Spectroscopic and electrochemical studies on the interaction of an inclusion complex of β-cyclodextrin/fullerene with bovine serum albumin in aqueous solution

The potential effect of human exposure to carbonaceous nanomaterials (e.g., fullerenes or their derivatives) in the environment has become a concern. In the current study, we report the interaction of one water-soluble fullerene with bovine serum albumin using spectroscopic and electrochemical methods under aqueous solutions. The novel supramolecular inclusion complex of the water-soluble fullerene (beta-CD)(2)/C-60 was synthesized and characterized. In the mechanism discussed, the spectroscopic methods such as fluorescence quenching and ultraviolet-visible absorption, proved that the fluorescence quenching of BSA by (beta-CD)(2)/C-60 was the result of the formation of (beta-CD)(2)/C-60-BSA complex and that the mechanism of quenching might be a static quenching procedure. The binding constants K-a, the number of binding sites n, and the corresponding thermodynamic parameters Delta G, Delta H, and Delta S at different temperatures were calculated through fluorescence spectroscopy, then as an auxiliary method, the electrochemical impedance spectroscopy (EIS) experiments confirmed this conclusion. The results indicated that the electrostatic interactions play a major role in (beta-CD)(2)/C-60-BSA association. The circular dichroism spectra show the conformation change of the effect of (beta-CD)(2)/C-60 on the conformation of BSA, which was confirmed by the results of the three-dimensional fluorescence spectra. Site marker competitive experiments indicate that the binding of (beta-CD)(2)/C-60 to BSA primarily took place in site I. The distance r between donor (BSA) and acceptor ((beta-CD)(2)/C-60) was obtained according to fluorescence resonance energy transfer (FRET). This work aims to demonstrate the mechanisms of the formation of the complex between water-soluble fullerene and protein under physiological conditions, as well as the remediation for the possible unwarranted biological effects of water-soluble fullerene. (C) 2011 Elsevier B.V. All rights reserved.