Carbon Nanotubes Translocation through a Lipid Membrane and Transporting Small Hydrophobic and Hydrophilic Molecules

Abstract

Carbon nanotubes (CNTs) are extensively adopted in the applications of biotechnology and biomedicine. Their interactions with cell membranes are of great importance for understanding the toxicity of CNTs and the application of drug delivery. In this paper, we use atomic molecular dynamics simulations to study the permeation and orientation of pristine and functionalized CNTs in a lipid bilayer. Pristine CNT (PCNT) can readily permeate into the membrane and reside in the hydrophobic region without specific orientation. The insertion of PCNTs into the lipid bilayer is robust and independent on the lengths of PCNTs. Due to the presence of hydroxyl groups on both ends of the functionalized CNT (FCNT), FCNT prefers to stand upright in the lipid bilayer center. Compared with PCNT, FCNT is more suitable to be a bridge connecting the inner and outer lipid membrane. The inserted CNTs have no distinct effects on membrane structure. However, they may block the ion channels. In addition, preliminary explorations on the transport properties of CNTs show that the small hydrophobic molecule carbon dioxide can enter both PCNT and FCNT hollow channels. However, hydrophilic molecule urea is prone to penetrate the PCNT but finds it difficult to enter the FCNT. These results may provide new insights into the internalization of CNT in the lipid membrane and the transport properties of CNTs when embedded therein.

Coarse-grained modeling of polystyrene-modified CNTs and their interactions with lipid bilayers

“…75 It has been shown that hydroxyl-modified CNTs tend to be vertical to the bilayer center when the length of the CNT is shorter than the bilayer thickness. 81 However, by varying the grafting density of PSCOOH at the end of CNTs, we didn't observe a hindrance effect. But wider tilt angle distributions were observed mostly at ~10°-20° range (cf.…”

“…CNTs spontaneously diffuse into the membranes as reported elsewhere. 29,30,81 In homogeneous bilayers which consist of a single lipid component, the APL can be calculated simply by dividing the average box area into half the lipid number. However, this method is not suitable for heterogeneous bilayers containing various types of lipids of different sizes, such as CHOL.…”

Simulation of the Motion of Three Methane Molecules inside a Closed Carbon Nanotube

“…For modeling, the structure of a closed single-walled carbon nanotube was chosen, which is 348 carbon atoms 12 C, located in space so that, while remaining a surface crystal, this structure had a significant space inside, isolated by the surface of the tube from the external environment. Three model CH 4 methane molecules were placed in this space, located on the symmetry axis of the nanotube as follows.…”

The effects of molecular and nanoscopic additives on phospholipid membranes

“…At high CNT densities, lipid-mediated interactions facilitate CNT diffusion and drive CNTs to assemble into clusters of 2D hexagonal arrays spaced apart by the annular lipid shells [440]. Other simulations found that while CNTs had virtually no effect on the structural properties of the membrane they cause slight ordering in neighboring lipid tails [407].…”