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Effects of microplastics on mammalian cells: A single-live-cell screening approach via FTIR microspectroscopy with ZnS solid immersion lenses
Summary
Scientists tested how tiny plastic particles (microplastics) affect two types of human and animal cells using a new light-based scanning technique. They found that even plastic particles too small to visibly harm or kill cells still caused measurable changes inside them—meaning microplastics may be quietly altering cell behavior even when cells appear "fine" on the surface. This matters because it suggests we may be underestimating microplastic exposure risks by only checking whether cells survive, rather than looking for subtler internal changes.
Microplastics (MPs) are persistent pollutants that are of growing concern to animals and humans. Morphological changes, oxidative stress, cyto- and genotoxicity are just a few effects reported in cells. Due to the large variety in MPs, there is an urgent need to find new analytical methods that can quickly identify affected cellular components and guide subsequent targeted analysis. Here, we propose Fourier-transform infrared microspectroscopy (µFTIR) with ZnS hemisphere solid immersion lenses as a screening tool for measuring the impact of MP exposure in single living cells. Macrophage-like (J774A.1) and lung epithelial (A549) cells were exposed to polystyrene (PS) beads of varying sizes (100 nm – 1 µm) and surface functionalizations (aminated, carboxylated, unfunctionalized) to demonstrate the approach. µFTIR spectra were collected from cells, and principal component analysis (PCA) was used to detect changes following exposure. In J774A.1 cells, 1 µm aminated and carboxylated MPs decreased cell viability and significant spectral changes were observed, across all PS types, including non-toxic ones. In A549 cells, no strong decrease in cell viability was detected, but PCA results showed significant spectral changes following exposure to 500 nm and 100 nm PS particles. Additionally, APS also altered specific cellular biomarkers, suggesting interaction between the MPs and cells due to the surface functionalization. Comparisons with cellular effects of MNPs described in literature (such as phagocytosis or endocytosis mechanisms) are in accordance with the spectral changes observed. These results demonstrate that single-live-cell µFTIR is a fast and cost-effective screening tool to detect biochemical changes in cells, find potential biomarkers, and contribute to understanding the cellular metabolism.