Rapid Hyperpolarization and Purification of the Metabolite Fumarate in Aqueous Solution

Abstract

Hyperpolarized fumarate is a promising agent for carbon-13 magnetic resonance metabolic imaging of cellular necrosis. 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 hyperpolarized fumarate solutions are contaminated with the catalyst, unreacted reagents, and reaction side product molecules, and are hence unsuitable for use <i>in vivo</i>. 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 at a chosen concentration in a clean aqueous solvent. Significant advances in the reaction conditions and reactor equipment allow us to form hyperpolarized fumarate at a concentration of several hundred millimolar, at <sup>13</sup>C polarization levels of 30-45%.

Zero- to Ultralow-Field NMR Spectroscopy of Small Biomolecules

“…22,25 Agreement between simulated and measured spectra combined with narrow linewidths under ZULF conditions enables chemical identification of biomolecules in liquids, and combination with hyperpolarization techniques is poised to be especially promising. 26 The coupling constants extracted for [1-13 C]-glycine, [2,3-13 C 2 ]-fumarate, and [1-13 C]-D-glucose, extracted by matching the experimentally observed and simulated spectra, correlate well with those obtained from the literature. However, we should note that while it is possible to obtain high-resolution zerofield spectra of these important biomolecules in solution, the obtained signal-to-noise ratio (SNR) is low, necessitating hundreds of averages.…”

Temperature Cycling Enables Efficient 13C SABRE-SHEATH Hyperpolarization and Imaging of [1-13C]-Pyruvate

“…15,16 Here, we present a combination of advances including the use of temperature cycling to overcome the in vivo polarization threshold of 10% with SABRE-SHEATH. The results of this study also indicate that further optimization of [1- 13 C]pyruvate SABRE-SHEATH is possible to maximize the critical molar polarization, defined as the product of concentration and polarization (introduced by Knecht et al 21 ), which is ultimately the most important hyperpolarization parameter required for in vivo translation. 7,12,22 Previous demonstrations of parahydrogen induced polarization (PHIP) on pyruvate have shown the feasibility of in vivo studies.…”

“…The initial results of this study also indicate that further optimization of the pyruvate SABRE-SHEATH process can yield higher molar polarization levels (concentration × %P) as needed for in vivo studies. 10,21,23 The spectrum and results shown in figure 2A are the maximum achieved single-shot polarization during this study. This data shows 14.3% polarization on the bound pyruvate species, and 10.8% on the free pyruvate corresponding to a total sample polarization of 11.8% on pyruvate.…”

Simultaneous 15N polarization of several biocompatible substrates in ethanol–water mixtures by signal amplification by reversible exchange (SABRE) method

“…Potentially, the proposed method can be used to remove the toxic catalyst from solution by dissolving the hyperpolarized mixture in water: we anticipate that upon further dilution, the catalyst (having limited solubility in water) will precipitate and a neat hyperpolarized fluid will be obtained. [49] Our valued colleague and good friend Konstantin ("Kostya") L. Ivanov became one of the first victims of the COVID-19 pandemic in our community. He passed away on March 5, 2021, in a hospital in Novosibirsk.…”