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Hyperpolarized fumarate is a promising biosensor for carbon-13 magnetic resonance metabolic imaging. Such molecular imaging applications require nuclear hyperpolarization to attain sufficient signal strength. Dissolution dynamic nuclear polarization is the current state-of-the-art methodology for hyperpolarizing fumarate, but this is expensive and relatively slow. Alternatively, this important biomolecule can be hyperpolarized in a cheap and convenient manner using parahydrogen-induced polarization. However, this process requires a chemical reaction, and the resulting solutions are contaminated with the catalyst, unreacted reagents, and reaction side-product molecules, and are hence unsuitable for use in vivo. In this work we show that the hyperpolarized fumarate can be purified from these contaminants by acid precipitation as a pure solid, and later redissolved to a desired concentration in a clean aqueous solvent. Significant advances in the reaction conditions and reactor equipment allow for formation of hyperpolarized fumarate at 13C polarization levels of 30-45%.

Parahydrogen induced polarization (PHIP) is a chemistry based, cheap and easy to handle hyperpolarization method that allows to increase the sensitivity of magnetic resonance signals of several orders of magnitude. This powerful tool has not coalesced in the field of biomedical studies due to the lack of suitable hyperpolarization substrates, of commercial parahydrogen polarizers and to the presence of metal complex in the solutions of products. Here is reported an overview of the recent advances in these fields, with particular attention to the issues that have been tackled in order to allow the translation of parahydrogen based hyperpolarization methods into a widely applicable molecular imaging tool for biomedical research. [ABSTRACT FROM AUTHOR]