Two near-infrared hybrid rhodol dyes (probes A and B) for sensitive ratiometric visualization of pH changes were prepared by incorporating hemicyanine dyes into traditional rhodol dyes to manipulate the probe π-conjugation changes involving rhodol hydroxyl group in spiropyran switches upon pH changes. Probes A and B show sharp absorption peaks at 535 nm and fluorescence peaks at 558 nm with similar π-conjugation with closed spiropyran forms at basic pH 10.2. However, acidic pH effectively converts the spiropyran switches into hemicyanine moieties with significantly extended π-conjugations, resulting in new near-infrared emissions at 687 nm and 690 nm for probes A and B, respectively. As a result, probes A and B display ratiometric fluorescence responses to pH downgrades from 10.2 to 3.6 with visible fluorescence decreases at 558 nm, and corresponding increases of the near-infrared fluorescence peaks at 687 nm and 690 nm, respectively. They exhibit fast, sensitive, and selective fluorescence responses to pH changes with low cytotoxicity and excellent cell permeability. The probes were successfully applied to ratiometrically detect pH changes in mitochondria, and visualize mitophagy process caused by cell nutrient starvation.

Near-infrared hybrid rhodol dyes with spiropyran switches for sensitive ratiometric sensing of pH changes in mitochondria

2019 Fall National Meeting

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