Strongly phosphorescent and water-soluble gold(I)-silver(I)-cysteine nanoplatelets via versatile small biomolecule cysteine-assisted synthesis for intracellular hypochlorite detection.

Abstract

In biological systems, abnormal levels of hypochlorite (ClO-) could result in cell dysfunctions. Herein, we report a facile, one-step and green approach based on the versatile small biomolecule cysteine both serving as reducing agent and ligand for synthesizing the strongly photoluminencent and water-soluble Au(I)-Ag(I)-cysteine complexes nanoplatelets (Au(I)-Ag(I)-Cys nanoplatelets) for intracellular hypochlorite detection. Multiple spectroscopic and microscopical tools have been used to characterize the resultant Au(I)-Ag(I)-Cys nanoplatelets. It was found that with the cysteine-assisted synthesis approach, the Ag(I) doping to the Au(I) complexes could form the supramolecular organometallic nanoplatelets. Inside, the Au(I)-Ag(I) metallophilic interactions showing an Au to Ag charge transfer property were formed, thereby enhancing the photoluminescence (PL) intensity via the charge transfer from the bioligand s S to the metal-metal center. The quantum yield (QY) was measured to show a maximum 16-fold enhancement (i.e., from 0.85 to 13.8%). Interestingly, in the presence of ClO-, the metal-thiolate ligand structure of the as-synthesized Au(I)-Ag(I)-Cys nanoplatelets could be oxidatively damaged, causing the PL quenching, thereby producing the effect of biorecognition towards ClO- anions. The ClO--induced PL quenching produced two linear regions at ClO- concentrations of 0.01-5.0\xa0μM and 5.0-1000\xa0μM with a limit of detection (LOD) of 8.0\xa0nM (S/N\xa0=\xa03). The ClO--induced PL quenching was specific over the other typical reactive oxygen species (ROS) and the potential interfering substances in biological samples. In addition, the Au(I)-Ag(I)-Cys nanoplatelets had good biocompatibility. Thus, they could be further developed as a biosensor for detecting endogenous ClO- anions in living cells.