【作者】 王超；

【导师】 苏星光；

【作者基本信息】 吉林大学 ， 分析化学， 2010， 博士

【摘要】 从20世纪80年代开始研究的纳米技术在90年代获得了突破性进展,它对生物医学工程领域的渗透与影响是显而易见的,纳米生物技术是目前国际生物技术领域的热点研究课题,美国、日本、德国和我国均已将纳米生物技术列入国家重点发展领域。目前,纳米生物技术的应用涵盖从疾病诊断到靶向药物治疗和基因修复的诸多方面,其中,最受关注的是将半导体量子点用作生物标记、生物传感器和影像对比剂等。本论文以水相合成法制备了三种纳米粒子,并将所合成的三种纳米粒子应用于化学检测、生物医学检测及成像中。主要内容包括:论文第一章主要介绍了量子点的合成、生物医学应用以及应用中所遇到的问题和解决方法,阐明了本论文的研究意义及主要内容。论文第二章主要介绍了以巯基丁二酸（MSA）为稳定剂,通过回流和水热方法制备高质量的CdTe量子点。并利用所合成的CdTe量子点通过层层自组装的方法,制备成CdTe/PDDA量子点多层膜,并通过多层膜的荧光猝灭来检测水溶液中汞离子(Hg²⁺)的浓度。论文第三章主要介绍了通过反相微乳法合成CdTe量子点/二氧化硅（CdTe/SiO₂）复合纳米粒子,以及将其作为荧光探针用于生物检测和细胞标记。论文第四章主要介绍了以巯基丙酸为稳定剂,利用成核掺杂的方法,在水溶液中合成Mn²⁺掺杂的ZnSe量子点（Mn:ZnSe d-dots）。由于这种掺杂型的量子点不含重金属元素Cd,从而减少了量子点的生物毒性。此外,我们还考察了所合成的Mn:ZnSe d-dots的光稳定性,与CdTe量子点相比,Mn:ZnSe d-dots具有更好的光稳定性。论文第五章,利用溴化乙啶（EB）作为探针,详细研究了前面几章中所合成的三种纳米粒子（CdTe QDs,CdTe/SiO₂和Mn:ZnSe d-dots）与DNA分子之间的相互作用。研究结果表明,无论是在暗处还是在紫外光照射下,CdTe QDs都是最容易造成DNA损伤的纳米粒子;与CdTe QDs相比,CdTe/SiO₂ NPs引起的DNA损伤大大减小,而Mn:ZnSe d-dots作为一种新型的掺杂型量子点几乎不引起DNA分子的损伤,这使其作为荧光标记物在生物医学研究领域具有巨大的应用潜力。更多还原

