Nanodiamond-enhanced MRI

TL;DR

This paper introduces a novel MRI technique using the Overhauser effect to enable high-contrast, noninvasive imaging of nanodiamonds in vivo, leveraging hyperpolarization for long-term tracking.

Contribution

It demonstrates the first application of the Overhauser effect for MRI of nanodiamonds at room temperature and low magnetic fields, enabling continuous hyperpolarization and long-term in vivo tracking.

Findings

High contrast MRI of nanodiamonds achieved in water at room temperature.

Optimal conditions for maximum enhancement identified.

Potential for indefinite long-term in vivo tracking of nanodiamonds.

Abstract

Nanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton-electron double resonance technique developed to detect free radicals in vivo, can enable high contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to $^1$H spins in the surrounding water solution, creating MRI contrast on-demand. We further examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous hyperpolarization via the Overhauser mechanism, in combination with excellent in vivo stability, raises the possibility of performing noninvasive tracking of nanodiamonds over indefinitely long periods of time.