【作者】 赵义丽；

【导师】 王静媛；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2010， 博士

【摘要】 本论文通过发散法合成了星形和扇形两种PAMAM树枝状分子,并对其光学性质以及光学性质的影响因素进行了详细的研究。通过对这两种树枝状分子进行修饰,得到了10种不同的PAMAM树枝状配体,这些配体含有可以与量子点表面阳离子相作用的基团(氨基或羧基),通过与原始油溶性量子点的配体交换反应,便可以得到水溶性和生物相容性的量子点。得到的PAMAM树枝状配体包覆的量子点保持了原始量子点的光学性质,并且具有较小的粒径,在水溶液或PBS缓冲溶液中均有较好的分散性。由于PAMAM树枝状配体的保护作用,使量子点具有较好的耐热性能、抗光氧化性能、抗化学氧化性以及耐酸性等。在常态下储存数月之久,量子点的水溶液中也未发现沉淀析出,说明这种PAMAM树枝状配体包覆的量子点有很好的稳定性。在合成树枝状配体时,我们将PEG、叶酸和紫杉醇等功能性分子修饰到其表面,得到了多功能性的树枝状配体,这种树枝状配体包覆的量子点也具有多功能性。连接叶酸和紫杉醇的量子点可以作为肿瘤靶向成像和靶向治疗的双功能纳米粒子,同时,还可以通过荧光来实时监测紫杉醇对肿瘤细胞的治疗效果。本论文的研究在癌症早期诊断和靶向治疗领域将有重要意义。本论文是在国家自然科学基金:用树枝状大分子包覆磁性纳米量子点做为双探针分子的构筑(基金号:20574028)的资助下完成的,另外还得到了吉林大学2009年研究生创新研究计划项目:特异性识别肿瘤细胞的探针分子的制备(基金号:20091010)的资助更多还原

【Abstract】 Semiconductor quantum dots (QDs) have attracted considerable interest for molecular, cellular, and in-vivo imaging applications, due to their unique optical and electrical properties, such as narrow and size-tunable emission spectra (typical full width at half maximum, 30 nm), broad absorption profiles, and superior photostability. However, currently most of the reported syntheses lead to QDs coated with hydrophobic molecules, which make them insoluble in water. QDs with such hydrophobic capping cannot be used directly in applications that require aqueous solubility or an effective charge transport property. This obstacle is usually eliminated by surface ligand exchange reactions where the appropriate functionality is introduced with a new capping ligand.Poly(amidoamine) (PAMAM) dendrimers, with numerous functional groups, are more dense than linear ligands. Furthermore, the terminal groups (amine, carboxyl, and hydroxyl) of PAMAM dendrimers can be modified with different functionalities and can be linked with various biomolecules. These unique structural features of PAMAM dendrimers make them ideal nanoplatforms to conjugate biologically important substances (e.g., imaging agents, argeting molecules, and drugs) for subsequent imaging, targeting, and treatment of biological systems.This paper is focused on the synthesis of star-shaped structural feature Tetra-dendron polyamidoamine (PAMAM) dendrimers and cone-shaped structural feature di-dendron PAMAM dendrimers with ethylenediamine (EDA) and mono-Boc-protected EDA as a core, respectively. Strong UV absorbance spectra and fluorescence spectra from tetra-dendron dendrimers or di-dendron dendrimers with different terminal groups (-NH2, -COOCH3, -OH) were studied under different conditions by varying experimental parameters such as pH value and concentration. The result shows a rapid increase of fluorescence intensity at low pH. Furthermore, it was confirmed that the concentration of two dendrimers plays an important role in fluorescence intensity. The increase of fluorescence intensity was linear with respect to concentration at low concentration regions, but the intensity increases slowly at high concentration regions.We developed eight kinds of PAMAM dendrimer ligands with different functional groups and describe a process for transferring octadecylamine-stabilized CdSe/ZnS core-shell semiconductor nanocrystals (QDs-ODA) from chloroform into water through a ligand exchange process. The resulting dendrimer-coated nanocrystals were soluble in various aqueous media, including all common biological buffer solutions tested. These water-soluble nanocrystals dissolved in water exhibit the same fluorescence and absorption spectra as the ODA-CdSe/ZnS core-shell nanocrystals dissolved in organic solvents such as chloroform. Furthermore, the stability of dendrimer-coated nanocrystals was quantitatively examined against sintering, acid etching, oxidation with H2O2 and photo-oxidation. Under ambient conditions, there is no precipitate out of the solution. In addition to their superior performance, the synthetic chemistry of dendrimer ligands and the corresponding dendrimer-coated nanocrystals is relatively simple and with high yield.Pyrene is widely used as a fluorescent probe to measure the hydrophobicity of localized domains and microenvironments because its fluorescence emission spectra are very sensitive to polarity changes. The present research systematically examines the hydrophobicity of localized domains of QDs capping with hydrophilic dendrimer ligands to detect the efficiency of exchange reaction between different hydrophilic ligands and hydrophobic QDs using pyrene as a reporting probe. Furthermore, the ligand exchange kinetics of ligand 2 and ligand 3 has also been researched.We report the design and synthesis of folate-poly(ethylene glycol)-polyamidoamine (FPP) functionalized CdSe/ZnS quantum dots (QDs), in which the QD plays a key role in imaging, whereas the folate-poly(ethylene glycol) (PEG) conjugates of polyamidoamine (PAMAM) dendrimer serve as targeted system to folate receptor in tumor cell. Because of membrane expression of FA-receptors in tumor cells, this class of ligand-exchanged QDs is able to target the tumor cells. We have evaluated FPP-coated QDs and QDs without folate in HeLa cells and shown that cellular uptake in case of FPP-coated QDs is significant than non-folate QDs in vivo imaging experiment. These insights are important toward the design and development of nanoparticle agents for optical detection of tumor cells and bio-imaging.Because of the unique structural properties of PAMAM dendrimers, dual functional nanoparticles for tumor imaging and targeted therapy using PAMAM dendrimer-coated quantum dots. These dual function of nanoparticles exhibit the same fluorescence and absorption spectra as the dendrimer-coated QDs. The resulting dual function of nanoparticles were found to be soluble in various aqueous solvent, such as PBS buffer solution, and there are no aggregation in the solution. Furthermore, the size of dual function of nanoparticles is very small (around 30nm).更多还原