Protein adsorption on functionalized multiwalled carbon nanotubes with amino-cyclodextrin

A novel amino-cyclodextrin was synthesized, and it was covalently attached to multiwalled carbon nanotubes (MWNTs). The functionalized MWNTs (f-MWNTs) have very good aqueous dispersibility. Bovine serum albumin (BSA) was adsorbed onto f-MWNTs through noncovalent interactions, including the hydrophobic interaction of the residues of BSA with the wall of MWNT and the guest-host interaction of the residues with the cyclodextrin (CD) moieties of f-MWNTs. The ultraviolet-visible (UV-vis) absorption of the f-MWNT-BSA hybrid was measured with UV-vis spectrometer, and the absorbance can be described well with the Beer-Lambert law. The X-ray diffraction patterns have indicated that the crystalline form of BSA has been changed after the adsorption of BSA on f-MWNTs. The circular dichroism spectra have shown that a high percentage of α-helical content can be retained for BSA adsorbed on f-MWNTs. The results also indicate that the change of secondary structure of BSA is mainly due to the hydrophobic interaction of the residues of BSA with the wall of f-MWNT, whereas the secondary structure is much less affected by the interaction of the CD moieties with BSA.