Résumé:

In this paper, we report the synthesis of monodisperses and size controlled (6 and 18 nm) magnetic nanoparticles (NPs), from the pyrolysis of iron oxyhydroxide with oleic acid in high temperature solvents. The SQUID measurements revealed that the iron oxide nanoparticles exhibit a superparamagnetic behavior at room temperature. In order to evaluate the potential application of these NPs in Nuclear Magnetic Resonance (NMR) imaging, we investigated using 1 H NMR spectroscopy the modifications of T1 and T2 relaxation times at a magnetic field (4.7 Tesla) for different concentrations of NPs. The following transverse (r2 ) and longitudi- nal (r1 ) relaxivities were found : (r2 = 17.85 mM −1 s−1 , r1 = 6.90 mM −1 s−1 ) and (r2 = 9.20 mM −1 s−1 , r1 = 4.30 mM −1 s−1 ) for a nanoparticle size 18 and 6 nm, respectively. These results confirm that these magnetic NPs present a high con- trast enhancement capacity and have both high r1 and r2 relaxivities responsible for positive or negative enhancement properties. This effect increases with the nanoparticle size. We also developped a new recognition motif (coating) of sac- charide type (Rhamnose) for targeting at the tissular and cellular levels biological models (plants) in order to track the flow of the water and saccharide (main drivers of plant growth) in NMR imaging. Moreover, we demonstrated that this saccahride motif provides a good biocompatibility and biodistribution in physiological medium.