Herynek Vít, Rajsiglová Lenka, Babič Michal, Švábová Monika, Kohout Jaroslav, Veverka Miroslav, Kmječ Tomáš, Kubíčková Lenka, Karela Jiří, Gregar Filip, Loula Martin, Matějková Stanislava, Šefc Luděk, Vannucci Luca
Center for Advanced Preclinical Imaging (CAPI), First Faculty of Medicine, Charles University, Prague 120 00, Czech Republic.
Laboratory of Immunotherapy, Institute of Microbiology, Czech Academy of Sciences, Prague 142 00, Czech Republic.
ACS Appl Nano Mater. 2025 Jul 16;8(29):14867-14881. doi: 10.1021/acsanm.5c03013. eCollection 2025 Jul 25.
Magnetic nanoparticles have been at the center of biomedical research for decades, primarily for their applications in magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). Superparamagnetic particles, typically based on iron oxide crystals, are effective in both modalities, although each requires distinct magnetic properties for optimal performance. We investigated the performance of nanoparticles based on a nickel-substituted ferrite core and compared them to standard maghemite iron oxide nanoparticles. We synthesized γ-FeO and Ni Fe O nanoparticles and coated them with a statistical copolymer poly-(,-dimethylacrylamide--acrylic acid). In vitro testing included X-ray diffraction (XRD), Mössbauer spectroscopy, magnetometry, magnetic resonance relaxometry, magnetic particle spectroscopy, and imaging. In vivo testing involved monitoring of nanoparticle biodistribution using MPI and MRI after intracardial application in a murine model. Mössbauer spectra suggest that the Ni-substituted nanoparticles consist of a stoichiometric NiFeO ferrite and a poorly crystalline antiferromagnetic iron-(III) oxide-hydroxide phase. Amorphous-like impurities in Ni Fe O nanoparticles were probably responsible for lower saturation magnetization than that of γ-FeO nanoparticles, as was proved by magnetometry, which led to lower relaxivity. However, MPI revealed a higher signal in the spectrum and superior imaging performance of Ni Fe O compared to γ-FeO particles, likely due to shorter Néél and Brownian relaxation times. Both types of nanoparticles showed similar performance in bimodal MRI/MPI imaging in vivo. They were detected in the liver immediately after application and appeared in the spleen within 24 h. Long-term localization in the lymph nodes was also observed. Substituting an iron with a nickel ion in the core altered the magnetic properties, leading to lower saturation magnetization and an increased signal in the magnetic particle spectra, which enhanced their performance in MPI. This study demonstrates that γ-FeO and Ni Fe O nanoparticles are both suitable for combined MRI/MPI imaging; magnetic particle imaging provides a highly specific signal for anatomical magnetic resonance images.
几十年来，磁性纳米颗粒一直是生物医学研究的核心，主要用于磁共振成像（MRI）和磁粒子成像（MPI）。超顺磁性颗粒通常基于氧化铁晶体，在这两种成像方式中都很有效，尽管每种成像方式都需要不同的磁特性以实现最佳性能。我们研究了基于镍取代铁氧体核的纳米颗粒的性能，并将其与标准的磁赤铁矿氧化铁纳米颗粒进行了比较。我们合成了γ-FeO和NiFeO纳米颗粒，并用统计共聚物聚（N，N-二甲基丙烯酰胺-co-丙烯酸）对它们进行了包覆。体外测试包括X射线衍射（XRD）、穆斯堡尔光谱、磁测量、磁共振弛豫测量、磁粒子光谱和成像。体内测试涉及在小鼠模型中的心内应用后，使用MPI和MRI监测纳米颗粒的生物分布。穆斯堡尔光谱表明，镍取代的纳米颗粒由化学计量的NiFeO铁氧体和结晶性较差的反铁磁性氢氧化铁（III）相组成。NiFeO纳米颗粒中类似非晶态的杂质可能是导致其饱和磁化强度低于γ-FeO纳米颗粒的原因，磁测量结果证明了这一点，这导致了较低的弛豫率。然而，MPI显示，与γ-FeO颗粒相比，NiFeO在光谱中的信号更高，成像性能更优，这可能是由于更短的奈耳和布朗弛豫时间。两种类型的纳米颗粒在体内双模态MRI/MPI成像中表现出相似的性能。应用后立即在肝脏中检测到它们，并在24小时内出现在脾脏中。还观察到它们在淋巴结中的长期定位。在核心中用镍离子取代铁会改变磁特性，导致饱和磁化强度降低，磁粒子光谱中的信号增加，从而提高了它们在MPI中的性能。这项研究表明，γ-FeO和NiFeO纳米颗粒都适用于联合MRI/MPI成像；磁粒子成像为解剖磁共振图像提供了高度特异性的信号。
