(473b) Membrane-Mediated Interactions Between Carbon Nanotubes Embedded in a Lipid Bilayer

Understanding behavior of nanoparticles embedded in lipid membranes is important for development of novel biomedical devices and assessment of potentially harmful effects of nanomaterials on living cells. The current work is focused on theoretical and computational investigation of interactions between nanoparticles embedded into a lipid bilayer. In this talk we present results of our coarse-grained molecular dynamics (MD) simulations of carbon nanotubes (CNTs) in a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer. There are no long-range interactions between the considered nanoparticles in solution. However, embedding them into a bilayer may give rise to long-range membrane-mediated interactions. Indeed, our simulations indicate presence of long-range interactions between CNTs embedded in a DPPC bilayer.

One possible cause of these interactions is associated with a stress induced by the nanoparticles in the membrane interior. In order to minimize this stress, the nanoparticles would either repel or attract each other, depending on the specifics of their interactions with the surrounding lipids. However, our simulations rule this mechanism out. We observe that perturbations of the membrane structure and stress profile induced by a single CNT residing in the hydrophobic core of the membrane are very short-ranged.

Therefore, we investigate an alternative mechanism of the membrane-mediated interactions between CNTs. This alternative mechanism is associated with effect of the CNTs on the membrane fluctuations. CNTs embedded in a membrane impose a significant constraint on the membrane undulations. This, in turn, creates a force acting between the nanotubes. This effect was predicted theoretically almost two decades ago [Golestanian et al., Phys. Rev. E, 54,6725 (1996)]. However, to the best of our knowledge, it has not been observed in MD simulations or experiments for nanoparticles embedded into a lipid membrane. In the current talk, we present computational evidence for this effect and perform a quantitative comparison between the theory and the MD simulations.