NOVEL MAGNETIC NANOPARTICLES FOR MRI: DEPENDENCE OF NUCLEAR RELAXATION ON MICROSCOPIC PARAMETERS

Superparamagnetic nanoparticles have wide applications in various fields, for example in clinical field as contrast agents for Magnetic resonance imaging (MRI). In this perspective, we have synthesized superparamagnetic iron oxide nanoparticles coated with rhamnose sugar (SCIONs) of different size, to be applied as T2 contrast agents for MRI, the sugar coating being specific to target preferentially skin cancer cells. The experimental results on our samples confirmed the efficiency of our samples in MRI and allow to propose them as possible future specific targeting MRI contrast agents. The link of sugar on the surface of the nanoparticles has been performed by means of a novel synthesis technique using phosphonate moiety as a bridge. As an additional value by using this synthetic route, homogeneous nanoparticles of identical shape and size have been obtained. The TEM images of the nanoparticles confirmed the uniform size and shape of the synthesized nanoparticles. The studies of the particle size distribution reveals that the nanoparticles are monodispersed with an average 3 percentage error. The magnetic measurements performed using SQUID magnetometer proved their superparamagnetic behavior. The proton NMR relaxivity measurements performed at room and physiological conditions in a wide frequency range highlighted the efficiency of SCIONs (i.e., the transverse relaxivity r2) as negative contrast agents for MRI. The SCIONs - 7, 10 and 16 have the transverse relaxivity r2 higher than the commercial contrast agent Endorem,whereas for SCION-4, the value of r2 is slightly lower than Endorem in the measured frequency range. In order to understand the physical mechanisms causing the nuclear relaxation behavior the experimental results 1/T1 vs ν of SCIONs have been fitted using the seminal model. The fitting was appreciably good and henceforth, this thesis is the first systematic experimental confirmation for the superparamagnetic relaxation heuristic model used with different particle diameters.