Preparation and Characterization of Double Shell Fe3O4 Cluster@Nonporous SiO2@Mesoporous SiO2 Nanocomposite Spheres and Investigation of their In Vitro Biocompatibility

Background: Multifunctional core-shell magnetic nanocomposite particles with tunable characteristics have been paid much attention for biomedical applications in recent years. A rational design and suitable preparation method must be employed to be able to exploit attractive properties of magnetic nanocomposite particles. Objectives: Herein, we report on a simple approach for the synthesis of magnetic mesoporous silica nanocomposite particles (MMSPs), consisted of a Fe3O4 cluster core, a nonporous silica shell and a second shell of the mesoporous silica of suitable sizes for biomedical applications and evaluate their cytotoxicity effects on human cancer prostate cell lines. Materials and Methods: Clusters of magnetite (Fe3O4) nanoparticles were coated by a layer of nonporous silica using Stöber method. The coating step was completed by an outer layer of mesoporous silica via template-removing method. Structural properties of MMSPs were investigated by FTIR, HR-S(T)EM,  BET,  XRD techniques and magnetic properties of MMSPs by VSM instrument. MTT and LDH assays were employed to study the cytotoxicity of MMSPs. Results: Obtained results revealed that decreasing the precursor concentration and the reaction time at the nonporous silica shell formation step decreases the thickness of the nonporous silica shell and consequently leads to the formation of smaller MMSPs. The as-prepared MMSPs have a desirable average size of 180±10 nm, an average pore size of 3.01 nm, a high surface area of 390.4 m2.g-1 and a large pore volume of 0.294 cm3.g-1. In addition, the MMSPs exhibited a superparamagnetic behavior and a high magnetization saturation value of 21±0.5 emu/g. Furthermore, the viability tests of DU-145 cell lines exposed to various concentrations of these particles demonstrated negligible cytotoxicity effects of the as-prepared particles. Conclusions: These results demonstrate interesting properties of MMSPs prepared in this study for biomedical applications.