Two birds with one stone: A novel dual-functional fluorescent probe for simultaneous monitoring and real-time imaging of alkaline pH and viscosity in living cells

Viscosity and pH are two crucial microenvironment parameters, and their abnormal fluctuations at the cellular level can act as key indicators of various diseases diagnosis. Considering that the traditional viscosity/pH meters cannot work in the cellular environment, developing some viscosity/pH-sensitive fluorescent probes is urgently demanded. Herein, a novel dual-functional camphor-based fluorescent probe PN-SP for viscosity and pH detection was constructed based on spiropyran open/closed-ring switching strategy. PN-SP exhibited an intense green emission in response to alkaline pH while a bright red fluorescence was observed in high-viscosity media, which could avoid some problems caused by the use of multiple probes such as cross-talk spectrum and different localizations. The sensing performances of PN-SP were also demonstrated for monitoring viscosity and pH fluctuations in living HeLa cells by means of different emisson channels. Therefore, we believed that this work will provide guidance for designing some dual-functional fluorescent probes.