A low cytotoxic and sensitive NIR probe for the "on-off" fluorescence detection of Cu2+and imaging in living cells and animals

Excessive copper ions pose a great risk to biological systems. It is of prime importance to establish a sensitive and reliable analytical tool for the real-time monitoring Cu2+ in biosystems. Herein, a novel near-infrared fluorescence probe RhB-ENP based on hemicyanine-modified xanthene skelon was synthesized and characterized for selective detection of Cu2+. Due to Cu2+-triggered spirolactam ring-opening mechanism, probe RhB-ENP exhibited fluorescence turn-off behavior with good selectivity and rapid response with the Cu2+. And the fluorescence intensity showed an excellent linear correlation with Cu2+ (0-4 mu M). Besides, the probe represented obvious fluorescence to Cu2+when the pH ranged from 6.0 to 8.5. The formation of stable complex with 1:1 binding stoichiometry was supported by Job's plot, ESI-MS and DFT studies. Significantly, RhB-ENP had been effectively applied for the recognition of Cu2+ both in vitro and in vivo assays. All these results prove that RhBENP can act as a potentially promising tool for the study of Cu2+-related biology and pathology in biological systems.