Interaction of carboxylated single-walled carbon nanotubes with bovine serum albumin

Carboxylated single-walled carbon nanotubes (c-SWNTs) were synthesized prosperously in order to improve dispersion of raw carbon nanotubes. Then, bovine serum albumin (BSA) was used as the template protein to study the biocompatibility of c-SWNTs by UV–Vis, fluorescence and circular dichroism (CD) spectroscopic methods at the molecular level. Results from fluorescence spectrum showed obvious decreases in fluorescence intensity of BSA induced by c-SWNTs, indicating the occurrence of interaction between BSA and c-SWNTs. Static quenching effect of c-SWNTs was verified by linear Stern–Volmer plots and KSV values. Thermodynamic parameters at different temperatures demonstrated that the interaction between c-SWNTs and BSA was mainly favored by hydrophobic force. In addition, Na+ interfered with the quenching effect of c-SWNTs, which revealed that electrostatic force played a role in binding roles of BSA to c-SWNTs simultaneously. The results of UV and synchronous fluorescence spectrum validated that hydrophobicity of amino acid residues expressly increased with the addition of c-SWNTs. The content of α-helix structure in BSA decreased by 14.06% with c-SWNTs viewed from CD spectrum. Effect of SWNTs on the conformation of BSA could be controlled by the surface chemistry of SWNTs.

The interaction between carboxylated single-walled carbon nanotubes (c-SWNTs) and bovine serum albumin (BSA) was studied by spectroscopic methods. Quenching mechanism and binding constants were acquired. Changes in the structure of BSA were inspected by synchronous fluorescence spectra, UV–Vis spectra and CD spectrum.Figure optionsDownload as PowerPoint slideHighlights
► The interaction between c-SWNTs and BSA was investigated by multiple spectroscopic methods.
► Quenching mechanism was static quenching.
► Changes in structure of BSA were inspected by synchronous fluorescence, UV–Vis and CD spectrum.