Promising insights into the kosmotropic effect of magnetic nanoparticles on proteins: The pivotal role of protein corona formation

Abstract

Increasing concerns about biosafety of nanoparticles (NPs) has raised the need for detailed knowledge of NP interactions with biological molecules especially proteins. Herein, the concentration-dependent effect of magnetic NPs (MNPs) on bovine serum albumin and hen egg white lysozyme was explored. The X-ray diffraction patterns, zeta potential, and dynamic light scattering measurements together with scanning electron microscopy images were employed to characterize MNPs synthesized through coprecipitation method. Then, we studied the behavior of two model proteins with different surface charges and structural properties on interaction with Fe 3 O 4. A thorough investigation of protein-MNP interaction by the help of intrinsic fluorescence at different experimental conditions revealed that affinity of proteins for MNPs is strongly affected by the similarity of protein and MNP surface charges. MNPs exerted structure-making kosmotropic effect on both proteins under a concentration threshold; however, binding strength was found to determine the extent of stabilizing effect as well as magnitude of the concentration threshold. Circular dichroism spectra showed that proteins with less resistance to conformational deformations are more prone to secondary structure changes upon adsorption on MNPs. By screening thermal aggregation of proteins in the presence of Fe 3 O 4 , it was also found that like chemical stability, thermal stability is influenced to a higher extent in more strongly bound proteins. Overall, this report not only provides an integrated picture of protein-MNP interaction but also sheds light on the molecular mechanism underling this process.

The Effect of Trehalose Coating for Magnetite Nanoparticles on Stability of Egg White Lysozyme

“…Therefore, the small size of the molecules and their positive charge cause the aggregation of the protein on the surface of the negatively charged magnetic NPs [ 58 ]. The large surface area of NPs, the formation of a protein corona structure, and the interaction of protein molecules with water molecules at the surface of the NPs can create a kosmotropic effect [ 44 , 59 ]. There is a concentration range of NPs which can have either stabilizing (kosmotropic) or degrading (chaotropic) effects.…”

“…Choosing the right concentration of NPs and a suitable coating will result in a stronger corona and, consequently, a denser hydration layer around the protein. There are some protein–ligand studies from the past decade [ 28 , 44 , 61 , 69 , 70 , 71 , 72 , 73 , 74 ] which are listed in Supplementary Materials Table S1 . According to the obtained results in this study, the kosmotropic effect can occur in a certain concentration range of 0.001–0.04 mg mL −1 and 0.001–0.01 mg mL −1 for Fe 3 O 4 @Tre and Fe 3 O 4 NPs, respectively.…”

“…In addition to strengthening the adsorbent interactions by binding to the residues, it reduces the effect of NPs in preferential hydration and acts as a kosmotrop agent to make the protein structure more orderly. So far, improvements in the HEWL globular and bovine serum albumin (BSA) protein stability has been reported [ 44 , 59 , 75 ] in the presence of different concentrations of NPs, and the results indicate the dual concentration-dependent effect of NPs on the stability and structure of the protein. The structure-making and structure-breaking performance of NPs on HEWLs have been reported for low and high NP–protein ratios.…”

“…The structure-making and structure-breaking performance of NPs on HEWLs have been reported for low and high NP–protein ratios. Fattah et al [ 44 ] reported the kosmotropic concentration range for magnetite NPs to be about 0.77 mg/μmol for BSA and 0.47 mg/μmol for HEWL. The results of their CD and UV–vis spectroscopy tests showed that the α-helix percentage of BSA is about 53.68%, 41.19%, and 34.7% for no-ligand, 0.02 mg/mL, and 0.1 mg/mL of NPs, respectively, and 26.29%, 27.92%, and 29.56% for HEWL.…”

“…Therefore, when magnetic NPs and HEWL are in contact with each other, a protein corona will form on the surface of the NPs. In the meantime, a harder and more stable corona is formed with greater affinity, which leads to the formation of a denser hydration layer around the protein [ 41 , 42 , 43 , 44 , 45 ]. However, highly soluble kosmotropic solvents stabilize native protein structures by burying hydrophobic residues while in the presence of chaotropic co-solvents.…”