UC San Diego

With the development of nanoscience and nanotechnology, the biocompatibility of nanomaterials is becoming increasingly important. As one of the most prevalent nanomaterials, metal oxide nanoparticles in particular are receiving growing attention due to their potential negative impacts to the environmental and human health upon exposure. Nanoparticles, once introduced in biological fluids, can adsorb proteins forming protein corona, which can cause protein conformational change and function loss. Although many studies have been focusing on the above effects, details of protein interaction with nanoparticles and consequential structural change on nanoparticle surfaces still remain unclear as these processes can be affected by various factors. Therefore, a systematic study on the impacts of influential factors on the behavior of proteins at the nano-bio interface is strongly desired.

The research in the present dissertation pursues a greater understanding of the effects of various parameters on the protein-nanoparticle surface interactions and protein structural change upon adsorption. Specifically, nanoparticle- and environmental-related factors including nanoparticle surface chemistry, pH, co-adsorption of phosphate, and temperature were explored. Spectroscopic and thermogravimetric analysis of bovine serum albumin (BSA) adsorption on TiO2 and SiO2 nanoparticles as a function of pH highlighted the importance of both pH and nanoparticle surface chemistry on protein behavior at nano-bio interfaces. The study shows that protein interaction is strongest on TiO2 surface. Especially, at acidic pH, BSA is completely denatured on TiO2 and protein surface coverage was a factor of three to ten times higher than on SiO2. Detailed secondary structural analysis of BSA adsorption with and without the presence of phosphate indicates that the co-adsorption of phosphate could prevent surface-induced denaturation at very acidic conditions. Furthermore, the effects of surface adsorption on temperature-dependent conformational change of BSA and fibrinogen (Fib) on TiO2 nanoparticles was investigated. Adsorbed BSA exhibits much less change in its secondary structure with increasing temperature than its solution phase, whereas Fib in dissolved and adsorbed states display very similar trend in their structural change as a function of temperature. Moreover, to complement our understanding of protein adsorption on nanoparticles, hydrogen/deuterium exchange mass spectrometry was carried out as a novel method to investigate the role of specific amino acid residues in protein-surface interaction.

Thus, the research in this dissertation provide important insights into understanding the behavior of proteins at the nano-bio interface, specifically the effects of various influences on protein-surface interaction and protein structure.