Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587 Berlin, Germany.
Departament of Physics, FFCLRP, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP 14040-91, Brazil.
Phys Med Biol. 2021 Jan 8;66(1):015002. doi: 10.1088/1361-6560/abcd19.
Magnetic particle imaging (MPI) is a promising medical imaging technique for visualizing the three-dimensional distribution of tracer materials, specifically iron oxide nanoparticles (IONP). The optimization of magnetic nanoparticles (MNP) plays an essential role to improve the image resolution and sensitivity of imaging techniques.
In this work, the optimization of commercial IONP (EMG 700, Ferrotec) coated with anionic surfactants was carried out using magnetic separation (MS) technique, by a low gradient magnetic separation (LGMS) (<15 T m) method, to improve their performance as MPI tracers.
The magnetophoretical behavior of the samples in different concentrations ranging from 2 to 120 mmol l was investigated over 24 h of separation. The samples were characterized by dynamic light scattering (DLS), AC susceptibility (ACS), magnetic particle spectroscopy (MPS) and they were imaged in a preclinical MPI scanner, before and after MS.
DLS results showed that by increasing the concentration from 2 to 120 mmol l the hydrodynamic diameter of MNP decrease from 75 to 47 nm and size distribution decrease from 0.19 to 0.11 after 4 min MS. In addition, the MPS results demonstrated the third harmonic amplitude normalized to the iron amount [Formula: see text] and harmonic ratio [Formula: see text] of signal increase from 8.38 to 10.59 Am kg (Fe) and 24.21-26.60, respectively. Furthermore, the MPI images of the samples after separation showed higher MPI resolution.
Therefore, LGMS can be considered as a valuable method to narrow and control the size distribution of MNP for MPI.
磁性粒子成像（MPI）是一种很有前途的医学成像技术，可用于可视化示踪剂材料的三维分布，特别是氧化铁纳米颗粒（IONP）。优化磁性纳米颗粒（MNP）对于提高成像技术的图像分辨率和灵敏度起着至关重要的作用。
在这项工作中，通过低梯度磁场分离（LGMS）（<15 T m）方法，使用磁分离（MS）技术对涂有阴离子表面活性剂的商用 IONP（EMG 700，Ferrotec）进行了优化，以改善其作为 MPI 示踪剂的性能。
在 24 小时的分离过程中，研究了不同浓度（2 至 120 mmol l）的样品的磁流变性行为。通过动态光散射（DLS）、交流磁化率（ACS）、磁性粒子光谱（MPS）对样品进行了表征，并在临床前 MPI 扫描仪中对分离前后的样品进行了成像。
DLS 结果表明，随着浓度从 2 至 120 mmol l 的增加，MNP 的水动力直径从 75 纳米减小到 47 纳米，并且在 4 分钟 MS 后粒径分布从 0.19 减小到 0.11。此外，MPS 结果表明，归一化到铁含量的三阶谐波幅度[公式：见文本]和信号的谐波比[公式：见文本]分别从 8.38 增加到 10.59 Am kg（Fe）和 24.21-26.60。此外，分离后样品的 MPI 图像显示出更高的 MPI 分辨率。
因此，LGMS 可以被认为是一种有价值的方法，可以对 MNP 的尺寸分布进行收窄和控制，以用于 MPI。
