Formation of aggregates, icosahedral structures and percolation clusters of fullerenes in lipids bilayers: The key role of lipid saturation.

Carbon nanoparticles (CNPs) are attractive materials for a great number of applications but there are serious concerns regarding their influence on health and environment. Here, our focus is on the behavior of fullerenes in lipid bilayers with varying lipid saturations, chain lengths and fullerene concentrations using coarse-grained molecular dynamics (CG-MD) simulations. Our findings show that the lipid saturation level is a key factor in determining how fullerenes behave and where the fullerenes are located inside a lipid bilayer. In saturated and monounsaturated bilayers fullerenes aggregated and formed clusters with some of them showing icosahedral structures. In polyunsaturated lipid bilayers, no such structures were observed: In polyunsaturated lipid bilayers at high fullerene concentrations, connected percolation-like networks of fullerenes spanning the whole lateral area emerged at the bilayer center. In other systems only separate isolated aggregates were observed. The effects of fullerenes on lipid bilayers depend strongly on fullerene aggregation. When fullerenes aggregate, their interactions with the lipid tails change.