A near-infrared fluorescent probe for the detection of Cu in Chinese herbal medicine and imaging in living cells.

Copper is one of the common among the heavy metal pollution in Chinese herbal medicine (CHM). So, it is essential to develop rapid and accurate testing method to quantify the Cu content in CHM. Herein, we prepared a coordination-based near-infrared fluorescent probe (NRh6G-FA) by introducing a hemicyanine dye in rhodamine 6G scaffold. NRh6G-FA had a high sensitivity, anti-interference performance, fast response (within 60 s), visualization (from light yellow to green) for Cu and excellent sensing performance for the detection of Cu at low concentrations (LOD = 0.225 μM). The most likely mechanism was verified on the basis of Job's plot, ESI-HRMS and DFT calculations. NRh6G-FA could be successfully applied for the detection and "naked eye" recognition of Cu in CHM samples. Moreover, NRh6G-FA was used to visualize Cu in living MCF-7 cells by confocal fluorescence imaging.