Abstract
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%.
Highlights
Contributed by Alexander Pines, February 17, 2021
The drawback to producing hyperpolarized fumarate via parahydrogen-induced polarization (PHIP) is that, in addition to the desired fumarate product, the reaction solutions contain a plethora of additional chemicals, most notably the ruthenium catalyst, unreacted reagents, and reaction side products
Para-enriched hydrogen gas was rapidly bubbled through a precursor solution (Materials and Methods) in a heated steel reactor
Summary
Contributed by Alexander Pines, February 17, 2021 Signal enhancements on the order of 105 can be achieved for solution-state samples using hyperpolarization techniques such as dissolution dynamic nuclear polarization (dDNP) [1, 2] or parahydrogen-induced polarization (PHIP) [3,4,5]. This allows the injection of hyperpolarized probe molecules in vivo, and subsequent imaging of metabolism [6,7,8,9,10]. The drawback to producing hyperpolarized fumarate via PHIP is that, in addition to the desired fumarate product, the reaction solutions contain a plethora of additional chemicals, most notably the ruthenium catalyst, unreacted reagents, and reaction side products
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