Multifunctional modalities of iron oxide magnetic nanoparticles: applications in diagnostics and magnetic fluid hyperthermia.

This PhD thesis, Multifunctional modalities of iron oxide magnetic nanoparticles: applications in diagnostics and magnetic fluid hyperthermia, has two major purposes. The first goal is to assess the anti-tumor efficacy and the potential of combining Hadron Therapy and Magnetic Fluid Hyperthermia (MFH) against pancreatic tumor cells; this is carried out with a perspective to establishing solid protocols for desirable future clinical applications. The second goal is to evaluate the Magnetic Resonance Imaging (MRI) image contrast efficiency of magnetic nanoparticles. This is accomplished by means of 1H Nuclear Magnetic Resonance relaxometry, magnetometry and morpho-dimensional characterization techniques, with a particular focus on the effect of size and coating. Data for this research were collected thanks to cross-collaborations between national and international research groups and hospital structures. For the MFH therapy, the properties of the magnetic nanoparticles that were employed have been optimized in order to maximize their heat release, and, at the same time, to give the patient an amount of magnetic material as low as possible, thus reducing any risk of detrimental side effects to his health. Cell culture conditions and hyperthermic treatment (partly of magnetic origin) were optimized to maximize the efficacy of the therapy, with the aim of decreasing the survival of cancer cells. Given the advantages of hadron therapy over conventional radiotherapy, it was decided to combine the hyperthermic treatment with the first one. This was possible thanks to the fact that Pavia, where most of the work behind this thesis was performed, hosts a state-of-the-art hadron therapy center, the CNAO foundation. This center is the only one in Italy where cancer patients can be treated with both protons and carbon ions. Two main results can be highlighted from the clonogenic survival data collected at 15 days after the combined therapeutic treatment. Firstly, at all hadrons/photon irradiation doses, an additional killing effect – i.e toxicity - of about 50-60% can be ascribed to the cellular uptake of the nanoparticles, with respect to simple irradiation of culture cells. Secondly, a significant killing effect of hyperthermia was observed for both irradiation protocols, consisting in an additional 15-30% of total survival decrease. The enhanced efficacy of Hadron Therapy applied immediately after hyperthermia lays the foundations for future preclinical studies. Furthermore, these encouraging results point in the direction of further investigating this combination, with a view to finally translating it to clinical applications. As to the second goal - i.e. the investigation of the properties of magnetic nanoparticles by means of nuclear magnetic resonance relaxometry and magnetometry - this thesis specifically concerned the influence of coating on the nuclear relaxation times. Two sets of samples, each consisting of four samples with different coatings, were obtained by means of the same synthesis procedure, while the nanoparticles coating has been realized with different polymers. A heuristic model for the field dependence of the NMR relaxivity curves allowed us to evaluate several parameters: among them, the saturation magnetization, the minimum approach distance, etc. Moreover, through the acquisition and analysis of experimental NMR dispersion curves, we observed that the relaxivities r1 and r2 of the four samples analyzed, for both sets, did not show significant differences in the whole range of frequencies investigated, at least within the experimental errors. Thus, we concluded that the four different coatings we analyzed on our spherical MNPs give essentially similar magnetic and relaxometric behavior.