Fibrinogen binding-dependent cytotoxicity and degradation of single-walled carbon nanotubes

Carbon nanotubes are widely used in the area of biomedicine, and the binding of protein to carbon nanotubes are believed to play an important role in the potential cytotoxicity of nanomaterials. In this work, we investigated the effects of human fibrinogen-surface coatings on the biodegradation and cytotoxicity of carboxylated single-walled carbon nanotubes (SWCNTs). It was found that the electrostatic and π-π stacking interactions might be the crucial factors in stabilizing the binding of fibrinogen with SWCNTs by both theoretical and experimental approaches. Although naked SWCNTs could induce significant toxicity to macrophages, coating these nanomaterials with fibrinogen could greatly attenuate their toxicity. On the other hand, although SWCNTs and fibrinogen-preincubated SWCNTs were resistant to biodegradation in resting macrophages, both naked and fibrinogen-coated SWCNTs could be effectively and similarly degraded through myeloperoxidase (MPO) and peroxynitrite (ONOO^-)-dependent pathways in activated macrophages, where NADPH oxidase played a determinant role in the biodegradation process. Importantly, degraded SWCNTs by ONOO^- pathway in vitro induced less cytotoxicity than non-degraded nanotubes. These findings demonstrated that the binding of fibrinogen to SWCNTs could reduce cytotoxicity without affecting the biodegradation of nanotubes in activated inflammatory cells, providing a new route to design the safer nanotubes for future biomedical applications.