The effects of adsorbed benzo(a)pyrene on dynamic behavior of polystyrene nanoplastics through phospholipid membrane: A molecular simulation study

Nanoplastics (NPs) are mainly generated from the decomposition of plastic waste and industrial production, which have attracted much attention due to the potential risk for humans. The ability of NPs to penetrate different biological barriers has been proved, but the understanding of molecular details is very limited, espe-cially for organic pollutant-NP combinations. Here, we investigated the uptake process of polystyrene NPs (PSNPs) combined with benzo(a)pyrene (BAP) molecules by dipalmitoylphosphatidylcholine (DPPC) bilayers by molecular dynamics (MD) simulations. The results showed that the PSNPs can adsorb and accumulate BAP molecules in water phase and then carried BAP molecules to enter DPPC bilayers. At the same time, the adsorbed BAP promoted the penetration of PSNPs into DPPC bilayers effectively by hydrophobic effect. The process of BAP-PSNP combinations penetrating into DPPC bilayers can be summarized into four steps including adhesion on the DPPC bilayer surface, uptake by the DPPC bilayer, BAP molecules detached from the PSNPs, and the PSNPs depolymerized in the bilayer interior. Furthermore, the amount of adsorbed BAP on PSNPs affected the prop-erties of DPPC bilayers directly, especially the fluidity of DPPC bilayers that determine the physiologic function. Obviously, the combined effect of PSNPs and BAP enhanced the cytotoxicity. This work not only presented a vivid transmembrane process of BAP-PSNP combinations and revealed the nature of the effects of adsorbed benzo (a)pyrene on the dynamic behavior of polystyrene nanoplastics through phospholipid membrane, but also provide some necessary information of the potential damage for organic pollutant-nanoplastic combinations on human health at a molecular level.

Automated summary

In this study, the uptake process of polystyrene nanoparticles (PNPs) combined with benzo(a)pyrene (BAP) molecules by dipalmitoylphosphatidylcholine (DPPC) bilayers was investigated using molecular dynamics simulations. The results showed that the PNPs can adsorb and accumulate BAP molecules in water and then enter DPPC bilayers, with the adsorbed BAP promoting the penetration of PNPs by hydrophobic effect. The process of BAP-PNP combinations penetrating DPPC bilayers can be summarized into four steps: adhesion, uptake, detachment, and depolymerization. The amount of adsorbed BAP also affects the properties of DPPC bilayers and enhances cytotoxicity. This study provides insights into the transmembrane process and the effects of absorbed BAP on the behavior of polystyrene nanoparticles, as well as the potential damage to human health.