The Role of Surface Modification of Silica-Coated Fe3O4 Nanoparticles in the Structure and Enzyme Activity of Lysozyme

To use magnetic iron oxide nanoparticles (Fe 3 O 4 ) for drug delivery, it is essential to modify the coated surface of nanoparticles with appropriate functional groups to decrease their toxicity. This study aims to explore how silica-coated magnetic iron oxide nanoparticles decorated with –NH 2 , –SH, and –OH affect the structure and function of lysozyme. Magnetite iron oxide nanoparticles were synthesized and coated with mesoporous silica (mSiO 2 @Fe 3 O 4 ) and next decorated with functional groups of –NH 2 , –SH, and –OH then physically and structurally characterized using FTIR, VSM, XRD, DLS, zeta potential, FESEM, and TEM. Afterward, it assessed the effects of the synthesized nanoparticles on structural and conformational changes of hen egg white lysozyme (HEWL) as a model protein. The interaction between lysozyme and nanoparticles was evaluated through ATR-FTIR spectroscopy, intrinsic fluorescence, ANS and thioflavin T (ThT) fluorescence, and thermal aggregation assay. Our findings demonstrated that mSiO 2 @Fe 3 O 4 altered the lysozyme’s conformation and decreased its activity, whereas NH 2 -mSiO 2 @Fe 3 O 4 increased lysozyme activity and prevented lysozyme aggregation. All the synthesized nanoparticles with the functional groups increased the protein stability during the thermal aggregation and inhibited lysozyme aggregation.