Preparation of silica based core/shell nanostructures for bioimaging and drug delivery

Abstract

In recent years, the development of nanostructured materials for biomedical applications has been continued by many researchers. Various nanomaterials have been studied as promising candidates and among them, silica based core/shell nanostructured materials were conducted to study actively due to their low toxicity, easy modification, inexpensive process, etc. In this research, we synthesized two types of silica based core/shell nanostructured materials. First, RITC-doped core/mesoporous shell silica nanostructured materials were synthesized for investigating the possibility to act as theranostic nanocarriers. RITC-encapsulated core silica nanoparticles were prepared by sol-gel process. The cores were further grown to various size by coating with pure silica through the Stöber method. Furthermore, mesoporous shells were coated again by using cetyl trimethylammonium bromide (CTAB) as porous guiding agent. The shape, size, and fluorescence of the as-prepared nanostructured materials were confirmed by using transmission electron microscopy (TEM), dynamic laser scattering (DLS), and photoluminescence (PL) spectroscopy. Ibuprofen loading and release experiments in buffer solution (pH 7.4) showed that these nanostructured materials were available for drug delivery system. In addition, cytotoxicity test and fluorescent imaging were carefully conducted to investigate the cell-level behavior of the nanostructured materials. From these results, we demonstrated that the as-synthesized nanostructured materials had the potential applicability as theranostic nanocarriers. Second, iron oxide core/RITC-doped silica shell nanostructured materials were prepared. The as-prepared nanostructured materials were suitable for dual imaging. The synthesis of the nanostructured materials was based on reverse micelle method and iron oxide nanocrystals coat with RITC-doped silica. The as-prepared nanostructured materials were analyzed to confirm the shape, size, and distribution by TEM and DLS. In addition, fluorescent properties were discussed through the analysis of PL. By WST-1 assay, we confirmed that the as-prepared nanostructured materials showed low toxicity to cells. Finally, through in vivo and in vitro MR and fluorescent imaging, we verified that the as-prepared nanostructured materials could be used as dual imaging contrast agents. The as-prepared nanostructured materials were intended to improve the diagnostic accuracy and broaden the diagnostic scope of diseases by performing both MR and fluorescence imaging.