Hyperpolarization of N-Pyridinium by Using Parahydrogen Enables Access to Reactive Oxygen Sensors and Pilot In Vivo Studies.

Magnetic resonance with hyperpolarized contrast agents is one of the most powerful and noninvasive imaging platforms capable for investigating in vivo metabolism. While most of the utilized hyperpolarized agents are based on C nuclei, a milestone advance in this area is the emergence of N hyperpolarized contrast agents. Currently, the reported N hyperpolarized agents mainly utilize the dissolution dynamic nuclear polarization (d-DNP) protocol. The parahydrogen enhanced N probes have proven to be elusive and have been tested almost exclusively in organic solvents. Herein, we designed a reaction based reactive oxygen sensor N-boronobenzyl-2-styrylpyridinium (N-BBSP) which can be hyperpolarized with para-hydrogen. Reactive oxygen species plays a vital role as one of the essential intracellular signalling molecules. Disturbance of the HO level usually represents a hallmark of pathophysiological conditions. This HO probe exhibited rapid responsiveness toward HO and offered spectrally resolvable chemical shifts. We also provide strategies to bring the newly developed probe from the organic reaction solution into a biocompatible injection buffer and demonstrate the feasibility of in vivo N signal detection. The present work manifests its great potential not only for reaction based reactive sensing probes but also promises to serve as a platform to develop other contrast agents.