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2014-11-24 - Colloque/Présentation - communication orale - Anglais - 17 page(s)

Henrard Daniel , Vuong Quoc Lam , Delangre Sébastien , Valentini Xavier, Nonclercq Denis , Gossuin Yves , "Characterization of iron oxide nanoparticles by NMR relaxometry and magnetometry: effects of size distribution and agglomeration" in YBMRS, Spa, Belgique, 2014

  • Codes CREF : Résonance magnétique nucléaire (biophysique) (DI131B), Physique (DI1200), Physique du spin (genre RMN) (DI1234), Biophysique (DI3113)
  • Unités de recherche UMONS : Physique biomédicale (M104), Histologie (M118)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Physique des matériaux (CRPM)

Abstract(s) :

(Anglais) Iron oxide nanoparticles (NP) are of great interest in nanomedicine. They are used in Magnetic Resonance Imaging (MRI) as negative contrast agent, in tumor targeting, in drug delivery and in magnetic hyperthermia. With suited sequences they could even generate positive contrast. In this work, we explore the effects of size distribution, magnetization and agglomeration of different-sized magnetite NP (Fe3O4) on NMR relaxation and magnetometry experiments. Indeed, these parameters play a key role in their efficiency as MRI contrast agents. First, using a Vibrating Sample Magnetometer (VSM), Zero-Field-Cooling (ZFC) measurements are carried out. The particle size distribution can be obtained by fitting the obtained curves with the standard ZFC theory[1]: each NP is considered to be either blocked or superparamagnetic, depending on its size and on the temperature. Then, nuclear magnetic relaxation dispersion (NMRD) profiles were recorded at 37°C using a Fast Field Cycling (FFC) relaxometer. Fitting the data with the RMG model[2] allows to get the average NP radius and the saturation magnetization. NMRD profiles are also more sensitive to the agglomeration of the NP. Finally, direct measurements of the size distribution and of the NP agglomeration were carried out by transmission electron microscopy (TEM). The comparison of these three sets of results allows to finely characterize iron oxide NP in aqueous solutions since the different techniques are sensitive to different factors. For example, we obtained larger NP radii and lower saturation magnetizations from the NMRD profiles than those obtained from magnetometric experiments. This is consistent since magnetometry is sensitive to the iron oxide monocrystals (even if clustered in a larger structure), while relaxometry will consider a cluster as a global, less magnetized particle. NP radii measured by TEM are very similar to those obtained from magnetometric experiments which is consistent too. On the other side, distribution widths are larger in magnetometric experiments than in TEM. In a later work, biological samples containing iron oxide NP will be studied in order to optimize protocols of iron quantification by magnetometry. [1] Lévy M., Gazeau F., Bacri J-C., Wilhelm C. and Devaud M., Physical Review B 2011, 84, 075480. [2] Roch A., Gillis P., Ouakssim A. and Muller R.N., J. Magn. Magn. Mater 1999, 201, 77-79.