Design, synthesis and evaluation of ¹⁵N- and ¹³C-labeled molecular probes as hyperpolarized nitric oxide sensors

Nitric oxide (NO) is an important signaling molecule involved in a wide range of biological processes. Development of non-invasive, real-time detection of NO is greatly desired yet remains challenging. Here we report the design and development of novel ¹⁵N- and ¹³C-labeled NO-sensing probes for hyperpolarized nuclear magnetic resonance (HP-NMR) studies. These probes undergo selective and rapid reaction with NO to generate in situ AZO-products that can be monitored with distinguishable NMR signals as a read-out. This study also allows for a direct comparison of the ¹⁵N and ¹³C nuclei performances in hyperpolarized reaction-based probes. The simple and general SABRE-SHEATH hyperpolarization method works on the ¹⁵N- and ¹³C-NO-sensing probes. Measured long spin-lattice relaxation (T₁) values, especially for ¹⁵N-NO probes, will allow for real-time reaction-based imaging of NO.