Hyperpolarization of ¹⁵N-Pyridinium by Using Parahydrogen Enables Access to Reactive Oxygen Sensors and Pilot In Vivo...

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 ¹³C nuclei, a milestone advance in this area is the emergence of ¹⁵N hyperpolarized contrast agents. Currently, the reported ¹⁵N hyperpolarized agents mainly utilize the dissolution dynamic nuclear polarization (d-DNP) protocol. The parahydrogen enhanced ¹⁵N probes have proven to be elusive and have been tested almost exclusively in organic solvents. Herein, we designed a reaction based reactive oxygen sensor ¹⁵N-boronobenzyl-2-styrylpyridinium (¹⁵N-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 H₂O₂ level usually represents a hallmark of pathophysiological conditions. This H₂O₂ probe exhibited rapid responsiveness toward H₂O₂ 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 ¹⁵N 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.