Development of a ratiometric fluorescent pH probe for cell imaging based on a coumarinaquinoline platform

It is highly desirable to develop ratiometric pH probes with a well-resolved emission spectrum for biological imaging applications. In this work the design, synthesis, photophysical properties and cellular imaging studies of a new linked coumarinaquinoline probe is described. The major features of the novel probe include two well-resolved (>100 nm) emission peaks, strong fluorescence under acidic conditions, a pKa of 4.69, low cytotoxicity and good cell membrane permeability; features which render the probe useful for monitoring pH variations from neutral to acidic conditions in living cells.