聚合物涂层对作为磁共振成像造影剂的磁铁矿纳米颗粒性能的影响：一项对比研究。

BACKGROUND: Superparamagnetic iron oxide nanoparticles (SPIONs) are the most commonly used negative MRI contrast agent which affect the transverse (T2) relaxation time. The aim of the present study was to investigate the impact of various polymeric coatings on the performance of magnetite nanoparticles as MRI contrast agents. METHODS: Ferrofluids based on magnetite (Fe3O4) nanoparticles (SPIONs) were synthesized via chemical co-precipitation method and coated with different biocompatible polymer coatings including mPEG-PCL, chitosan and dextran. RESULTS: The bonding status of different polymers on the surface of the magnetite nanoparticles was confirmed by the Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The vibrating sample magnetometer (VSM) analysis confirmed the superparamagnetic behavior of all synthesized nanoparticles. The field-emission scanning electron microscopy (FE-SEM) indicated the formation of quasi-spherical nanostructures with the final average particle size of 12-55 nm depending on the type of polymer coating, and X-ray diffraction (XRD) determined inverse spinel structure of magnetite nanoparticles. The ferrofluids demonstrated sufficient colloidal stability in deionized water with the zeta potentials of -24.2, -16.9, +31.6 and -21 mV for the naked SPIONs, and for dextran, chitosan and mPEG-PCL coated SPIONs, respectively. Finally, the magnetic relaxivities of water based ferrofluids were measured on a 1.5 T clinical MRI instrument. The r2/r1 value was calculated to be 17.21, 19.42 and 20.71 for the dextran, chitosan and mPEG-PCL coated SPIONs, respectively. CONCLUSIONS: The findings demonstrated that the value of r2/r1 ratio of mPEG-PCL modified SPIONs is higher than that of some commercial contrast agents. Therefore, it can be considered as a promising candidate for T2 MRI contrast agent.

背景：超顺磁性氧化铁纳米颗粒（SPIONs）是最常用的影响横向（T2）弛豫时间的阴性MRI造影剂。本研究的目的是研究各种聚合物涂层对磁铁矿纳米颗粒作为MRI造影剂性能的影响。

方法：基于磁铁矿（Fe3O4）纳米颗粒（SPIONs）的铁磁流体通过化学共沉淀法合成，并用包括mPEG-PCL、壳聚糖和葡聚糖在内的不同生物相容性聚合物涂层进行包覆。

结果：通过傅里叶变换红外光谱（FT-IR）和热重分析（TGA）证实了磁铁矿纳米颗粒表面不同聚合物的键合状态。振动样品磁强计（VSM）分析证实了所有合成纳米颗粒的超顺磁性行为。场发射扫描电子显微镜（FE-SEM）表明形成了准球形纳米结构，最终平均粒径为12-55nm，具体取决于聚合物涂层的类型，X射线衍射（XRD）确定了磁铁矿纳米颗粒的反尖晶石结构。铁磁流体在去离子水中表现出足够的胶体稳定性，裸SPIONs以及葡聚糖、壳聚糖和mPEG-PCL包覆的SPIONs的ζ电位分别为-24.2、-16.9、+31.6和-21mV。最后，在1.5T临床MRI仪器上测量了水基铁磁流体的磁弛豫率。葡聚糖、壳聚糖和mPEG-PCL包覆的SPIONs的r2/r1值分别计算为17.21、19.42和20.71。

结论：研究结果表明，mPEG-PCL修饰的SPIONs的r2/r1比值高于一些商业造影剂。因此，它可被视为T2 MRI造影剂的有前途的候选者。