【Abstract】 Quantum dots （QDs）, also named semiconductor nanocrystals or semiconductor nanoparticles, are a kind of spherical or quasi-spherical nanoparticle, which are usually composed of atoms from groups II–VI, III–V, or IV–VI of the periodic table. QDs are nanocrystals with the diameter within 10 nm, composed of nanometer-sized crystalline clusters of a few hundred to a few thousand atoms, which have different properties compared with the bulk crystals. As a result of their small size, QDs possess high surface-to-volume ratios, such that many of their chemical and physical properties are dominated by their surface, not by their bulk volume. One extraordinary property of QDs is that the particle size determines many of the QDs’properties, most importantly the wavelength of fluorescence emission. Typical QDs have been exploited in inorganic ion sensors, organic small molecule sensors, biological macromolecule sensors, biological labeling, cell labeling, cellular effector and reporters, animal imaging and therapy. Thus far, one of the fastest developing and most exciting interfaces of nanotechnology is the use of quantum dots （QDs） in biology.In chapter 1, we described the extraordinary optical properties of QDs and developments in methods for their synthesis. Then we focused on the biomedical application, and the toxicity of QDs and potential barriers to their use in practical biomedical applications. Finally, we provided insights into improvements aimed at decreasing the toxicity of QDs, and the significance and contents of this dissertation.In chapter 2, we studied the synthesis and application of aqueous CdTe QDs. We choose a new ligand mercaptosuccinic acid （MSA） as stabilizer for CdTe QDs synthesis in both refluxing and hydrothermal routes. The stabilizer MSA composed of both thioglycolic acid （TGA）-like and 3-mercaptopropionic acid （MPA）-like moieties, which can accelerate the growth of CdTe QDs in the whole synthesis process. We optimized the condition of two routes by varying the ratio of precursors and reaction temperature. Ultimately, the CdTe QDs obtained by two routes all have high PL QY and narrowing size distribution. These MSA modified CdTe QDs have carboxyl groups on their surface and can be easily combined with antibodies or antigens for biomedical applications. Then using the synthesized CdTe QDs, we fabricated multilayer CdTe QDs films on quartz slides by LbL assembling of poly（dimethyldiallyl ammonium chloride） （PDDA） and CdTe QDs capped with mercaptosuccinic acid （MSA）. Through the electrostatic interactions, PDDA and CdTe QDs were alternately deposited on the quartz slides, thus photostable QDs multilayer films were obtained. The fluorescence of PDDA/QDs multilayer films was sensitive to the existence of Hg （II） ions. The fluorescence of multilayer films was quenched effectively by Hg （II） ions. The concentration of Hg（II） in aqueous solution can be determined through the fluorescence quenching of multilayer films.In chapter 3, we embedded aqueous CdTe QDs in silica spheres by reverse microemulsion method and functionalized the silica spheres as photostable fluorescent probes were applied to biological labels. As the intermediate silica species can carry negative charges at pH 11, the same pH as CdTe QDs stabilized by MSA, only one QD can be coated by silica sphere, which may weaken the fluorescence intensity of CdTe@SiO₂ core-shell nanoparticles and limit their applications. With the aim of embedding more CdTe QDs in silica spheres, we used poly（dimethyldiallyl ammonium chloride） （PDDA） to balance the electrostatic repulsion between CdTe QDs and silica intermediates, which enhanced the fluorescence intensity of CdTe/SiO₂ composite nanoparticles effectively. The modified surface of silica nanoparticles has amino groups as functional groups which combine with biomolecules and methylphosphonate groups as stabilizing groups which reduce aggregation of silica nanoparticles. The CdTe/SiO₂ composite nanoparticles were linked with biotin-labeled mouse IgG via covalent binding. Furthermore, they can recognize FITC-labeled avidin and avidin on the surface of polystyrene microspheres successfully through the high affinity between avidin and biotin. Finally, the CdTe/SiO₂ composite nanoparticles were used to label the MG63 osteosarcoma cell, which demonstrates the application of CdTe/SiO₂ composite nanoparticles as fluorescent probes in bioassay and fluorescence imaging is feasible.In chapter 4, we attempted to prepare Mn:ZnSe d-dots by a nucleation–doping strategy with mercaptopropionic acid as the capping reagent in aqueous solution. Mn:ZnSe d-dots are new generation fluorescence emitter, which have great application potentials in biomedical fields for no heavy metal element addition during the synthesis process. Compared with organometallic synthesis, aqueous synthesis is cheaper, simpler, less toxic and Mn:ZnSe d-dots synthesized in aqueous solution are biologically compatible, making them much more suitable for biomedical applications. The optimal precursor ratio and the kind of stabilizer for obtaining Mn:ZnSe d-dots with good PL emission properties were studied in detail. As compared with CdTe QDs synthesized in aqueous solution, Mn:ZnSe d-dots have much better photostability, indicating that they can be applied as outstanding fluorescent labels for biological assays, imaging of cells and tissues, and even in vivo investigations.In chapter 5, we explored another fluorescent method for systematically investigated the DNA damage induced by a series of previously synthesized water-soluble nanoparticles, including CdTe QDs, CdTe/SiO₂ composite nanoparticles （CdTe/SiO₂ NPs）, and Mn-doped ZnSe QDs （Mn:ZnSe d-dots）. Ethidium bromide （EB） is a fluorescent compound, which is normally used to probe DNA structure in drug-DNA and protein-DNA interactions by its intercalating in the DNA double helix to enhance its fluorescence. Once the double helix structure of DNA molecules is destroyed, the fluorescence of EB will be quenched. It was found that ionic strength, pH value and UV irradiation influenced the PL emission properties of CdTe QDs, CdTe/SiO₂ NPs and Mn:ZnSe d-dots, and also influenced the interaction of DNA molecules with them. Among the three kinds of nanoparticles, DNA molecules were most easily damaged by CdTe QDs whether in the dark or under UV irradiation. The CdTe/SiO₂ NPs led to much less DNA damage when compared with CdTe QDs, as a silica overcoating layer could isolate the QDs from the external environment. Mn:ZnSe d-dots as a new class of non-cadmium doped QDs demonstrated almost no damage for DNA molecules, which have great potentials as fluorescent labels in the applications of biomedical assays, imaging of cells and tissues, even in vivo investigations.更多还原