Fluorescence quenching and related interactions among globular proteins (BSA and lysozyme) in presence of titanium dioxide nanoparticles

Abstract

In recent days, nanoparticles (NPs) are used in various industries, and their release in the environment is a matter of concern for both environment and living systems. It is, therefore, necessary to study the protein-NPs systems for better understanding the impacts of NPs on living organisms. In this article, the structure, optical properties, and related conformation of the globular proteins, bovine serum albumin and lysozyme, are explored in the presence of titanium dioxide nanoparticles. The interactions are analyzed by fluorescence quenching and Fourier transform infrared spectroscopy techniques. In the presence of NPs, the fluorescence quenching of the proteins is observed, and it is found that the mixture of both static and dynamic quenching is present, but the contribution from static is more than dynamic. Mostly the higher order complex formation and excited state quenching at higher NPs concentration are responsible for the fluorescence quenching. The interaction is also studied in different pH environments and depending upon the isoelectric points of the respective proteins. With fluorescence quenching, a substantial amount of red-shift of protein emission is also observed in the presence of the quencher. The change in the microenvironment of the tryptophan residues may be responsible for this type of shift. • Interaction between globular proteins and titanium oxide nanoparticles (TiO 2 NPs) is studied. • Fluorescence quenching of globular proteins (BSA and lysozyme) is observed in presence of TiO 2 NPs. • Higher order complex formation and excited state quenching play the major role in quenching. • The interaction is pH dependent and relatively more at lower pH. • Red-shift in protein emission was observed due to change in microenvironment induced by TiO 2 NPs.