Book of Abstracts - Ruhr-Universität Bochum

P-57
ISBOMC `10 5.7 – 9.7. 2010 Ruhr-Universität Bochum
New Hyperpolazied probes for 13 C-MRI
S. Aime, a E. Cerutti, a S. Ellena, a R. Gobetto, a F. Reineri, a D. Santelia, a A. Viale a
a Department of Chemistry I.F.M., University of Torino, Via P. Giuria n° 7,
10125 Torino, Italy, E-mail: roberto.gobetto@unito.it
The extraordinary NMR signal enhancement obtained from Para-Hydrogen Induced Polarization
(PHIP) has been exploited in the investigation hydrogenation mechanisms and, more recently, in the
development of hyperpolarized contrast agents for MRI applications. In particular the high
signal/noise ratio that can be achieved on heteronuclei such as 13 C or 15 N allows to obtain molecules
that can be traced in vivo. In fact the complete absence of those signals in biological tissues leads to
images in which the background signal derives uniquely from instrumental noise. Furthermore, due to
long T1 values that can be reached on these nuclei, hyperpolarization can be maintained for enough
time to allow the acquirement of images in in vivo conditions.
In order to produce a 13 C hyperpolarized contrast agent using this approach, an unsaturated substrate is
necessary (usually a triple bond containing molecule, that is efficiently para-hydrogenated in the
presence of a suitable catalyst), with an adjacent carbonyl group to which hyperpolarization is
transferred due to its coupling with parahydrogen protons. This group is also characterized by a long
T1 value (which limits the polarization loss due to relaxation). 2 Then, in order to use heteronuclear-
PHIP for MRI application, longitudinal hyperpolarization must be obtained from spin order which
derives directly from parahydrogenation. This task can be achieved by means of both field cycling
procedure or an appropriate pulse sequence.
We present the synthesis and parahydrogenation experiments of a series of novel substrates with the
aim of obtaining an in-depth understanding of the potential of these species as 13 C hyperpolarized
contrast agents. Particular attention is focused on bio-compatible and water soluble parahydrogenated
products. Problems concerning catalyst and organic solvent elimination have been also tackled.
References
1) K. Golman, O. Axelsson, H. Johannesson, S. Mansson, C. Olofsson, J.S. Petersson, Magn. Res.
Med. 2001, 46, 1.
2) F. Reineri, A. Viale, G. Giovenzana, D. Santelia, W. Dastrù, R. Gobetto, S. Aime, J. Am. Chem.
Soc. 2008, 130, 15047.
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