Washington Red (WR) dyes and their imaging applications

Near-infrared (NIR) fluorescent dyes with optimum photophysical properties are highly useful for bioimaging in living systems, but such dyes are still rare. Recently, our laboratory developed a unique class of NIR fluorescent dyes with high quantum yields and large Stokes shifts. These dyes, named as Washington Red (WR), were found to be useful scaffolds to develop NIR fluorescent imaging probes upon easy modifications on their phenolic hydroxyl group. In this chapter, we provide a comprehensive summary of this work, including the design and synthesis of WR dyes, their photophysical properties studies, and applications in developing NIR probes to image H₂S in cells. The detailed experimental protocols are described.