Evaluation of the Effect of Post-Synthesis Oxidation on Iron Oxide Nanoparticle Performance in Magnetic Particle Imaging

The aim of this study is to quantify the effect of post synthesis oxidation on the magnetic properties of iron oxide nanoparticles synthesized through a high throughput platform. Iron oxide nanoparticles have a wide range of applications in biomedicine, including more recently as tracers for Magnetic Particle Imaging (MPI). Iron oxide nanoparticles generate a signal in the MPI machine from their nonlinear dynamic magnetization. Some of the properties that make it a desirable imaging modality include negligible signal attenuation from tissue or background and the absence of ionizing radiation, compared to other techniques such as CT or X-Ray. Optimization of tracers for MPI can improve the sensitivity and resolution of the imaging modality, allowing for the use of lower field gradients and reducing capital and operation costs. A high throughput platform was designed for particle synthesis to accelerate data collection and assess reproducibility by allowing for 8 simultaneous syntheses. Once synthesis results were consistent in the high throughput platform, focus shifted towards understanding the effects of post synthesis oxidation on the magnetic properties of the particles. Two control groups of 8 samples each were synthesized via the high throughput platform, and then compared to two oxidation studies performed on two sets of synthesis with a 1% O₂/Ar mixture at 300 °C for 3 and 30 hours. After synthesis and characterization via TEM, DLS, and UV vis, particles were coated with polymer to make them stable in aqueous phase and magnetic characterization was performed. MPI relaxation scans on particle samples in an aqueous environment determined MPI signal intensity and resolution, showing significant improvement for samples oxidized post-synthesis. Statistical analysis on the samples was performed to determine the effects of the post synthesis oxidation and quantify variations between the samples. Ultimately, synthesis with post synthesis oxidation in the high throughput platform led to an increase in signal intensity in MPI, while decreasing the full width at half maximum, indicating improvement in resolution.