Hydrophobic Biomimetic Nanoparticles drives Size-dependent Remodelling in Asymmetric Bilayers

The interactions between heterogeneous components in a biomimetic bilayer can control its physical properties such as its rigidity, local and bulk curvature and propensity towards phenomena such as membrane fission and fusion. In particular, nanoparticles (NPs) have been subjects of intense interest due to their similar scale to the bilayer width and its ability to affect local membrane structure. Generally, it is understood that hydrophobic components are energetically favoured to adsorb within the hydrophobic interior of a biomimetic bilayer. However, how such NPs interact in the presence of heterogeneous aggregates in the bilayer has been the subject of much debate. To better understand the effects of the integration of nanoscale components on heterogeneous mixed bilayer, we have simulated a series of generic hydrophobic NPs interacting with a phase-separating two-component surfactant bilayer. We find that the hydrophobic NP tends to aggregate at the phase interface, acting as a line tension relaxant i.e. a lineactant on the phase separated interface, which results in a variety of demixing behavior. We demonstrate that depending on the size of the NP, the localized softening of surfactants and the formation of a mixing gradient of surfactants can drive the a cap/bud formation around the NP, as well as the formation of a NP-micelle structure