A novel fluorescence “turn off-on” nano-sensor for detecting Cu2+ and Cysteine in living cells

In this work, a novel fluorescent sensor (quercetin-Pluronic-F127 nano-micelles) was prepared by the facile self-assembly method with natural quercetin (Qc) and Pluronic-F127 (F127). Qc-F127 nano-micelles were characterized by TEM which indicated that Qc have successfully entered into the amphiphilic micelle. The nano micelles with sizes of 25 to 40 nm showed a strong green fluorescence (FL). The sensor exhibits high sensitivity and selectivity towards Cu2+ with a linear range of 5 × 10−8-4 × 10−6 mol L−1, the detection limit of 1 × 10−8 mol L −1. Moreover, the Qc-F127 nano-micelles can be used to detect Cu2+ in vitro due to their good biocompatibility. Besides Cu2+ sensing, when Cysteine (Cys) were added, the FL intensity of Qc-F127-Cu(II) system could be restored due to the chelation interactions between Cu2+ ions and the sulfydryl and amino groups of Cys. So, Qc-F127-Cu(II) system can used to detect Cys, and the linear range and the limit of detection of the Qc-F127-Cu2+ system were 3 × 10−7-3.5 × 10−5 mol L−1 and 6 × 10−8 mol L −1. Moreover, Qc-F127-Cu(II) has been used for imaging of Cys in cells, which demonstrates its values for potential application in biological systems.