Phase-Encoded Hyperpolarized Nanodiamond for Magnetic Resonance Imaging

Abstract

Surface-functionalized nanomaterials are of interest as theranostic agents that detect disease and track biological processes using hyperpolarized magnetic resonance imaging (MRI). Candidate materials are sparse however, requiring spinful nuclei with long spin-lattice relaxation ( T 1 ) and spin-dephasing times ( T 2 ), together with a reservoir of electrons to impart hyperpolarization. Here, we demonstrate the versatility of the nanodiamond material system for hyperpolarized 13 C MRI, making use of its intrinsic paramagnetic defect centers, hours-long nuclear T 1 times, and T 2 times suitable for spatially resolving millimeter-scale structures. Combining these properties, we enable a new imaging modality, unique to nanoparticles, that exploits the phase-contrast between spins encoded with a hyperpolarization that is aligned, or anti-aligned with the external magnetic field. The use of phase-encoded hyperpolarization allows nanodiamonds to be tagged and distinguished in an MRI based on their spin-orientation alone, and could permit the action of specific bio-functionalized complexes to be directly compared and imaged.

Tailored nanodiamonds for hyperpolarized C13 MRI

“…4a and demonstrate a clear difference favoring DNP via the outer peak. Corresponding results also show that characteristic decay rates differ for nanodiamond polarized by different pathways [9,21]. We present this as evidence suggesting spin diffusion is somewhat suppressed in these nanodiamond samples, preventing bulk spins far away from paramagnetic sites from rapidly equilibrating local differences in polarization.…”

Robust optical polarization of nuclear spin baths using Hamiltonian engineering of nitrogen-vacancy center quantum dynamics

“…allowing for rapid electron spin polarisation to be generated optically or chemically far above thermal equilibrium and subsequently transferred to surrounding nuclei [1][2][3][4][5][6][7]. These systems present a unique opportunity for polarising and initialising spin baths and unlocking the potential of nanoscale applications including the initialisation of quantum simulators based on nuclear spin arrays in diamonds [8], magnetic resonance imaging (MRI) tracers via diamond * qiong.chen@uni-ulm.de, ilai.schwartz@uni-ulm.de, martin.plenio@uni-ulm.de nanoparticles [9][10][11][12][13] and the enhancement of nanoscale nuclear magnetic resonance (NMR) using NV spin ensembles [7,[14][15][16].…”

“…(ii) The hyper-polarisation of nanodiamonds as MRI biomarkers. Nanodiamonds have been previously polarised at cryogenic temperatures (1-3K) and high magnetic fields [9,[11][12][13]. However, optical polarisation via NV centres at room temperature offers several key advantages such as less complex and costly experimental setups and faster polarisation build-up time [10].…”

Background-free dual-mode optical and13C magnetic resonance imaging in diamond particles

“…Conventional methods, in contrast, require high magnetic field ( 3 T) and low temperature ( 4 K) and polarization buildup can take several hours ( 18 ). While the absolute polarization is lower in our method, we circumvent the high polarization loss (as large as 99%) ( 19 ) accrued upon thawing and sample transfer out of the cryostat. Technologically, our technique aids end-user operation—MW amplifiers and sweep sources are low cost and readily available, and hyperpolarized particles can be delivered by a portable device ( 10 ).…”