Controlled synthesis of MnFe2O4 nanoparticles and Gd complex-based nanocomposites as tunable and enhanced T1/T2-weighted MRI contrast agents

Abstract

Successful development of magnetic nanoparticles (MNPs) with optimal size, shape, and composition is very desirable because they would increase the image contrast of magnetic resonance imaging (MRI). Here, we report a new precursor-mediated growth process of monodisperse MnFe₂O₄ NPs with controlled size and shape. MnFe₂O₄ NPs with plate-like shapes, spherical, and cubic can be successfully prepared by simply tuning the amount of Fe(acac)₃ and Mn(acac)₂ in oleic acid. Magnetism and MR properties of the particles were found to depend on their size and shape. These MnFe₂O₄ NPs, when conjugated with gadolinium and folic acid (FA), showed a simultaneous bright signal enhancement on the T₁-weighted images and significant signal reduction on the T₂-weighted image. In vitro MR imaging experiments also show that the developed multifunctional Gd:FA-DTPA-PEG-DIB-MnFe₂O₄ NPs enable targeted dual-contrast T₁- and T₂-weighted MR imaging of tumor cells over-expresses the folate receptor in vitro, and the T₁- and T₂-weighted MRI has been greatly improved. Our results clearly indicate that such an approach of forming multifunctional Gd:FA-DTPA-PEG-DIB-MnFe₂O₄ NPs is of great significance for T₁- and T₂-weighted MR imaging of specific cancer cells with high accuracy.