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ACS Appl Mater Interfaces. 2018 Aug 1;10(30):25080-25089. doi: 10.1021/acsami.8b06569. Epub 2018 Jul 20.

Surface Design of Eu-Doped Iron Oxide Nanoparticles for Tuning the Magnetic Relaxivity.

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Department of Chemical Engineering , Pohang University of Science and Technology , 77 Cheongam-Ro , Nam-Gu, Pohang , Gyeongbuk 37673 , Korea.
School of Chemical Engineering , Yeungnam University , 280 Daehakro , Gyeongsan , Gyeongbuk 38541 , Korea.
Department of Medical & Biological Engineering , Kyungpook National University , 80 Daehakro , Bukgu, Daegu 702-701 , Korea.
Korea Multi-Purpose Accelerator Complex , Korea Atomic Energy Research Institute , 181 Mirae-ro , Geoncheon-eup, Gyeongju , Gyeongbuk 305-353 , Korea.


Relaxivity tuning of nanomaterials with the intrinsic T1- T2 dual-contrast ability has great potential for MRI applications. Until now, the relaxivity tuning of T1 and T2 dual-modal MRI nanoprobes has been accomplished through the dopant, size, and morphology of the nanoprobes, leaving room for bioapplications. However, a surface engineering method for the relaxivity tuning was seldom reported. Here, we report the novel relaxivity tuning method based on the surface engineering of dual-mode T1- T2 MRI nanoprobes (DMNPs), along with protein interaction monitoring with the DMNPs as a potential biosensor application. Core nanoparticles (NPs) of europium-doped iron oxide (EuIO) are prepared by a thermal decomposition method. As surface materials, citrate (Cit), alendronate (Ale), and poly(maleic anhydride- alt-1-octadecene)/poly(ethylene glycol) (PP) are employed for the relaxivity tuning of the NPs based on surface engineering, resulting in EuIO-Cit, EuIO-Ale, and EuIO-PP, respectively. The key achievement of the current study is that the surface materials of the DMNP have significant impacts on the r1 and r2 relaxivities. The correlation between the hydrophobicity of the surface material and longitudinal relaxivity ( r1) of EuIO NPs presents an exponential decay feature. The r1 relaxivity of EuIO-Cit is 13.2-fold higher than that of EuIO-PP. EuIO can act as T1- T2 dual-modal (EuIO-Cit) or T2-dominated MRI contrast agents (EuIO-PP) depending on the surface engineering. The feasibility of using the resulting nanosystem as a sensor for environmental changes, such as albumin interaction, was also explored. The albumin interaction on the DMNP shows both T1 and T2 relaxation time changes as mutually confirmative information. The relaxivity tuning approach based on the surface engineering may provide an insightful strategy for bioapplications of DMNPs and give a fresh impetus for the development of novel stimuli-responsive MRI nanoplatforms with T1 and T2 dual-modality for various biomedical applications.


biosensor; dual-mode T1−T2 MRI nanoprobes; hydrophobicity; relaxivity tuning; surface design


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