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

Abstract

Inspired by the biosilification process, a highly benign synthesis strategy is successfully developed to synthesize PEOlated Fe3O4@SiO2 nanoparticles (PEOFSN) at room temperature and near‐neutral pH. The success of such a strategy lies in the simultaneous encapsulation of Fe3O4 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 Fe3O4‐nanocrystal‐loaded polymeric micelles. Consequently, the surface of the Fe3O4@SiO2 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 Fe3O4 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 r2/r1 ratio with long‐term stability under high magnetic field, as well as the lack of cytotoxicity.

Silica Nanocapsules of Fluorescent Conjugated Polymers and Superparamagnetic Nanocrystals for Dual‐Mode Cellular Imaging

“…[ [36][37] XRD was used to study the crystal structure of the as-synthesized SPIONs and BMFSNs. The XRD spectrum in Figure 5a shows the formation of a crystalline cubic structure of magnetite (Fe 3 O 4 ) in the as-synthesized SPIONs, as reflected by their characteristic peaks of (220), (311), (400), (422), (611), and (440) planes.…”

“…The BMFSN is prepared by using the bioinspired silification, a process of forming silica nanocapsules by using a template of Pluronic F127 polymeric micelles at room temperature and near-neutral pH conditions, which mimicks the behavior of marine organisms. [36][37] The feature of this method is the confinement of the silica shell formation at the interface between the core and corona of the F127 polymeric micelles, and therefore retains part of the PEO corona to be free to provide colloidal stability to the resultant silica nanocapsules in water and simulated biological environment. We have performed systematic investigations into their physical and optical properties, cell viability, and their magnetic resonance enhancement behavior.…”

“…Such behavior is consistent with our previous report for which a low level of nonspecific uptake of PEOlated Fe 3 O 4 @SiO 2 nanoparticles by brain macrophage cells was observed. [37] Hence, these results suggest that the antifouling behavior of the BMFSNs can be exploited in concert with their magnetic guided capability to target specific tissues in vivo.…”

Silica passivated conjugated polymer nanoparticles for biological imaging applications

“…The bioinspired silification method was adapted from work by [31][32][33] . CN-PPV was prepared in THF by dissolving 1 mg of polymer into 1 ml of THF to make a 1 mg/ml polymer solution.…”

“…We have also studied the effect of surface chemistry of CPNs and how this affects uptake and internalisation in phagocytic cells 30 . We report the possibility of using silica to encapsulate a CP/pluronic micelle which is prepared using a modified bioinspired silification approach 31,32 . The process involves simultaneously encapsulating a conjugated polymer inside the micelles, then forming a silica layer between the interface of the core and shell.…”