Fluoride doped γ-Fe₂O₃ nanoparticles with increased MRI relaxivity

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Imaging

Background:

• Iron oxide nanoparticles (IONs) are investigated for Magnetic Resonance Imaging (MRI) contrast enhancement and targeted therapeutics.
• MRI contrast agent efficiency is determined by longitudinal (r1) and transverse (r2) relaxivities.

Purpose of the Study:

• To investigate the effect of controlled fluoride doping and citric acid functionalization on the MRI contrast properties of gamma-iron oxide (γ-Fe2O3) nanoparticles.
• To elucidate the relationship between magnetic properties, particularly magnetic anisotropy, and the observed relaxivity enhancements.

Main Methods:

• Controlled fluorination of γ-Fe2O3 nanoparticles.
• Characterization using Powder X-ray Diffraction (PXRD), Mössbauer spectroscopy, High-Resolution Electron Microscopy (HREM), and magnetometry.
• Measurement of longitudinal (r1) and transverse (r2) relaxivities at 3 T and 11 T magnetic fields.

Main Results:

• Fluoride-doped γ-Fe2O3 nanoparticles exhibited a 3-fold increase in r1 and a 17-fold increase in r2 at 3 T, and a ~6-fold increase in r1 and a 14-fold increase in r2 at 11 T.
• Structural integrity (crystal structure, Fe oxidation state, particle size) was maintained post-fluorination.
• A significant increase in the coercive field was observed, indicating enhanced magnetic anisotropy.

Conclusions:

• Chemically induced magnetic anisotropy is the primary factor responsible for the substantial increase in relaxivity of the fluorinated γ-Fe2O3 nanoparticles.
• These findings suggest a promising strategy for developing advanced IONs with superior MRI contrast capabilities.