A Fluoran-Based Cu²⁺-Selective Fluorescent Probe and its Application in Cell Imaging

Based on a fluoran skeleton, we herein reported a new fluorescent probe FLACu for Cu²⁺ by facile modification of the spirolactone of dye 1 with phenylhydrazine. Taking advantage of the spirolactam moiety, FLACu only delivers a specific "off-on" fluorescence signal output towards Cu²⁺ when treated with various metal ions, which has been well elucidated as the result of spirolactam ring opening and hydrolysis processes induced by copper ion. Meanwhile, the limit of detection (LOD) for FLACu has been estimated to be 35.4 nM and a pH range of 5.0-9.0 is evaluated to be suitable for Cu²⁺ detection. Significantly, FLACu shows low cell cytotoxicity and can be further ultilzied in the detection of exogenous Cu²⁺ in the living Hela cells.