Interactions of ultra-fine polystyrene nanoparticles with lung surfactant monolayers and bilayers: A combined...

Airborne nanoplastics represent an emerging threat to respiratory health, yet their interactions with lung surfactant remain poorly characterized. Here, we combine atomistic molecular dynamics simulations and experiments to investigate the effects of ultra-fine polystyrene (PS) nanoparticles on lung surfactant monolayers and bilayers, the structures that together reflect the complex architecture of real lung surfactant. Simulations showed that polystyrene nanoparticles embedded in the hydrophobic core of the surfactant, increase lipid chain order and disrupt its fluidity, with effects dependent on the polymer length. In particular, lipid sorting occurs near polystyrene, including cholesterol exclusion and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol) enrichment. Experimental measurements, including surface pressure, fluorescence spectroscopy, and Brewster angle microscopy, confirmed the PS-induced structural changes. The results indicate that polystyrene nanoparticles may initially accumulate in the alveolar monolayer and subsequently migrate into the underlying bilayer reservoirs, promoting deeper tissue penetration. These findings highlight the potential of nanoplastics to impair surfactant function and affect lung health.