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Comparison of PET tracing and biodistribution between 64Cu-labeled micro-and nano-polystyrene in a murine inhalation model
Summary
Using advanced PET imaging in mice, researchers tracked where inhaled micro and nanoplastics traveled in the body and found that nano-sized particles cleared from the lungs much faster than micro-sized ones but accumulated more in the liver, spleen, and other organs. Micro-sized particles stayed in the lungs longer, with peak retention at 24 hours, while nano-sized particles spread quickly throughout the body. This is one of the first studies to directly visualize how inhaled plastic particles distribute through living mammals, confirming that smaller particles pose a greater risk of reaching organs beyond the lungs.
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 Cu with PET in mice. METHODS: We used 0.2-0.3-µm sized mPS and 20-nm sized nPS throughout. Cu-DOTA-mPS, Cu-DOTA-nPS and/or CuCl 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 SUV 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 Cu-DOTA-PS in tissue. RESULTS: PET image demonstrated that the amount of Cu-DOTA-mPS retained within the lung was significantly higher than Cu-DOTA-nPS until 72 h; SUV values of Cu-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 Cu-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 Cu-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.