Magnetic nanoparticle-mediated hyperthermia is a very promising therapy for cancer treatment. In this field, superparamagnetic iron oxide nanoparticles have been commonly employed because of their intrinsic biocompatibility, but they present some limitations that restrict their heating efficiency (specific absorption rate, SAR). Therefore, we have investigated how tuning the size and shape of these iron oxide nanoparticles can be useful to enhance their hyperthermia responses. Monodisperse and crystalline iron oxide nanoparticles have been synthesized by thermal decomposition in two different shapes (spheres and cubes) in a wide range of sizes, ∼10–100 nm. We have thoroughly characterized them both structurally (X-ray diffraction and transmission electron microscopy) and magnetically (physical property measurement system), and then we have analyzed their heating efficiency using a combination of calorimetric and AC magnetometry measurements (0–800 Oe, 300 kHz). We have been able to delimit a range of optimum sizes to maximize the heating efficiency of these nanoparticles depending on their shape. We find that the nanospheres exhibit the highest heating efficiency for sizes around 30–50 nm, while the nanocubes show a sharp increase in the heating efficiency around 30–35 nm. The SAR variation has been related to the magnetic anisotropy of the nanoparticles that depends on their size, shape, arrangement, and dipolar interactions.

中文翻译：

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通过调整其形状和大小来提高氧化铁纳米颗粒的加热效率

磁性纳米粒子介导的高温疗法是用于癌症治疗的非常有前途的疗法。在该领域，超顺磁性氧化铁纳米颗粒由于其固有的生物相容性而被普遍采用，但是它们存在一些限制其加热效率（比吸收率，SAR）的限制。因此，我们研究了如何调节这些氧化铁纳米颗粒的尺寸和形状，以增强其热疗反应。单分散的和结晶的氧化铁纳米粒子已经通过热分解以两种不同的形状（球形和立方体）合成，尺寸范围约为10-100 nm。我们已经在结构上（X射线衍射和透射电子显微镜）和磁性（物理性质测量系统）对它们进行了彻底的表征，然后我们结合量热法和交流磁法测量（0-800 Oe，300 kHz）分析了它们的加热效率。我们已经能够根据其形状来确定最佳尺寸范围，以使这些纳米颗粒的加热效率最大化。我们发现，纳米球在30–50 nm左右的尺寸下显示出最高的加热效率，而纳米立方体在30–35 nm左右的加热效率上则急剧增加。SAR变化与纳米粒子的磁各向异性有关，纳米粒子的尺寸，形状，排列和偶极相互作用取决于纳米粒子的磁各向异性。我们已经能够根据其形状来确定最佳尺寸范围，以使这些纳米颗粒的加热效率最大化。我们发现，纳米球在30–50 nm左右的尺寸下显示出最高的加热效率，而纳米立方体在30–35 nm左右的加热效率上则急剧增加。SAR变化与纳米粒子的磁各向异性有关，纳米粒子的尺寸，形状，排列和偶极相互作用取决于纳米粒子的磁各向异性。我们已经能够根据其形状来确定最佳尺寸范围，以使这些纳米颗粒的加热效率最大化。我们发现，纳米球在30–50 nm左右的尺寸下显示出最高的加热效率，而纳米立方体在30–35 nm左右的加热效率上则急剧增加。SAR变化与纳米粒子的磁各向异性有关，纳米粒子的尺寸，形状，排列和偶极相互作用取决于纳米粒子的磁各向异性。