Construction of a Mitochondrial Targeted H <sub>2</sub>O <sub>2</sub> Fluorescence Probe with a Large Stokes Shift and its Application in Bacterial Infection

Macrophages are crucial innate immune system cells that have the ability to generate large amounts of H2O2 in the cytoplasm to combat germs. Macrophage mitochondria also produce H2O2 to participate in the antimicrobial response when infected by bacteria. However, visualization of H2O2 production in the mitochondria of bacterially infected macrophages is extremely challenging due to the lack of appropriate research methods. Here, using confocal fluorescence imaging in conjunction with the development of a novel fluorescent H2O2 probe that targets the mitochondria, we report for the first time that H2O2 production in the mitochondria of bacterially infected macrophages (Raw264.7 cells) was visualized with a fluorescent probe. In addition, the developed probe has accurate mitochondrial targeting ability, large Stokes shift, fast response capability, high selectivity and sensitivity (detection limit of 4.346×10-7 M), and the probe can be used to detect H2O2 in living cells and zebrafish. Therefore, this work is expected to be used to further reveal the biological function of H2O2 in subcellular mitochondria.