Comparison of PET tracing and biodistribution between 64 Cu-labeled micro-and nano-polystyrene in a murine inhalation model

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 64 Cu with PET in mice. Methods We used 0.2–0.3-µm sized mPS and 20-nm sized nPS throughout. 64 Cu-DOTA-mPS, 64 Cu-DOTA-nPS and/or 64 CuCl 2 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 max 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 64 Cu-DOTA-PS in tissue. Results PET image demonstrated that the amount of 64 Cu-DOTA-mPS retained within the lung was significantly higher than 64 Cu-DOTA-nPS until 72 h; SUV max values of 64 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 64 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 64 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. Graphical abstract