Synthesis of PEOlated Fe₃O₄@SiO₂ Nanoparticles via Bioinspired Silification for Magnetic Resonance Imaging

Inspired by the biosilification process, a highly benign synthesis strategy is successfully developed to synthesize PEOlated Fe 3 O 4 @SiO 2 nanoparticles (PEOFSN) at room temperature and near‐neutral pH. The success of such a strategy lies in the simultaneous encapsulation of Fe 3 O 4 nanocrystals and silica precursors into the core of PEO‐based polymeric micelles. The encapsulation results in the formation of a silica shell being confined to the interface between the core and corona of the Fe 3 O 4 ‐nanocrystal‐loaded polymeric micelles. Consequently, the surface of the Fe 3 O 4 @SiO 2 nanoparticle is intrinsically covered by a layer of free PEO chains, which enable the PEOFSN to be colloidally stable not only at room temperature, but also upon incubation in the presence of proteins under physiological conditions. In addition, the silica shell formation does not cause any detrimental effects to the encapsulated Fe 3 O 4 nanocrystals with respect to their size, morphology, crystallinity, and magnetic properties, as shown by their physicochemical behavior. The PEOFSN are shown to be good candidates for magnetic resonance imaging (MRI) contrast agents as demonstrated by the high r 2 / r 1 ratio with long‐term stability under high magnetic field, as well as the lack of cytotoxicity.