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 (β-CD)2/C60 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 (β-CD)2/C60 was the result of the formation of (β-CD)2/C60–BSA complex and that the mechanism of quenching might be a static quenching procedure. The binding constants Ka, the number of binding sites n, and the corresponding thermodynamic parameters ΔG, ΔH, and ΔS 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 (β-CD)2/C60–BSA association. The circular dichroism spectra show the conformation change of the effect of (β-CD)2/C60 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 (β-CD)2/C60 to BSA primarily took place in site I. The distance r between donor (BSA) and acceptor ((β-CD)2/C60) 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.