Representative secondary PET micro and nanoplastics via ethylene glycol fragmentation (EGF): Physicochemical and immuno-toxicological properties

Polyethylene terephthalate (PET) micro and nanoplastics (MNPs) are widely dispersed pollutants with significant environmental and health implications. Current preparation methods of representative secondary PET MNPs are limited. In this study, we developed a scalable, standardized ethylene glycol fragmentation (EGF)-based method to generate PET MNPs from three distinct plastic sources (commercial pellets, bottle-grade, and film-grade). PET samples were depolymerized using ethylene glycol and sodium carbonate under controlled thermal conditions. Two fractions (Ea and Eb) were collected and analyzed, fraction Ea consisted of covalently fragmented BHET-oligomer-based nanoplastics (∼200–375 nm), while fraction Eb comprised non-covalent BHET-based larger microplastic aggregates (∼1.2–1.9 µm). EGF method turned out to be more efficient than published trifluoroacetic acid (TFA) method giving mainly BHET-oligomer-based nanoplastics with higher yields and improved MNPs size control. MNPs generated by EGF showed a size range between 200 and 375 nm with good colloidal stability. In vitro assays showed that both type (covalent and non-covalent) of PET nanoplastics reduced THP-1 macrophage viability in a dose-dependent manner which was associated with IL-1β release, and triggered an M1-polarizing cytokine profile, thus indicating potential toxicity and proinflammatory activity. Our EGF-based synthesis platform enables controlled production of PET MNPs with source-dependent characteristics and biologically relevant behavior. These standardized MNPs and the THP-1 macrophages biosensor model provide useful tools for environmental toxicology research.