Combined spectroscopy and cyclic voltammetry investigates the interaction between [(η6-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin

Abstract

In this article, the interaction between [(η⁶-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin (HSA) was investigated systematically under physiological conditions by using some spectroscopic methods (UV-vis absorption spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, CD spectroscopy), mass spectroscopy and cyclic voltammetry. The experimental results indicated that this anticancer drug could quench the intrinsic fluorescence of HSA through static quenching mechanism. The Stern–Volmer quenching model has been successfully applied, and the Stern–Volmer quenching constants together with the modified Stern–Volmer quenching constants at different temperatures were also calculated. The corresponding thermodynamic parameters ΔH, ΔG and ΔS were also calculated. The binding of this anticancer drug and HSA resulted in the formation of drug–HSA complex, and the electrostatic interaction played a major role in the complex stabilization. The distance r between the donor (HSA) and the acceptor (drug) was obtained through fluorescence resonance energy transfer theory. Competitive experiments indicated that the binding site of this anticancer drug to HSA was located at site I. The results of synchronous fluorescence spectra, three-dimensional fluorescence spectra, FT-IR spectra and CD spectra indicated that the microenvironment and the conformation of HSA were changed noticeably due to the presence of this anticancer drug. The results of mass spectra and cyclic voltammetry further confirmed the interaction between HSA and this anticancer drug. These results indicated that the biological activity of HSA was dramatically affected by the [(η⁶-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug.