Department of Translational Imaging, The Methodist Hospital Research Institute, Houston, Texas, United States of America.
PLoS One. 2013;8(2):e57332. doi: 10.1371/journal.pone.0057332. Epub 2013 Feb 25.
A plethora of magnetic nanoparticles has been developed and investigated under different alternating magnetic fields (AMF) for the hyperthermic treatment of malignant tissues. Yet, clinical applications of magnetic hyperthermia are sporadic, mostly due to the low energy conversion efficiency of the metallic nanoparticles and the high tissue concentrations required. Here, we study the hyperthermic performance of commercially available formulations of superparamagnetic iron oxide nanoparticles (SPIOs), with core diameter of 5, 7 and 14 nm, in terms of absolute temperature increase ΔT and specific absorption rate (SAR). These nanoparticles are operated under a broad range of AMF conditions, with frequency f varying between 0.2 and 30 MHz; field strength H ranging from 4 to 10 kA m(-1); and concentration cMNP varying from 0.02 to 3.5 mg ml(-1). At high frequency field (∼30 MHz), non specific heating dominates and ΔT correlates with the electrical conductivity of the medium. At low frequency field (<1 MHz), non specific heating is negligible and the relaxation of the SPIO within the AMF is the sole energy source. We show that the ΔT of the medium grows linearly with cMNP , whereas the SARMNP of the magnetic nanoparticles is independent of cMNP and varies linearly with f and H(2) . Using a computational model for heat transport in a biological tissue, the minimum requirements for local hyperthermia (Ttissue >42°C) and thermal ablation (Ttissue >50°C) are derived in terms of cMNP , operating AMF conditions and blood perfusion. The resulting maps can be used to rationally design hyperthermic treatments and identifying the proper route of administration - systemic versus intratumor injection - depending on the magnetic and biodistribution properties of the nanoparticles.
已经开发并研究了大量的磁性纳米粒子，在不同的交变磁场（AMF）下用于恶性组织的热疗。然而，磁性热疗的临床应用仍然很少，主要是由于金属纳米粒子的能量转换效率低和所需的高组织浓度。在这里，我们研究了具有 5nm、7nm 和 14nm 核心直径的商业超顺磁性氧化铁纳米粒子（SPIOs）制剂在绝对温升ΔT 和比吸收率（SAR）方面的热性能。这些纳米粒子在广泛的 AMF 条件下运行，频率 f 范围为 0.2 至 30MHz；磁场强度 H 范围为 4 至 10kA m(-1)；纳米粒子浓度 cMNP 范围为 0.02 至 3.5mg ml(-1)。在高频场（约 30MHz）下，非特异性加热占主导地位，ΔT 与介质的电导率相关。在低频场（<1MHz）下，非特异性加热可以忽略不计，并且 AMF 中的 SPIO 弛豫是唯一的能量源。我们表明，介质的ΔT 与 cMNP 呈线性增长，而磁性纳米粒子的 SARMNP 与 cMNP 无关，与 f 和 H(2) 呈线性变化。使用生物组织内热传输的计算模型，根据 cMNP、操作 AMF 条件和血液灌注，导出了局部热疗（Ttissue >42°C）和热消融（Ttissue >50°C）的最小要求。生成的地图可用于合理设计热疗，并根据纳米粒子的磁性和生物分布特性确定适当的给药途径-全身与肿瘤内注射。
