Functionalization of carbon nanotubes with bovine serum albumin in homogeneous aqueous solution

Single-walled (SWNTs) and multiple-walled (MWNTs) carbon nanotubes were solubilized via the esterification of nanotube-bound carboxylic acids by oligomeric polyethylene glycol compounds. The water-soluble samples were used as starting materials in reactions with bovine serum albumin (BSA) protein in ambient aqueous solutions. The reaction conditions were designed for thermodynamically favorable transformation from ester to amide linkages, yielding SWNT-BSA and MWNT-BSA conjugates. The results show that the use of soluble starting nanotube materials in an indirect functionalization method represents a valuable approach to the biomodification of carbon nanotubes.