Two-Photon Fluorescent Probes of Biological Zn(II) Derived from 7-Hydroxyquinoline

A new fluorescent probe for monitoring Zn2+ was synthesized based on the structure of 7-hydroxyquinoline. Compared with 8-substituted quinolines, the new probe exhibited higher selectivity for Zn2+ over Cd2+. Its fluorescence enhancement (14-fold) and nanomolar range sensitivity (Kd = 0.117 nM) were favorable toward biological applications. Experiments also showed that a cell-permeable derivative of the new probe was potentially useful for two-photon imaging in living cells.