Scrutiny the interaction of irinotecan with human serum albumin by multi-spectroscopic techniques: identification of possible binding site of the drug

Irinotecan is considered to be one of the most effective anticancer drug for colorectal cancer therapy. In this study, the role of human serum albumin (HSA), as safe drug delivery systems, in binding of irinotecan were surveyed. The interactions between irinotecan and HSA have been studied by fluorimetry, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. By the analysis of fluorescence spectra, it was observed that irinotecan has an ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. According to Stern–Volmer equation, the binding parameters between irinotecan and HSA were determined. The enthalpy change (ΔH ◦) and entropy change (ΔS ◦) were calculated to be -۲۹.۸۲kJ mol−۱ and -۲۲.۱۵J mol−۱ K−۱, indicating that the hydrogen bonds and van der Waals interactions played a dominant role in the binding. The distance, r, between donor (HSA) and acceptor (irinotecan) was obtained according to the forster’s theory of non-radiation energy transfer. Changes in the CD spectra and FT-IR spectra were observed upon drug binding. The quantitative analysis of CD spectra represented that irinotecan induced alterations in the secondary structure of the protein via increasing in the content of α-helical structure of protein.

کلیدواژه ها:

Fluorescence quenching ، Stern–Volmer ، Circular Dichroism (CD) ، Fourier transform infrared (FT-IR)