Category Archives: Nanodiamonds

Nanodiamond as a New Hyperpolarizing Agent and Its 13C MRS #DNPNMR

Dutta, Prasanta, Gary V. Martinez, and Robert J. Gillies. “Nanodiamond as a New Hyperpolarizing Agent and Its 13C MRS.” The Journal of Physical Chemistry Letters 5, no. 3 (February 6, 2014): 597–600.

https://doi.org/10.1021/jz402659t

In this work, we have hyperpolarized carbonaceous nanoparticles (D ≈ 10 nm), that is, “nanodiamonds”, with 1.1% 13C (natural abundance) using dynamic nuclear polarization (DNP). The polarization buildup curve showed a signal enhancement with relative intensity up to 4700 at 1.4 K and 100 mW microwave power. 13C magnetic resonance spectra (MRS) were obtained from the sample at 7 T, and the signal decayed with a T1 of 55 ± 3s. Notably, polarization was possible in the absence of added radical, consistent with previous results showing endogenous unpaired electrons in natural nanodiamonds. These likely contribute to the shorter T1’s compared to those of highly pure diamond. Despite the relatively short T1, these observations suggest that natural nanodiamonds may be useful for in vivo applications.

Direct hyperpolarization of micro- and nanodiamonds for bioimaging applications – Considerations on particle size, functionalization and polarization loss

Kwiatkowski, G., et al., Direct hyperpolarization of micro- and nanodiamonds for bioimaging applications – Considerations on particle size, functionalization and polarization loss. J Magn Reson, 2018. 286: p. 42-51.

https://www.ncbi.nlm.nih.gov/pubmed/29183003

Due to the inherently long relaxation time of (13)C spins in diamond, the nuclear polarization enhancement obtained with dynamic nuclear polarization can be preserved for a time on the order of about one hour, opening up an opportunity to use diamonds as a new class of long-lived contrast agents. The present communication explores the feasibility of using (13)C spins in directly hyperpolarized diamonds for MR imaging including considerations for potential in vivo applications.

Direct hyperpolarization of micro- and nanodiamonds for bioimaging applications – Considerations on particle size, functionalization and polarization loss

Kwiatkowski, G., et al., Direct hyperpolarization of micro- and nanodiamonds for bioimaging applications – Considerations on particle size, functionalization and polarization loss. J Magn Reson, 2018. 286: p. 42-51.

https://www.ncbi.nlm.nih.gov/pubmed/29183003

Due to the inherently long relaxation time of (13)C spins in diamond, the nuclear polarization enhancement obtained with dynamic nuclear polarization can be preserved for a time on the order of about one hour, opening up an opportunity to use diamonds as a new class of long-lived contrast agents. The present communication explores the feasibility of using (13)C spins in directly hyperpolarized diamonds for MR imaging including considerations for potential in vivo applications.

Nanodiamond-enhanced MRI via in situ hyperpolarization

Waddington, D.E.J., et al., Nanodiamond-enhanced MRI via in situ hyperpolarization. Nat Commun, 2017. 8: p. 15118.

https://www.ncbi.nlm.nih.gov/pubmed/28443626

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 polarization transfer technique, 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 1H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time.

Hyperpolarized Nanodiamond Surfaces #DNPNMR

Rej, E., et al., Hyperpolarized Nanodiamond Surfaces. J Am Chem Soc, 2017. 139(1): p. 193-199.

https://www.ncbi.nlm.nih.gov/pubmed/28009158

The widespread use of nanodiamond as a biomedical platform for drug-delivery, imaging, and subcellular tracking applications stems from its nontoxicity and unique quantum mechanical properties. Here, we extend this functionality to the domain of magnetic resonance, by demonstrating that the intrinsic electron spins on the nanodiamond surface can be used to hyperpolarize adsorbed liquid compounds at low fields and room temperature. By combining relaxation measurements with hyperpolarization, spins on the surface of the nanodiamond can be distinguished from those in the bulk liquid. These results are likely of use in signaling the controlled release of pharmaceutical payloads.

