Tailored nanodiamonds for hyperpolarized C13 MRI

T Boele,T Gaebel,D J Reilly,A Hasija,D R Mccamey,D E J Waddington,E Rej,L J Brown

doi:10.1103/physrevb.101.155416

Abstract

Nanodiamond is poised to become an attractive material for hyperpolarized 13C MRI if large nuclear polarizations can be achieved without the accompanying rapid spin-relaxation driven by paramagnetic species. Here we report enhanced and long-lived 13C polarization in synthetic nanodiamonds tailored by acid-cleaning and air-oxidation protocols. Our results separate the contributions of different paramagnetic species on the polarization behavior, identifying the importance of substitutional nitrogen defect centers in the nanodiamond core. These results are likely of use in the development of nanodiamond-based imaging agents with size distributions of relevance for examining biological processes.

Highlights

Hyperpolarized 13C magnetic resonance imaging (MRI) leverages a >10 000-fold enhancement in 13C polarization achieved via dynamic nuclear polarization (DNP), a process in which spin polarization is transferred from electron spins to 13C nuclei [1]
As nuclear T1 relaxation and DNP behavior depend on the paramagnetic defects in nanodiamond we begin our results with continuous wave electron paramagnetic resonance (CW EPR) characterization measurements
We have tailored the composition of paramagnetic defect sites in nanodiamond and mapped how those alterations affect hyperpolarization via DNP

Summary

Introduction

Hyperpolarized 13C magnetic resonance imaging (MRI) leverages a >10 000-fold enhancement in 13C polarization achieved via dynamic nuclear polarization (DNP), a process in which spin polarization is transferred from electron spins to 13C nuclei [1]. Two promising candidates are silicon and diamond, which have dilute spin systems of 29Si and 13C at 4.7 and 1.1% natural abundance, respectively. Both silicon and diamond nanoparticles have been investigated and reported to maintain T1 relaxation times that approach the hours-long T1 times of their bulk counterparts [8,9,10,11]. Silicon and diamond nanoparticles can be hyperpolarized via DNP using their endogenous paramagnetic defects as a source of free electrons [9,12,13,14,15,16,17] and still have sufficiently long spin-spin relaxation times (T2) to allow for MRI with useful spatial resolution [18,19,20,21]

Methods

Results

Conclusion