Fe3O4/SiO2 Core/Shell Nanocubes: Novel Coating Approach with Tunable Silica Thickness and Enhancement in Stability and Biocompatibility

Abstract

Magnetic nanoparticles are frequently coated with SiO2 to improve their stability, biocompatibility and functionality for they become promising for many biomedical applications, such as MR imaging contrast agents, magnetically-targeted drug delivery vehicles, agents for hyperthermia, etc. In our study, we demonstrated a novel and time reducing modified sol-gel approach for obtaining a uniform Fe3O4/SiO2 core/shell nanocubes. Furthermore, the thickness of the silica shell is easily controlled in the range of 5-16 nm by adjusting the reaction parameters. The core/shell nanocubes samples were characterized by X-ray diffractometry (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometer (EDS), fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). The as-prepared Fe3O4/SiO2 core/shell nanocubes showed good stability in air for at least 4 month as well as against annealing condition of up to 300°C in presence of H2 gas as a strong reducing agent. Furthermore, high magnetization value of 50.7 emu/g was obtained for the sample with thin silica thickness (5 nm) as a consequence of shell thickness controlled. Moreover, the biocompatibility of the core/shell nanocube was enhanced in comparison to that of pristine Fe3O4 nanocubes. In addition, the Fe3O4/SiO2 nanocubes were functionalized by Aminopropy-ltriethoxysilane, and then conjugated with streptavidin-Cy3 successfully as indicated by fluorescence microscopy.