Hematite Nanoparticles from Unexpected Reaction of Ferrihydrite with Concentrated Acids for Biomedical Applications.

The development of synthetic ways to fabricate nanosized materials with a well-defined shape, narrow-sized distribution, and high stability is of great importance to a rapidly developing area of nanotechnology. Here, we report an unusual reaction between amorphous two-line ferrihydrite and concentrated sulfuric or other mineral and organic acids. Instead of the expected dissolution, we observed the formation of new narrow-distributed brick-red nanoparticles (NPs) of hematite. Different acids produce similar nanoparticles according to scanning (SEM) and transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDX). The reaction demonstrates new possibilities for the synthesis of acid-resistant iron oxide nanoparticles and shows a novel pathway for the reaction of iron hydroxide with concentrated acids. The biomedical potential of the fabricated nanoparticles is demonstrated by the functionalization of the particles with polymers, fluorescent labels, and antibodies. Three different applications are demonstrated: i) specific targeting of the red blood cells, e.g., for red blood cell (RBC)-hitchhiking; ii) cancer cell targeting in vitro; iii) infrared ex vivo bioimaging. This novel synthesis route may be useful for the development of iron oxide materials for such specificity-demanding applications such as nanosensors, imaging, and therapy.

Spindle-like MRI-active europium-doped iron oxide nanoparticles with shape-induced cytotoxicity from simple and facile ferrihydrite crystallization procedure.

Nanoparticles (NPs) that can provide additional functionality to the nanoagents derived from them, e.g., cytotoxicity or imaging abilities, are in high demand in modern nanotechnology. Here, we report new spindle-like iron oxide nanoparticles doped with Eu3+ that feature magnetic resonance imaging (MRI) contrasting properties together with shape-related cytotoxicity (unusual for such low 2.4% Eu content). The NPs were prepared by a novel procedure for doping of iron oxide nanoparticles based on the crystallization of amorphous ferrihydrite in the presence of hydrated europium(iii) oxide and were thoroughly characterized. Cytotoxicity of low Eu-doped spindle-like hematite nanoparticles was confirmed by MTT assay and further studied in detail by imaging flow cytometry, optical and electron microscopies. Additionally, enhancement of MRI contrast properties of NPs upon doping with europium was demonstrated. According to the MRI using mice as an animal model and direct inductively coupled plasma mass spectrometry (ICP-MS) 153Eu biodistribution measurements, these particles accumulate in the liver and spleen. Therefore, NPs present a novel example of a multimodal component combining magnetic imaging and therapeutic (cytotoxic) abilities for development of theranostic nanoagents.