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Contrast ability of magnetic nanoparticles (MNPs) is critical for the sensitive and accurate diagnosis of cancer with magnetic resonance imaging (MRI). However, the low sensitivity of current contrast agents (CAs) remains a major limitation to meet clinical needs. Shape and composition engineering are two important means for improving the contrast ability of MNPs. Herein, we report a facile method incorporating both approaches to manufacture zinc ferrite octapods with a large effective radius and various Zn doping ratios. The saturated magnetizations and T2 relaxivities of these engineered octapods both show an interesting trend with ascending zinc doping level. Particularly, the r2 value of ZnxFe3–xO4 (x = 0.44) octapods at 7.0 T is 989.1 mM–1s–1, and the highest T2 relaxivity ever reported, which is 10.2 times higher than the commercial sample, Feraheme. With the aid of this octapod sample, contrast-enhanced MRI (CE-MRI) for detecting orthotopic and metastatic hepatic tumors could be accomplished even a...

For in vivo imaging, it is important that imaging agents could be harmlessly eliminated from the body after performing their functions. Gadolinium-based magnetic resonance contrast agents have been...

Manganese-doped magnetite nanoparticles as magnetic resonance imaging (MRI) contrast agents have been well developed in recent years due to their higher saturation magnetization and stronger transverse (T2) contrast ability compared to parent magnetite. However, the underlying role that manganese doping plays in altering the contrast ability of magnetite is still not thoroughly understood. Herein, we investigate the effects of manganese doping on changes of ferrite crystal structures, magnetic properties, and contrast abilities. We developed a successful one-pot synthesis of uniform manganese-doped magnetite (MnxFe3–xO4) nanoparticles with different manganese contents (x = 0–1.06). The saturation magnetization and T2 contrast ability of ferrite nanoparticles increase along with rising manganese proportion, peak when the doping level of MnxFe3–xO4 reaches x = 0.43, and decrease dramatically as the manganese percentage continues to augment. At high manganese doping level, the manganese ferrite nanoparticles...

Cation exchange is a powerful means to adjust the properties of nanocrystals through composition change with morphology retention. Herein, we demonstrate that cation exchange can engineer the composition of iron oxide nanocrystals to dramatically improve their contrast ability in magnetic resonance imaging (MRI). We successfully construct manganese and zinc engineered iron oxide nanoparticles with diverse shapes (sphere, cube, and octapod) by facile cation exchange reactions. Extended X-ray absorption fine structure (EXAFS) study indicates that Mn2+ and Zn2+ ions are doped into the crystal lattice of ferrite, and more importantly, most of them are distributed in Td sites of ferrite. These engineered shaped-anisotropic iron oxide nanoparticles exhibit both high saturated magnetization and large effective boundary radii, which leads to remarkable transverse relaxivity (r2), for example, 754.2 mM–1 s–1 for zinc engineered octapod iron oxide nanoparticles. These engineered iron oxide nanoparticles, as high-pe...

Controlled synthesis of monodisperse iron oxide (IO) nanostructures with diverse morphology remains a major challenge. In this work, IO nanostructures with various shapes and surface structures were synthesized by thermal decomposition of iron oleate (FeOL) in the presence of sodium oleate (NaOL). In a mild condition using 1-octadecene (ODE) as solvent, NaOL may preferentially bind to Fe3O4{111} facets and lead to the formation of Fe3O4{111} facet exposed IO plates, truncated octahedrons, and tetrahedrons. While in a high-boiling temperature tri-n-octylamine (TOA) solvent, we obtained Fe3O4{100} facet exposed IO cubes, concaves, multibranches, and assembled structures by varying the molar ratios of NaOL/FeOL. Moreover, we demonstrated that IO nanoparticles (NPs) with metal-exposed surface structures have enhanced T1 relaxation time shortening effects to protons, and IO NPs with anisotropic shapes are superior in protons T2 relaxation shortening due to the larger effective radii compared to that of spheric...