Improved magnetic relaxivity via hierarchical surface structure of dysprosium-engineered superparamagnetic iron oxide nanoparticles in ultra-high magnetic field

To date, it is unknown whether the combination of Dy ions and superparamagnetic iron oxide (SPIO: Fe3O4) NPs can offer improved performance in UHF-MRI. In this work, we provide a paradigm of hierarchical surface-structured (His) DyxFe3-xO4 NPs as T-2 MRI nanoprobes at UHF (9.4T). We found that His-DyxFe3-xO4 NPs (x = 0.2) possess a higher transverse relaxivity than unmodified His-SPIO NPs and a significantly enhanced r(2)/r(1) ratio (up to10.4 times higher) than those of reported Dy-based T-2 MRI probes at 9.4 T. Furthermore, we demonstrate the effects of surface design of DyxFe3-xO4 NPs on their magnetic relaxivity and in vivo performance at UHF. The markedly enhanced r(2)/r(1) of His-DyxFe3-xO4 NPs (x = 0.2) at 9.4 T is mainly attributed to decreased r(1) relaxivity owing to the surface design and the possible disturbance of the Dy-Fe superexchange interaction. This work could provide an insightful strategy for the design of lanthanide-doped magnetic nanosystems as potential T-2 MRI nanoprobes in UHF. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.