Metal oxide nanoparticles as potential MRI contrast agents

Jones, Naomi E.

Abstract

Magnetic resonance imaging (MRI) is a common medical imaging modality that does not require the administration of radiopharmaceuticals, as it relies on the inherent nuclear spin of the protons in the tissues and organs. However, it lacks sensitivity in comparison to imaging techniques such as positron emission tomography (PET) and therefore changes at a cellular level are difficult to detect. To increase the level of information that can be obtained from MR images, contrast agents such as superparamagnetic iron oxide nanoparticles (SPIONs) or gadolinium based chelates can be used. Contrast agents work by making areas of the image where the agent is concentrated either lighter or darker; this is known as T₁ and T₂ relaxation respectively. Typically, gadolinium based chelates influence T₁ relaxation times, and SPION affect T₂ relaxation times of the hydrogen protons within the target organ or tissue. Recently, research has expanded from the use of chelated compounds with an increasing focus on improving and refining the properties of nanoparticles as contrast agents.

The work described here focusses on the preparation of new cation and anion doped SPION-based contrast agents with improved imaging properties for MRI. Specifically, the following series of oxide nanoparticles were prepared: Fe₂−xDyxO₃, Fe₂−xGdxO₃, Gd₂−xMnxO₃, Gd₂−xFexO₃, Dy₂−xFexO₃ and Fe₂O₃−xF₂x.

The nanoparticles were prepared via either co-precipitation or solid state reactions. Powder X-ray diffraction, ICP-AES, TEM, SEM, XPS, Mössbauer spectroscopy and magnetic measurements were performed to characterise the samples. The potential of selected samples to be developed into contrast agents was tested at the Royal Infirmary in Hull.

The nanoparticles prepared in this work that show the most potential for improving T₁ relaxation rates at 3 T are the Gd₂−xMnxO₃ nanoparticle series. Of these Gd₁.₉₈Mn₀.₀₂O₃, Gd₁.₉₀Mn₀.₁₀O₃, Gd₁.₇₉Mn₀.₂₁O₃ nanoparticles in addition to Fe₁.₉₆Gd₀.₀₄O₃ nanoparticles also show potential for use at 11.7 T as T₁ contrast agents.

Fe₁.₉₆Gd₀.₀₄O₃ and Fe₁.₉₉Dy₀.₀₁O₃ nanoparticles exhibited high T₂ relaxation rates at 11.7 T compared to those of prepared γ-Fe₂O₃ nanoparticles.

Fe₂O₃−xF₂x nanoparticles exhibited high T₂ relaxation rates at both 3 T and 11.7 T compared against γ-Fe₂O₃ nanoparticles, showing their potential for use both at clinical and higher magnetic field strengths.

Citation

Jones, N. E. (2015). Metal oxide nanoparticles as potential MRI contrast agents. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4218445

• Thesis Type: Thesis
• Deposit Date: Aug 22, 2016
• Publicly Available Date: Feb 23, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4218445
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Jun 1, 2015