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Date of Award
Matthew J. Allen
The research projects described in this dissertation focus on studying the influence of molecular parameters and field strength on the relaxivity and the kinetic inertness of EuII-containing complexes within the context of magnetic resonance imaging. The results of these studies enable the prediction of influence structural properties of EuII-containing cryptates on the relaxivity and kinetic inertness.
EuII-containing cryptates EuII3.1–EuII3.3 and the adducts of EuII3.3 with β-cyclodextrin, poly-β-cyclodextrin, human serum albumin were used to explore the influence of molecular parameters including water-exchange rate, rotational correlation time, and electronic relaxation time on the relaxivity at wide range of field strengths using 1H-NMR, 17O-NMR, and EPR spectroscopies. EuII3.1 and EuII3.2 were characterized in solid and solution state, and EuII3.3 was characterized in solution state. In the solid state, a chloride counterion was coordinated to EuII; however, conductivity and 17O-NMR experiments suggest that the chloride ions dissociate in solution. This is the first report to demonstrate that it is possible to obtain high relaxivity enhancement through non-covalent interaction between functionalized EuII-containing cryptate with slowly tumbling substrates like β-CD, poly- β-CD, and HSA.
In addition to relaxometric studies, dissociation rates of EuII-containing cryptates have been measured using UV–visible spectroscopy and murexide in water. The EuII-murexide interaction was studied using UV–visible spectroscopy and IR spectroscopy. The dissociation rate of EuII-containing cryptates EuII3.1, EuII3.2, EuII3.4, EuII3.5, EuII3.6 were measured at pH values of 6.5, 7, 7.5, 8, and 9. Murexide was used as a scavenger ligand to trap dissociated EuII from the cryptates which responds linearly to change in EuII concentration. The rate of dissociation increases in the order of EuII3.1 < EuII3.2, EuII3.6 < EuII3.5 < EuII3.4. This finding demonstrates the utility of murexide as an indicator to measure the dissociation rate of EuII-containing complexes that do not have a metal complex-specific absorption profile relative to uncomplexed EuII.
These studies of MRI relevant properties and the kinetic inertness of EuII-containing cryptates provide insights in to the design of future EuII-based MRI contrast agents with high efficiency and kinetic stability.
Lenora, Chamika, "Magnetic-Resonance-Imaging Relevant Properties And Kinetic Inertness Of Lanthanide Cryptates" (2018). Wayne State University Dissertations. 2041.