Magnetic iron-oxide nanoparticles have been developed as contrast agents in magnetic resonance imaging (MRI) and as therapeutic agents in magnetic hyperthermia. They have also recently been demonstrated as contrast and elastography agents in magnetomotive optical coherence tomography (MM-OCT) and elastography. Protein-shell microspheres containing suspensions of these magnetic nanoparticles in lipid cores, and with functionalized outer shells for specific targeting, have also been demonstrated as efficient contrast agents for imaging modalities such as MM-OCT and MRI, and can be easily modified for other modalities such as ultrasound, fluorescence, and luminescence imaging. By leveraging the benefits of these various imaging modalities with the use of only a single agent, a magnetic microsphere, it becomes possible to use a wide-field imaging method (such as MRI or small animal fluorescence imaging) to initially locate the agent, and then use MM-OCT to obtain dynamic contrast images with cellular level morphological resolution. In addition to multimodal contrast-enhanced imaging, these microspheres could serve as drug carriers for targeted delivery under image guidance. Although the preparation and surface modifications of protein microspheres containing iron oxide nanoparticles have been previously described and feasibility studies conducted, many questions regarding their production and properties remain. Since the use of multifunctional microspheres could have high clinical relevance, here we report a detailed characterization of their properties and behavior in different environments to highlight their versatility. The work presented here is an effort for the development and optimization of nanoparticle-based microspheres as multimodal contrast agents that can bridge imaging modalities on different size scales, especially for their use in MM-OCT and MRI.

中文翻译：

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用于磁动势和多模态成像的磁性纳米粒子种子微球的表征

磁性氧化铁纳米粒子已被开发为磁共振成像 (MRI) 中的造影剂和磁热疗中的治疗剂。它们最近还被证明是磁动光学相干断层扫描 (MM-OCT) 和弹性成像中的造影剂和弹性成像剂。含有这些磁性纳米颗粒悬浮液的蛋白质壳微球体，以及用于特定靶向的功能化外壳，也已被证明是用于 MM-OCT 和 MRI 等成像模式的有效造影剂，并且可以轻松修改为其他模式如超声、荧光和发光成像。通过仅使用单一试剂（磁性微球），利用这些不同成像方式的优势，可以使用宽视野成像方法（如 MRI 或小动物荧光成像）来初步定位代理，然后使用 MM-OCT 获得具有细胞水平形态分辨率的动态对比图像。除了多模态对比度增强成像外，这些微球还可以作为药物载体，在图像引导下进行靶向递送。尽管先前已经描述了含有氧化铁纳米颗粒的蛋白质微球的制备和表面改性并进行了可行性研究，但关于其生产和性质的许多问题仍然存在。由于多功能微球的使用可能具有很高的临床相关性，因此我们在这里报告了它们在不同环境中的特性和行为的详细表征，以突出它们的多功能性。