Novel fluorescent probes for relay detection copper/citrate ion and application in cell imaging.

Two novel fluorescent probes, 2‑(2'‑hydroxyphenyl)‑4‑(2'‑hydroxymethyl‑8‑quinolinamino)methyloxazole (L1), and 2‑(2'‑hydroxyphenyl)‑4‑(2'‑methyl‑8‑quinolinamino)methyloxazole (L2), exhibited colorimetric and "turn off" fluorometric response to Cu2+ ion in DMSO/H2O solution (v/v = 1/1, 0.01 M, Tris-HCl buffer, pH 7.20) and the corresponding detection limit were found to be 2.14 × 10-8 and 2.70 × 10-8 M, which were much lower than drinking water permission concentrations by the United States Environmental Protection Agency (U.S. EPA) and World Health Organization (WHO). The L1-Cu2+ and L2-Cu2+ complexes ensemble detected citrate anions (CA) sequentially through fluorescence recovery response due to the extrusion of Cu2+ ion from the complexes. The binding processes were investigated by UV-vis, fluorescence, IR and DFT calculation. Furthermore, the vivo sensitivity experiments of Cu2+ ion and CA was demonstrated through fluorescence imaging in living cells.