Exosomes are lipid bilayer vesicles released by cells and serve as natural carriers for cell–cell communication. Exosomes provide a promising approach to the diagnosis and treatment of diseases and are considered as an alternative to cell therapy. However, one main restriction in their clinical application is that the current understanding of these vesicles, especially their in vivo behaviors and distributions, remains inadequate. Here, we reviewed the current and emerging methods for in vivo imaging and tracking of exosomes, including fluorescence imaging, bioluminescence imaging, nuclear imaging, X-ray imaging, magnetic resonance imaging, photoacoustic imaging, and multimodal imaging. In vivo imaging and tracking of exosomes by these methods can help researchers further understand their uptake mechanism, biodistribution, migration, function, and therapeutic performance. The pioneering studies in this field can elucidate many unknown exosomal behaviors at different levels. We discussed the advantages and limitations of each labeling and imaging strategy. The advances in labeling and in vivo imaging will expand our understanding of exosomes and promote their clinical application. We finally provide a perspective and discuss several important issues that need to be explored in future research. This review highlights the values of efficient, sensitive, and biocompatible exosome labeling and imaging techniques in disease theranostics.

中文翻译：

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用于治疗诊断的外泌体的体内成像和跟踪

外泌体是细胞释放的脂质双层囊泡，可作为细胞间通讯的天然载体。外泌体为疾病的诊断和治疗提供了一种有前途的方法，并被认为是细胞疗法的替代品。然而，它们临床应用的一个主要限制是目前对这些囊泡的理解，尤其是它们的体内行为和分布，仍然不足。在这里，我们回顾了当前和新兴的方法体内外泌体的成像和跟踪，包括荧光成像、生物发光成像、核成像、X射线成像、磁共振成像、光声成像和多模态成像。体内通过这些方法对外泌体进行成像和跟踪可以帮助研究人员进一步了解它们的摄取机制、生物分布、迁移、功能和治疗性能。该领域的开创性研究可以在不同层面阐明许多未知的外泌体行为。我们讨论了每种标记和成像策略的优点和局限性。标签和技术的进步体内成像将扩大我们对外泌体的理解并促进其临床应用。我们最后提供了一个视角并讨论了未来研究中需要探索的几个重要问题。这篇综述强调了高效、灵敏和生物相容的外泌体标记和成像技术在疾病治疗学中的价值。