Effects of carbon nanotubes (CNTs) on structural and elastic properties of lipid bilayers are investigated by coarse grained molecular dynamics (CGMD) simulations. The investigations are performed for nanotubes of different lengths and at different nanotube concentrations. The considered structural properties of the bilayers include shapes of their dividing surfaces and lipid tilt and area. It is demonstrated that CNTs embedded in lipid membranes induce long-range perturbations of the membrane shape and lipid tilt. Inhibiting large-wavelength membrane fluctuations (e.g., by confining a system to a small simulation box), leads to a qualitatively different response of the membrane to the CNT-induced perturbations. Elastic properties of the membranes containing CNTs are assessed by measurement of the spectral intensity of the membrane undulations. The spectral intensity increases with addition of nanotubes, which indicates softening of the membrane. This effect becomes more prominent with increasing the CNT length and concentration.
Keywords: molecular dynamics simulations, coarse-grained molecular model, biomembranes, carbon nanotubes, nanotoxicity, membrane deformation, bending modulus, lipid tilt, membrane-mediated interactions, fluctuations