Surface patterning of single-walled carbon nanotubes enhances their perturbation on a pulmonary surfactant monolayer: frustrated translocation and bilayer vesiculation

Abstract

The pulmonary surfactant monolayer (PSM) is a complex material lining the air–water interface of lung alveoli to avoid its collapse by reducing surface tension. Once external particles are inhaled and captured by the PSM, this property might be perturbed to induce inhalation toxicity. However, relatively little is known regarding the detailed interaction between inhaled particles and the PSM. Here, by applying the coarse-grained molecular dynamics simulation method, we probe how inhaled single-walled carbon nanotubes (SWCNTs) interact with the PSM. For pristine SWCNTs, they are found to insert into or be wrapped by the PSM, depending on the tube size and the PSM tension. For hydrophilic tubes, they spontaneously translocate across the PSM, regardless of the tension. In contrast to SWCNTs with unique surface properties, the surface patterning of SWCNTs enhances their perturbation on the PSM. Under expansion, the PSM translocation is frustrated via inducing the ordered or disordered lipid arrangement adhering to the patterned tube surface. Under compression, the lipid rearrangements further self-adjust and grow into bilayers, which protrude along the tube surface and finally develop into vesicles. The stripe width and stripe orientation, among other factors, are found to be the most important factors that determine whether and how the vesiculation takes place.