Bejko Megi, Yaman Yasmina Al, Keyes Anthony, Bagur Auriane, Rosa Patrick, Gayot Marion, Weill Francois, Mornet Stéphane, Sandre Olivier
University of Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, 33600, Pessac, France.
University of Bordeaux, CNRS, Bordeaux INP, ICMCB, UMR 5026, 33600, Pessac, France.
Chemphyschem. 2024 Nov 18;25(22):e202400023. doi: 10.1002/cphc.202400023. Epub 2024 Sep 16.
Iron oxide nanoflowers (IONFs) that display singular magnetic properties can be synthesized through a polyol route first introduced almost 2 decades ago by Caruntu et al., presenting a multi-core morphology in which several grains (around 10 nm) are attached together and sintered. These outstanding properties are of great interest for magnetic field hyperthermia, which is considered as a promising therapy against cancer. Although of significantly smaller diameter, the specific adsorption rate (SAR) of IONFs reach values on the order of 1 kW g, as large as "magnetosomes" that are natural magnetic nanoparticles typically ~40 nm found in certain bacteria, which can be grown artificially but with much lower yield compared to chemical synthesis such as the polyol route. This work aims at better understanding the structure-property relationships, linking the internal IONF nanostructure as observed by high resolution transmission electron microscopy (HR-TEM) to their magnetic properties. A library of mono- and multicore IONFs is presented, with diameters ranging from 11 to 30 nm in a narrow size distribution. More particularly, by relating their structural features (diameter, morphology, defects…) to their magnetic properties investigated by utilizing AC magnetometry over a wide range of alternating magnetic field (AMF) conditions, we showed that the SAR values of all synthesized batches vary with overall diameter and number of constituting cores. These variations are in qualitative agreement with theoretical predictions either by the Linear Response Theory (LRT) at low fields or with the Stoner-Wohlfarth (SW) model at larger amplitudes, and with numerical simulations reported previously. More precisely, our results show a continuous (almost quadratic) increase of SAR with IONF diameter for AMF amplitudes of 20 kA m and above, whatever the frequency between 146 and 344 kHz, and a pronounced maximum at an IONF diameter of 22 nm for amplitudes of 16 kA m and below. Thank to this understanding of the impact of size and core multiplicity, stable colloidal solutions of IONPs can be synthesized with diameters targeting a SAR value adapted to the theragnostic approach envisioned.
具有独特磁性的氧化铁纳米花（IONFs）可以通过大约20年前由卡伦图等人首次引入的多元醇路线合成，呈现出多核形态，其中几个晶粒（约10纳米）连接在一起并烧结。这些优异的性能对于磁场热疗具有极大的吸引力，磁场热疗被认为是一种很有前景的癌症治疗方法。尽管IONFs的直径明显更小，但其比吸收率（SAR）达到1kW/g左右的值，与某些细菌中发现的天然磁性纳米颗粒“磁小体”（通常约40纳米）一样大，磁小体可以人工培养，但与多元醇路线等化学合成方法相比产量要低得多。这项工作旨在更好地理解结构-性能关系，将高分辨率透射电子显微镜（HR-TEM）观察到的IONF内部纳米结构与其磁性联系起来。展示了一个单核和多核IONFs库，其直径在11至30纳米之间，尺寸分布狭窄。更具体地说，通过将它们的结构特征（直径、形态、缺陷等）与其在广泛的交变磁场（AMF）条件下利用交流磁强计研究的磁性相关联，我们表明所有合成批次的SAR值随总体直径和构成核心的数量而变化。这些变化在定性上与低场下的线性响应理论（LRT）或较大振幅下的斯托纳-沃尔法特（SW）模型的理论预测以及先前报道的数值模拟一致。更确切地说，我们的结果表明，对于20kA/m及以上的AMF振幅，无论频率在146至344kHz之间，SAR随IONF直径持续（几乎呈二次方）增加；对于16kA/m及以下的振幅，在IONF直径为22纳米时出现明显的最大值。由于对尺寸和核心多重性影响的这种理解，可以合成具有靶向适应于所设想的治疗诊断方法的SAR值的直径的IONPs稳定胶体溶液。
