Nanomaterials for bio-imaging and therapeutics

Unrestricted In this thesis we studied the applications of colloidal nanocrystal quantum dots (QD) in bio-medical studies. We investigate the synthesis of QD and report a relatively simple method for synthesizing QD. To produce QDs that are more stable and have higher fluorescent quantum efficiency than those produced by other methods (typically CdSe/ZnS core/shell structures), we developed a CdSe/ZnSe/ZnS (core/shell/shell) nanocrystal complex, capped with the small molecule mercaptoacetic acid (MAA) for aqueous solubilization and low toxicity. These MAA-capped QDs can be used as the visualization aid for a multi-functional probe combining the functions of viruses and carbon nanotubes (CNT). A mild method of tagging virus through a polycationic solution, Polybrene, at 4°C is developed. This method can preserve most viral infectivity. The probes can be used to induce higher death rate in cells under near-infrared laser irradiation than in the cells without them, and thus, after additional improvements, may find applications in the study of cancer therapy. The optical properties of MAA-capped QDs are pH dependent. In particular, the fluorescence intensity increases with pH (pH between 4 and 10) of the environment. The results lead to a new venue to exploit QD as nano-scale sensors for localized physical and chemical properties in cells.

【无限制】本论文针对胶体纳米晶量子点（colloidal nanocrystal quantum dots, QD）在生物医学研究中的应用展开研究。我们对量子点的合成方法进行了探究，并报道了一种相对简便的量子点合成方案。为制备稳定性优于传统CdSe/ZnS核壳结构量子点、且荧光量子效率更高的产物，我们开发了CdSe/ZnSe/ZnS核壳壳纳米晶复合物，并以小分子巯基乙酸（mercaptoacetic acid, MAA）对其进行包覆，以实现水溶液增溶并降低生物毒性。经巯基乙酸包覆的量子点可作为可视化辅助工具，用于构建整合病毒与碳纳米管（carbon nanotubes, CNT）功能的多功能探针。此外，我们开发了一种在4℃条件下通过聚阳离子溶液聚凝胺（Polybrene）对病毒进行温和标记的方法，该方法可保留绝大多数病毒的感染活性。实验结果表明，搭载该探针的细胞在近红外激光辐照下的死亡率高于未搭载探针的对照组细胞；经进一步优化后，该技术有望应用于癌症治疗相关研究。巯基乙酸包覆量子点的光学性质具有pH依赖性，具体表现为荧光强度随环境pH（4至10区间）升高而增强。上述研究结果为将量子点开发为用于检测细胞内局部物理与化学特性的纳米级传感器开辟了全新途径。