Ferrite‐based ferri/superparamagnetic nanoparticles can be rapidly heated by an external alternating magnetic field (AMF) to induce tissue necrosis of the adjacent microenvironment, but in addition provide magnetic resonance imaging (MRI) contrast utilizing enhanced water relaxivity. Here we characterized nanoensembles of Fe‐Co mixed spinel ferrites (i.e. Fe_xCo_1‐xFe₂O₄, where x ranges from 0.2 to 0.8) synthesized by chemical co‐precipitation. With nanoensembles of increasing Co content the saturation magnetization improved, while lattice parameter remained relatively constant. MRI water (transverse) relaxivity at 11.7 T was also boosted with increasing Co content. Efficiency of AMF‐induced heating was quite comparable for the nanoensembles with either chitosan or polyethylene glycol (PEG) coating except for PEG‐coated Fe_0.2Co_0.8Fe₂O₄, which was twice as less efficient as others. While toxicity of the nanoensembles with either coating examined on 9L tumor cell cultures showed no significant differences, upon AMF exposure (i.e. heat‐induced necrosis) Fe_xCo_1‐xFe₂O₄ composition with different values of x showed quite dramatic effects on cell death of tumor cells with both coatings. This study lays the ground work for further characterization of other mixed spinel ferrites, and in addition we expect that chitosan and PEG coated Fe_xCo_1‐xFe₂O₄ of all the compositions will have good potential for preclinical applications in vivo. Copyright © 2016 John Wiley & Sons, Ltd.

中文翻译：

---

通过热疗和亲水性FexCo1-xFe2O4纳米复合体的MRI对比改善了癌细胞的特异性损失能力

基于铁氧体的铁氧体/超顺磁性纳米粒子可以通过外部交变磁场（AMF）迅速加热，以诱导相邻微环境的组织坏死，但同时利用增强的水弛豫性提供磁共振成像（MRI）对比。在这里，我们对Fe-Co混合尖晶石铁氧体（即Fe _x Co _1-x Fe ₂ O _4）的纳米特征进行了表征。，其中x介于0.2到0.8之间）是通过化学共沉淀法合成的。随着Co含量的增加，饱和磁化强度提高，而晶格参数保持相对恒定。随着Co含量的增加，在11.7 T时的MRI水（横向）弛豫性也得到了增强。对于带有壳聚糖或聚乙二醇（PEG）涂层的纳米组件，AMF诱导的加热效率相当可比，除了PEG涂层的Fe _0.2 Co _0.8 Fe ₂ O ₄效率比其他涂层低两倍。尽管在9L肿瘤细胞培养物中检测到的带有两种涂层的纳米集成体的毒性均没有显着差异，但在AMF暴露（即热诱导坏死）时，Fe _x Co _1-x具有两个x值的Fe ₂ O ₄组成对具有两种涂层的肿瘤细胞的细胞死亡显示出相当显着的影响。这项研究为进一步表征其他尖晶石混合铁氧体奠定了基础，此外，我们期望所有组合物中的壳聚糖和PEG包覆的Fe _x Co _{1 x} Fe ₂ O ₄都具有体内临床前应用的良好潜力。版权所有©2016 John Wiley＆Sons，Ltd.