Molecular insights into the resistance of phospholipid heads to the membrane penetration of graphene nanosheets.

The interaction between nanomaterials and phospholipid membranes underlies many emerging biological applications. To what extent hydrophilic phospholipid heads shield the bilayer from the integration of hydrophobic nanomaterials remains unclear, and this open question contains important insights for understanding biological membrane physics. Here, we present molecular dynamics (MD) simulations to clarify the resistance of phospholipid heads to the membrane penetration of graphene nanosheets. With 130 simulation trials, we observed that ∼22% graphene nanosheets penetrate the POPC bilayer. Sharp corners of the nanosheets should have a lower energy barrier than nanosheet edges, but interestingly, the membrane penetration mainly starts from the edge-approaching orientation. We thoroughly analyzed the pentration pathway and propulsion, indicating that the membrane penetration of graphene nanosheets is dominated by the joint effects of nanosheet edges and corners. Furthermore, the molecular origin of the resistance is clarified by evaluating the bilayers of different phospholipids, which successfully correlates the penetration resistance of phospholipid heads with the correlated motions of neighboring phospholipids for the first time. These results are expected to inspire future studies on the dynamic behavior of phospholipids, bio-nano interfaces, and design of biological nanomaterials.