Metal-Ion-Responsive Fluorescent Probes for Two-Photon Excitation Microscopy

Metal-ion-responsive fluorescent probes are powerful tools for visualizing labile metal ion pools in live cells. To take full advantage of the benefits offered by two-photon excitation microscopy, including increased depth penetration, reduced phototoxicity, and intrinsic 3D capabilities, the photophysical properties of the probes must be optimized for nonlinear excitation. This review summarizes the challenges associated with the design of two-photon excitable fluorescent probes and labels and offers an overview on recent efforts in developing selective and sensitive reagents for the detection of metal ions in biological systems.