Magnetite Nanodiscs as Vortex-Enhanced MRI Contrast Agents: A Novel Approach in Medical Imaging

Abstract

Magnetic nanoparticles can serve as contrast agents for magnetic resonance imaging (MRI) to enhance sensitivity and improve imaging contrast. This study investigated anisotropic magnetite nanodiscs (MNDs) with vortex magnetization, which exhibit high saturation magnetization and low magnetocrystalline anisotropy. These properties contribute to the minimization of magnetostatic energy. The vortex magnetization grants these particles, which are over 100 nm in diameter, a zero net magnetization, thereby inducing superparamagnetic-like behavior. Due to these distinctive characteristics, MNDs have been explored as novel contrast agents in magnetic resonance imaging. The study demonstrated their ability to enhance transverse relaxation at 7 T and to act as T1 contrast agents at very low magnetic fields. Additionally, MNDs strongly influence the magnetization transfer contrast (MTC) of immobilized water present in biological specimens and tissues, enabling them to function as multimodal MRI contrast agents that not only work as relaxation-based contrast agents but also modify tissue MTC.