Kosmotropic and chaotropic effect of biocompatible Fe3O4 nanoparticles on egg white lysozyme; the key role of nanoparticle-protein corona formation

Accurate understanding of the interaction between different types of nanoparticles and proteins is very important in various fields, especially in Nano-biotechnology. Concentration-dependent nanoparticles can cause structural changes in proteins. There are several procedures to increase the efficiency of nanoparticles in these interactions. In this study, the effect of magnetic nanoparticles (MNPs) including Fe3O4 and Fe3O4 @RA (Rosmarinic acid coated with Fe3O4) was estimated on the stability and activity of egg white Lysozyme (EWL). The synthesis of MNPs was done using co-precipitation method; then they were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), vibrating sample magnetometer (VSM), CHNS elemental analysis, dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM). The results of fluorescence analysis showed that both MNPs can have two opposite effects on the tertiary structure of EWL, depending on their concentration. Accordingly, at the concentrations below a concentration threshold (0.0083 and 0.0067 for Fe3O4 NPs and Fe3O4 @RA, respectively), they improve the structure of the EWL (kosmotropic-like effect) and at the concentrations above it, they gradually cause its degradation (chaotropic-like effect). Changes in the protein activity against Micrococcus luteus bacteria based on UV analysis data were also fully consistent with the fluorescence analysis. In order to study the secondary structure of EWL, CD Spectra showed an increase in the helicity of EWL after interaction with both MNPs (3.7% and 1.1% increase in the helicity for 0.02 and 0.1 mg.mL(-1) of Fe3O4 respectively, and also 5.5% and 2% for 0.02 and 0.1 mg.mL(-1) of Fe3O4 @RA respectively) and a decrease in this factor after interaction with pure RA (0.9% and 4.1% decrease in the helicity for 0.02 and 0.1 mg.mL(-1) of pure RA respectively). (c) 2021 Published by Elsevier B.V.