Thiazole-based ratiometric fluorescence pH probe with large Stokes shift for intracellular imaging

• Published in: Sensors and actuators. B, Chemical Chemical, 2016-10, Vol.233, p.566-573
• Main Authors: Zhang, Wen-Jia, Fan, Li, Li, Zeng-Bo, Ou, Ting, Zhai, Hua-Jin, Yang, Jun, Dong, Chuan, Shuang, Shao-Min
• Format: Article
• Language: English
• Subjects: Binding; Cinnamaldehyde; Ethylene; Extreme acidity; Fluid flow; Fluorescence; Imaging; Intracellular imaging; Monitors; pH probe; Ratiometric fluorescence; Thiazole-based probe
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2016.04.122

A ratiometric pH probe with large Stokes shift of 177nm under acidic conditions for monitoring intracellular pH fluctuations in live cells with lysosomal targeting ability and extreme acidity in E. coli cells. [Display omitted] •A thiazole-based ratiometric emission pH probe BTDB is synthesized.•BTDB exhibits a remarkable emission ratio (I425nm/I595nm) enhancement with decreasing pH from 7.0 to 1.2.•The pKa is 2.34 and the linear pH response range lies in the extremely acidic pH range of 2.3–4.0.•BTDB exhibits large Stokes shift of 177nm under acidic conditions.•BTDB can monitor lysosomal pH fluctuations in HeLa cells, and pH changes in E. coli cells with ratiometric response. A ratiometric fluorescent pH probe 4-((1E, 3E)-4-(benzo[d]thiazol-2-yl)buta-1, 3-dienyl)-N, N-dimethylbenzenamine (BTDB) was synthesized via ethylene bridging of thiazol and cinnamaldehyde for extremely acidic sensing. BTDB exhibits ratiometric fluorescence emission (I425nm/I595nm) characteristics with pKa of 2.34 and a large Stokes shift of 177nm under acidic conditions. The linear response to pH is in the range of 2.3–4.0. Quantum chemical calculations with the B3LYP exchange functional theory demonstrated that the ratiometric response of the probe to acidic pH was due to H+ binding with the N of cinnamaldehyde and the induced decreases of the intramolecular charger transfer (ICT) process. The as-prepared probe displayed excellent cell membrane permeability was further applied successfully to monitor pH fluctuations in live cells with excellent lysosomal targeting ability, and extreme acidity in Escherichia coli cells.