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2009-06-04 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Henoumont Céline , Vander Elst Luce , Laurent Sophie , Muller Robert , "Proton relaxometric study of Gd-C4-thyroxin-DTPA, a potential new MRI contrast agent" in 6th conference on field cycling NMR relaxometry, Turin, Italie, 2009

  • Codes CREF : Résonance magnétique nucléaire (biophysique) (DI131B), Chimie (DI1300)
  • 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) At present, gadolinium complexes represent the main category of contrast agents which are clinically used for Magnetic Resonance Imaging (MRI). Many efforts are made in order to increase their efficacy i.e. their relaxivities, which represent the increase of the water proton relaxation rate induced by 1 mmol per liter of the gadolinium chelates. To reach this objective, complexes having a high affinity for an endogenous macromolecule are well appropriate since the increase of the molecular size of the gadolinium complex due to its non covalent interaction with the macromolecule increases its relaxivity in the range of magnetic fields used in clinical MRI (0.5-1.5 T). This work reports the characterization by proton relaxometry of a potential new MRI contrast agent, the Gd-C4-thyroxin-DTPA, which is assumed to have a relatively high affinity for human serum albumin (HSA). Firstly, its NMRD profile was recorded in water on solutions of increasing concentration. The obtained curves show a hump at high field, between 0.5 and 1.5 T, which increases as the concentration of the chelate increases. This can be explained by an aggregation of the molecules in solution at concentration larger than 0.6 mM. Secondly, the NMRD profile of Gd-C4-thyroxin-DTPA was recorded in the presence of HSA 4%. The large increase of relaxation rate observed at high field shows that this chelate has a high affinity for HSA.The relaxivity of the bound complex at 20 MHz and 310K was estimated to be of the order of 45-50 s-1mM-1. Finally, competition experiments were performed with ibuprofen and salicylate, of which the binding site on HSA is known. The NMRD profiles of Gd-C4-thyroxin-DTPA were recorded in the presence of HSA 4% and of different concentrations in each of the competitors. The results show a more important decrease of the water proton relaxation rate on all magnetic fields in the presence of ibuprofen which means that Gd-C4-thyroxin-DTPA shares one of the binding sites of ibuprofen on HSA.