“O-PTIR combines the molecular specificity of infrared (IR) absorption with the spatial resolution of visible light, overcoming the diffraction limits of conventional IR techniques to achieve sub-micron resolution (~500 nm).”
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Reporting in Environmental Science: Nano, researchers at Lund University, Sweden investigate whether polystyrene (PS) nanoplastics influence intracellular amyloid protein aggregation in neuronal cells — a question central to understanding the molecular link between environmental plastic pollution and Alzheimer’s Disease (AD). While micro- and nanoplastics (MNPs) have been detected in human brain tissue, the specific mechanisms by which they may drive neurodegeneration had remained undefined. Critically, the study identifies a significant blind spot in current environmental risk assessments: nanoplastic exposure promotes pathological protein misfolding at sub-lethal doses where standard cytotoxicity assays show no alarm.
To characterize the interaction between PS and amyloid-β (Aβ), the authors employed a multi-modal approach including fluorescence microscopy, transmission and scanning electron microscopy (TEM/SEM), and small-angle X-ray scattering (SAXS). Co-incubation of recombinant Aβ(1-42) with PS resulted in the formation of larger, more complex aggregated structures compared to Aβ alone, with SAXS confirming an increase in the radius of gyration from 106.7 ± 2.7 nm (PS alone) to 112.1 ± 3.9 nm (PS + Aβ). Immunofluorescence analysis in N2Aswe neuronal cells further showed that PS co-localized with lysosomal marker Lamp1, and that cells exposed to PS exhibited sustained lysosomal activity and increased Caspase-3 levels over 48 hours, consistent with apoptotic signaling.
High-resolution O-PTIR hyperspectral mapping of N2Aswe cells directly revealed that PS exposure induced a marked increase in the 1630 cm⁻¹ β-sheet signal alongside a reduction in antiparallel and unordered β-sheet structures — indicating a reorganization of protein conformation toward more aggregated, fibrillar β-sheet forms. Analysis of over 4,000 individual spectra using Principal Component Analysis (PCA) confirmed a clear and systematic separation between PS-exposed and control cells, with the wavenumbers contributing most strongly to group separation being those associated with β-sheet structural elements.
O-PTIR spectroscopy provided the critical molecular-level evidence in this study, confirming the spatial co-localization of PS and Aβ(1-42) within the same aggregate area and resolving subcellular structural changes in protein conformation at sub-diffraction resolution (~500 nm). This capability — bridging bulk biophysical observations with spatially resolved intracellular structural mapping — revealed mechanistic detail that conventional infrared techniques and bulk assays cannot achieve. The authors conclude that the nanoplastic surface acts as a catalytic scaffold for amyloid aggregation, identifying a plausible molecular pathway by which environmental plastic pollution contributes to the risk and progression of neurodegenerative disease.
Authors:
Iran Augusto Neves da Silva, Agnes Paulus, Valeriia Skoryk, Kar Yan Su, Fátima Herranz-Trillo, and Oxana Klementieva
Lund University, Sweden
