Size-sorted anionic iron oxide nanomagnets as colloidal mediators for magnetic hyperthermia.

By Jean-Paul Fortin, C. Wilhelm, J. Servais, C. Ménager, J. Bacri, F. Gazeau. Journal of the American Chemical Society, 2007

943 citations recorded by the source corpus.

Iron oxide colloidal nanomagnets generate heat when subjected to an alternating magnetic field. Their heating power, governed by the mechanisms of magnetic energy dissipation for single-domain particles (Brown and Néel relaxations), is highly sensitive to the crystal size, the material, and the solvent properties. This study was designed to distinguish between the contributions of Néel and Brownian mechanisms to heat generation. Anionic nanocrystals of maghemite and cobalt ferrite, differing by their magnetic anisotropy, were chemically synthesized and dispersed in an aqueous suspension by electrostatic stabilization. The particles were size-sorted by successive electrostatic phase separation steps. Parameters governing the efficiency of nanomagnets as heat mediators were varied independently; these comprised the particle size (from 5 to 16.5 nm), the solvent viscosity, magnetic anisotropy, and the magnetic field frequency and amplitude. The measured specific loss powers (SLPs) were in quantitative agreement with the results of a predictive model taking into account both Néel and Brown loss processes and the whole particle size distribution. By varying the carrier fluid viscosity, we found that Brownian friction within the carrier fluid was the main contributor to the heating power of cobalt ferrite particles. In contrast, Néel internal rotation of the magnetic moment accounted for most of the loss power of maghemite particles. Specific loss powers were varied by 3 orders of magnitude with increasing maghemite crystal size (from 4 to 1650 W/g at 700 kHz and 24.8 kA/m). This comprehensive parametric study provides the groundwork for the use of anionic colloidal nanocrystals to generate magnetically induced hyperthermia in various media, including complex systems and biological materials.

Subfields: Biomaterials, Biomedical Engineering, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/0a1abe72f44684c3e95bbb2190dec19f3616c773

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Citations in the corpus

Progress in applications of magnetic nanoparticles in biomedicine (2009, background): “It is interesting to note that the ILP of the bestheating synthetic particles reported to date, Fortin’s maghemite particles [79], have an ILP of 3.”
Diverse Applications of Nanomedicine (2017, neutral): “1088/0022-3727/42/22/224001 [566] Fortin, J.”
Tuning the Magnetic Properties of Nanoparticles (2013, background): “In another study of magnetic nanoparticles having diameters of 5, 10, 12.8, and 14 nm, measurements at 400 kHz and 24.5 kA/m amplitude showed a maximum SLP of 447 W/g for the 14 nm Fe3O4 MNPs [78].”
Magnetic Nanomaterials for Hyperthermia-based Therapy and Controlled Drug Delivery (2011, background): “Hence, one can expect to achieve high heating rate at desirable sizes for core-shell MNPs. Reduce toxicity and increase biocompatibility—”
Exchange-coupled magnetic nanoparticles for efficient heat induction. (2011, background): “Thermal energy is produced continuously as these particles return to their relaxed state”