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A Universal Scaling Law to Predict the Efficiency of Magnetic Nanoparticles as MRI T2-Contrast Agents

Authors

  • Quoc L. Vuong,

    1. Université de Mons, Biological Physics Department, 20 Place du Parc, 7000 Mons, Belgium
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  • Jean-François Berret,

    1. Université Denis Diderot Paris-VII, CNRS UMR7057, Matière et Systèmes Complexes, 10 rue Alice Domon et Léonie Duquet, 75013 Paris, France
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  • Jérôme Fresnais,

    1. UPMC Univ Paris 06, CNRS UMR7195, Physicochimie, Colloïdes et Sciences Analytiques, 4 place Jussieu, 75005 Paris, France
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  • Yves Gossuin,

    Corresponding author
    1. Université de Mons, Biological Physics Department, 20 Place du Parc, 7000 Mons, Belgium
    • Université de Mons, Biological Physics Department, 20 Place du Parc, 7000 Mons, Belgium
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  • Olivier Sandre

    Corresponding author
    1. Université de Bordeaux, CNRS UMR5629, Laboratoire de Chimie des Polymères Organiques, ENSCBP, 16 Avenue Pey Berland, 33607 Pessac, France
    • Université de Bordeaux, CNRS UMR5629, Laboratoire de Chimie des Polymères Organiques, ENSCBP, 16 Avenue Pey Berland, 33607 Pessac, France.
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Abstract

Magnetic particles are very efficient magnetic resonance imaging (MRI) contrast agents. In recent years, chemists have unleashed their imagination to design multi-functional nanoprobes for biomedical applications including MRI contrast enhancement. This study is focused on the direct relationship between the size and magnetization of the particles and their nuclear magnetic resonance relaxation properties, which condition their efficiency. Experimental relaxation results with maghemite particles exhibiting a wide range of sizes and magnetizations are compared to previously published data and to well-established relaxation theories with a good agreement. This allows deriving the experimental master curve of the transverse relaxivity versus particle size and to predict the MRI contrast efficiency of any type of magnetic nanoparticles. This prediction only requires the knowledge of the size of the particles impermeable to water protons and the saturation magnetization of the corresponding volume. To predict the T2 relaxation efficiency of magnetic single crystals, the crystal size and magnetization – obtained through a single Langevin fit of a magnetization curve – is the only information needed. For contrast agents made of several magnetic cores assembled into various geometries (dilute fractal aggregates, dense spherical clusters, core–shell micelles, hollow vesicles…), one needs to know a third parameter, namely the intra-aggregate volume fraction occupied by the magnetic materials relatively to the whole (hydrodynamic) sphere. Finally a calculation of the maximum achievable relaxation effect – and the size needed to reach this maximum – is performed for different cases: maghemite single crystals and dense clusters, core-shell particles (oxide layer around a metallic core) and zinc-manganese ferrite crystals.

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