A turn-on fluorescent strategy for biothiols determination by blocking of Hg (II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters.

Fluorescent adenine (A)-rich DNA-templated gold nanoclusters were demonstrated to be a novel probe for the determination of biothiols (including cysteine, glutathione and homocysteine). The fluorescence intensity of adenine-rich DNA-templated gold nanoclusters could be greatly quenched by Hg (II) ions through the formation of gold nanoclusters-Hg (II) system. When biothiols (cysteine as the model) were introduced into the system, the fluorescence intensity recovered due to the formation of more stable Hg (II)-thiol coordination complex by Hg-S metal-ligand bonds, which inhibited the Hg (II)-mediated fluorescence quenching of adenine-rich DNA-templated gold nanoclusters. On the basis of fluorescent phenomenon, on-off-on fluorescence strategy has been designed for the sensitive determination of biothiols. The method allowed sensitive detection of cysteine with a linear detection range from 100 nM to 5 μM and a limit of detection of 30 nM. Additionally, the assay can be applied for the detection of biothiols levels in human plasma samples. Therefore, it can provide a simple and rapid fluorescent platform for biothiols detection.