Thermal Unfolding Process of Lysozyme on PEGylated Gold Nanoparticles Reveals Length-Dependent Effects of PEG Layer

Characterization of bio-nano interface is crucial for developing safer and more efficient nanoparticles in nanomedical application. PEGylation is commonly used in nanocarrier for drug delivery, as it confers nanoparticles good stability, stealth effect and better targeting specificity compared with those without PEGylation. However, the protein binding state on PEGylated AuNP is still limited known. In present work, we prepared 13 nm AuNPs and then PEGylated them with thiol PEG methoxy. Lysozyme is selected as a model protein and to investigate the interactions on protein-PEGylated/AuNP interface. The thermal unfolding processes of lysozyme in absence and presence of PEGylated AuNP were measured by synchrotron radiation based circular dichroism (SRCD), dynamic light scattering (DLS) and infrared spectroscopy (IR). The results suggest that in terms of secondary structural changes, α helix content is decreased, while β sheet content is increased, and thus the adsorbed lysozyme may be present in PEG layer.