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2010-10-20 - Colloque/Présentation - poster - Anglais - 1 page(s)

Henoumont Céline , Vander Elst Luce , Verbruggen I., Laurent Sophie , Willem R., Muller Robert , "Study of the iron oxide nanoparticles surface by HR-MAS" in 32nd discussion meeting and joint Benelux/german MR conference, Allemagne, 2010

  • Codes CREF : Résonance magnétique nucléaire (biophysique) (DI131B), Chimie des colloïdes (DI1329), Imagerie médicale, radiologie, tomographie (DI3243)
  • Unités de recherche UMONS : Chimie générale, organique et biomédicale (M108)
  • Instituts UMONS : Institut des Sciences et Technologies de la Santé (Santé), Institut des Biosciences (Biosciences)

Abstract(s) :

(Anglais) Research in magnetic resonance imaging (MRI) has been evolving in the past years towards molecular imaging, which allows an earlier diagnosis of some diseases by the detection of molecules that are expressed, or overexpressed, in pathological conditions. In this context, the contrast agents must recognize specific targets. They are thus composed of a magnetic part (the contrastophore), which is responsible for the MRI contrast, and of a vector, which has to show high affinity and specificity for the biological target. For several years, our laboratory has been using small peptides as vectors. They are grafted on a magnetic core, which is increasingly selected as a superparamagnetic iron oxide nanoparticle. This contrastophore has indeed the advantages to be very efficient and to allow grafting of several peptides. This offers the possibility of a more efficient recognition of the molecular contrast agent by its target (concept of multivalency). The comprehensive characterization of the nanoparticle and of its coating remains a major challenge. As demonstrated in a recent publication[1], a new method in this field is HR-MAS NMR spectroscopy. The authors have shown that using HR-MAS NMR enables one to significantly narrow the resonances originating from organic molecules associated with magnetic nanoparticles and therefore to visualize the parts of the molecules that are endowed with a sufficient conformational mobility at the nanoparticle-liquid interface. In the present work, two types of nanoparticles stabilized by phosphonate groups and grafted with molecules of biological interest have been studied by 1H HR-MAS NMR spectroscopy. The first ones, grafted with PEG chains terminated by a methoxy group, show a well resolved signal around 3.6 ppm, corresponding to the methoxy group. The signal corresponding to the PEG chain is more difficult to observe because of its proximity to the water signal. Nevertheless, HR-MAS NMR allows us, in that case, to evidence the grafting of the PEG chains onto the iron oxide nanoparticles. The second type of nanoparticles were grafted with a small peptide targeting apoptotic cells[2]. A small signal around 1.3 ppm appears on the HR-MAS spectra, tentatively assigned to the terminal amino acid of the chain. Further studies needed to understand why the other signals of the peptide remain “invisible”, are currently in progress. Literature : [1] Polito, L.; Colombo, M.; Monti, D.; Melato, S.; Caneva, E.; Prosperi, D. J. Am. Chem. Soc. 2008, 130, 12712-12724. [2] Laumonier, C.; Segers, J.; Laurent, S.; Michel, A.; Coppée, F.; Belayew, A.; Vander Elst, L.; Muller, R. N. J.Biomol.Screen. 2006, 11, 537-545.