Fluorescent dyes have the ability of changing color in response to pH-changes. This can be utilized for measuring pH in living cells. Changes in cellular pH can reflect a range of physiological processes, including muscle contraction, endocytosis, cell proliferation, apoptosis, and ion transport 1.
Fluorescent pH-indicators can be either stand-alone-dyes or dyes coupled to a macromolecule, such as dextran. The advantage of using fluorescent dextran derivatives is that the molecules can be accumulated in to specific intracellular compartments2. Compared to microelectrode techniques, fluorescent pH-indicators also have greater spatial sampling capability1. Another advantage of the probes and indicators is that they don’t bind to cellular proteins2.
Dextran derivatives involving dye-entities like FITC, TRITC or Texas Red™ have in recent years been reported3. These dyes can be combined in a single dextran in order to achieve more accurate results. In such cases the different pH-responses of FITC and TRITC (or Texas Red™) are employed for a more information-dence readout.