Coupling Bio-molecules With Quantum Dots And Its Application

Shell@core quantum dots (QDs) are a new kind of novel fluorescent label material for nanobiophotonics. Comparing with the traditional organic dyes, QDs possess tunable fluorescence emission, high photo-stability and attractive spectrum with almost symmetrical narrow emission and broad excitation; and the fluorescence intensity of QDs is scores of times than that of organic dyes. Due to such optical properties, in recent years more and more important results have been achieved in cell labeling, biomolecular detection and immunoassay. Nowadays the research about QDs has become one of the most attractive fields in life science. And here the thesis mainly focuses on the surface modification of QDs, the coupling between proteins and QDs, bioactivity detection and biological application of the QD-protein conjugates. The main results are as the following:1. Different reagents are used to modify the 568nm-emission QDs and there influences on the optical qualities of QDs are discussed. A good method of modification by which the excellent optical qualities of QDs are kept is found.2. The water-soluble QDs were linked to the antibodies using the coupling reagents ethyl-3-(dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The linking process was shown to be effective by ultra-filter centrifugation and column purification. After comparing the quantities of Abs and water-soluble QDs involved in the linking reaction via column purification, the molar Abs:QD ratio in the reaction is discussed. The circular dichroism (CD) spectra of Abs and QD–Ab conjugates were very similar to each other, indicating that the secondary structure of Abs remained largely intact after the conjugation. Finally, antigen (Ag)–antibody (Ab) recognition reactions performed on the surface of a glass slide showed that the conjugate retained the activity of Abs and is suitable for immunoassay.3. A method of labeling holo-transferrin (Tf) with water-soluble QDs and the bioactivity of the QD-Tf conjugate are discussed. Firstly the Tf are linked to QDs using the coupling reagents EDC and NHS and the QD-Tf conjugate are separated with column G-150. And then the concentration of the conjugate are estimated and the molar Abs:QD ratio in the conjugate is speculated to be 1.6. Finally the bioactivity of the QD-Tf conjugate is detected to be kept by the ligand-receptor binding assay on the surface of cell.