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Enhancement of Relaxivity Rates of Gd–DTPA Complexes by Intercalation into Layered Double Hydroxide Nanoparticles

Authors

  • Zhi Ping Xu Dr.,

    1. ARC Centre for Functional Nanomaterials, School of Engineering
    2. Australia Institute of Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia, Fax: (+61) 7-33463973
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  • Nyoman D. Kurniawan Dr.,

    1. Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
    2. Centre for Magnetic Resonance, The University of Queensland, Brisbane, QLD 4072, Australia
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  • Perry F. Bartlett Prof. Dr.,

    1. Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
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  • Gao Qing Lu Prof. Dr.

    1. ARC Centre for Functional Nanomaterials, School of Engineering
    2. Australia Institute of Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia, Fax: (+61) 7-33463973
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Abstract

In this paper we report the preparation and characterization of [Gd(dtpa)]2− intercalated layered double hydroxide (LDH) nanomaterials. [Gd(dtpa)]2− (gadolinium(III) diethylene triamine pentaacetate) was transferred into LDH by anionic exchange. The intercalation of [Gd(dtpa)]2− into LDH was confirmed by X-ray diffraction for the new phase with the interlayer spacing of 3.5–4.0 nm and by FTIR for the characteristic vibration peaks of [Gd(dtpa)]2−. The morphology of the nanoparticles was influenced by the extent of [Gd(dtpa)]2− loading, in which the poly-dispersity quality decreased as the [Gd(dtpa)]2− loading was increased. Compared with the morphology of the original Mg2Al–Cl–LDH nanoparticles (hexagonal plate-like sheets of 50–200 nm), the modified LDH–Gd(dtpa) nanoparticles are bar-like with a width of 30–60 nm and a length of 50–150 nm. LDH–Gd(dtpa) was expected to have an increased water proton magnetic resonance relaxivity due to the intercalation of [Gd(dtpa)]2− into the LDH interlayer that led to slower molecular anisotropic tumbling compared with free [Gd(dtpa)]2− in solution. Indeed, LDH–nanoparticle suspension containing ≈1.6 mM [Gd(dtpa)]2− exhibits a longitudinal proton relaxivity r1 of ≈16 mM−1 s−1 and a transverse proton relaxivity r2 of ≈50 mM−1 s−1 at room temperature and a magnetic field of 190 MHz, which represents an enhancement four times (r1) and 12 times (r2) that of free [Gd(dtpa)]2− in solution under the same reaction conditions. We have thus tailored LDH–nanoparticles into a novel contrast agent with strong relaxivity, promising for great potential applications in magnetic resonance imaging.

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