Hazard assessment of nanoplastics is driven by their surface-functionalization. Effects in human-derived primary endothelial cells.

During plastic waste degradation into micro/nanoplastics (MNPLs) their physicochemical characteristics including surface properties (charge, functionalization, biocorona, etc.) can change, potentially affecting their biological effects. This paper focuses on the surface functionalization of MNPLs to determine if it has a direct impact on the toxicokinetic and toxicodynamic interactions in human umbilical vein endothelial cells (HUVECs), at different exposure times. Pristine polystyrene nanoplastics (PS-NPLs), as well as their carboxylated (PS-C-NPLs) and aminated (PS-A-NPLs) forms, all around 50 nm, were used in a wide battery of toxicological assays. These assays encompassed evaluations on cell viability, cell internalization, induction of intracellular reactive oxygen species (iROS), and genotoxicity. The experiments were conducted at a concentration of 100 µg/mL, chosen to ensure a high internalization rate across all treatments while maintaining a sub-toxic concentration. Our results show that all PS-NPLs are internalized by HUVECs, but the internalization dynamic depends on the particle's functionalization. PS-NPLs and PS-C-NPLs internalization modify the morphology of the cell increasing its inner complexity/granularity. Regarding cell toxicity, only PS-A-NPLs reduced cell viability. Intracellular ROS was induced by the three different PS-NPLs but at different time points. Genotoxic damage was induced by the three PS-NPLs at short exposures (2 h), but not for PS-C-NPLs at 24 h. Overall, this study suggests that the toxicological effects of PSNPLs on HUVEC cells are surface-dependent, highlighting the relevance of using human-derived primary cells as a target.

Harmful effects of true-to-life nanoplastics derived from PET water bottles in human alveolar macrophages.

The increasing presence of secondary micro/nanoplastics (MNPLs) in the environment requires knowing if they represent a real health concern. To such end, an important point is to test representative MNPLs such as the denominated true-to-life MNPLs, resulting from the degradation of plastic goods in lab conditions. In this study, we have used polyethylene terephthalate (PET) NPLs resulting from the degradation of PET water bottles. Since inhalation is an important exposure route to environmental MNPLS, we have used mouse alveolar macrophages (MH-S) as a target cell, and the study focused only on the cells that have internalized them. This type of approach is novel as it may capture the realistic adverse effects of PETNPLs only in the internalized cells, thereby mitigating any biases while assessing the risk of these MNPLs. Furthermore, the study utilized a set of biomarkers including intracellular reactive oxygen species (ROS) levels, variations on the mitochondrial membrane potential values, and the macrophage polarization to M1 (pro-inflammatory response) and M2 (anti-proinflammatory response) as possible cellular effects due to PETNPLs in only the cells that internalized PETNPLs. After exposures lasting for 3 and 24 h to a range of concentrations (0, 25, 50, and 100 µg/mL) the results indicate that no toxicity was induced despite the 100% internalization observed at the highest concentration. Significant intracellular levels of ROS were observed, mainly at exposures lasting for 24 h, in an indirect concentration-effect relationship. Interestingly, a reduction in the mitochondrial membrane potential was observed, but only at exposures lasting for 24 h, but without a clear concentration-effect relationship. Finally, PETNPL exposure shows a significant polarization from M0 to M1 and M2 subtypes. Polarization to M1 (pro-inflammatory stage) was more marked and occurred at both exposure times. Polarization to M2 (anti-inflammatory stage) was only observed after exposures lasting for 24 h. Due to the relevance of the described biomarkers, our results underscore the need for further research, to better understand the health implications associated with MNPL exposure.

Titanium-doped PET nanoplastics of environmental origin as a true-to-life model of nanoplastic.

The increased presence of secondary micro/nanoplastics (MNPLs) in the environment requires urgent studies on their potentially hazardous effects on exposed organisms, including humans. In this context, it is essential to obtain representative MNPL samples for such purposes. In our study, we have obtained true-to-life NPLs resulting from the degradation, via sanding, of opaque PET bottles. Since these bottles contain titanium (TiO2NPs), the resulting MNPLs also contain embedded metal. The obtained PET(Ti)NPLs were extensively characterized from a physicochemical point of view, confirming their nanosized range and their hybrid composition. This is the first time these types of NPLs are obtained and characterized. The preliminary hazard studies show their easy internalization in different cell lines, without apparent general toxicity. The demonstration by confocal microscopy that the obtained NPLs contain Ti samples offers this material multiple advantages. Thus, they can be used in in vivo approaches to determine the fate of NPLs after exposure, escaping from the existing difficulties to follow up MNPLs in biological samples.