Targeted drug delivery (TDD) based on magnetic nanoparticles (MNPs) and external magnetic actuation is a promising drug delivery technology compared to conventional treatments usually utilized in cancer therapy. However, the implementation of a TDD system at a clinical site based on considerations for the actual size of the human body requires a simplified structure capable of both external actuation and localization. To address these requirements, we propose a novel approach to localize drug carriers containing MNPs by manipulating the field-free point (FFP) mechanism in the principal magnetic field. To this end, we devise a versatile electromagnetic actuation (EMA) system for FFP generation based on four coils affixed to a movable frame. By the Biot–Savart law, the FFP can be manipulated by appropriately controlling the gradient field strength at the target area using the EMA system. Further, weighted-norm solutions are utilized to correct the positions of FFP to improve the accuracy of FFP displacement in the region of interest (ROI). As MNPs, ferrofluid is used to experiment with 2D and 3D localizations in a blocked phantom placed in the designed ROI. The resultant root mean square error of the localizations is observed to be approximately 1.4 mm in the 2D case and 1.6 mm in the 3D case. Further, the proposed movable EMA is verified to be capable of simultaneously scanning multiple points as well as the actuation and imaging of MNPs. Based on the success of the experiments in this study, further research is intended to be conducted in scale-up system development to design precise TDD systems at clinical sites.

中文翻译：

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基于无磁场点的MNP定位和驱动：可移动电磁驱动的可行性

与通常用于癌症治疗的常规治疗相比，基于磁性纳米颗粒（MNP）和外部磁激励的靶向药物递送（TDD）是一种有前途的药物递送技术。然而，基于对人体实际大小的考虑，在临床部位实施TDD系统需要能够同时进行外部致动和定位的简化结构。为了满足这些要求，我们提出了一种通过在主磁场中操纵无场点（FFP）机制来定位包含MNP的药物载体的新颖方法。为此，我们基于固定在可移动框架上的四个线圈，设计了一种用于FFP生成的通用电磁致动（EMA）系统。根据毕奥-萨伐尔定律，可以通过使用EMA系统适当控制目标区域的梯度场强度来操纵FFP。此外，利用加权范数解来校正FFP的位置，以提高FFP在感兴趣区域（ROI）中的位移精度。作为MNP，铁磁流体用于在设计的ROI中放置的封闭模型中对2D和3D定位进行实验。在2D情况下观察到的定位结果的均方根误差约为1.4 mm，在3D情况下观察到的误差为1.6 mm。此外，所提出的可移动EMA已被验证为能够同时扫描多个点以及MNP的激活和成像。基于这项研究中实验的成功，