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

Abstract

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.