A Novel Single-Labeled Fluorescent Oligonucleotide Probe for Silver(I) Ion Detection in Water, Drugs, and Food

Due to the high toxicity of silver­(I) ions, a method for the rapid, sensitive, and selective detection for silver­(I) ions in water, pharmaceutical products, and food is of great importance. Herein, a novel single-labeled fluorescent oligonucleotide (OND) probe based on cytosine–Ag­(I)–cytosine coordination and the inherent fluorescence quenching ability of the G-quadruplex is designed to detect silver­(I) ions. The formation of a hairpin structure in the OND–Ag­(I) complex brings the hexachloro fluorescein (HEX) labeled at the 5′-end of the OND probe close to the G-quadruplex located at the 3′-end of the OND probe, leading to a fluorescence quenching due to photoinduced electron transfer between HEX and the G-quadruplex. Through this method, silver­(I) ions can be detected quantitatively, the linear response range is from 1 to 100 nmol/L with a detection limit of 50 pmol/L, and no obvious interference occurs with other metal ions with a 10-fold concentration. This assay is simple, sensitive, and selective, and it can be used to detect silver­(I) ions in actual water, drug, and food samples