Acid-treated multi-walled carbon nanotubes coated with lung surfactant protein SP-A do not induce a lung inflammatory response

The potential toxicity of carbon nanotubes (CNTs) in the lungs has not been widely investigated at the protein level. Previous studies have focused on addressing pulmonary toxicity primarily at the tissue and cellular levels. However, studying the interaction between carbon nanotubes and the lung surfactant proteins A (SP-A) and D (SP-D), two versatile and potent innate immune molecules in the lungs, can yield important information about the mechanisms involved in lung toxicity. Here, we investigated whether SP-A-coated acid treated multi-walled carbon nanotubes (MWCNT_ox) induced an inflammatory response. We found that although SP-A coated MWCNT_ox were avidly taken up by alveolar macrophages, they did not induce an inflammatory response as measured by the enhancement of levels of nitric oxide, a key marker for inflammation, when carbon nanotubes were incubated with IFN-γ primed alveolar macrophages. Thus, the binding of SP-A to carbon nanotubes does not trigger inflammation.