Surface-functionalized polystyrene nanoparticles alter transmembrane potential via ion-selective pores maintaining global bilayer integrity

Although nanoplastics have well-known toxic effects towards the environment and living organisms, their molecular toxicity mechanisms, including the nature of nanoparticle-cell membrane interactions, are still under investigation. We employ dynamic light scattering (DLS), quartz crystal microbalance with dissipation monitoring (QCM-D) and electrophysiology to investigate the interaction between polystyrene nanoparticles (PS NPs) and phospholipid membranes. Our results show that PS NPs adsorb onto lipid bilayers creating soft inhomogeneous films that include disordered defects. PS NPs form an integral part of the generated channels so that the surface functionalization and charge of the NP determine the pore conductive properties. The large difference in size between nanoparticle diameter and lipid bilayer thickness (∼60 nm vs ∼5 nm) suggests a particular and complex lipid-NP assembly that is able to maintain overall membrane integrity. In view of that, we suggest that nanoparticle-induced toxicity in cells could operate in more subtle ways than membrane disintegration, such as inducing lipid reorganization and transmembrane ionic fluxes that disrupt the membrane potential.