A novel selective and sensitive fluorescent turn-on chemodosimeter based on rhodamine hydrazone for copper ions and its application to bioimaging

To develop a selective and sensitive fluorescent turn-on chemodosimeter for copper ions in neutral buffered media, a novel rhodamine hydrazone derivative bearing a piperidinyl group was synthesized. Upon addition of Cu2+, the ring-opening process of rhodamine spirolactam was found to result in remarkably enhanced fluorescent and colorimetric labeling, whereas very little fluorescence variations or color changes were observed in the presence of other metal ions (K+, Na+, Ca2+, Mg2+, Mn2+, Ag+, Sn2+, Hg2+, Pb2+, Fe2+, Fe3+, Zn2+, Co2+, and Ba2+). The detection limit of this newly developed probe was shown to be up to 76 ppb. Importantly, the probe was successfully used for fluorescence imaging in Caco-2 cells.