DNA-functionlized silver nanoclusters as label-free fluorescent probe for the highly sensitive detection of biothiols and acetylcholinesterase activity

We have developed a label-free fluorescent probe using DNA-templated silver nanoclusters (Ag NCs). The DNA-Ag NCs probe was a simple, non-toxic, and sensitive method and could be used to detect biothiols and the activity of acetylcholinesterase (AChE). The fluorescent intensity of DNA-Ag NCs was quenched significantly in the prescence of biothiols, which might be attributed to the formed nonfluorescent complex between Ag NCs and biothiols, the aggregation of Ag NCs, and the efficient energy transfer from DNA-Ag NCs to thiol group. The cysteine (Cys) and glutathione (GSH) could be detected as low as 0.134 μM and 0.172 μM, respectively, within a good linear range from 0-5.0 μM (R2 = 0.991) for Cys, and 0.5-4.5 μM (R2 = 0.983) for GSH. In addition, the proposed method could also detect selectively the activity of AChE in the range from 0-4 U/L, with a detection limit of 0.071 U/L. We believed that the proposed approach laid a foundation for the researchers in bioimaging, pharmacology, diagnostics, and other fields.