Highly Sensitive and Selective Colorimetric and Off-On Fluorescent Chemosensor for Cu2+ in Aqueous Solution and Living Cells

The design and synthesis of a novel rhodamine spirolactam derivative and its application in fluorescent detections of Cu(2+)in aqueous solution and living cells are reported. The signal change of the chemosensor is based on a specific metal ion induced reversible ring-opening mechanism of the rhodamine spirolactam. It exhibits a highly sensitive "turn-on" fluorescent response toward Cu2+ in aqueous solution with an 80-fold fluorescence intensity enhancement under 10 equiv of Cu2+ added. Ibis indicates that the synthesized chemosensor effectively avoided the fluorescence quenching for the paramagnetic nature of Cu2+ via its strong binding capability toward Cu2+. With the experimental conditions optimized, the probe exhibits a dynamic response range for Cu2+, from 8.0 x 10(-7) to 1.0 x 10(-5) M, with a detection limit of 3.0 x 10(-7) M. The response of the chemosensor for Cu2+ is instantaneous and reversible. Most importantly, both the color and fluorescence changes of the chemosensor are remarkably specific for Cu2+ in the presence of other heavy and transition metal ions (even those that exist in high concentration) which meet the selective requirements for biomedical and environmental monitoring application. The proposed chemosensor has been used for direct measurement of Cu2+ content in river water samples and imaging of Cu2+ in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.