Harnessing PET to track micro- and nanoplastics in vivo

The proliferation of plastics in the environment continues at an alarming rate. Plastic particles have been found to be persistent and ubiquitous pollutants in a variety of environments, including sea water, fresh water, soil, and air. In light of this phenomenon, the scientific and medical communities have become increasingly wary of the dangers posed to human health by chronic exposure to microplastics (< 5 mm diameter) and nanoplastics (< 100 nm diameter). A critical component of the study of the health effects of these pollutants is the accurate determination of their pharmacokinetic behavior in vivo. Herein, we report the first use of molecular imaging to track polystyrene (PS) micro- and nanoplastic particles in mammals. To this end, we have modified PS particles of several sizes-diameters of 20 nm, 220 nm, 1 µm, and 6 µm-with the chelator desferrioxamine (DFO) and radiolabeled these DFO-bearing particles with the positron-emitting radiometal zirconium-89 (⁸⁹Zr; t_1/2 ~ 3.3 d). Subsequently, positron emission tomography (PET) was used to visualize the biodistribution of these radioplastics in C57BL/6J mice at 6, 12, 24, and 48 h after ingestion. The imaging data reveal that the majority of the radioplastics remain in the gastrointestinal tract and are eliminated through the feces by 48 h post-ingestion, a result reinforced by acute biodistribution studies. Ultimately, this work suggests that nuclear imaging-and PET in particular-can be a sensitive and effective tool in the urgent and rapidly growing effort to study the in vivo behavior and potential toxicity of micro- and nanoplastics.