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Thioflavin T as an Efficient G‑Quadruplex Inducer for the Highly Sensitive Detection of Thrombin Using a New Föster Resonance Energy Transfer System

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journal contribution
posted on 05.08.2015, 00:00 by Xingfen Liu, Xiaoxiao Hua, Quli Fan, Jie Chao, Shao Su, Yan-Qin Huang, Lianhui Wang, Wei Huang
We report a new Föster resonance energy transfer (FRET) system that uses a special dye, thioflavin T (ThT), as an energy acceptor and a water-soluble conjugated polymer (CP) with high fluorescence as an energy donor. A simple, label-free, and sensitive strategy for the detection of thrombin in buffer and in diluted serum was designed based on this new system using ThT as an efficient inducer of the G-quadruplex. The difference between the blank and the positive samples was amplified due to distinctive FRET signals because thrombin has little effect on the intercalation of ThT into the G-quadruplex. In the absence of the target, ThT induces the aptamer to form a G-quadruplex and intercalates into it with strong fluorescence. The electrostatic attractions between the negatively charged G-quadruplex and positively charged CP allow a short donor–acceptor distance, resulting in a high FRET signal. However, in the presence of the target, the aptamer forms a G-quadruplex–thrombin complex first, followed by the intercalation of ThT into the G-quadruplex. A long distance exists between the donor and acceptor due to the strong steric hindrance from the large-sized thrombin, which leads to a low FRET signal. Compared with previously reported strategies based on the FRET between the CP and dye, our strategy is label-free, and the sensitivity was improved by an order of magnitude. Our strategy also shows the advantages of being simple, rapid (about 50 min), sensitive, label-free, and low-cost in comparison to strategies based on the FRET between quantum dots and dyes.