Kinetics and toxicity of nanoplastics in ex vivo exposed human whole blood as a model to understand their impact on human health

The ubiquitous presence of nanoplastics (NPLs) in the environment is considered of great health concern. Due to their size, NPLs can cross both the intestinal and pulmonary barriers and, consequently, their presence in the blood compartment is expected. Understanding the interactions between NPLs and human blood components is required. In this study, to simulate more adequate real exposure conditions, the whole blood of healthy donors was exposed to five different NPLs: three polystyrene NPLs of approximately 50 nm (aminated PS-NH₂, carboxylated PS-COOH, and pristine PS- forms), together with two true-to-life NPLs from polyethylene terephthalate (PET) and polylactic acid (PLA) of about 150 nm. Internalization was determined in white blood cells (WBCs) by confocal microscopy, once the different main cell subtypes (monocytes, polymorphonucleated cells, and lymphocytes) were sorted by flow cytometry. Intracellular reactive oxygen species (iROS) induction was determined in WBCs and cytokine release in plasma. In addition, hemolysis, coagulation, and platelet activation were also determined. Results showed a differential uptake between WBC subtypes, with monocytes showing a higher internalization. Regarding iROS, lymphocytes were those with higher levels, which was observed for different NPLs. Changes in cytokine release were also detected, with higher effects observed after PLA- and PS-NH₂-NPL exposure. Hemolysis induction was observed after PS- and PS-COOH-NPL exposure, but no effects on platelet functionality were observed after any of the treatments. To our knowledge, this is the first study comprehensively evaluating the bloodstream kinetics and toxicity of NPL from different polymeric types on human whole blood, considering the role played by the cell subtype and the NPLs physicochemical characteristics in the effects observed after the exposures.