The Study Of Quantum-dot-tagged Aptamer Biosensor

Based on the feature of aptamer conformation change specifically and fluorescence resonance energy transfer (FRET) between quantum dot (QD) as donor and organic fluorophore as acceptor, we devised a biosensor to detect the target of aptamer. This thesis includes the following parts:1.Based on the feature of adenosine triphosphate (ATP) aptamer and the advantage of 605 nm QD/Cy5 FRET pair, we established an efficient biosensor for rapid and convenient detection of ATP, possessing the advantage of specific detection.In the absence of ATP, the capture DNA hybridizes with both 3'-biotin-modified DNA and 3'-Cy5-labelled DNA, which induces the close distance between 605 nmQD and Cy5. Under such a condition, 605 nmQD is excited at 488 nm, and Cy5 emits fluorescence at 670 nm in virtue of FRET. In contrast, when ATP is present, aptamer-ATP interaction causes aptamer conformation change, leading to the dissociation of 3'Cy5-labelled DNA from the hybridization complex, and the fluorescence intensity change of both donor and acceptor.2.Based on the feature of thrombin aptamer and the advantage of 605 nm QD/Cy5 FRET pair, we established a biosensor to detect potassium ion.In the absence of potassium ion, 3'-Cy5-modified aptamer DNA binds to streptavidin-conjugated 605 nmQD through biotin-streptavidin interaction. Under such a condition, 605 nmQD is excited at 488 nm, and Cy5 emits fluorescence at 670 nm in virtue of FRET. The fluorescence intensity of 605 nmQD is high, and the Cy5 fluorescence intensity is low. In contrast, when potassium ion is present, aptamer-potassium ion interaction causes aptamer conformation change, which induces the close distance between 605 nmQD and Cy5. 605 nmQD fluorescence intensity decreased but Cy5 fluorescence increased with potassium ion concentration increase.