| Bioprobes are functional molecules or complexes used to measure the presence or concentration of biological molecules, microorganisms, etc., by translating a biochemical interaction at the probe surface into a quantifiable physical signal, usually consisted of both targeting unit and signal unit. Quantum dot (QD), as one of the first nanomaterials to be integrated with the biological sciences, has extensive application prospect in biomedicine due to their excellent fluorescent characteristics, such as high levels of brightness, photostability and size-tunable, narrow, Gaussian emission spectra that can be excited at a single wavelength. Bare nanoparticles as signal unit always cannot interact directly with biological systems and provide a rigid foundation for the development of QD-based bioprobes. The incorporation of the targeting molecules or complexes to QDs without losing any function is the key in the preparation of QD-based bioprobes. In this work, with the modification of both QD surfaces and bio-surfaces, the compatibility between QDs with targeting units was focused on so that the preparation of QD-based bioprobes can be facilitated. Main works in this dissertation are as follows:1. The modification of quantum dots with grafted polyacrylic acid polymer.A platform for QD modification and functionalization based on amphiphilic polymers was developed. Results showed that the grafting ratio of amphiphilic polymer palyed an important role in QDs modification. The prepared amphiphilic polymer coating QDs were small, stable and bright. Besides, various functional groups (-NH2,-COOH,-SH, NT A, and so on) were derived on the polymer so that the functionalized polymer coated QDs could be easily labeled with biomolecules such as protein, DNA, and so on.2. Renovation of organic ligand shells on lipophilic QDs.The effect of surface ligand losing on QD stability and solubilization was investigated. A renovation method for organic ligand shells on QDs with octylamine was established. The QDs after renovation possessed good photophysical properties compare with non-agglomerated QDs in the same batch, which could be easily encapsulated with amphiphilic molecules. Results showed that the interface between the inorganic core and the organic ligand shell not only affected the stability of hydrophobic QDs, but also palyed a critical role in the water-solubilization of QDs.3. Preparation of single quantum dot coupled single long-chain DNA molecule complex based on polymerase chain reaction.A new PCR strategy was used for the construction of single QD-labeled single long DNA probes. Using maize total genomic DNA as templates, a specific sequence of fatty aldehyde dehydrogenase gene (rf2e1), a single copy gene, was amplified with QD labeled primer. Electrophoresis, AFM and fluorescence spectroscopy experiments confirmed that the one-to-one QD-labeled long DNA conjugates were successfully prepared and retained fluorescence properties of QDs. This one-to-one QD-labeled long DNA probe was used to map a single-copy gene on large maize chromosomes. Labeling a single long DNA to a single QD by this modified PCR strategy will enable substantial advances in detection of small single-copy DNA fragments, single molecule imaging and quantitative analysis, as well as possible fabrication of more complex nanostructures.4. Surface modification and QD labeling of enveloped viruses.A host cell-assisted surface labeling strategy for enveloped viruses with high efficiency, good versatility, simple procedures and low technical barriers was proposed, offering a good example for solving problems with biological systems. Taking the advantages of natural assembly process of viruses inside host cells, the infectivity of functionalized viruses can be preserved to the largest extent. Then, after binding with streptavidin-X, the viruses will acquire new functions because of the characteristics of the X. Then, after binding with streptavidin-QDs, it will be a powerful candidate method for labeling enveloped viruses with QDs. |
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