Two-Photon Excited Fluorescent Imaging for Cu~(2+) in Living Cells

Based on the spirolactam (nonfluorescent) to ring-open amide (fluorescent) equilibrium, a dye FD2 was demonstrated as a highly selective sensor for Cu2+ over other metal ions. This probe is the first Cu2+ chemosensor with turn-on (85-fold) two-photon excited fluorescence.Moreover, two-photon fluorescent microscopy experiments further establish that FD2 can be used for sensing Cu2+ within living cells.