Proton and Carbon-13 Dynamic Nuclear Polarization of Methylated β-Cyclodextrins

Abstract

H and C dynamic nuclear polarizations have been studied inC-enriched β-cyclodextrins doped with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical. H andC polarizations raised above 7.5 and 7%, respectively, and for both nuclear species, the transfer of polarization from the electron spins appears to be consistent with a thermal mixing scenario for a concentration of 9 C nuclei per molecule. When the concentration is increased to 21C nuclei per molecule, a decrease in the spin-lattice relaxation and polarization buildup rates is observed. This reduction is associated with the bottleneck effect induced by the decrease in the number of electron spins per nucleus when both the nuclear spin-lattice relaxation and the polarization occur through the electron non-Zeeman reservoir. C nuclear spin-lattice relaxation has been studied in the 1.8-340 K range, and the effects of internal molecular motions and of the free radicals on the relaxation are discussed.C hyperpolarization performances and room-temperature spin-lattice relaxation times show that these are promising materials for future biomedical applications.

Cyclodextrin‐Based Organic Radical Contrast Agents for in vivo Imaging of Gliomas

“…[27] Moreover, the use of CD functionalized with a single TEMPO unit has found application as doping agent for proton and carbon-13 dynamic nuclear polarization studies of natural and modified CDs. [28][29][30] The introduction of seven radical units on the small rim of the β-CD cone (compound CD71 in Figure 1) allowed to increase the magnetic moment (μeff/μB ≈ 4.2) and 1 H water relaxivity (r1 = 1.596 mM −1 s −1 ) compared to the analogous derivative with a single TEMPO unit (μeff/μB ≈ 1.7 and r1 = 0.323 mM −1 s −1 ). Unfortunately, this compound was not suitable for the direct application as in vivo CA, due to its low solubility in water.…”

Molecular Dynamics and Hyperpolarization Performance of Deuterated β-Cyclodextrins

“…13 C-enriched samples CD21d (totally methylated with 21 deuterated methyl groups per molecule) and the corresponding TEMPO-doped sample (CD21Rd) were prepared as reported in the Supporting Information. The data presented here are compared with those obtained in a previous work and related to a TEMPO-doped sample of totally methylated 13 C-enriched cyclodextrins without deuterium and named CD21R.…”

“…The enhancement factor and the final DNP-enhanced polarization were derived as those for 1 H. Figures and show the temperature dependence of the 1 H and the 13 C nuclear spin–lattice relaxation and polarization rates, for T ≤ 4.2 K, respectively. In Figure 13 C, the data for the sample with protonated methyl groups were taken from ref . Figure reports the temperature dependence of the 1 H and 13 C DNP-enhanced polarization.…”

“…Fit parameters: for 1 H, a = 0.025 ± 0.008 K – b s –1 and b = 2.06 ± 0.23; for 13 C, a = 0.023 ± 0.003 K – b s –1 and b = 0.77 ± 0.15. For comparison, the 13 C data of the protonated sample (green triangles) taken from ref are also shown.…”

“…Accordingly, their applications nowadays span from the development of nanovectors for cancer treatment and for gene delivery to the development of contrast agents. − Hence, the possibility to perform DNP on β-CD would allow to follow through in vivo molecular imaging the fate of the drug hosted by the CDs. In previous works, , we managed to raise 1 H and 13 C nuclear polarizations up to 10 and 7%, respectively. However, the room-temperature relaxation times were found to be too short to allow for any future molecular imaging application.…”