Effect of gold nanoparticle structure on the conformation and function of adsorbed proteins

Many applications of nanobiomaterials rely on or are enhanced by specific, protein-mediated interactions with biological systems. These interactions can be engineered by chemically modifying the surface of the material to affect protein adsorption, or by altering the topography of the nanoscale surface. The covalent attachment or adsorption of proteins onto materials can greatly affect their structure and function, giving rise to either beneficial effects or to unpredictable and potentially undesirable effects. Thus, it is essential to develop a detailed understanding of how nanostructured surface characteristics, such as atomic-scale topography, surface energy, and chemical structure may affect protein adsorption, structure, function, and stability. Herein we observe that nanoparticle morphology and protein surface coverage affect the structure, activity, and stability of adsorbed lysozyme (Lyz) and α-chymotrypsin (ChT) in a manner that is protein specific. Wet chemical methods were used to synthesize gold nanocubes (AuNC) with {100} facets and gold nanooctahedra (AuNO) with {111} facets. Differences in adsorption on AuNC and AuNO are observed, which may be attributed to the atomic topography of the material. Nanoparticles, as well as the final form of the resulting protein conjugates, were thoroughly characterized through various physical, microscopic, and spectroscopic techniques. As a result, additional insight into the influence of nanoscale surface properties was obtained, which will enhance our fundamental understanding of how such properties affect protein structure and function, and will hence assist us in strategically engineering protein–nanomaterial conjugates for a variety of biomedical applications.