[Spectroscopic Studies on the Interaction of Human Serum Albumin and Water-Soluble Carboxyl Carbon Nanotubes].

The interaction between nanomaterials and biological macromolecules (including protein) is the important basis of biological safety assessments of nanomaterials. In this paper, the fluorescence spectroscopy, synchronous fluorescence spectroscopy and circular dichroism spectroscopy) were used to analyze the interaction between four water-soluble carboxyl carbon nanotubes (long-SWCNTs-COOH, short-SWCNTs-COOH, DWCNTs-COOH and MWCNTs-COOH) and human serum albumin. Results showed that the four water-soluble carboxylated carbon nanotubes could quench the intrinsic fluorescence of human serum albumin at different extents. Under the same concentration, the quenching ability of four carboxylated carbon nanotubes were in the order of DWCNTs-COOH<MWCNTs-COOH<long-SWCNTs-COOH<short-SWCNTs-COOH. The synchronous fluorescence spectroscopy of human serum albumin in the absence and presence of four carbon nanotubes indicated that the binding location of MWCNTs-COOH was close to tryptophan (Trp) residue and DWCNTs-COOH was close to the tyrosine (Tyr) residues while those of long-SWCNT-COOH and short-SWCNT-COOH have no significant difference to two amino acid residues. The four water-soluble carboxyl carbon nanotubes could cause slight changes of the CD spectra of human serum albumin as well as the α-helix and β-sheet contents of human serum albumin. The above results indicate the fluorescence quenching effect of carbon nanotubes on human serum albumin was related to their structural properties. During the binding process, the human serum albumin conformation remained unchanged, and there were slight changes as to its secondary structure, but there is no obvious dose-response relationship could be observed. The mechanism was also discussed.