Perturbation of the pulmonary surfactant monolayer by single-walled carbon nanotubes: a molecular dynamics study

Abstract

Single-walled carbon nanotubes (SWCNTs) are at present synthesized on a large scale with a variety of applications. The increasing likelihood of exposure to SWCNTs, however, puts human health at a high risk. As the front line of the innate host defense system, the pulmonary surfactant monolayer (PSM) at the air-water interface of the lungs interacts with the inhaled SWCNTs, which in turn inevitably perturb the ultrastructure of the PSM and affect its biophysical functions. Here, using molecular dynamics simulations, we demonstrate how the diameter and length of SWCNTs critically regulate their interactions with the PSM. Compared to their diameters, the inhalation toxicity of SWCNTs was found to be largely affected by their lengths. Short SWCNTs with lengths comparable to the monolayer thickness are found to vertically insert into the PSM with no indication of translocation, possibly leading to accumulation of SWCNTs in the PSM with prolonged retention and increased inflammation potentials. The perturbation also comes from the forming water pores across the PSM. Longer SWCNTs are found to horizontally insert into the PSM during inspiration, and they can be wrapped by the PSM during deep expiration via a tube diameter-dependent self-rotation. The potential toxicity of longer SWCNTs comes from severe lipid depletion and the PSM-rigidifying effect. Our findings could help reveal the inhalation toxicity of SWCNTs, and pave the way for the safe use of SWCNTs as vehicles for pulmonary drug delivery.

Interfacial rheology for the assessment of potential health effects of inhaled carbon nanomaterials at variable breathing conditions

“…The analogous trend was found for NH particles at similar concentration, although these particles have much lower values of SSA and AR (≈ 400 m 2 /g, and ≤ 25, respectively). The observed effects may be caused by adsorption of LS molecules to the nanoparticles resulting in surfactant depletion, both on the interface and in the aqueous phase 22,41,42 . It should be noted though that the reported SSA values (Table 2) may be not equal to the area accessible for the adsorption of LS molecules.…”

Dependence of fullerene aggregation on lipid saturation due to a balance between entropy and enthalpy

“…In addition, it has been shown that modeling lipid systems is a particular strength of the Martini model, see e.g. Refs 46,60–62 . Another related question is how good is the Martini model for describing fullerene aggregation?…”

The asbestos-carbon nanotube analogy: An update

“…In vitro experiments show that the size and concentration of carbon nanotubes significantly change the mechanical response of the surfactant monolayer (Valle et al, 2015; Melbourne et al, 2015). Recent coarse-grained molecular dynamics simulations suggest that ultrashort SWCNTs (less than 5.5 nm) can insert into the surfactant monolayer via self-rotation (Yue et al, 2017), where the interaction morphology is determined by the length and diameter of SWCNTs and membrane tension of the surfactant (Xu et al, 2017). However, the detailed interaction between carbon nanotubes and lipid molecules could not be fully captured by coarse grained molecular dynamics simulations, and the energetics and molecular behaviors of lipids when carbon nanotubes translocate through the surfactant monolayer remain elusive.…”