Spectroscopic and Computational Analysis of Protein Binding on Copper Nanoparticles: an Insight into Ligand and Nanocarrier Interaction

The interaction of copper nanoparticles (CuNP) with bovine serum albumin (BSA) under physiological conditions was studied using spectroscopic techniques. The analysis of the adsorption of BSA by CuNP indicated that it followed the Langmuir adsorption isotherm and a pseudo second-order expression. The quenching of BSA intrinsic fluorescence was observed upon its binding to CuNP. The calculation of a modified Stern–Volmer constant revealed that the binding of CuNP to BSA complies with the static mechanism. The binding constant, the binding site, and the thermodynamic parameters of the BSA–CuNP interaction were evaluated using fluorescence quenching data at 298, 310, and 333 K. The binding constant decreased with increase in temperature, and the binding of BSA to CuNP involved one single site. Negative free energy (ΔG), positive enthalpy (ΔH), and entropy change (ΔS) calculations suggested that the binding of BSA to CuNP was spontaneous and hydrophobic forces played a key role in stabilizing the complex. An evaluation of the Hill coefficient indicated negative cooperativity. Minor conformational changes were observed in the circular dichroism spectra when BSA was bound to CuNP.