A rosamine-based red-emitting fluorescent sensor for detecting intracellular pH in live cells

Abstract

A rosamine-based pH probe has been developed by a one-step synthesis. The probe was non-fluorescent in neutral environments resulting from the photoinduced electron transfer (PET) by the electron donating amine-containing side chain which was interpreted theoretically by means of TDDFT calculations, whereas, it behaved as an OFF–ON pH probe (pKa=4.73) with a 400-fold enhancement in the red fluorescent signal upon binding with H+. This strategy currently seems to break the research bottleneck to prepare rhodamine probes based on the structural optimization between spirocyclic and open-cycle forms for realization of “OFF–ON” signal switch and acidic organelles staining as regards progress in some areas of cell biology and biomedicine. Subsequently, its high selectivity, good cell membrane permeability, excellent photostability and fine reversibility make it favorable for intracellular pH imaging. The confocal fluorescent microscopic images of subcellular distributions of probe 1 and its colocalizations with LysoTracker Green DND-26 in live HeLa cells were achieved successfully, suggesting that the probe could be used as a red-emitting lysosome-specific probe for in cellulo imaging.