Study On Functionalized Fluorescent Quantum Dots Probes As Biomarker For Disease Diagnosis

Quantum dots (QDs), also known as semiconductor nanocrystals, because of their unique optical and electrical properties,have attracted great interest and attention from physicists, chemists and biologists, and have become a most frequently studied matter in the nanotechnology field. In this paper, the hydrophobic high quality QDs were first prepared and surface modification was followed to prepare water-soluble QDs. Then through the coupling of biological macromolecules with QDs, the QDs bioconjugates were used in the preliminary study of diagnosis of disease.1. In this paper, we successfully prepared CdSe quantum dots (QDs) by colloid chemistry method, which were high crystallization and monodisperse. About the different types of CdSe QDs, the emission wavelength region were between 535nm and 580nm, the region of the full width at half maximum (fwhm) of the photoluminescence (PL) peak were between 23nm and 29nm, the quantum yield (QY) was as high as 0.73. And then, the influences of reaction time and ligand on optical property of QDs had been discussed. From ultraviolet visible spectra (UV-Vis) and photoluminescence (PL), we could get the results: with the increase of reaction time and the concentration of ODA and TOPO, the size of QDs was increased, as well as the absorption and emission spectra were clearly red shifted; using TOP to prepare Se precursors benefited to prepare different QDs with various colors. We used successive ion layer adsorption and reaction (SILAR) method to modify CdSe QDs, which could lead us to gain different core/shell QDs with several different structures. And we compared optical properties, size, and inner structures of pure CdSe QDs and modified CdSe QDs with UV, PL, HRTEM and XRD, and so on. After surface passivation, the QY of all the core shell QDs had improved from about 0.1 to about 0.4~0.7, and the fwhm region was between 30nm and 40nm. The introduction of the CdxZn1-xS shell could benefit the growth of core/shell QDs and prefect the crystal properties, which could more efficiently protect the core QDs.2. There were four methods in this paper for the water-solublization of hydrophobic QDs. Namely, ligand exchange, amphiphilic polymer self-assembly, ultrasound emulsification and silica coating. The results showed that: a simple modification of ligand exchange modification is easy, but the colloid stability of products is poor and low QY; Amphiphilic polymer self-assembly modification of QDs is simple, but have difficult and cumbersome purification; ultrasound emulsification modified method is simple, and purification procedure is easy with centrifugation, but with big size and uneven size distribution; silica coating is a mature technology, good at preparation of ultrafine particles and with narrow size distribution, but a longer preparation period. In this paper, effect of varying types of QDs on the QY after silica-encapsulation is systematically studied. The results showed that QDs with appropriate structure and composition of shells can much better retain the initial QY after silanization. Different methods have their own shortcomings, thus we could choose proper modification method for different biomedical applications.3. We also prepared two different QDs fluorescence microspheres, which could be applied as biochips. The results gained from fluorescence microscopy and PL indicated that several PS-QDs fluorescence encoding microspheres could be successfully gained by swelling; stained effect used with core-shell QDs was obviously better than that used with core QDs; fluorescence microspheres with different intensities could be easily gained through the change of reaction time, which could not gained through the change of sweller.4. Multi-functional fluorescent magnetic nanoparticles were prepared in two ways: ultrasound emulsification and silica-coating. TEM characterization showed that ultrasound emulsification is opt for preparation of big size nanoparticles with ca.200nm, a wide size distribution; while ultrafine nanoparticles with ca.40nm, monodisperse distribution were obtained with silica-coating. With the help of EDX analysis, it proved that the samples obtained with the above two methods contain both quantum dots and magnetic nanoparticles in a single nanoparticle. The effects of both QY and magnetic response of the multi-functional fluorescent magnetic nanoparticles were taken into account; we designed experiments for the balance of QY and response to the magnetic effect.5. Specific fluorescent nano probes used for the suspending detection were prepared by using the as-prepared water-soluble QDs and biological macromolecules (such as antibodies). Combination of the carboxyl polystyrene (PS) microspheres prepared in our lab, the as-prepared specific QDs-probes were designed and used for the suspending fluorescent detection in liquid phase. Antigen-antibody reaction can be occurred on the surface of antigen-coated PS microspheres.6. Preparation of hydrophilic multi-color quantum dots for high-throughput biological detection. In this paper, two colors of QDs were used to link two antibodies, and then added into the antigen pre-coated polystyrene plates. The results showed that the mixed antigen sample hole can be observed in two colors of fluorescent signal. That means multi-color fluorescent QDs can be used to the high-throughput biodetection.7. The preparation of fluorescent QDs nano-probe for the detection of avian influenza virus. Hydrophilic QDs were bioconjugated with the avian influenza virus antibodies, and such bioconjugates have specific targeting ability to the avian influenza virus. The results showed that the as-prepared QDs nano-probes have excellent detection ablility to the avian influenza virus. The detection is rapid and sensitive, suitable for rapid detection in the import and export port.To sum up, in this study, the newly nanotechnology and disease diagnosis technology were combined to develop a novel kind of fluorescent detection system. Making full use of the advantages of QDs and the coupling of specific biological molecules to construct a specific, sensitive and strong stable fluorescent diagosis reagent for the diagnosis of diseases. The research results in this paper provide foundation for the real-use of QDs in the diagonis area.