Quantum-mechanical simulation programs for the relaxation of Bi-1H-systems have been developed to study the dependence of QRE efficiency on design parameters like quadrupole resonance frequencies, dynamics of the molecules and exchange rate of water molecules with the QN. In addition simple, fast applicable tools were developed for a coarse prediction of QRE frequencies as well as quadrupolar relaxation in solid precursors. Calculations predict a theoretical relaxivity enhancement of 5-10 compared to water for 10mMol concentration after full optimization of the NPs. DFT calculations have shown the dependence of NQR frequencies on bound ligands and also long-ranging structural effects, e.g. subtle changes of binding angles, thus supporting the fine tuning of the CAs.
A family of Bi-aryl compounds with several substituents was synthesised and an extremely versatile strategy for covalently bonding them onto different NPs was elaborated. All compounds were characterised with respect to crystal properties and purity. Nuclear Quadrupole Spectroscopy (NQRS) revealed resonance frequencies close to target values for clinical scanners and showed the relevance of structural order of the Bi centres.
A number of highly biocompatible functional NPs based on polysaccharide (PS), especially ethyl cellulose and Dextran, were synthesised. Then composite NPs with selected Bi compounds as well as polymer-coated Bi-Aryl nanocrystallites were produced.
Triaryl-Bi-compounds were also successfully bonded to cyclodextrin, thus providing a well-reproducible model-system for basic investigations and highly ordered Bi-centres.
All NPs were comprehensively characterised in terms of the physical and chemical properties relevant for QRE. Finally solids as well as liquid dispersions were investigated for QRE of intrinsic and solvent 1H, respectively, by Fast Field Cycling (FFC) NMR relaxometry.
For testing QRE imaging, a clinical 3T MRI scanner was equipped with an insert for FFC to shift B0 away from the nominal value. Technical challenges comprising installation, correction of system imperfections and sequence design were tackled to make the system fully operative. The capability of generating contrast from relaxivity dispersion has been proven for the first time at 3T. Actual QRE imaging was not yet possible because of still insufficient signal from the available samples.
A patent was submitted to the European Patent Office.
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