Resumen de Magnetic nanostructures based on metal oxides for biomedical applications
The synthesis of magnetic nanoparticles, and the influence of their shape, size, properties, and coatings on their applications, has been extensively studied during the last decades. In spite of the great efforts dedicated to the topic, there exist still several drawbacks that hamper their regular and routine use in many of the potential applications. Some of those issues are, for example, the reproducibility of the synthesis (necessary for a large-scale production), the aggregation of the nanoparticles or the toxicity of the materials. Facing these challenges, this thesis is focused on the syntheses of more efficient and suitable magnetic nanoparticles for their use in biomedicine. The synthetic route chosen has been thermal decomposition, trying to produce the most crystalline nanostructures and maintaining and increasing their properties by mixing various metals. The main disadvantages of this synthesis are its low reproducibility and the subsequent hydrophilic treatment necessary to disperse the nanoparticles in aqueous medium. Keeping this in mind, the following studies and tasks have been carried out for this thesis: i) systematic study of the synthesis and the reproducibility of the thermal decomposition method to obtain iron oxide magnetic nanoparticles, at different reaction times and temperatures and with different reactants; ii) synthesis of metal ferrite nanoparticles (MxFe3-xO4) varying systematically the M/Fe ratio, checking the reproducibility of the synthesis, and studying the influence of that variation on the structural and magnetic properties, on the heating ability under alternating magnetic fields and on the relaxation times for magnetic resonance imaging;
iii) preparation of heterostructured iron-oxide@iron-oxide nanoparticles with different sizes and shapes and evaluation of the cell death induced by these nanostructures through magnetic hyperthermia in breast, pancreas and uveal melanoma tumour cell lines; iv) preparation of heterostructured ironoxide@ manganese-oxide nanoparticles with different sizes and shapes that are good heat mediators under alternating magnetic fields and that, when internalized in cells, are transformed from T2 contrast agents to T1 contrast agents in magnetic resonance imaging. The stabilization in aqueous suspensions for the ferrites and the heterostructures maintaining suitable magnetic properties was achieved using coatings with hydrophilic molecules
