A pyrazolo[1,5-a]pyridine-based ratiometric fluorescent probe for sensing Cu in cell.

Ratiometric fluorescent probes based on FRET mechanism have attracted great attention due to their large pseudo-Stokes shifts and built-in correction for environmental effects. However, most donors failed to meet the requirement that the emission of the donor must overlap well with the absorption of the acceptor. Therefore, searching for new fluorophore to construct FRET system is in great need. In this paper, a new fluorescent dye pyrazolo[1,5-a]pyridine was synthesized and used as a donor in the FRET system for ratiometric sensing of Cu. The probe is based on FRET and PET mechanism. It shows high selectivity and sensitivity toward Cu (detection limit 30 nM). Furthermore, it was successfully used to detect Cu in Glioma cells.