Toxicological Profiling of Highly Purified Single‐Walled Carbon Nanotubes with Different Lengths in the Rodent Lung and Escherichia Coli

Carbon nanotubes (CNTs) exhibit a number of physicochemical properties that contribute to adverse biological outcomes. However, it is difficult to define the independent contribution of individual properties without purified materials. We prepared a library of highly purified SWCNTs of different lengths from the same base material by density gradient ultracentrifugation, designated as short (318 nm), medium (789 nm), and long (1215 nm) SWCNTs. In vitro screening showed length-dependent IL-1β production, in order of long > medium> short. However, there were no differences in transforming growth factor (TGF-β1) production in BEAS-2B cells. Oropharyngeal aspiration showed that all the SWCNTs induced pro-fibrogenic effects in mouse lung at 21 days post-exposure but there were no differences between tube lengths. In contrast, these SWCNTs demonstrated length-dependent antibacterial effects on E. coli, with long SWCNT exerting stronger effects than the medium or short tubes. These effects were reduced by Pluronic F108 coating or supplementing with glucose. Our data show that length-dependent effects on pro-inflammatory response in macrophage cell line and antibacterial effects, but not on collagen deposition in the lung. These data demonstrate that over the length scale tested, the biological response to highly purified SWCNTs is dependent on the complexity of the nano/bio interface.