Department of Bioengineering, Rice University , Houston, Texas 77005, United States.
Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
ACS Nano. 2017 Jul 25;11(7):6808-6816. doi: 10.1021/acsnano.7b01762. Epub 2017 Jun 21.
The ability to generate heat under an alternating magnetic field (AMF) makes magnetic iron oxide nanoparticles (MIONs) an ideal heat source for biomedical applications including cancer thermoablative therapy, tissue preservation, and remote control of cell function. However, there is a lack of quantitative understanding of the mechanisms governing heat generation of MIONs, and the optimal nanoparticle size for magnetic fluid heating (MFH) applications. Here, we show that MIONs with large sizes (>20 nm) have a specific absorption rate (SAR) significantly higher than that predicted by the widely used linear theory of MFH. The heating efficiency of MIONs in both the superparamagnetic and ferromagnetic regimes increased with size, which can be accurately characterized with a modified dynamic hysteresis model. In particular, the 40 nm ferromagnetic nanoparticles have an SAR value approaching the theoretical limit under a clinically relevant AMF. An in vivo study further demonstrated that the 40 nm MIONs could effectively heat tumor tissues at a minimal dose. Our experimental results and theoretical analysis on nanoparticle heating offer important insight into the rationale design of MION-based MFH for therapeutic applications.
在交变磁场（AMF）下产生热量的能力使磁性氧化铁纳米粒子（MIONs）成为生物医学应用的理想热源，包括癌症热消融治疗、组织保存和细胞功能的远程控制。然而，对于控制 MIONs 发热的机制以及用于磁流体加热（MFH）应用的最佳纳米颗粒尺寸，缺乏定量的理解。在这里，我们表明，尺寸较大（>20nm）的 MIONs 的比吸收率（SAR）明显高于 MFH 的广泛使用的线性理论所预测的值。在超顺磁和铁磁状态下，MIONs 的加热效率随尺寸的增加而增加，这可以用改进的动态磁滞模型进行准确描述。特别是，在临床相关的 AMF 下，40nm 的铁磁纳米颗粒具有接近理论极限的 SAR 值。体内研究进一步证明，40nm 的 MIONs 可以以最小的剂量有效地加热肿瘤组织。我们对纳米颗粒加热的实验结果和理论分析为基于 MION 的 MFH 在治疗应用中的合理设计提供了重要的见解。
