Abstract
Aims: The stability of solutions of fullerene C-60 with human serum albumin (C-60/HSA) has not been studied in detail. In this study, we report on the preparation of stable C-60/HSA solutions that are formed via the formation of C-60/HP-beta-CyD nanoparticles, i.e. by transferring C-60 molecules from HP-beta-CyD to HSA molecules, and an investigation of the reactive oxygen species on the behavior of the resulting C-60/HSA.
Main methods: Structural and functional properties were examined by spectroscopic techniques, including circular dichroism (CD), fluorescent spectra (FI), and electron spin resonance spin-trapping method, and by cell viability test using A549 cells.
Key finding: Aqueous C-60/HSA solutions with a small distribution size, excellent dispersion stability and a high dispersion concentration were obtained without the use of organic solvents. CD and FI spectra indicated that the HSA had undergone structural changes as the result of C-60/HSA formation. Binding experiments indicated that C-60/HSA had increased Site I and Site II-ligand binding capabilities. The HSA, in the form of C-60/HSA was, therefore, conformationally altered, and its binding capabilities were enhanced. Radical scavenging studies using the 1,1'-diphenyl-2-picrylhydrazyl radical showed that C-60/HSA had an increased antioxidant activity, compared to HSA alone. Further, C-60/HSA efficiently generated not only superoxide anion radicals O-2(center dot-) but also singlet oxygen O-1(2) through photoirradiation. C-60/HSA showed cell toxicity characteristics after light irradiation, but no toxicity was observed in the absence of irradiation.
Significance: C-60/HSA not only has an excellent stability and antioxidant activity, but also has substantial phototoxicity properties. It thus appears that HSA can be used as a carrier of C-60 in drug delivery systems for photodynamic therapy. (C) 2013 Elsevier Inc. All rights reserved.