Recent studies showed the presence of microplastic in human lungs. There remains an unmet need to identify the biodistribution of microplastic after inhalation. In this study, we traced the biodistribution of inhaled micro-sized polystyrene (mPS) and/or nano-sized PS (nPS) using 64Cu with PET in mice. We used 0.2–0.3-µm sized mPS and 20-nm sized nPS throughout. 64Cu-DOTA-mPS, 64Cu-DOTA-nPS and/or 64CuCl2 were used to trace the distribution in the murine inhalation model. PET images were acquired using an INVEON PET scanner at 1, 12, 24, 48, and 72 h after intratracheal instillation, and the SUVmax for interesting organs were determined, biodistribution was then determined in terms of percentage injected dose/gram of tissue (%ID/g). Ex vivo tissue-radio thin-layer chromatography (Ex vivo-radioTLC) was used to demonstrate the existence of 64Cu-DOTA-PS in tissue. PET image demonstrated that the amount of 64Cu-DOTA-mPS retained within the lung was significantly higher than 64Cu-DOTA-nPS until 72 h; SUVmax values of 64Cu-DOTA-mPS in lungs was 11.7 ± 5.0, 48.3 ± 6.2, 65.5 ± 2.3, 42.2 ± 13.1, and 13.2 ± 2.3 at 1, 12, 24, 48, and 72 h respectively whereas it was 31.2 ± 3.1, 17.3 ± 5.9, 10.0 ± 3.4, 8.1 ± 2.4 and 8.9 ± 3.6 for 64Cu-DOTA-nPS at the corresponding timepoints. The biodistribution data supported the PET data with a similar pattern of clearance of the radioactivity from the lung. nPS cleared rapidly post instillation in comparison to mPS within the lungs. Higher accumulation of %ID/g for nPS (roughly 2 times) were observed compared to mPS in spleen, liver, intestine, thymus, kidney, brain, salivary gland, ovary, and urinary bladder. Ex vivo-radioTLC was used to demonstrate that the detected gamma rays originated from 64Cu-DOTA-mPS or nPS. PET image demonstrated the differences in accumulations of mPS and/or nPS between lungs and other interesting organs. The information provided may be used as the basis for future studies on the toxicity of mPS and/or nPS.

中文翻译：

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小鼠吸入模型中 64Cu 标记的微米级和纳米级聚苯乙烯的 PET 示踪和生物分布比较

最近的研究表明人类肺部存在微塑料。确定吸入后微塑料的生物分布仍然是一个未满足的需求。在这项研究中，我们使用 64Cu 和 PET 追踪了小鼠吸入的微米级聚苯乙烯 (mPS) 和/或纳米级 PS (nPS) 的生物分布。我们始终使用 0.2–0.3 µm 大小的 mPS 和 20 nm 大小的 nPS。使用 64Cu-DOTA-mPS、64Cu-DOTA-nPS 和/或 64CuCl2 来追踪小鼠吸入模型中的分布。使用 INVEON PET 扫描仪在气管内滴注后 1、12、24、48 和 72 小时采集 PET 图像，并确定感兴趣器官的 SUVmax，然后根据注射剂量/克组织的百分比确定生物分布（%内径/克）。使用离体组织无线电薄层色谱（Ex vivo-radioTLC）证明组织中存在 64Cu-DOTA-PS。PET图像显示，直到72小时，肺内保留的64Cu-DOTA-mPS量显着高于64Cu-DOTA-nPS；64Cu-DOTA-mPS在肺中的SUVmax值在1、12、24、48和72小时分别为11.7±5.0、48.3±6.2、65.5±2.3、42.2±13.1和13.2±2.3，而其为31.2±3.1 、 17.3 ± 5.9、 10.0 ± 3.4、 8.1 ± 2.4 和 8.9 ± 3.6 对于 64Cu-DOTA-nPS 在相应的时间点。生物分布数据支持 PET 数据，具有类似的肺部放射性清除模式。与 mPS 相比，nPS 在滴注后在肺内迅速清除。与 mPS 相比，在脾、肝、肠、胸腺、肾、脑、唾液腺、卵巢和膀胱中观察到 nPS 的 %ID/g 积累更高（大约 2 倍）。Ex vivo-radioTLC 用于证明检测到的伽马射线源自 64Cu-DOTA-mPS 或 nPS。PET 图像显示了肺和其他感兴趣器官之间 mPS 和/或 nPS 积累的差异。所提供的信息可用作未来 mPS 和/或 nPS 毒性研究的基础。