A near-infrared ratiometric fluorescence probe base on spiropyran derivative for pH and its application in living cells

The intracellular pH has a significant effect on several essential biological processes such as material transfer, enzymatic action, cell apoptosis et al. Thus, it is necessary to monitor pH fluctuation in living cells. Here, we designed a near-infrared ratiometric fluorescence probe for pH detection. The spectroscopic responses of probe to pH variations were investigated in CH 3 OH/PBS (v/v, 1:1) mixed solution at different pH values. The experimental results showed that the probe is sensitive to acidity, and the p K a of probe is calculated to be 4.85. When the pH was decreased from 9.0 to 1.0, the color of probe solution change from purple to yellow was found by naked eye. Moreover, the probe can be a practical tool for assessing cellular pH by cell imaging.