Hyperpolarized (15)N-labeled, deuterated tris (2-pyridylmethyl)amine as an MRI sensor of freely available Zn(2).

Dynamic nuclear polarization (DNP) coupled with (15)N magnetic resonance imaging (MRI) provides an opportunity to image quantitative levels of biologically important metal ions such as Zn(2+), Mg(2+) or Ca(2+) using appropriately designed (15)N enriched probes. For example, a Zn-specific probe could prove particularly valuable for imaging the tissue distribution of freely available Zn(2+) ions, an important known metal ion biomarker in the pancreas, in prostate cancer, and in several neurodegenerative diseases. In the present study, we prepare the cell-permeable, (15)N-enriched, d(6)-deuterated version of the well-known Zn(2+) chelator, tris(2-pyridylmethyl)amine (TPA) and demonstrate that the polarized ligand had favorable T(1) and linewidth characteristics for (15)N MRI. Examples of how polarized TPA can be used to quantify freely available Zn(2+) in homogenized human prostate tissue and intact cells are presented.