Monitoring intracellular pH using a hemicyanine-based ratiometric fluorescent probe

Monitoring intracellular pH using ratiometric fluorescent probes can provide further insights into various biological processes including many diseases. Although ratiometric fluorescent probes with dual emission can efficiently exclude interferences (probe concentration, instrumental efficiency, and environmental conditions) compared with traditional off-on fluorescent probes, development of pH-responsive fluorescent probes with dual emission remains relatively unexplored and challenging. Herein we reported a new hemicyanine-based ratiometric fluorescent probe 1 with a hydroxyl group. The probe 1 exhibits dual emission and shows a real-time and selective fluorescence response to micro-environmental pH conditions in a range of 6.0 ∼ 8.0. Further studies revealed that 1 could exclusively enter and accumulate into mitochondria and monitor the pH micro-environmental conditions through fluorescence imaging in HepG2 cells. We suggest that this probe might be used as a probe to elucidate the role of pH in many physiological processes.