Blocking of carbon nanotube based nanoinjectors by lipids: a simulation study

Carbon nanotubes (CNTs) are possible nanoinjectors for the introduction of therapeutic agents into cells. To explore their interactions with a lipid bilayer membrane and to model the nanoinjection process, we used coarse-grained molecular dynamics to simulate the penetration of dipalmitoylphosphatidylcholine (DPPC) bilayers by single-walled CNTs. Lipids are extracted from a bilayer during CNT penetration and reside on both the inner and the outer tube surfaces. Lipids that interact with the CNT interior wall spread out and hence can "block" the tube. However, the degree of lipid lining of the inner surface is strongly dependent upon the tube penetration velocity, with fewer lipids extracted from the bilayer at higher rates. There is no apparent effect on bilayer integrity after CNT penetration, with the bilayer able to self-seal. Our findings reveal some of the complexities of the interactions of lipids with CNT nanoinjectors and suggest a need to further characterize the influence of, for example, CNT functionalization and cargo on lipid blocking of CNTs.