Design and synthesis of a multifunctional rhodamine-based chemosensor for simultaneous detection of Cu2+, Zn2+ and endogenous histidine (His) and its application in living HeLa cells and zebrafishes

Abstract

In organisms, the over ingesting of Cu2+ and Zn2+ will result in the poisoning of living cells, which severely damages the human body. Meanwhile, endogenous Histidine (His) can cause metabolic disorders like Histidinemia (His). Therefore, it is a pressing matter to design an effective method that accurately detects the amount of Cu2+, Zn2+, and His. In our study, through the nucleophilic addition and substitution reactions synthesis methods, a novel multifunctional probe, Rhodamine derivatives with vinyl functional groups at the end (RHDA) was designed and synthesized. The probe RHDA can recognize Cu2+ and Zn2+ separately, and the experiment further substantiates that the RHDA probe can demonstrate various turn-on colorimetric and fluorescent signals, i.e., selectively detecting Cu2+ in DMSO/H2O solution (v/v=4/6) with the “naked-eye” show evident and significant color change from colorless to pink and Zn2+ with strong green fluorescence in DMF/H2O (v/v=1/1). Under optimal conditions, they could be identified under the low detection limit of 0.10 μmol·L−1 and 16.0 nmol·L−1 for Cu2+ and Zn2+, respectively. Furthermore, Histidine (His) was recognized by the formed RHDA-Zn2+ with a fluorescence “turn-off” range of 0.03–10.0 μM and a detection limit of 230.0 nmol L−1. This article performed an extensive study of the sensing mechanisms of RHDA toward two metal ions and the ensemble RHDA-Zn2+ toward His. The practical application experiments in DMF/H2O (v/v=1/1) further established that the chemosensor RHDA exhibits good cell permeability and could be employed to monitor free Zn2+. Finally, the complex RHDA-Zn2+ could be applied to assay His in the living HeLa cells and zebrafishes, respectively.