Abstract
Hyperpolarization produces nuclear spin polarization that is several orders of magnitude larger than that achieved at thermal equilibrium thus providing extraordinary contrast and sensitivity. As a parahydrogen induced polarization (PHIP) technique that does not require chemical modification of the substrate to polarize, Signal Amplification by Reversible Exchange (SABRE) has attracted a lot of attention. Using a prototype parahydrogen polarizer, we polarize two drugs used in the treatment of tuberculosis, namely pyrazinamide and isoniazid. We examine this approach in four solvents, methanol-d4, methanol, ethanol and DMSO and optimize the polarization transfer magnetic field strength, the temperature as well as intensity and duration of hydrogen bubbling to achieve the best overall signal enhancement and hence hyperpolarization level.
Highlights
By producing nuclear spin polarization far beyond that available at thermal equilibrium, hyperpolarization can provide improved sensitivity for NMR, enabling the detection of less concentrated molecules
We investigated the Signal Amplification by Reversible Exchange (SABRE) polarization of two drugs that are used clinically, isoniazid and pyrazinamide [25]
According to the SABRE mechanism, optimum enhancement occurs when the differences in resonance frequency of the protons are of the same order as the scalar couplings [22]
Summary
By producing nuclear spin polarization far beyond that available at thermal equilibrium, hyperpolarization can provide improved sensitivity for NMR, enabling the detection of less concentrated molecules. Multiple studies have reported on the conversion of hyperpolarized 13C-labeled pyruvate to its metabolic products, alanine, lactate and carbonate in vivo [2,3,4,5,6], in which higher lactate production is an important indicator of cancer. This technique is already being translated to the clinic and a first trial is ongoing [7]. By incorporating this pure spin state into a molecule through a hydrogenation reaction, large sig-
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