Evaluation of polyol‐made Gd³⁺‐substituted Co_0.6Zn_0.4Fe₂O₄ nanoparticles as high magnetization MRI negative contrast agents

Abstract

The structural, microstructural, and magnetic properties of~5-nm-sized Co 0.6 Zn 0.4 Fe 2-x Gd x O 4 nanoparticles were investigated in order to evaluate their capability to enhance the magnetic resonance imaging contrast as high magnetization agents. A focus was made on the solubility of Gd 3+ cations within the spinel lattice. By coupling X-ray diffraction to X-ray fluorescence spectroscopy, we demonstrated that only a limited fraction of Gd 3+ can substitute Fe 3+ ions into the whole crystal structure and does not exceed 6 at.-%. At this concentration, the room temperature (27°C) saturation magnetizations of the prepared superparamagnetic nanocrystals were found to be close to 80 emu g À1 .Coating these nanoparticles with hydrophilic dopamine ligands leads to the formation of 50-nm-sized clusters in water. As a consequence, relatively high r 2 /r 1 ratios of transverse to longitudinal proton relaxivities and high r 2 values were measured in the resulting colloids at physiological temperature (37°C) for an applied magnetic field of 1.41 T: 33 and 188 mM À1 sec À1 , respectively, for the richest system in gadolinium. Moreover, after incubation with healthy human model cells (fibroblasts) at doses as high as 10 μg mL À1 , they induce neither cellular death nor acute cellular damage making the engineered probes particularly valuable for negative magnetic resonance imaging contrasting.

Structural and magnetic properties of CoFe2O4 ferrite nanoparticles doped by gadolinium

“…They reported that the solubility limit of Gd 3+ cations in the CoFe 2 O 4 ferrite is lower than 20% and higher than 10% [28]. In other study, the structural properties of polyol-made Co 0.6 Zn 0.4 Fe 2−x Gd x O 4 nanoparticles was investigated by Walid Mnasri et al The Gd 3+ concentration increased up to its solubility limit, which was obtained for the sample Co 0.56 Zn 0.33 Fe 2.03 Gd 0.06 O 4 (x = 0.06) [29]. It can be concluded that, preparation rout is a factor influential in solubility limit.…”

“…Figure 12 also shows the comparative behaviour of H C and k 1 for both temperatures. Magnetocrystallline anisotropy originates from magnetic dipole-dipole interactions, whereby its anisotropy energy density is proportional to M S [29]. Thus, the increase of M S at 10 K is an intrinsic cause of k 1 growth at this temperature.…”