Tracing the In Vivo Fate of Polystyrene Nanoplastics via a Lanthanide Copolymerization Labeling Strategy.

The widespread detection of plastic particles in environmental and biological matrices has raised health concerns, yet quantitative evidence on the in vivo behavior of submicron and nanoplastics (S/NPs) remains limited. Here, we developed a sensitive tracking platform by stably incorporating lanthanide elements into polystyrene (PS) S/NPs via emulsion copolymerization. Using this methodology, we systematically investigated in mice the gastrointestinal transit, barrier translocation, biodistribution, and pharmacokinetics of lanthanide-doped PS particles with distinct surface properties: 80 nm (negative), 80 nm (positive), and 500 nm (positive). Following oral gavage (500 mg/kg), only 0.01-0.04% of the administered dose translocated to major organs; 500 nm particles exhibited slower gastrointestinal transit but higher barrier translocation than their 80 nm counterparts. After intravenous injection (10 mg/kg), both PS NPs accumulated predominantly in the liver and spleen, with positively charged particles showing enhanced uptake. Laser ablation-ICP-MS imaging revealed time-dependent redistribution within splenic microregions and preferential retention in iron-enriched brain areas. Complementary analyses, including zeta potential evolution in simulated gastrointestinal media, immunofluorescence staining of intestinal tight junctions, and transmission electron microscopy, provided mechanistic insights into particle behavior. By integrating a stable labeling strategy with advanced mass spectrometry-based tools, this study establishes a quantitative platform for accurately assessing S/NP in vivo fate, offering critical insights for environmental health risk assessment.