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Published on: April 29, 2017
Comparison of PET tracing and biodistribution between 64Cu-labeled micro-and nano-polystyrene in a murine inhalation
Joycie Shanmugiah1,2, Javeria Zaheer1, Changkeun Im1,2
1Division of RI Application, Korea Institute of Radiological and Medical Sciences, 75 Nowon-Gil, Gongneung-Dong, Nowon-Gu, Seoul, 01812, Korea.
Introduction:
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.
Methods:
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.
Results:
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.
Conclusion:
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.
Insights
Microplastic biodistribution after inhalation differs by size. Micro-sized polystyrene (mPS) remains longer in lungs than nano-sized PS (nPS), which distributes more widely to other organs.
Area of Science:
- Environmental Science
- Toxicology
- Biomedical Imaging
Background:
- Microplastics are detected in human lungs, but their biodistribution after inhalation is unknown.
- Understanding microplastic fate is crucial for assessing health risks.
Purpose of the Study:
- To trace the biodistribution of inhaled micro-sized polystyrene (mPS) and nano-sized polystyrene (nPS) in mice.
- To compare the lung retention and systemic distribution of mPS versus nPS.
Main Methods:
- Inhaled 0.2-0.3 µm mPS and 20 nm nPS labeled with 64Cu were administered to mice via intratracheal instillation.
- Positron Emission Tomography (PET) imaging was used to track biodistribution at various time points (1-72 hours).
- Ex vivo radio-thin-layer chromatography (radioTLC) confirmed the presence of labeled microplastics in tissues.
Main Results:
- Micro-sized PS (mPS) showed significantly higher retention in the lungs compared to nano-sized PS (nPS) up to 72 hours post-instillation.
- Nano-sized PS (nPS) cleared more rapidly from the lungs and exhibited higher accumulation in organs like the spleen, liver, and kidneys.
- PET imaging revealed distinct biodistribution patterns for mPS and nPS, highlighting size-dependent translocation.
Conclusions:
- Inhaled microplastic biodistribution is size-dependent, with larger particles retained longer in the lungs.
- Nano-sized microplastics translocate more readily to systemic organs, suggesting different exposure risks.
- This study provides a foundation for future research into the toxicity of inhaled microplastics.
