A charge transfer type pH responsive fluorescent probe and its intracellular application

A new charge transfer pH fluorescent probe BTP has been prepared by the ethylene bridging of benzothiazole and pyridine. The probe exhibits a specific fluorescent response to pH with a large Stokes shift, and the pH-induced emission enhancement factor (EEF) is about 22-fold when the pH is increased from 3.2 to 5.2. The presence of metal cations such as Na(+), K(+), Ca(2+), Mg(2+) and other transition metal cations does not interfere with its fluorescent pH response. In addition, the intracellular pH fluorescent imaging ability of the probe has been confirmed on macrophage cells using a confocal microscope.