One-Step Preparation of Highly Stable Copper-Zinc Ferrite Nanoparticles in Water Suitable for MRI Thermometry

Superparamagnetic ferrite nanoparticles coated with a polymer layer are widely used for biomedical applications. The objective of this work is to design nanoparticles as a magnetic resonance imaging (MRI) temperature-sensitive contrast agent. Copper-zinc ferrite nanoparticles coated with a poly(ethylene glycol) (PEG) layer are synthesized using a one-step thermal decomposition method in a polymer matrix. The resulting nanoparticles are stable in water and biocompatible. Using Mössbauer spectroscopy and magnetometry, it was determined that the grown nanoparticles exhibit superparamagnetic properties. Embedding these particles into an agarose gel resulted in significant modification of water proton relaxation times T ₁, T ₂, and T ₂* determined by nuclear magnetic resonance measurements. The results of the spin-echo T ₂-weighted MR images of an aqueous phantom with embedded Cu_0.08Zn_0.54Fe_2.38O₄ nanoparticles in the presence of a strong temperature gradient show a strong correlation between the temperature and the image intensity. The presented results support the hypothesis that CuZn ferrite nanoparticles can be used as a contrast agent for MRI thermometry.