Development of methods for fabricating nanoparticles composed of magnetite, gold, and silica toward diagnostic imaging

Abstract

Nontoxic nanoparticle contrast agents with multiple imaging functions are required for medical diagnostic imaging, and coating the nanoparticle contrast agents with less toxic materials meets this requirement. This work proposes a method for fabricating magnetite, gold (Au), and silica nanoparticles toward diagnostic imaging. The proposed method involved four steps: the synthesis of magnetite (Fe3O4) nanoparticles, synthesis of Au nanoparticles, formation of a composite of Fe3O4 and Au (Fe3O4/Au), and silica coating of Fe3O4/Au nanoparticles. The synthesis of 6.3 ± 1.2 nm-sized Fe3O4 nanoparticles was performed via a salt-based reaction in an aqueous solution containing FeCl3, FeCl2, citric acid, HCl, and NaOH. The synthesis of 2.2 ± 0.4 nm-sized Au nanoparticles was performed with a reduction of HAuCl4 in an aqueous solution containing tetrakis (hydroxymethyl) phosphonium chloride, and NaOH. The silica coating of Fe3O4/Au nanoparticles was performed with a sol–gel reaction in ethanol containing Fe3O4 nanoparticles, Au nanoparticles, poly-diallyldimetheylammonium chloride, tetraethylorthosilicate, NaOH, and water under sonication. The Fe3O4/Au/SiO2 nanoparticles were degraded in a fetal bovine serum/phosphate-buffered saline solution, PEGylated Fe3O4/Au/SiO2 (Fe3O4/Au/SiO2–PEG) nanoparticles adsorbed protein after PEGylation, and Fe3O4/Au/SiO2–PEG nanoparticles had a magnetic property and an X-ray imaging ability, revealing that the composite nanoparticles were expected to function as a safe and excretable contrast agent of MRI and X-ray.