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The genotoxic and carcinogenic potential of secondary polyethylene terephthalate nanoplastics containing titanium dioxide
Summary
This study assessed the genotoxic and carcinogenic potential of secondary PET nanoplastics containing titanium dioxide, derived from grinding opaque plastic milk bottles, using validated cell-based assays. Secondary PET-TiO2 nanoplastics showed genotoxic activity, indicating that real-world nanoplastics from consumer plastic waste carry measurable cancer-related risk.
People are constantly exposed to micro- and nanoplastics (MNPLs) generated from the breakdown of larger plastic waste. MNPLs can accumulate in human tissues and potentially have an impact on human health. This study aimed to assess the genotoxic and carcinogenic potential of secondary polyethylene terephthalate doped with titanium dioxide (PET-TiO2), which was obtained by grinding opaque milk bottles. The micronucleus (MN) assay is a validated method to assess genotoxic initiating carcinogens. However, carcinogenesis is a process that also includes promotion and progression, which cannot be detected by short-term genotoxicity assays. The OECD-validated Bhas-42 cell transformation assay (CTA) enables in vitro simulation of the in vivo initiation and promotion stages of carcinogenesis, thus allowing the detection of a broader range of carcinogens. In this study, the induction of MN was assessed in Human B lymphoblastoid TK6 cells that were exposed for 21 h (1.5 cell cycles) to five concentrations of PET-TiO2 (0.61–50 μg/mL) or two of TiO2 (0.72–2,15 μg/mL). After, cells were allowed to recover in the presence of cytochalasin B for 21 h and were analyzed by fluorescence microscopy. In parallel, a CTA assay was performed as recommended by the OECD GD 231. Bhas 42 cells were treated with PET-TiO2 (6.25–200 μg/mL) or TiO2 (4.3–8.6 μg/mL) either from day 1 to 4, or from day 4 to 14, for the initiation and promotion assays, respectively. The number of transformed foci was scored on day 21. In addition, cellular internalization was investigated by transmission electron microscopy. Preliminary results showed that PET-TiO2 did not increase the frequency of MN. However, PET-TiO2 showed cell-transforming effects in both initiatiation and promotion conditions at the highest concentrations. Internalization analysis are ongoing. The project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 965196. Also see: https://micro2024.sciencesconf.org/558853/document