Clara Pereira - Architectured design of superparamagnetic Fe3O4 nanoparticles for application as MRI contrast agents: mastering size and magnetism for enhanced relaxivity

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    "Architectured design of superparamagnetic   Fe3O4 nanoparticles for application as MRI   contrast agents: mastering size and magnetism for enhanced   relaxivity”,   Clara Pereira,*   André M. Pereira, Mariana Rocha, Cristina Freire,    Carlos F. G. C. Geraldes,* Journal of Materials    Chemistry B   2015,   3, 6261–6273. DOI:   10.1039/c5tb00789e

    *Corresponding author








  This work reports the mastered design of novel water-dispersible   superparamagnetic iron oxide nanomaterials with enhanced magnetic   properties and reduced size. A straightforward cost-effective   aqueous coprecipitation route was developed, based on the use of   three new coprecipitation agents: the polydentate bases   diethanolamine, triethanolamine and triisopropanolamine. Through   the selection of these alkanolamines which presented different   complexing properties, an improvement of the surface spin order   could be achieved upon the reduction of the nanomaterial   dimensions (from 8.7 to 3.8 nm) owing to the complexation of the   polydentate bases with the subcoordinated iron cations on the   particle surface. In particular, the alkanolamine with the   highest chelating ability (triethanolamine) led to the   nanomaterial with the smallest size and the thinnest magnetic   “dead” layer. In order to evaluate the importance of the dual   control of size and magnetism, the relaxometric properties of the   nanomaterials were investigated, whereby maximum values of   transverse relaxivity r2 of   300.30 and 253.92 mM−1  s−1 at 25 and 37 °C, respectively (at   20 MHz) were achieved, making these nanomaterials potential   T2-weighted MRI contrast   agents. Moreover, these values were significantly higher than   those reported for commercial   T2 contrast agents and other   iron oxides with identical dimensions. Hence, we were able to   demonstrate that the r2  enhancement cannot only be achieved by an increase of   particle/cluster size, but also through the precise control of   the surface magnetic properties while constraining the   nanomaterial dimensions. These achievements open up new   perspectives on the mastered design of magnetic nanoprobes,   overcoming the limitations related to the deleterious effect of   size reduction.

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