A rhodamine-based fluorescent probe for the detection of lysosomal pH changes in living cells

Sensing and monitoring of pH changes in live cells are of great importance for understanding of cellular signaling responses. In this study, we developed a highly sensitive and selective pH sensor, rhodamine-based fluorescence dye 1. The fluorescent emission of 1 at 588 nm increased with the pH decreasing (from pH 7.0–4.0) due to the ring-opening of spirolactam by H+. 1 exhibited good water solubility, high quantum yield, and fast response to pH changes. Moreover, 1 can stain lysosomes in living cells with high photostability and low cytotoxicity. Importantly, 1 was used for monitoring pH changes in lysosomes induced by chloroquine, artesunate and dexamethasone. Therefore, our work provides the potential of probe 1 for visualizing the intracellular changes of pH in clinical and medical applications.