On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid-State and Dissolution 13 C NMR Spectroscopy #DNPNMR

Bretschneider, C.O., et al., On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid-State and Dissolution 13 C NMR Spectroscopy. ChemPhysChem, 2016: p. n/a-n/a.

http://www.ncbi.nlm.nih.gov/pubmed/27416769

Dynamic nuclear polarization (DNP) is a versatile option to improve the sensitivity of NMR and MRI. This versatility has elicited interest for overcoming potential limitations of these techniques, including the achievement of solid-state polarization enhancement at ambient conditions, and the maximization of 13 C signal lifetimes for performing in vivo MRI scans. This study explores whether diamond’s 13 C behavior in nano- and micro-particles could be used to achieve these ends. The characteristics of diamond’s DNP enhancement were analyzed for different magnetic fields, grain sizes, and sample environments ranging from cryogenic to ambient temperatures, in both solution and solid-state experiments. It was found that 13 C NMR signals could be boosted by orders of magnitude in either low- or room-temperature solid-state DNP experiments by utilizing naturally occurring paramagnetic P1 substitutional nitrogen defects. We attribute this behavior to the unusually long electronic/nuclear spin-lattice relaxation times characteristic of diamond, coupled with a time-independent cross-effect-like polarization transfer mechanism facilitated by a matching of the nitrogen-related hyperfine coupling and the 13 C Zeeman splitting. The efficiency of this solid-state polarization process, however, is harder to exploit in dissolution DNP-enhanced MRI contexts. The prospects for utilizing polarized diamond approaching nanoscale dimensions for both solid and solution applications are briefly discussed.

The phenomenology of optically pumped 13C NMR in diamond at 7.05 T: Room temperature polarization, orientation dependence, and the effect of defect concentration on polarization dynamics

Scott, E., M. Drake, and J.A. Reimer, The phenomenology of optically pumped 13C NMR in diamond at 7.05 T: Room temperature polarization, orientation dependence, and the effect of defect concentration on polarization dynamics. J. Magn. Reson., 2016. 264: p. 154-162.

http://www.sciencedirect.com/science/article/pii/S1090780716000252

Room temperature optical illumination of NV− imbibed single crystal diamonds with a 532 nm laser produces 13C polarization enhancements up to 200 times greater than that of the thermal equilibrium value at 7.05 T. We report high field NV− mediated 13C polarization as a function of the number and type (NV− and P1) of defects in commercially available diamonds. Surprisingly, both positive and negative 13C polarizations are observed depending on the orientation of the crystal with respect to the external magnetic field and the electric field vector of the optical illumination. The data reported herein cannot be explained by a previously proposed mechanism.

Hyperpolarized Nanodiamond with Long Spin Relaxation Times

Rej E, Gaebel T, Boele T, Waddington D, Reilly D. Hyperpolarized Nanodiamond with Long Spin Relaxation Times. ARXIV. 2015.

http://arxiv.org/abs/1502.06214

The use of hyperpolarized agents in magnetic resonance (MR), such as 13C-labeled compounds, enables powerful new imaging and detection modalities that stem from a 10,000-fold boost in signal. A major challenge for the future of the hyperpolarizaton technique is the inherently short spin relaxation times, typically < 60 seconds for 13C liquid-state compounds, which limit the time that the signal remains boosted. Here, we demonstrate that 1.1% natural abundance 13C spins in synthetic nanodiamond (ND) can be hyperpolarized at cryogenic and room temperature without the use of toxic free- radicals, and, owing to their solid-state environment, exhibit relaxation times exceeding 1 hour. Combined with the already established applications of NDs in the life-sciences as inexpensive fluorescent markers and non-cytotoxic substrates for gene and drug delivery, these results extend the theranostic capabilities of nanoscale diamonds into the domain of hyperpolarized MR.

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