Near-infrared fluorescent probe for the simultaneous dual-color monitoring of pH changes in two organelles

Crosstalk between the lysosome and the endoplasmic reticulum (ER) is essential for maintaining intracellular homeostasis and normal physiological activities. However, simultaneously visualizing the lysosome and ER by using a single fluorescent probe is of considerable significance and challenge. In this work, we developed a near-infrared (NIR) pH probe (F–CCOH) by introducing 7-hydroxycoumarin into the curcumin difluoroboron skeleton. The F–CCOH probe presented strong red emission (630 nm) under acidic conditions and NIR emission (755 nm) under basic conditions, which was attributed to the deprotonation of the hydroxyl group on coumarin. Moreover, by monitoring changes in the fluorescent intensity of F–CCOH in two channels, the pH variety of the lysosomes and ER in living cells can be visualized simultaneously. The experimental results showed that pH changes in the lysosome and ER were opposite during dexamethasone-induced apoptosis. This finding is extremely valuable for revealing the crosstalk between lysosome and ER in physiological activities.