Lévy Michael, Wilhelm Claire, Siaugue Jean-Michel, Horner Olivier, Bacri Jean-Claude, Gazeau Florence
Laboratoire Matière et Systèmes Complexes (MSC), UMR CNRS 7057, Université Paris-Diderot, Bâtiment Condorcet-Case 7056, F-75205 Paris Cedex 13, France.
J Phys Condens Matter. 2008 May 21;20(20):204133. doi: 10.1088/0953-8984/20/20/204133. Epub 2008 May 1.
By combining magnetic properties with nanosized biocompatible materials, superparamagnetic nanoparticles may serve as colloidal heating mediators for cancer therapy. This unique potential has attracted attention for designing new magnetic nanoparticles with high efficiency heating properties. Their heating power under high frequency magnetic field is governed by the mechanisms of magnetic energy dissipation for single-domain particles due both to internal Néel fluctuations of the particle magnetic moment and to the external Brownian fluctuations. These mechanisms are highly sensitive to the crystal size, the particle material, and the solvent properties. Here we explore the heating properties of maghemite particles with large particle sizes, in the range 15-50 nm, synthesized through a new procedure which includes a hydrothermal process. Particle shape and size distribution, hydrodynamic volume, and magnetic anisotropy are characterized, respectively, by transmission electron microscopy, dynamic magnetically induced birefringence, and ferromagnetic resonance. Together with our previous data on low diameter particles (Fortin J P et al 2007 J. Am. Chem. Soc 129 2628-35), this study provides the whole size dependence of heating efficiency in the range 5-50 nm and assesses the balance between Néel and Brownian contributions to thermal losses. In agreement with theoretical predictions, the heating efficiency shows a maximum for an optimal size of about 15 nm.
通过将磁性与纳米尺寸的生物相容性材料相结合，超顺磁性纳米颗粒可作为癌症治疗的胶体加热介质。这种独特的潜力吸引了人们对设计具有高效加热性能的新型磁性纳米颗粒的关注。它们在高频磁场下的加热功率由单畴颗粒的磁能耗散机制决定，这既归因于颗粒磁矩的内部奈尔涨落，也归因于外部布朗涨落。这些机制对晶体尺寸、颗粒材料和溶剂性质高度敏感。在此，我们探索通过一种包括水热过程的新方法合成的粒径在15 - 50纳米范围内的大粒径磁赤铁矿颗粒的加热性能。分别通过透射电子显微镜、动态磁致双折射和铁磁共振来表征颗粒形状和尺寸分布、流体动力学体积以及磁各向异性。结合我们之前关于低直径颗粒的数据（Fortin J P等人，2007年，《美国化学会志》129卷，2628 - 35页），本研究给出了5 - 50纳米范围内加热效率的完整尺寸依赖性，并评估了奈尔和布朗对热损失贡献之间的平衡。与理论预测一致，加热效率在约15纳米的最佳尺寸处出现最大值。
