Fluorescent dye labeling is a common strategy to analyze the fate of administered nanoparticles in living organisms. However, to which extent the labeling processes can alter the original nanoparticle biodistribution has been so far neglected. In this work, two widely used fluorescent dye molecules, namely, ATTO488 (ATTO) and Sulfo-Cy5 (S-Cy5), have been covalently attached to a well-characterized CXCR4-targeted self-assembling protein nanoparticle (known as T22-GFP-H6). The biodistribution of labeled T22-GFP-H6-ATTO and T22-GFP-H6-S-Cy5 nanoparticles has been then compared to that of the non-labeled nanoparticle in different CXCR4+ tumor mouse models. We observed that while parental T22-GFP-H6 nanoparticles accumulated mostly and specifically in CXCR4+ tumor cells, labeled T22-GFP-H6-ATTO and T22-GFP-H6-S-Cy5 nanoparticles showed a dramatic change in the biodistribution pattern, accumulating in non-target organs such as liver or kidney while reducing tumor targeting capacity. Therefore, the use of such labeling molecules should be avoided in target and non-target tissue uptake studies during the design and development of targeted nanoscale drug delivery systems, since their effect over the fate of the nanomaterial can lead to considerable miss-interpretations of the actual nanoparticle biodistribution.

中文翻译：

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荧光染料标记改变了肿瘤靶向纳米颗粒的生物分布。

荧光染料标记是分析生物体中施用纳米颗粒的命运的常用策略。然而，到目前为止，标记过程可以在多大程度上改变原始纳米颗粒的生物分布。在这项工作中，两个广泛使用的荧光染料分子，即ATTO488（ATTO）和Sulfo-Cy5（S-Cy5），已共价连接至靶向性良好的CXCR4靶向的自组装蛋白纳米颗粒（称为T22-GFP -H6）。然后，在不同的CXCR4 +肿瘤小鼠模型中，将标记的T22-GFP-H6-ATTO和T22-GFP-H6-S-Cy5纳米粒子的生物分布与未标记的纳米粒子的生物分布进行了比较。我们观察到，虽然亲本T22-GFP-H6纳米颗粒主要（尤其是在CXCR4 +肿瘤细胞中）积累，标记的T22-GFP-H6-ATTO和T22-GFP-H6-S-Cy5纳米颗粒在生物分布模式方面发生了巨大变化，在肝脏或肾脏等非目标器官中积累，同时降低了肿瘤靶向能力。因此，在设计和开发靶向纳米级药物递送系统的过程中，应避免在目标和非目标组织摄取研究中使用此类标记分子，因为它们对纳米材料命运的影响会导致对纳米材料的大量误解。实际的纳米颗粒生物分布。