Diameter dependent cell cytotoxicity of ultra-short carbon nanotubes: a molecular dynamics study

Aim and Background: The expanding industrial and biological applications of carbon nanotubes (CNTs) may lead to their exposure to human cells and subsequent probable toxicities. The mechanism and severity of such disorders can be influenced by the physicochemical properties of the CNTs. In this study, the diameter dependency and molecular mechanism of CNT cytotoxicity were investigated using molecular dynamic simulation. Methods: A total of two CNTs of similar length (5nm) and various diameters (1.5 and 4.5nm) were placed horizontally on both sides of the as-prepared bilayer membrane. The simulations were carried out using the GROMACS simulation package for 100ns. Results and discussion: Early in the simulation time, all CNTs were moved toward the membrane and attached to the headgroups of the lipid bilayer. In both narrow and thick CNTs, the one on the outside of the membrane laid on the membrane horizontally and stuck to the same side until the end of simulation. In the case of inner nanotubes, the CNTs tended to have a vertical orientation along the bilayer. The narrow CNT then penetrated through the membrane vertically and set up a transmembrane position. However, this didn’t happen to the thick CNT as some lipids entered the tube and made it horizontal again so it could attach to the membrane, likewise the outside CNTs. Conclusion: The results of this study suggest the severe cytotoxicity of narrow, ultra-short CNTs (less than 10nm in length and 2nm in diameter), as they can easily perform a nonselective channel through the biological membranes and disrupt their homeostasis.