title: Highly sensitive label-free fluorescent detection of Hg2+ ions by DNA molecular machine-based Ag nanoclusters.
abstract: We present here a highly selective and sensitive label-free method to detect Hg(2+) ions in aqueous solution by using DNA molecular machine-based fluorescent Ag nanoclusters (AgNCs). This mechanism is based on the Hg(2+) ions triggering machine-like operations of DNA and the "product" of the machine being used to stabilize fluorescent AgNCs. In this method, a tailored DNA, containing a sequence for Hg(2+) ions recognition, a sequence-specific nicking site for Nb BbvC I and a sequence complementary to the DNA as a template for the synthesis of fluorescent AgNCs, was firstly designed. In the presence of Hg(2+) ions, the machine's function operations were triggered. A series of machine-like operations, including replication, scission, and displacement then occurred with the addition of polymerase/dNTPs/Nb BbvC I, which manufactured lots of "product" DNA. The "product" DNA could act as a template for the preparation of fluorescent AgNCs. Thus the fluorescence of the AgNCs could be used as a signal transduction of this DNA machine, which was related to the concentration of the Hg(2+) ions. The repeated synthesis of the "product" and its template effect for AgNCs synthesis led to signal amplification in the assay of Hg(2+) ions. A linear response to the concentration of Hg(2+) ions was observed in the range from 0.08 nM to 20 nM and a detection limit of 0.08 nM was obtained. By contrast, the operation of the machine could not be executed in an Hg(2+) ion-free system. Moreover, the detection was not only label-free but also specific for Hg(2+) ions without being affected by other metal ions.
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry & Chemical Engineering, College of Biology, Hunan University, Changsha 410082, China.
authors: Jinjin
authors: J
authors: Yin
authors: Xiaoxiao
authors: X
authors: He
authors: Xuekun
authors: X
authors: Jia
authors: Kemin
authors: K
authors: Wang
authors: Fengzhou
authors: F
authors: Xu
mesh_terms: D004247:DNA / Q000737:chemistry; D007477:Ions / Q000032:analysis / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis* / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry; D049329:Nanostructures; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D007477:Ions; D014874:Water Pollutants, Chemical; D012834:Silver; D004247:DNA; D008628:Mercury