Two-Photon Probes for Zn2+ Ions with Various Dissociation Constants. Detection of Zn2+ Ions in Live Cells and Tissues by Two-Photon Microscopy

A series of Zn2+-selective two-photon fluorescent probes (AZn-M1-AZnN)that had a wide range of dissociation constants (K-d(TP) = 8 nm-12 mu m) were synthesized. These probes showed appreciable water solubility (> 3 mu m), cell permeability, high photo-stability, pH insensitivity at pH > 7, significant two-photon action cross-sections (86-110 GM) upon complexation with Zn2+, and can detect the Zn2+ ions in HeLa cells and in living tissue slices of rat hippocampal at a depth of > 80 mu m without mistargeting and photobleaching problems. These probes can potentially find application in the detection of various amounts of Zn2+ ions in live cells and intact tissues.