Preparation And Application Of Water-soluble CdSe/ZnS Fluorescent Quantum Dots Modified With Polymaleic Anhydride And Silica

Compared with conventional organic fluorescent dye, quantum dots as a new kind of fluorescentmaterial have many incomparable superiorities, such as wide and continuous absorption spectrum, narrowand symmetric emission spectrum; large stoke displacement, small spectral overlap, high sensitivity; stronganti-bleaching, long fluorescent lifetime and high stability. These physical properties of fluorescentquantum dots can be changed by controlling the particle size and composition. Fluorescent quantum dotshave many important applications in the field of biosensors, cell labeling, cell separation and drug delivery.However, the currently-used fluorescent quantum dots are generally synthesized in the high-temperatureorganic solvent, modified with a layer of hydrophobic organic ligand, the quantum dots can not be welldissolved in water, making it difficult applied directly to the biomedical field. Therefore, the need foraqueous transfer and surface modification are necessary.There are three main methods for surface modification and aqueous transfer. The first method is ligandexchange; the second method is based on the silica coating method; the third method is based on theamphiphilic polymer. These transfer methods have mangy advantages and disadvantages. Ligand exchangemethods can generate a small particle size, silica and amphiphilic polymer-coated quantum dots with verygood stability. In this paper, the method of ligand exchange and silica encapsulation are used to synthesizewater-soluble quantum dots, the application of water-soluble quantum dots in the field of cell labeling andbiological detection have also been preliminary explored, the main work and the results obtained are asfollows:Chapter Two: A robust ligand exchange approach is used to prepare biocompatible CdSe/ZnS quantumdots. In this method, polymaleic anhydride ligand are used to replace original hydrophobic oleic acid ligandand form a protection shell with multiple hydrophilic groups to coat and protect CdSe/ZnS. Theas-prepared aqueous quantum dots exhibit small particle size and good colloidal stability in aqueoussolutions with a wide range of pH, salt concentrations and under thermal treatment, which are necessary forbiological applications. The use of this new class of aqueous quantum dots for effective cell imaging showsstrong fluorescence signal to human embryonic stem cell （HESC）, which demonstrate that PMA-CdSe/ZnSare fully satisfied with the requirements of preparing high quality biological probe. Chapter Three: A reverse microemulsion method is also used to transfer the quantum dots. In thismethod, the silica is successfully coated on the surface of hydrophobic CdSe/ZnS quantum dots, and thewater-soluble SiO₂-CdSe/ZnS is further modified with the help of of3-aminopropyl trimethoxy silane（APTMS）, octadecyl trimethoxysilane （OTMS） and polymaleic acid n-hexadecanol alcohol ester （PMAH）respectively. The quantum dots modified with-NH2or the-COOH exhibit good colloidal stability inaqueous solutions with a wide range of pH, salt concentrations and under thermal treatment. Even in swineurine, the quantum dots SiO₂-CdSe/ZnS-OTMS-PMAH also retain high fluorescence. As a biomarkermaterial, the SiO₂-CdSe/ZnS-OTMS-PMAH binding with testing strip can be used to detect clenbuterol inswine urine, and the detection sensitivity （0.1ng/mL） is30times higher than the sensitivity of colloidalgold strip.