Binding of human IgG to single-walled carbon nanotubes accelerated myeloperoxidase-mediated degradation in activated neutrophils

The binding of protein to carboxylated single-walled carbon nanotubes (SWCNTs) was believed to play an important role in the biological effects of nanotubes. However, the effects of protein-SWCNTs interactions on the oxidative degradation of nanotubes were not stressed enough. Here, we investigated the binding of human immunoglobulin G (IgG) to SWCNTs, and found that the preferred binding site was located in the Fc region of IgG. The hydrophobic and electrostatic interactions might be the crucial factors in stabilizing the binding of SWCNTs with IgG. Through the competitive binding of IgG and myeloperoxidase (MPO) to nanotube surfaces, the binding of IgG could impair MPO-induced SWCNTs biodegradation in vitro. However, both SWCNTs and IgG-SWCNTs were significantly degraded in zymosan-stimulated neutrophils, and the degradation degree was more for IgG-SWCNTs. These results suggest that the binding of IgG may be an important determinant for MPO-mediated SWCNTs biodegradation in activated human inflammatory cells.