Protein Dispersant Binding on Nanotubes Studied by NMR Self-Diffusion and Cryo-TEM Techniques

Abstract

Carbon nanotubes can be dispersed by a variety of molecules. We investigate the dynamics of protein-assisted carbon nanotube dispersion in water. We find that in equilibrium, only a small fraction of the dispersants is indeed adsorbed to the nanotube surface, while there is a fast exchange process between the adsorbed and free protein molecules. Self-diffusion NMR spectroscopy in combination with cryo-transmission electron microscopy imaging are employed.

Polymer Binding to Carbon Nanotubes in Aqueous Dispersions: Residence Time on the Nanotube Surface As Obtained by NMR Diffusometry

“…We obtain A F−127 ≈ 40 nm 2 which is similar to the value obtained (albeit which a much larger experimental error 19 ) for BSA. Here we note that SWCNTs prepared by other methods (e.g., SWNT forest) seem to exhibit other (ca.…”

“…This is in contrast to what has been observed for the association of BSA to CNT. 19 On the other hand, the lack of fast exchange was also concluded for another nonionic surfactant Tween80 bound to SWCNT. 20 That dispersant is also characterized by having a polyethyleneoxide polar head.…”

“…We also observe that the exchange between bound and free states is slower for F-127 than for BSA. 19 For the protein, a partial unfolding of the peptide was assumed for it to be able to bind to the CNT surface. A short lifetime of the partially unfolded state may limit the residence time of BSA.…”

Tunable Carbon Nanotube/Protein Core‐Shell Nanoparticles with NIR‐ and Enzymatic‐Responsive Cytotoxicity

“…The efficiency of protein binding and surface coverage depends strongly on the protein structures and conformations,10 the NT diameter, and the surface chemistry 8. It has also been suggested that a fast exchange process between adsorbed proteins and free unattached protein molecules exists 9. The equilibrium between adsorbed proteins on single‐walled nanotubes (SWNTs) with free proteins in solution was confirmed by Karajanagi et al,11 and was further observed in NT dispersions assisted by peptides12 and surfactants 13.…”

“…However, by investigating the dynamics of protein‐assisted NT dispersions in water, Frise et al found that protein molecules typically cover only a very small fraction of the NT surface 9. The efficiency of protein binding and surface coverage depends strongly on the protein structures and conformations,10 the NT diameter, and the surface chemistry 8.…”