Synthesis And Characterization Of Core-shell Nanoparticle-Based Surface-enhanced Raman Tags For Bioanalytical Applications

Nanoparticle-based surface-enhanced Raman scattering (SERS) tags developed with the integration of nanotechnology and SERS possesses broad implications in a variety of areas in biology and analytical chemistry. This dissertation poeuces on the research on biocompatible core-shell nanoparticle-based Ag@SiO₂ surface-enhanced Raman scattering (SERS) tags including the synthesis and characteristic of nanoparticle-based Ag@SiO₂ surface-enhanced Raman scattering (SERS) tags and the applications of this SERS tags in DNA detection and immunoassays. Moreover, porous titania film coated Fe₃O₄@Ag@TiO₂ magnetic nanocomposite has been prepared as a novel substrate for efficient surface-enhanced Raman scattering. The details are summarized as follows:1. The synthesis of core-shell nanoparticle-based Ag@SiO₂ SERS tagsIn chapter 2, we synthesized core-shell nanoparticle-based Ag@SiO₂ SERS tags using W/O reverse micelle technique. Using the proposed method, different processes including the preparation of silver nanoparticles, the conjugation of dye molecules and the formation of silica shell resulted from the hydrolyzation and condensation of tetraethyl orthosilicate(TEOS) were completed in a microreactor. Compared to the method reported in literature, the proposed methodology eliminates the necessity of vitrophilic pretreatment during the preparation of metal nanoparticles. Furthermore, core-shell nanoparticle-based Ag@SiO₂ SERS tags prepared in our work, in which the dye molecules are adsorbed on the surface of silver core by strong chemical bond and the silver core and dye molecules are embedded in silica shell, possess advantages of providing highly efficient SERS signal and favorable stability.2. The synthesis of porous Fe₃O₄@Ag@TiO₂ nanocomposite SERS substrateIn chapter 3, we prepared a novel SERS substrate which not only exhibited strong surface enhanced Raman scattering signal upon contacting with the common Raman active dyes, but also possessed the property of supermagnetism. The SERS matrix was the nanocomposite of Fe₃O₄@Ag core-shell nanoparticles encapsulated with a thin porous TiO₂ layer. This matrix has the potential of being used as a SERS substrate for separation and preconcentration of the analyte.3. The applications of core-shell nanoparticle-based Ag@SiO₂ SERS tags in bioanalysisCore-shell nanoparticle-based Ag@SiO₂ SERS tags can be applied to bioanalysis owing to their silica shell, nice biocompatibility, easy functionalization with biomolecules and strong SERS signal and nice water-solubility.(1) In chapter 4, we employed Ag@SiO₂ SERS tags with oligonuleoties as detection probes and core-shell magnetic nanoparticles modified oligonuleoties as capture probes and separating tools to detect DNA related to HIV gene. This method possesses high selection and amplifying signal.(2) In chapter 5, we applied Ag@SiO₂ SERS tags embedded with isothiocyanate rhodamine B to an immunoassay for detecting human AFP. In the proposed system, a sandwich-type immunoassay was performed between Ag@SiO₂ nanoparticle-based Raman tags functionalized with polyclonal antibody and silica-coated magnetic nanoparticles modified with monoclonal antibody. Using this strategy, concentration of human AFP up to 0.12μg/ml was detected with a detection limit of 11.5 pg/ml.