Deuteration of the exchangeable hydrogens of [15N2]urea was found to prolong the T1 of the 15N sites to more than 3 min at physiological temperatures. This significant increase in the lifetime of the hyperpolarized state of [15N2]urea, compared to [13C]urea – a pre-clinically proven perfusion agent, makes [15N2]urea a promising perfusion agent. The molecular parameters that may lead to this profound effect were assessed by investigating small molecules with different molecular structures containing 15N sites bound to labile protons and determining the hyperpolarized 15N T1 in H2O and D2O. Dissolution in D2O led to marked prolongation for all of the selected sites. In whole human blood, the T1 of [15N2]urea was shortened. We present a general strategy for exploiting the markedly longer T1 outside the body and the quick decay in blood for performing multiple hyperpolarized perfusion measurements with a single hyperpolarized dose. Improved storage of the generated [15N2]urea polarization prior to the contact with the blood is demonstrated using higher temperatures due to further T1 prolongation.
Bibliographical noteFunding Information:
This project has received funding from the the European Research Council (ERC) under grant agreement No. 338040 to R.K B) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 667192.
© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
- NMR spectroscopy
- dissolution dynamic nuclear polarization
- isotopic effects