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The main objective of the preparation of the Fe3−xGaxO4 (0.14 ≤ x ≤ 1.35) system was to further the knowledge of the magnetic response of Ga3+-doped magnetite for application as MRI contrast agents. With this purpose, monodisperse nanoparticles between 7 and 10 nm with different amounts of gallium were prepared from an optimized protocol based on thermal decomposition of metallo-organic precursors. Thorough characterization of the sample was conducted in order to understand the influence of gallium doping on the structural, morphological and magnetic properties of the Fe3−xGaxO4 system. X-ray diffraction and X-ray absorption near-edge structure measurements have proved the progressive incorporation of Ga in the spinel structure, with different occupations in both tetrahedral and octahedral sites. Magnetization measurements as a function of field temperature have shown a clear dependence of magnetic saturation on the gallium content, reaching an Ms value of 110 Am2 kg−1 at 5 K for x = 0.14 (significantly higher than bulk magnetite) and considerably decreasing for amounts above x = 0.57 of gallium. For this reason, nanoparticles with moderate Ga quantities were water-transferred by coating them with the amphiphilic polymer PMAO to further analyse their biomedical potential. Cytotoxicity assays have demonstrated that Fe3−xGaxO4@PMAO formulations with x ≤ 0.57, which are the ones with better magnetic response, are not toxic for cells. Finally, the effect of gallium doping on relaxivities has been analysed by measuring longitudinal (T1−1) and transverse (T1−1) proton relaxation rates at 1.4 T revealing that nanoparticles with x = 0.14 Ga3+ content present remarkable T2 contrast and the nanoparticles with x = 0.26 have great potential to act as dual T1–T2 contrast agents. [ABSTRACT FROM AUTHOR]

To improve the selectivity of magnetic nanoparticles for tumor treatment by hyperthermia, Fe 3 O 4 nanoparticles have been functionalized with a peptide of the type arginine-glycine-aspartate (RGD) following a “click” chemistry approach. The RGD peptide was linked onto the previously coated nanoparticles in order to target α v β 3 integrin receptors over-expressed in angiogenic cancer cells. Different coatings have been analyzed to enhance the biocompatibility of magnetic nanoparticles. Monodispersed and homogeneous magnetite nanoparticles have been synthesized by the seed growth method and have been characterized using X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, transmission electron microscopy and magnetic measurements. The magnetic hyperthermia efficiency of the nanoparticles has also been investigated and cytotoxicity assays have been perfomed for functionalized nanoparticles. [ABSTRACT FROM AUTHOR]

The achievement of a successful heating power response of Fe 3 O 4 nanoparticles for being applied in magnetic hyperthermia entails an exhaustive control of their magnetic characteristics and therefore, of the synthesis method employed. Despite the fact that one of the best wet-chemical methods to finely adjust Fe 3 O 4 nanoparticles (NPs) size over 15 ​nm is the thermal decomposition of iron(III) oleate, the studies about the specific influence of iron(III) oleate precursor on the IONPs are particularly scarce. So, in this work five iron(III) oleate precursors have been systematically prepared varying synthesis conditions and it has been analyzed how their characteristics affect the features of the ulterior magnetite NPs. The refined synthesis method has yield monophasic and monodisperse NPs of magnetite (Fe 3 O 4) with different sizes (in the 10–40 ​nm range) and morphologies (cuboctahedral, octahedral and spherical). A complete chemical, structural, morphological and magnetic characterization have been performed to correlate the properties of the iron(III) oleate with the features of the subsequent magnetite NPs. [Display omitted] • A proper control of the reaction conditions of Fe(oleate) 2 precursor can lead tailored magnetic nanoparticles. • Well-faceted nano-octahedra Fe 3 O 4 nanoparticles, with good shape/size homogeneity can been obtained from Fe:Oleate ratio ≤3. • High saturation magnetization (Ms) and a Verwey temperature (Tv) similar to bulk magnetite displayed by octahedral NPs. • Good monodispersity of octahedral nanosystems easily corroborated by EMR measurements. [ABSTRACT FROM AUTHOR]