Styrene dyes serve as useful imaging probes and fluorescent sensors due to their strong fluorogenic response to environmental changes or binding to macromolecules. Previously, an indole-containing styrene dye had been reported to selectively bind RNA in the nucleolus and cytoplasm. In this work, we have investigated the positional and electronic effects of the donor indole by generating regioisomeric derivatives of the parent indole-styrene scaffold and replacing the electron-donating indole substituent with an indolizine moiety to yield our novel probes. The new probes exhibited large stokes shifts, enhanced molar extinction coefficients, and bathochromic shifts in their absorption and fluorescence profiles. In particular, the indolizine analogues showed good membrane permeability, &gt;50-fold fluorogenic response in the presence of RNA in solution, and displayed high contrast nucleoli signals in live cells. To the best of our knowledge, our probes have the highest fluorescence enhancement among the RNA dyes reported in the literature thus far. These indolizine-styrene probes are excellent dyes for visualizing RNA in live cells and can be used as a better alternative to the commercially available RNA dye, SYTO RNA Select.

Development of highly fluorogenic styrene-based probes for visualizing RNA in live cells

ACS Spring 2022

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