An off-on fluorescent probe for real-time sensing the fluctuations of intracellular pH values in biological processes

Minute fluctuation in the intracellular pH is usually related to common diseases. The construction of fluorescent probes with wide response range, high selectivity, excellent sensitivity and good reversibility for intracellular pH detection is of great significance. In this work, we developed a novel pH probe (ZJ) based on a 3-hydroxy naphthalimide derivative via the optimization of substitute groups. ZJ showed a satisfying fluorescence performance to pH changes. ZJ manifests a remarkable fluorescence enhancement at 468 nm (over 12-fold) from pH 2.5 to 10.0. Live cell imaging data uncovered that ZJ can be successfully used in monitoring intracellular pH changes led by chloroquine, inflammation and autophagy, and confirmed with flow cytometry analysis. All these features render ZJ a potential candidate to study pH-associated drug development and physiological and pathological processes. A novel off-on probe based on the 3-hydroxy naphthalimide is developed for imaging intracellular pH changes caused by chloroquine, inflammation and starvation, which would be helpful in the analysis of related drug development and disease. [Display omitted] •A new fluorescent off-on probe is developed for pH assay via the optimization of substitute groups.•The probe exhibits wide response range, high selectivity, excellent sensitivity and good reversibility for pH.•The probe is used to image intracellular pH changes led by chloroquine, inflammation and autophagy.