Coping with the Blues: Simple and Photo-Stable Dye for Long-Term Live-Cell Imaging.

Dyes for long-term imaging of live cells are rare, especially in the blue region, as they need to be nontoxic and photo-stable. New simple pyrene-derived dyes have been synthesized and fully characterized, showing good cellular uptake, intense emission, and excellent stability. Their unusual stability secret lies in their flexible conformation, evidenced by the solid-state structures of coordination compounds obtained from the dyes and by ¹H-NMR solution studies. Results show that under irradiation, the pyrene-based dye undergoes intersystem crossing (ISC) that leads to a configurational switching occurring at time scales that are faster than the formation of possible photobleaching products. Irradiation of these dyes over 24 hours shows great photostability that was evaluated in different solvents. The possible mechanism of the stability of these dyes is discussed here. Being nontoxic and emitting at only a specific wavelength, these compounds are perfect for staining the cytosol of live cells and long-term imaging in parallel with other dyes of different colors.