Characterization and application of hydrophobin-dispersed multi-walled carbon nanotubes

Hydrophobins are amphiphilic proteins with high surface activity, which can readily adsorb on interfacial surfaces, especially on hydrophobic surfaces. Based on their properties, we used the class I hydrophobin isolated from Grifola frondosa (HGFI) to disperse multi-walled carbon nanotubes (MWCNTs) in water. MWCNTs could be effectively dispersed by 30-min sonication in a 0.1 mg/ml HGFI solution. Optical absorption and transmission electron microscopy provide evidence for individually stable dispersed MWCNTs. X-ray photoelectron, Fourier transform infrared, and Raman spectroscopies and thermogravimetric analysis suggest that HGFI can non-covalently bind to MWCNTs through hydrophobic interaction, rendering them hydrophilic. A quartz crystal microbalance and immunological sandwich assay were used to demonstrate that the HGFI-coated MWCNTs can be used to immobilize human immunoglobulin G in solution.