Department of Imaging Chemistry and Biology, School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London SE1 7EH, U.K.
Institute of Pharmaceutical Sciences, School of Cancer & Pharmaceutical Sciences, King's College London, Franklin Wilkins Building, London SE1 9NH, U.K.
Bioconjug Chem. 2022 Mar 16;33(3):473-485. doi: 10.1021/acs.bioconjchem.1c00597. Epub 2022 Feb 28.
Exosomes or small extracellular vesicles (sEVs) are increasingly gaining attention for their potential as drug delivery systems and biomarkers of disease. Therefore, it is important to understand their biodistribution using imaging techniques that allow tracking over time and at the whole-body level. Positron emission tomography (PET) allows short- and long-term whole-body tracking of radiolabeled compounds in both animals and humans and with excellent quantification properties compared to other nuclear imaging techniques. In this report, we explored the use of [Zr]Zr(oxinate) (a cell and liposome radiotracer) for direct and intraluminal radiolabeling of several types of sEVs, achieving high radiolabeling yields. The radiosynthesis and radiolabeling protocols were optimized for sEV labeling, avoiding sEV damage, as demonstrated using several characterizations (cryoEM, nanoparticle tracking analysis, dot blot, and flow cytometry) and techniques. Using pancreatic cancer sEVs (PANC1) in a healthy mouse model, we showed that it is possible to track Zr-labeled sEVs using PET imaging for at least up to 24 h. We also report differential biodistribution of intact sEVs compared to intentionally heat-damaged sEVs, with significantly reduced spleen uptake for the latter. Therefore, we conclude that Zr-labeled sEVs using this method can reliably be used for PET tracking and thus allow efficient exploration of their potential as drug delivery systems.
外泌体或小细胞外囊泡 (sEVs) 因其作为药物传递系统和疾病生物标志物的潜力而受到越来越多的关注。因此，使用允许随时间和全身水平进行跟踪的成像技术来了解它们的生物分布非常重要。正电子发射断层扫描 (PET) 允许对放射性标记化合物在动物和人类中的短期和长期全身跟踪，并具有与其他核成像技术相比的出色定量特性。在本报告中，我们探索了使用 [Zr]Zr(oxinate)（一种细胞和脂质体放射性示踪剂）对几种类型的 sEV 进行直接和腔内放射性标记的用途，实现了高放射性标记产率。放射性合成和放射性标记方案针对 sEV 标记进行了优化，避免了 sEV 损伤，这通过几种表征（冷冻电镜、纳米颗粒跟踪分析、斑点印迹和流式细胞术）和技术得到了证明。在健康小鼠模型中使用胰腺癌细胞外囊泡 (PANC1)，我们表明使用 PET 成像至少可以跟踪 Zr 标记的 sEV 长达 24 小时。我们还报告了完整 sEV 与故意热损伤 sEV 的差异生物分布，后者的脾脏摄取明显减少。因此，我们得出结论，使用这种方法标记的 Zr 标记 sEV 可以可靠地用于 PET 跟踪，从而可以有效地探索它们作为药物传递系统的潜力。
