Silicon-substituted xanthene dyes and their applications in bioimaging

Fluorescence imaging is one of the most powerful techniques for visualizing temporal and spatial changes of biological phenomena in living cells, and many fluorescent probes have been developed. In particular, xanthene dyes such as fluorescein and rhodamines have favorable characteristics, such as high water solubility, high fluorescence quantum yield and high molar extinction coefficient, and they have been utilized as fluorescent cores for fluorescent probes working in the green to red wavelength region. Recently, silicon-substituted xanthene dyes such as 2,7-N,N,N',N'-tetramethyl-9-dimethyl-10-hydro-9-silaanthracene (TMDHS), Si-rhodamines and TokyoMagentas, in which the O atom at the 10-position of xanthene is replaced with a Si atom, have been developed as novel far-red to near-infrared fluorescent cores that retain the key advantages of the parent structures. Fluorescent probes based on them have opened up new possibilities for imaging biological processes in living cells. This minireview covers recent progress in silicon-substituted xanthene dyes, including representative applications for in vivo tumor imaging, triple-color imaging of neuronal activity, and super-resolution microscopy.