Superparamagnetic iron oxide (SPIO) has been used as a contrast agent for magnetic resonance imaging (MRI) since the late 20th century. With the development of SPIO, cellular MRI has been recognized as a suitable and highly sensitive noninvasive modality with great potential to benefit translational research. In addition to its traditional diagnostic property, latest advances have conferred SPIO with multifunctionality. Several SPIO-based theranostic probes with targeting, therapeutic and diagnosis components have been successfully developed. The objective of this brief review is to summarize the characteristics, synthesizing methods, labeling approaches and current applications of SPIO-based cellular MRI in oncology. Herein, we first depict the history, classification and advantages of and the differences between T1- and T2/T2*-based SPIO contrast agents for cancer treatment. Second, we outline current coating materials that render SPIO less toxic and more biocompatible to mammalian cells. Finally, the cell labeling techniques and applications of SPIO-based MRI for tracking mesenchymal stem cell tumor–homing in preclinical models are introduced.

中文翻译：

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超顺磁性氧化铁的细胞磁共振成像：癌症中的方法和应用

自 20 世纪末以来，超顺磁性氧化铁 (SPIO) 已被用作磁共振成像 (MRI) 的造影剂。随着SPIO的发展，细胞MRI已被公认为一种合适且高度敏感的非侵入性方式，具有巨大的转化研究潜力。除了其传统的诊断特性外，最新进展还赋予 SPIO 多功能性。已经成功开发了几种具有靶向、治疗和诊断组件的基于 SPIO 的治疗诊断探针。这篇简短回顾的目的是总结基于 SPIO 的细胞 MRI 在肿瘤学中的特征、合成方法、标记方法和当前应用。在这里，我们首先描绘历史，用于癌症治疗的基于 T1 和 T2/T2* 的 SPIO 造影剂的分类、优点和区别。其次，我们概述了当前的涂层材料，这些材料使 SPIO 的毒性更小，对哺乳动物细胞的生物相容性更高。最后，介绍了基于SPIO的MRI在临床前模型中追踪间充质干细胞肿瘤归巢的细胞标记技术和应用。