Non-specific adsorption of streptavidin on single walled carbon nanotubes

We report the semi quantitative determination of the non specific adsorption of streptavidin onto raw and functionalized single walled nanotubes (SWNTs) using different approaches. SWNTs were covalently functionalized with carboxylated groups, amine groups and polyethylene glycol (PEG), and non-covalently functionalized with polyethylene glycol, Pluronic F-127 and Tween20. SWNTs covalent functionalization has been carried out through oxidation and acyl chloride formation. The non covalent functionalization was carried out by SWNTs dispersion in aqueous solution of the corresponding surfactant or polymer. A colorimetric test based on the horseradish peroxidase-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) was used to determine the presence of streptavidin onto the SWNTs. Streptavidin adsorption was also carried out by covalent bonding of biotin to SWNTs, to compare the specific and non-specific adsorption. Non specific streptavidin adsorption has been observed on pristine and all types of functionalized SWNTs tested. This adsorption of streptavidin on the surface of the SWNTs could be used to link other biomolecules to the nanotubes, using the high specific bonding between biotin and streptavidin.