Adhesion and Dimerization of Sphero-Cylindrical Nanoparticles on Lipid Membranes

We present a numerical investigation of the interaction of sphero-cylindrical nanoparticles (SCNP) with planar lipid bilayers, using molecular dynamics simulations of an implicit-solvent model. The SCNPs are generated using a bottom-up approach, where the hemispherical ends of the SCNPs are constructed as two icosahedra halves that are connected by a hexagonally tessellated cylinder.  We found that at relatively low adhesion strength, the SCNP adheres such that its principal axis is parallel to the membrane (parallel mode). At relatively high adhesion strength, the SCNP adheres such that its principal axis is perpendicular to the bilayer (normal mode). The transition adhesion strength between these two modes is found to decrease with increasing the diameter of the SCNP, for a fixed aspect ratio, or increasing its aspect ratio, for a fixed diameter. We also investigated the modes of adhesion of two SCNPs on the bilayer and found that, at weak adhesion strength, the SCNPS are in the parallel mode and apart from each other. However, as the adhesion strength is increased, the SCNPs dimerize into a sequence of modes including in-plane dimers, V-shape dimers, and two tubular dimer states.