Micro/Nanoplastics Drive Amyloid‑β Colloidal and Oxidative Reorganization: A Real-World Contaminant Stressor

Environmental micro- and nanoplastics (MNPs) are increasingly recognized as biologically active particulate contaminants, yet their influence on amyloid-beta (Aβ) structural behavior and oxidative chemistry remains insufficiently defined. In this study, consumer-derived polyethylene terephthalate (PET) MNPs were used as a real-world contaminant model to evaluate time-dependent interactions with Aβ at subagglomeration peptide concentrations. Aβ solutions (0.1-1000 pg/mL) were exposed to PET MNPs (10, 40, and 100 μg/mL) for 1-144 h and assessed using fluorescence spectroscopy, apparent Stern-Volmer-type analysis, turbidity, Rayleigh light scattering (RLS), zeta potential, dynamic light scattering (DLS), FTIR, Raman spectroscopy, UV-Vis slope factor analysis, cell-free dithiothreitol oxidative potential, and molecular docking. PET MNP exposure produced wavelength-, concentration-, dose-, and time-dependent fluorescence modulation. Apparent Stern-Volmer slopes were small and bidirectional rather than uniformly positive, indicating nonclassical fluorescence behavior rather than a single dynamic quenching or binding mechanism. Turbidity and RLS increased mainly during early exposure, suggesting formation of light-scattering Aβ-MNP-associated assemblies, whereas prolonged exposure was associated with reduced scattering signals, nanoscale DLS profiles, and fluctuating zeta potentials, indicating a change in the abundance or scattering behavior of species remaining in the measured postfiltration phase. The available data cannot distinguish interfacial reorganization from microsedimentation, localized precipitation, nonspecific vessel-wall adsorption, filtration-sensitive loss, or altered scattering efficiency. FTIR and Raman results indicated changes in Amide II/III, C-O/C-H, and aromatic-residue-associated regions, while DTT results showed modest but measurable enhancement of cell-free oxidative potential. Docking simulations suggested possible PET-Aβ contacts involving aggregation-prone aromatic and polar residues, providing mechanistic support for interfacial association. Overall, PET MNPs are best interpreted as dynamic modulators of Aβ colloidal, structural, and oxidative behavior, initially favoring Aβ-MNP association and followed by later changes in the nanoscale, spectroscopic, and optical characteristics of the measured phase, without establishing a specific aggregate morphology or late-stage mechanism.