A novel two-channel ratio fluorescent probe for monitoring intracellular pH fluctuations

Accurate measurement of pH is of great significance in the research of biology and medicine sciences. Cell is the basic unit of living organism and the proper pH of cytoplasm and organelles such as lysosome is the precondition to maintain its function. Alteration of pH may impair the normal process of cells and lead to occurrence of diseases. Sensitively sensing the pH of cytoplasm and organelles is of great value for biomedical research. Due to the complexity of biological microenvironment, it is still challenging to simultaneously detect the pH changes of cytoplasm and lysosome. Here, we reported a ratiometric pH probe with NIR fluorescence termed as PCHC, which realized sensitive cytoplasmic and lysosome pH detection. The probe was prepared by connecting coumarin with dicyanmethylene-4H-pyran via amidation reaction, and displays large Stoke-shift, good biosafety and pH selectivity. After entering the cell, the probe shows blue in cytoplasm and NIR fluorescence in lysosome due to respective pH. The ratio of blue and NIR fluorescence signal can be served as indicator to monitor pH change of cytoplasm and lysosome simultaneously, which has potential application for investigation of pH alteration related diseases.