Nanoparticles are under active investigation for the detection and treatment of cancer. Yet our understanding of nanoparticle delivery to tumors is limited by our ability to observe the uptake process on its own scale in living subjects. We chose to study single-walled carbon nanotubes (SWNTs) because they exhibit among the highest levels of tumor uptake across the wide variety of available nanoparticles. We target them using RGD (arginine-glycine-aspartic acid) peptide which directs them to integrins overexpressed on tumor vasculature and on the surface of some tumor cells (e.g., U87MG as used here). We employ intravital microscopy (IVM) to quantitatively examine the spatiotemporal framework of targeted SWNT uptake in a murine tumor model. IVM provided a dynamic microscale window into nanoparticle circulation, binding to tumor blood vessels, extravasation, binding to tumor cells, and tumor retention. RGD-SWNTs bound to tumor vasculature significantly more than controls (P<0.0001). RGD-SWNTs extravasated similarly compared to control RAD-SWNTs, but post-extravasation we observed as RGD-SWNTs eventually bound to individual tumor cells significantly more than RAD-SWNTs (p<0.0001) over time. RGD-SWNTs and RAD-SWNTs displayed similar signal in tumor for a week, but over time their curves significantly diverged (p<0.001) showing increasing RGD-SWNTs relative to untargeted SWNTs. We uncovered the complex spatiotemporal interplay between these competing uptake mechanisms. Specific uptake was delimited to early (1-6 hours) and late (1-4 weeks) time-points, while non-specific uptake dominated from 6 hours to 1 week. Our analysis revealed critical, quantitative insights into the dynamic, multifaceted mechanisms implicated in ligand-targeted SWNT accumulation in tumor using real-time observation.

中文翻译：

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小动物肿瘤模型中纳米颗粒递送和靶向的高分辨率连续活体显微成像


人们正在积极研究纳米颗粒用于癌症的检测和治疗。然而，我们对纳米颗粒递送至肿瘤的理解受到我们在活体受试者中观察其自身规模的吸收过程的能力的限制。我们选择研究单壁碳纳米管 (SWNT)，因为它们在各种可用纳米粒子中表现出最高水平的肿瘤摄取。我们使用RGD（精氨酸-甘氨酸-天冬氨酸）肽来靶向它们，该肽将它们引导至在肿瘤血管系统和某些肿瘤细胞表面上过度表达的整合素（例如，此处使用的U87MG）。我们采用活体显微镜 (IVM) 定量检查小鼠肿瘤模型中靶向单壁碳纳米管摄取的时空框架。 IVM 为纳米颗粒循环、与肿瘤血管的结合、外渗、与肿瘤细胞的结合以及肿瘤保留提供了动态的微观窗口。 RGD-SWNT 与肿瘤脉管系统的结合显着多于对照 (P<0.0001)。与对照 RAD-SWNT 相比，RGD-SWNT 的外渗情况类似，但随着时间的推移，我们观察到外渗后，RGD-SWNT 最终与单个肿瘤细胞的结合明显多于 RAD-SWNT (p<0.0001)。 RGD-SWNT 和 RAD-SWNT 在一周内在肿瘤中显示出相似的信号，但随着时间的推移，它们的曲线显着分化 (p<0.001)，显示相对于非靶向 SWNT 而言，RGD-SWNT 不断增加。我们发现了这些竞争性吸收机制之间复杂的时空相互作用。特异性摄取被限定为早期（1-6小时）和晚期（1-4周）时间点，而非特异性摄取在6小时至1周期间占主导地位。 我们的分析通过实时观察揭示了对肿瘤中配体靶向单壁碳纳米管积累所涉及的动态、多方面机制的关键、定量见解。