A multi-physics model was developed to study the delivery of magnetic nanoparticles (MNPs) to the stent-implanted region under an external magnetic field. The model is firstly validated by experimental work in literature. Then, effects of external magnetic field strength, magnetic particle size, and flow velocity on MNPs’ targeting and binding have been analyzed through a parametric study. Two new dimensionless numbers were introduced to characterize relative effects of Brownian motion, magnetic force induced particle motion, and convective blood flow on MNPs motion. It was found that larger magnetic field strength, bigger MNP size, and slower flow velocity increase the capture efficiency of MNPs. The distribution of captured MNPs on the vessel along axial and azimuthal directions was also discussed. Results showed that the MNPs density decreased exponentially along axial direction after one-dose injection while it was uniform along azimuthal direction in the whole stented region (averaged over all sections). For the beginning section of the stented region, the density ratio distribution of captured MNPs along azimuthal direction is center-symmetrical, corresponding to the center-symmetrical distribution of magnetic force in that section. Two different generation mechanisms are revealed to form four main attraction regions. These results could serve as guidelines to design a better magnetic drug delivery system.

中文翻译：

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高梯度场下磁性纳米粒子靶向支架表面的计算模型

开发了一个多物理模型来研究在外部磁场下磁性纳米粒子 (MNP) 向支架植入区域的输送。该模型首先通过文献中的实验工作进行验证。然后，通过参数研究分析了外部磁场强度、磁性颗粒大小和流速对 MNP 靶向和结合的影响。引入了两个新的无量纲数来表征布朗运动、磁力诱导的粒子运动和对流血流对 MNP 运动的相对影响。结果表明，较大的磁场强度、较大的 MNP 尺寸和较慢的流速可提高 MNP 的捕获效率。还讨论了沿轴向和方位角方向在船舶上捕获的 MNP 的分布。结果表明，单剂注射后，MNPs 密度沿轴向呈指数下降，而在整个支架区域（所有部分的平均值）沿方位角方向均匀。对于支架区域的开始部分，沿方位角方向捕获的 MNP 的密度比分布是中心对称的，对应于该部分的磁力中心对称分布。揭示了两种不同的生成机制，以形成四个主要的吸引力区域。这些结果可以作为设计更好的磁性药物输送系统的指南。捕获的 MNPs 沿方位角方向的密度比分布是中心对称的，对应于该截面中磁力的中心对称分布。揭示了两种不同的生成机制，以形成四个主要的吸引力区域。这些结果可以作为设计更好的磁性药物输送系统的指南。捕获的 MNPs 沿方位角方向的密度比分布是中心对称的，对应于该截面中磁力的中心对称分布。揭示了两种不同的生成机制，以形成四个主要的吸引力区域。这些结果可以作为设计更好的磁性药物输送系统的指南。