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Thursday, 21 November 2013

A Nanoscale Metal-Organic Framework for Magnetic Resonance Imaging (MRI)

ICN2, CBM (CNRS) and IBB (UAB) researchers report in the Journal of the American Chemical Society on a highly stable, non-cytotoxic nanoscale metal-organic framework with a large potential as contrast agent for Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is one of the most powerful diagnostic tools in medical science thanks to its noninvasive character and sub-millimeter spatial resolution. Based on the detection of nuclear spin reorientations under a magnetic field, MRI has been demonstrated to be very effective for assessing anatomical changes and monitoring organ functions. However, in many cases, the use of contrast agents (CAs) is necessary to enhance the intrinsic contrast of MR images; 35% of clinical MRI scans are currently performed with the assistance of CAs.

Nanoscale metal-organic frameworks (nanoMOFs), which have the advantage of high surface areas and endless possibilities to carry high Gd(III) concentrations per nanocrystal unit, are beginning to be investigated as an alternative class of nanoscale CAs. In this context, a team of researchers from the Institut Catala de Nanociencia i Nanotecnologia (ICN2) - PhD student Arnau Carné, RyC Researcher Dr Inhar Imaz, and ICREA Prof Daniel Maspoch -, the Centre de Biophysique Moleculaire (CBM-CNRS) - Dr Célia S. Bonnet, and Prof Eva Tóth -, and the Institut de Biotecnologia i de Biomedicina (IBB-UAB) - Dr Julia Lorenzo, have developed a new nanoMOF containing Gd(III) and fully studied its relaxation behavior.

The work has been published in the Journal of the American Chemical Society under the title “Relaxometry Studies of a Highly Stable Nanoscale Metal-Organic Framework Made of Cu(II), Gd(III), and the Macrocyclic DOTP” (link to the article). In the article, the researchers report the use of DOTP, a chelating ligand typically used to generate stable mononuclear lanthanide complexes, to synthesize a bimetallic Cu(II)- and Gd(III)-based MOF with promising relaxometric properties. This MOF is miniaturizable down to the nanometer length scale to form stable colloids; it is stable in water, physiological saline solution, and cell culture media; and it does not show cytotoxicity. It shows a maximum in r1 relaxivity of 15 mM-1·s-1 at 40 MHz, which remains constant over a wide pH range and increases with temperature.

Importantly, this is the first study of the dependence of the r1 relaxivity of a MOF as a function of a wide range of temperatures, magnetic fields, and pHs, which allowed us to conclude that an inner-sphere type of mechanism is operating and that Gd(III) centers inside the MOF structure also contribute to the relaxation effect. Synthesizing highly stable nanoMOFs and combining their relaxometric properties and porosities should be feasible, making it possible to also exploit them in theranostics.

For more information, please contact:

Prof Daniel Maspoch –ICREA Research Professor and Group Leader

Supramolecular NanoChemistry & Materials Group (NANOUP, visit www.nanoup.org)

Tel: +34 937 374 634

E-mail: daniel.maspoch@icn.cat

Funding: II thanks the Ministry of Economy and Competitiveness (Spain) for the Ramón y Cajal grant.

Link to the Journal of the American Chemical Society journal article: Relaxometry Studies of a Highly Stable Nanoscale Metal–Organic Framework Made of Cu(II), Gd(III), and the Macrocyclic DOTP