A pH-sensitive excited state intramolecular proton transfer fluorescent probe for imaging mitochondria and Helicobacter pylori

[Display omitted] •Because T2(OH)B showed large stokes shift through ESIPT process, it can be useful for fluorescent probe.•Owing to turn-on fluorescence emission behavior of T2(OH)B above physiological pHs, it was successfully applied for mitochondria of mammalian cells, as well as detected H. pylori adhered to mammalian cells.•Also, T2(OH)B displayed faster staining rates than commercially available MitoTracker red. An hydroxythiophene-conjugated benzothiazole (T2(OH)B) was synthesized as a pH sensitive fluorescent probe. T2(OH)B displayed dual emission behavior due to the excited state intramolecular proton transfer (ESIPT) process, while the methoxy analogs, T2(OMe)B, did not. T2(OH)B showed strong fluorescence enhancement above physiological pHs. The applicability of T2(OH)B as a biological pH indicator was demonstrated by its use for staining mitochondrial compartment and H. pylori. Owing to its strong fluorescence emission with a large stokes shift and its effective response to pH, T2(OH)B serves as a platform for the design of new types of fluorescent probes.