The Study On Preparation And Application Of Fluorescent Quantum-dot-based Composite Nanoparticles

Fluorescent silica-based composite nanoparticles usually refer to the quantum dots loaded on the silica, which can emit fluorescence by the excitation energy. Fluorescent silica-based composite nanoparticles have some unique advantages:(1) A large number of hydroxyl groups exists on the surface of composite nanoparticles, which can react with different kinds of silane reagents, in other words, it is convenient to be functionalized with carboxyl groups, amino groups, and thiol groups;(2) The fluorescence intensity of fluorescent silica-based composite nanoparticles is thousands or even tens of thousands of times than that of the single quantum dots;(3) The spherical surface curve is good for the exposed surface of antigenic determinant under the best condition to combine with antibody. All of these mentioned above make it a broad application prospect in the biomedical field. Therefore, this paper primarily describes the study of the preparation of fluorescent silica-based composite nanoparticles, and the application in biological detection combined with microporous immunofilter. The main contents in this thesis are listed as follows:1. We reported the preparation of carboxyl functionalized QD-embedded silica nanoparticles by combining layer-by-layer(Lb L) self-assembly technique and a multi-layer protection method. First, the obtained negatively charged silica spheres(d = 220 nm) were ready as templates for the subsequent preparation. Then, the positively charged polyelectrolyte(poly(diallyldimethylammonium chloride), PDDA) and polymaleic acid n-hexadecanol ester(PMAH) functionalized Cd Se/Zn S QDs(QDs-PMAH) were alternately adsorbed onto the silica spheres. Finally, multi-layer protection from silica shell and amphiphilic polymer layers was introduced on Si O2@PDDA@QDs nanoparticles. The transmission electron microscope(TEM), X-ray powder diffraction(XRD), dynamic light scattering(DLS) and fluorescent spectrum are used to characterize the Si O2@PDDA@QDs@Si O2@OTMS@PMAH nanoparticles. The results show that the number of QDs was estimated to be 400–900 per single Si O2@PDDA@QDs@Si O2@OTMS@PMAH nanoparticles. And the resulting nanoparticles imparted excellent fluorescence stability and good biological compatibility in aqueous solutions with a wide range of p H, PBS buffer, and under thermal treatment. In addition, we attempted to use the obtained multi-shell structured fluorescent nanoparticles to detect procalcitonin(PCT) antigen based on a lateral flow immunoassay(LFIA) biosensor system. The detection limit of fluorescence nanoparticles could achieve 0.1 ng/m L of PCT antigens, which was about two hundred times higher than that of commercial colloidal gold labeled LFIA strips.3. Because of great significance for simultaneous separation and label in biomedical field. The Lb L self-assembly technique, ligand exchange approach and a multi-layer protection method were used to obtain the amino functionalized Fe3O4@Si O2@PEI@QDs@Si O2@PEI magnetic fluorescent composite nanoparticles. First, Fe3O4 magnetic nanoparticles were prepared as magnetic nucleus to provide magnetism by hydrothermal method. Fe3O4 magnetic nanoparticles were encapsulated within a silica shell by TEOS hydrolysis. Then, the positively charged polyelectrolyte(poly(ethylenimine), PEI) were adsorbed onto the Fe3O4@Si O2 nanoparticles by Lb L technique. Meanwhile, PEI were used to replace original hydrophobic oleic acid ligand. In order to improve the stability of Fe3O4@Si O2@PEI@QDs nanoparticles, the silica shell were coated on nanoparticles again. Finally, Amino functionalization of the Fe3O4@Si O2@PEI@QDs@Si O2 magnetic fluorescent composite nanoparticles by PEI were characterized by TEM, XRD, and DLS. The resulting Fe3O4@Si O2@PEI@QDs@Si O2@PEI nanoparticles showed excellent stablility(p H, PBS buffer, and under thermal treatment) in aqueous solution.