title: A Hg(2+)-mediated label-free fluorescent sensing strategy based on G-quadruplex formation for selective detection of glutathione and cysteine.
abstract: A novel label-free fluorescent strategy for the detection of glutathione (GSH) and cysteine (Cys) is presented. The system consists of two single stranded DNA (ssDNA) with thymine-thymine (T-T) mismatches and used Hg(2+) as a mediator, and N-methyl mesoporphyrin IX (NMM) as the signal reporter. The assay is based on the competitive reaction of Hg(2+) with GSH/Cys and T-T mismatched double stranded DNA (dsDNA). In the absence of the target, two ssDNA containing T-T mismatches react with Hg(2+) to form a T-Hg(2+)-T dsDNA structure in the solution, which hampers the formation of a G-quadruplex structure. However, in the presence of the target, GSH/Cys reacts with Hg(2+) to keep DNA probes in a free single state, resulting in the effective formation of a G-quadruplex structure of the DNA probe (GP). Subsequently, due to the strong interaction between the G-quadruplex structure and NMM, fluorescence was greatly enhanced. This fluorescence strategy does not require any chemical modification, making the assay convenient and cost-effective. This method exhibited a linear relationship between peak fluorescence intensity and concentration of GSH in the range of 10-400 nM with a limit of detection (LOD) of 9.6 nM. A linear range for Cys detection was obtained in the concentration range of 10-500 nM with an LOD of 10 nM. Moreover, the proposed method worked well for the analysis of complex biological samples.
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China.
authors: Jingjin
authors: J
authors: Zhao
authors: Chunfei
authors: C
authors: Chen
authors: Liangliang
authors: L
authors: Zhang
authors: Jianhui
authors: J
authors: Jiang
authors: Guoli
authors: G
authors: Shen
authors: Ruqin
authors: R
authors: Yu
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D003545:Cysteine / Q000032:analysis / Q000097:blood*; D004277:DNA, Single-Stranded / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D054856:G-Quadruplexes; D005978:Glutathione / Q000032:analysis / Q000097:blood*; D006801:Humans; D057230:Limit of Detection; D008628:Mercury / Q000737:chemistry; D008652:Mesoporphyrins / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013941:Thymine / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D005456:Fluorescent Dyes; D008652:Mesoporphyrins; C065420:N-methylmesoporphyrin IX; D008628:Mercury; D005978:Glutathione; D003545:Cysteine; D013941:Thymine