A Novel Biscarbazole-Xanthene Hybrid Fluorescent Probe for Selective and Sensitive Detection of Cu2+ and Applications in Bioimaging

A new biscarbazole-fused xanthene hybrid dye MeBCX has been prepared by CH 3 SO 3 H-promoted condensation of 4-hydroxycarbazole and o -phthalic anhydride, followed by esterification with methanol, which exhibits good cell membrane permeability. Taking advantage of the spiro-controlled xanthene platform of the dye, a Cu 2+ -selective fluorescence “off-on” probe BCX-Cu has been successfully prepared with excellent performances in selectivity and sensitivity, and the detection limit is calculated to be 88.7 nM. The sensing mechanism is confirmed to involve a specific cascade reactions of Cu 2+ -induced spirolactam ring-opening and hydrolysis. In addition, living L929 cell imaging demonstrates the probe has living cell membrane permeability and shows great potential for tracing intracellular Cu 2+ through fluorescence imaging technology.