【作者】 孙利春；

【导师】 盖宏伟；

【作者基本信息】 湖南大学 ， 生物医学工程， 2011， 硕士

【摘要】 与常规的有机荧光染料相比,量子点具有激发光谱宽,发射光谱窄,量子产率高,光学稳定性好等优点,它已广泛应用于分子生物学,细胞生物学,生物化学,蛋白质组学、基因组学、药物筛选,医学诊断等领域。本文主要研究了几种化合物及脂质体包裹对量子点光学性质的影响,具体内容如下:1、几种化合物对量子点光学性质的影响。实验研究了巯基乙酸、半胱氨酸、二硫代苏糖醇、没食子酸乙酯、硫脲、谷胱甘肽,表面活性剂以及亚硫酸钠除氧对溶液中单个量子点闪烁、漂白、蓝移的影响。结果表明,巯基化合物巯基乙酸、半胱氨酸、二硫代苏糖醇、硫脲、谷胱甘肽,以及抗氧化剂没食子酸乙酯通过钝化量子点的表面缺陷态而抑制了量子点的闪烁;并且加入这几种化合物后,量子点的幂律分布指数αon减小,量子点“on”时间变长。一定浓度的三重态淬灭剂二硫代苏糖醇、谷胱甘肽,抗氧化剂没食子酸乙酯以及亚硫酸钠对量子点溶液除氧后,有效地抑制了量子点的漂白;临界胶束浓度以上的阳离子表面活性剂CTAB、CTAC可以保护量子点的受激三线态免遭淬灭,而加快了量子点的漂白。由此我们推测量子点的光氧化和三重态的积聚共同导致了量子点的光漂白。添加一定浓度的强还原剂二硫代苏糖醇和没食子酸乙酯,以及对溶液进行除氧后阻止了量子点核的氧化,从而抑制了量子点的蓝移。实验发现了几种有效抑制量子点闪烁、漂白与光谱蓝移的化合物,改善了量子点的光学性质,并初步阐释了量子点这些光学现象所隐藏的机理,从而有望进一步拓展量子点的应用范围。2、脂质体包裹对量子点光学性质的影响。实验采用逆相蒸发法将水溶性的羧基量子点包裹进脂质体,用荧光成像和散射成像相结合的方式,对其进行表征,并考察了脂质体包裹后对量子点光学性质的影响。结果表明,大部分量子点被包裹入脂质体;量子点被脂质体包裹后,其耐漂白能力降低。该方法提高了量子点的生物兼容性,但同时降低了量子点的光化学稳定性。更多还原

【Abstract】 Compared with conventional fluorescence dyes, quantum dots (QDs) have many excellent optical properties, such as broad excitation spectrum, narrow emission spectra, high quantum yields, good photostability and so on. They have gotten extensive use in molecular biology, cell biology, biochemistry, proteomics, genomics, drug screening, medical diagnosis, and so on. This thesis studied the influence of several compounds and liposome encapsulation on the optical properties of quantum dots. The main contents were as follows:1. The influence of several compounds on the optical properties of quantum dots. The effect of several compounds such as mercaptoacetic acid, cysteine, dithiothreitol, ethyl gallate, thiourea, glutathione, surfactants and sodium sulfite’s depleting oxygen to fluorescence blinking, photobleaching, blue shift of single quantum dots in solution was investigated in detail. The results of experiment proved that sulfhydryl compounds such as mercaptoacetic acid, cysteine, dithiothreitol, thiourea, glutathione, and antioxidant ethyl gallate could suppress blinking in quantum dots by passivating surface trap states of quantum dots. And the power-law distribution exponentialαon decreased which meant long“on”time after addition of these compounds. The addition of an appropriate dose of triplet quencher such as dithiothreitol, glutathione, and antioxidant ethyl gallate into the sample and depleting the oxygen from solution by use of sodium sulfite could inhibit photobleaching of quantum dots. We also found QDs’photobleaching was speeded up by cationic surfactants (hexadecyl trimethyl ammonium bromide, CTAB, hexadecyltrimethylammonium chloride, CTAC) because they could protect QDs’triplet excited state from quenching at a concentration above the critical micellar concentration (CMC) of them. Thus we speculate that photooxidation and accumulation of the triplet excited state together induce photobleaching of quantum dots. The oxidation of quantum dots cores was blocked by addition of an appropriate dose of strong reducing agents (dithiothreitol, ethyl gallate) and by efficient oxygen removal using sodium sulfite, and as a result, blue shift of quantum dots was suppressed. In a word, the optical properties of quantum dots were improved by several compounds which could effectively suppress the photobleaching, blue shift and blinking in quantum dots and the possible mechanism behind these optical phenomena was elucidated. Consequently, the application scope of quantum dots would expand further.2. The influence of liposome encapsulation on the optical properties of quantum dots. The water-souble carboxyl quantum dots were encapsulated in liposomes by the method of reverse-phase evaporation. It was characterized by the combination of fluorescent imaging and scattering imaging and we also investigated the impact of liposome encapsulation on the optical properties of quantum dots. The result indicated that most of the quantum dots were encapsulated in liposomes and the quantum dots had lower photobleaching resistance after liposome encapsulation. This method raised the biological compatibility of quantum dots, but meanwhile, the QDs’photostability was lowered.更多还原