A two photon fluorescent probe records the intracellular pH through 'OR' logic operation via internal calibration
Abstract Mapping the intracellular location and concentration of hydronium ions (H3O+ and their dynamics could be a useful diagnostic tool in modern clinical science. Current needs motivated us to develop a molecular pH probe 1, operating as a logic gate, and its analogue 2. The pyridyl moiety in 1 played a significant role in proton capture and release, in acidic to alkaline pH environments. In contrast, 2 failed to show a similar spectroscopic behavior. 1 shows emission maximum at 450 nm that is independent on the pH, with excitation at 353 nm or 410 nm in acid and alkaline pH, respectively. 1 was employed to provide input dependent (excitation wavelength) fluorescence images in a cellular milieu to detect pH changes in cellular organelles such as lysosomes and mitochondria. Furthermore, 1 provided information on the variation of the pH in the presence of cellular ROS. 1 was also found to enable the real time monitoring of cell acidification due to nutrient starvation, which is closely associated with mitochondrial malfunction, fusion and mitophagy processes. We envision that in due course 1 can open up new research avenues in the diagnostic sector for validating the pH in the cellular milieu.