Characterisation and application of ultra-high spin clusters as magnetic resonance relaxation agents

Abstract

In Magnetic Resonance Tomography (MRT) image contrast can be improved by adding paramagnetic relaxation agents such as lanthanide ions. Here we report on the use of highly paramagnetic isostructural Fe(III)/4f coordination clusters with a [Fe10Ln10] core to enhance relaxation. Measurements were performed over the range of (1)H Larmor frequencies of 10 MHz to 1.4 GHz in order to determine the relevant parameters for longitudinal and transverse relaxivities. Variation of the lanthanide ion allows differentiation of relaxation contributions from electronic states and molecular dynamics. We find that the transverse relaxivities increase with field, whereas the longitudinal relaxivities depend on the nature of the lanthanide. In addition, the Gd(III) analogue was selected in particular to test the interaction with tissue observed using MRT. Studies on biofilms used in waste water treatment reveal that the behaviour of the high-spin clusters is different from what is observed for common relaxation agents with respect to the penetration into the biofilms. The Fe10Gd10 cluster adheres to the surface of the biofilm better than the commercial agent Gadovist.

New insights into sodium alginate fouling of ceramic hollow fiber membranes by NMR imaging

“…Furthermore they do not penetrate into the alginate gel layer, this leads to the conclusion, that either the gel layer has a relatively dense structure as explained by the egg-box model 4,6,28 or the potential of agglomeration is high in the presence these potential seeds of nucleation as it was observed in the context of MRI on biofilms. [39][40][41] The latter possibility is unlikely as the MIONs disperse completely when added to an alginate solution, and no signature of agglomeration is observed. These findings lead us to the conclusion that the alginate layer in the presence of Ca 21 is dense enough to inhibit the ingress of the nanoparticles.…”

A multiscale subvoxel perfusion model to estimate diffusive capillary wall conductivity in multiple sclerosis lesions from perfusion MRI data

“…However, the concentrations arriving in the brain tissue sample are strongly diluted by diffusion and dispersion along the tortuous path through the vascular network, so that the influence on blood density and viscosity can be neglected in this study. The binary diffusion coefficient of Gadobutrol in plasma can be estimated by means of the Stokes‐Einstein radius, r hy = 0.9 nm, where μ P = 1.32 Pa s denotes the blood plasma viscosity, T the temperature in K, and k B the Boltzmann constant.…”

“…We are not aware of such measurements for Gadobutrol. Nevertheless, D ω values can be assumed to be similar for molecules with similar properties as Gadobutrol (hydrophilic, M = 604.715 g mol –1 , r hy ≈ 0.8 nm). For example, for sucrose (hydrophilic, M = 342.30 g mol –1 , r hy ≈ 0.45 nm) values in the order of 1.4 ⋅ 10 −6 m s –1 are reported for frog mesentery and skeletal muscle tissue, depending on the measurement method.…”

A Strongly Spin‐Frustrated FeIII7 Complex with a Canted Intermediate Spin Ground State of S=7/2 or 9/2

“…Over recent decades there has been a plethora of research into the design and synthesis of paramagnetic coordination clusters (CCs) with the aim of using their novel magnetic properties. For example, this research can be oriented with the idea of finding systems that can act as single‐molecule magnets (SMMs)1 or that can be regarded as giant spin superparamagnets2 with applications as molecular‐based coolers with favourable magnetocaloric parameters3 or else as potential contrast agents for MRI applications 4. However, CCs also provide opportunities to study more fundamental magnetic questions associated with the fact that the spins on the metal centres are quantum in nature 5.…”