Investigations of the molecular interactions between nisoldipine and human serum albumin in vitro using multi-spectroscopy, electrochemistry and docking studies

Nisoldipine represents a compound with diverse pharmacological activities. The interaction between nisoldipine and human serum albumin (HSA) was investigated using various methods, including UV–vis, three-dimensional fluorescence, synchronous fluorescence, electrochemical methods and molecular docking. The decreased quenching constant upon increasing temperatures and UV–vis absorption difference spectrum revealed that there was a static quenching mechanism rather than a dynamic quenching mechanism in the interaction of nisoldipine with human serum albumin. The thermodynamic parameters demonstrated that the binding of nisoldipine to human serum albumin was spontaneous and hydrogen bonding, hydrophobic interactions as well as electrostatic interactions played major roles in the binding process. The binding distance was 2.31 nm, indicating the presence of fluorescence energy transfer. Site marker competitive experiments and molecular docking demonstrated that the binding site of nisoldipine in human serum albumin was site I (subdomain IIA). In addition, three-dimensional fluorescence as well as synchronous fluorescence spectra suggested conformational changes of HSA due to the interaction with nisoldipine.