A water-soluble fluorescence turn on chemosensor for Cu2+ signaling: A combined photophysical and cell imaging study

A simple and effective fluorescence turn on chemosensor (ZPA) has been synthesized for rapid, sensitive and selective detection of copper ions (Cu2+) in fully aqueous buffer. The binding interaction between ZPA and Cu2+ was investigated through UV-vis absorption, fluorescence measurement, mass spectroscopy, and IR spectrum analysis. Cu2+ could specifically bind with the hydroxyl-O and imine-N atom in ZPA with high affinity (K-a = 6.08 x 10(7) M-1). Coordination of CO2+ to ZPA restricting the photoinduced electron transfer (PET) process in free ZPA and generating a more rigid ZPA/Cu2+ complex with an extended pi-electron conjugation system, sequentially leading to the fluorescence enhancement of ZPA. The detection limit (calculated to be 1.49 x 10(-8) M) was far below the limit in the World Health Organization (WHO) guidelines for drinking water (30 mu M) and the sensing process was fully reversible. Practical applications of ZPA for Cu2+ detection in real water samples were investigated with satisfactory results. Endowed with attributes like high binding affinity, specificity, relatively long excitation/emission properties and excellent bio-compatibility, ZPA demonstrated outstanding fluorescent imaging of intracellular Cu2+ in living cells. (C) 2018 Elsevier B.V. All rights reserved.