The aggregation of carbon nanotubes deteriorates their adverse effects on pulmonary surfactant monolayer

Abstract

The wide use of carbon nanotubes (CNTs) increases the concern of their potential risks upon human exposure, especially through respiratory tract. The small size of CNTs allows them to deposit into the deep lung where they inevitably interact with pulmonary surfactant (PS) monolayer and thus could profoundly influence the biophysical function of PS monolayer. Using coarse-grained molecular dynamics simulations, we studied how the aggregation state of CNTs regulated the interactions of different sized CNTs with the PS monolayer at the air-water interface. Compared with the dispersed CNTs, the aggregated CNTs induced more severe structure disturbance of the PS monolayer at both compression and expansion stages. The increased diameter, initial attack angle, and configuration irregularity of the aggregated CNTs enhanced the lipid disturbance around the CNTs and promoted the pore formation on the PS monolayer under a high surface tension. As a result, the aggregated CNTs tended to inhibit the biophysical function of the PS monolayer and were more difficult to be cleared from the monolayer than the dispersed CNTs. Our results suggest that the aggregated CNTs, rather than the dispersed ones, should be given more weight in assessing the pneumonic nanotoxicity caused by the inhaled CNTs.