Revealing Minor pH Changes of Mitochondria by a Highly Sensitive Molecular Fluorescent Probe

Mitochondrial pH is an important factor associated with cellular metabolism and pathological states. Thus, sensitively monitoring its minor change was essential. However, it was challengeable due to the lack of suitable probes. Here, a mitochondria-targeted probe ( NIR-OH-1 ) was synthesized. Based on the protonation/deprotonation of the hydroxy group and the assistance of carboxyl group on NIR-OH-1 molecular structure, a dramatic NIR activated signal was generated for sensing pH. Probe NIR-OH-1 displayed a good photo-stability and reversibility and could detect pH change without interference by other biologically active species. Importantly, NIR-OH-1 had an appropriate pK_a value (7.77) and tiny acid-base transition range, which was allowed to map the small pH changes of cellular mitochondrial. Moreover, NIR-OH-1 was also successfully applied in real-time monitoring mitochondrial pH-related pathological events in living cells under different stimulation, demonstrating the prospect of its clinical application in accurate mitochondrial pH detection under related physiological and pathological conditions.