Controlled dispersion and purification of protein-carbon nanotube conjugates using guanidine hydrochloride.

For the development of biofunctional carbon nanotubes for biosensors, drug carriers, and nanobiocatalysts, their aggregation and biofouling in aqueous solutions are crucial problems because this behavior leads to a reduction of their excellent optical and electrical properties and nanoscale size effects. This paper presents a new method for enhancing the dispersibility of protein-carbon nanotube conjugates and for exfoliating the protein from the carbon nanotube sidewalls through controlling the concentration of guanidine hydrochloride (Gdn·HCl) in the solution. In medium concentrations (2-3 M) of Gdn·HCl, the dispersibility of protein-carbon nanotube conjugates was found to be substantially increased without denaturation or aggregation of the proteins.