Surface Modification Of Magnetic Anocomposite And Its Biologic Application Research

Magnetic Fe3O4 nanoparticles were modified by other substances to get the nanocomposites which can be used in biologic field. Semiconductors were deposited on surface of magnetic Fe3O4 nanoparticles to get bifunctional nanocomposites. Functional groups were also used to modify magnetic Fe3O4 nanoparticles and connected them to biomolecular to form the nanocomposits named ultrasmall supreparamagnetic iron oxide nanoparticles– Aβ(SPION- Aβ). SiO2 was coated on magnetic Fe3O4 nanoparticles to get Fe3O4/SiO2 nanocomposites.Fe3O4/CdSe/ZnS magnetic fluorescent bifunctional nanocomposites were obtained by depositing heterogeneous semiconductor on magnetic nanoparticles. The structure and properties of the Fe3O4/CdSe/ZnS nanocomposites were fully characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), superconduct quantum interfere device (SQUID) and photoluminescence (PL). The results indicate that the Fe3O4/CdSe/ZnS nanocomposites are superparamagnetic and are about 8nm in size. The quantum yield of the nanocomposites increases from 2-3% in Fe3O4/CdSe to 10-15% in Fe3O4/CdSe/ZnS, together with a red shift of both the absorption peak and PL band. The increase of quantum yield is because of passivating the surface of magnetic-CdSe nanocomposites with a ZnS layer.Chemical reaction was adopted to modify surface of dextran-SPION to functional groups in this study. Fourier transforms infrared spectrometer (FTIR) and XPS were used to verify the functional groups of the modified dextran-SPION. Both morphology and magnetic property of samples were studied by TEM and vibrating sample magnetometer (VSM). The results indicate that unmodified and modified dextran-SPION were superparamagnetism and about 5nm in size. Finally, SPION was connected to biomolecular Aβto get nanocomposites named SPION-Aβ(SPION-Aβ). It was studied on transgenic mice and got obvious changes in their head imaging under magnetic field.A sol-gel procedure was used to cover Fe3O4 nanoparticles with SiO2 shell, forming a core/shell structure. The core/shell nanocomposites were synthesized by a two-step process. First, Fe3O4 nanoparticles were obtained through co-precipitation and dispersed in aqueous solution through electrostatic interactions in the presence of tetramethylammonium hydroxide (TMAOH). In the second step, Fe3O4 was capped with SiO2 generated from the hydrolyzation of tetraethyl orthosilicate (TEOS). The structure and properties of the formed Fe3O4/SiO2 nanocomposites were characterized and the results indicate that the Fe3O4/SiO2 nanocomposites are superparamagnetic and are about 30nm in size. Bioconjugation to IgG was also studied. Finally, the mechanism of depositing SiO2 on magnetic nanoparticles was discussed.