| Compared with conventional single component nanoparticles,Composite nanoparticles, especially core-shell structure composite nanoparticles, have more unique chemical and physical properties due to the combination of binary or multi-component nanocomposites. In recent years, various core-shell composite nanoparticles have been synthesized and studied, and their applications in the fields of biology and medicine have gained increasing attention and shown broad prospects in medical imaging, molecular diagnosis, fluorescent immunoassay, biochip, biosensor, biomaterial separation, and so on. Aiming at this important research direction, this thesis mainly focused on the study of synthesis, characterization and biomedical application of several types of dye-doped core-shell silica composite nanoparticles.First, a novel type of amino functionalized core-shell fluorescein isothiocyanate-doped silica nanoparticles was synthesized using a simple and effective approach of reverse microemulsion. Isothiocyanate coupled with a silane coupling agent, 3-aminopropyl-trimethoxysilane, was incorporated into silica sphere and the dye molecules were bound with silica sphere through hydrolysis and polymerization of tetraethoxysilane and 3-aminopropyl-trimethoxysilane. With the covalent binding between the dye molecules and silica sphere, the leakage of the dye was avoided. With amino groups on the surface, the nanoparticles can be directly conjugated with biological molecules with no need of complicated surface modification. The nanoparticles were spherical, monodisperse, uniform in size, pH sensitive, highly fluorescent and highly photostable. The pH response range was 3.6~9.7, respectively. More interestedly, the nanoparticles could be phagocytosed by murine neural stem cell and could be applied to detect pH value for single live cell.Second, Ru(bpy)32+ doped silica fluorescent nanoparticles were prepared using the water-in-oil (W/O) microemulsion method. Characterizations by transmission electron microscopy, fluorescent spectra, UV-Vis absorption spectra, photostable experiments and dyeleaking experiments show that the nanoparticles were monodisperse, uniform in size with the diameter being 60±6 nm. Due to a lot of fluorescent dye molecules of Ru(bpy)32+ encapsulated in the silica matrix that also severed to protect Ru(bpy)32+ dye from photodamaging oxidation, the nanoparticles were extremetly bright, photostable and chemical stable. The nanoparticles utilized as fluorescent probe were conjugated with streptavidin and successfully applied in fluorescent immunoassay of mouse IgG and detection of HIV p24 with protein microarray. Results show that good positive correlations between fluorescence intensities and concentrations of mouse IgG or p24 were presented with 10 pg/mL and 2.1ng/mL of analytical sensitivities, respectively. The nanoparticles also could be effectively swallowed by mouse neural stem cells and highly resolute images were obtained.Third, CdSe quantum dots was first prepared in aqueous solution at room temperature by a electron beam irradiation method using 2MeV 10mA GJ-2-II electronic accelerator as irradiation source and EDTA as stabilizer. Then a core-shell CdSe quantum dots-doped silica fluorescent nanoparticle were developed using the water-in-oil (W/O) microemulsion. It was found that the nanoparticles were spherical, monodisperse and uniform in size of 200±8 nm. Compared with pure CdSe quantum dots, the core-shell CdSe quantum dots-doped silica nanoparticle exhibited higher fluorescent intensity and higher photostability.Finally, the synthesized CdSe quantum dots wer utilized as a photocatalyst for degradation of methyl orange (MO). The impact factors including the sorts of catalyst, concentrations of catalyst and MO, were studied. Moreover, the reaction kinetics of photocatalysis was also investigated. Results demonstrated that degradation efficiency was affected by the concentrations of MO and CdSe quantum dots. Interestedly, the degradation efficiency of CdSe quantum dots was better than TiO2 under optimal conditions in this study.In conclusions, several different types of core-shell composite nanoparticles have been successfully synthesized. These dye or quantum dots doped composite silica nanoparticles exhibit excellent properties including photo,physics, and chemistry. They all can be applied in highly sensitive fluorescent immunoassay, sensor, cell imaging and biochip, and the CdSe quantum dots can be utilized as a photocatalyst for photocatalytic degradation.
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