Abstract: Objective To prepare a pH fluorescence probe based on styrylcyanine dyes for live cell imaging. Methods The Probe
1 was prepared by reaction of 4-pyridinecarboxaldehyde with 1,1,2-trimethylbenz[e]indole. The influence of pH on the
fluorescent properties was examined, and the cell viability was examined using cell counting kit-8. The Probe 1 was used as a
pH fluorescence probe in living cell. Results Probe 1 emitted green fluorescence under neutral and basic conditions but orange
fluorescence under acid condition. Probe 1 selectively stained the cytoplasmic regions of living cells without significantly
affecting the cell viability. Conclusion The pH-sensitive fluorescent probe prepared based on styrylcyanine possesses good
ability of cell membrane permeation for live cell fluorescent imaging.