Simulations of magnetic nanoparticle Brownian motion
Simulations of magnetic nanoparticle Brownian motion
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DOI：
10.1063/1.4770322
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发表时间：
2012-12-15
影响因子：
3.2
通讯作者：
Weaver, John B.
中科院分区：
文献类型：
--
作者：
Reeves, Daniel B.;Weaver, John B.
磁性纳米粒子在许多医学应用中都很有用，因为它们在细胞水平上与生物学相互作用，从而允许微环境研究。增强对磁性粒子动力学的理解可能会导致磁性粒子成像或通过增强 MRI 对比度直接成像的进步，并且对于布朗运动磁光谱中的纳米粒子传感至关重要。此外，像热疗这样的治疗技术需要有关粒子动力学的信息，以便在临床上有效、安全和可靠地使用。为此，我们通过朗之万方程方法开发并验证了旋转布朗纳米粒子的随机动力学模型。在没有场的情况下，达到平衡的弛豫时间与爱因斯坦的布朗运动模型相匹配。在静态场中，平衡磁化强度与朗之万函数一致。对于高频或低振幅驱动场，再现线性德拜近似的行为特征。在发生磁饱和的较高磁场状态下，磁化强度及其谐波与有效磁场模型相当。在另一个层面上，该模型已根据实验结果进行了基准测试，成功证明磁化谐波携带足够的信息来推断粘度和温度等环境参数。 (C) 2012 年美国物理研究所。 [http://dx.doi.org/10.1063/1.4770322]
Magnetic nanoparticles are useful in many medical applications because they interact with biology on a cellular level thus allowing microenvironmental investigation. An enhanced understanding of the dynamics of magnetic particles may lead to advances in imaging directly in magnetic particle imaging or through enhanced MRI contrast and is essential for nanoparticle sensing as in magnetic spectroscopy of Brownian motion. Moreover, therapeutic techniques like hyperthermia require information about particle dynamics for effective, safe, and reliable use in the clinic. To that end, we have developed and validated a stochastic dynamical model of rotating Brownian nanoparticles from a Langevin equation approach. With no field, the relaxation time toward equilibrium matches Einstein's model of Brownian motion. In a static field, the equilibrium magnetization agrees with the Langevin function. For high frequency or low amplitude driving fields, behavior characteristic of the linearized Debye approximation is reproduced. In a higher field regime where magnetic saturation occurs, the magnetization and its harmonics compare well with the effective field model. On another level, the model has been benchmarked against experimental results, successfully demonstrating that harmonics of the magnetization carry enough information to infer environmental parameters like viscosity and temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770322]