigating H2O2-related physiological and pathological events at the subcellular level.