Preparation and Characterisation of Highly Stable Iron Oxide Nanoparticles for Magnetic Resonance Imaging

David Kovář,Petr Skládal,Aneta Malá,Radovan Jiřík,Ondřej Slabý,Antonín Hlaváček,Michal Kalina,Jitka Mlčochová,Zdenka Fohlerová,Zenon Starčuk,Zdeněk Farka,Jaromír Hubálek

doi:10.1155/2017/7859289

Abstract

Magnetic nanoparticles produced using aqueous coprecipitation usually exhibit wide particle size distribution. Synthesis of small and uniform magnetic nanoparticles has been the subject of extensive research over recent years. Sufficiently small superparamagnetic iron oxide nanoparticles easily permeate tissues and may enhance the contrast in magnetic resonance imaging. Furthermore, their unique small size also allows them to migrate into cells and other body compartments. To better control their synthesis, a chemical coprecipitation protocol was carefully optimised regarding the influence of the injection rate of base and incubation times. The citrate-stabilised particles were produced with a narrow average size range below 2 nm and excellent stability. The stability of nanoparticles was monitored by long-term measurement of zeta potentials and relaxivity. Biocompatibility was tested on the Caki-2 cells with good tolerance. The application of nanoparticles for magnetic resonance imaging (MRI) was then evaluated. The relaxivities (r1,r2) and r2/r1 ratio calculated from MR images of prepared phantoms indicate the nanoparticles as a promising T2-contrast probe.

Highlights

Magnetic resonance imaging (MRI) is a noninvasive and powerful medical imaging technique
The values of T1 and T2 were calculated for each sample in manually drawn regions of interest (ROIs) using the Image Sequence Analysis tool (ParaVision v.5.1, Bruker BioSpin, Ettlingen, Germany). r1 and r2 relaxivities were calculated as the proportionality constants of the linear relation between the reciprocal relaxation time and γ-Fe2O3 measured at concentration
Well-dispersible, ultra-small, and hydrophilic iron oxide nanoparticles were synthesised by a chemical coprecipitation method

Summary

Background

Magnetic resonance imaging (MRI) is a noninvasive and powerful medical imaging technique. Iron oxide magnetic particles (IOMPs), which are the most common T2-contrast probes, shorten the transverse relaxation time and typically result in a lower signal. The size, shape, and composition of the magnetic NPs are dependent on the type of salts used (e.g., chlorides, sulfates, and nitrates), the molar ratio of iron ions in solution, the concentration and properties of the chosen base (typically NaOH or NH4OH), the reaction temperature, the presence of a detergent, the ionic strength, and the rate of base addition. The resulting product depends on the arrangement of the reaction, that is, whether the base is added to the iron ion solution or vice versa This method is preferred due to its simplicity and cost effectiveness and is noted for its high yields. The zeta potential was monitored over a long period and the properties of the NPs important for MRI were tested in a 9.4 T NMR system

Experimental Section

Results and Discussion

Conclusions