A reversible ratiometric two-photon lysosome-targeted probe for real-time monitoring of pH changes in living cells

of 5.62, and good reversibility. Furthermore, the probe was successfully used as a ratiometric TP lysosome-targeted fluorescence probe, not only for imaging of lysosomal pH, but also for visualizing chloroquine-induced changes of intracellular pH in real time in living cells with low cytotoxicity and autofluorescence. These proof-of concept studies demonstrate the practical application of the probe in biological systems.