Due to the matching sizes of nanomaterials with biological substances, their large specific surface areas, and their inorganic core materials, nanomaterials interact with biological systems differently than small molecules or biopolymers, objects we have previous knowledge of. With the increasing exposure of human beings to engineered nanomaterials (ENM) in the form of environmental pollutant or nanomedicine, it is greatly demanded that we obtain better understanding of the behavior of ENM inside the biological systems. Once the ENM enters the human body, they encounter enormous amounts of proteins and form the so-called protein "corona" on their surface. The biological effects of ENM could then be carried out by this protein "corona". For example, the protein corona could bear special signals recognizable by biological systems and thus govern the behaviors of ENM, such as clearance from circulation, penetration to membranous barriers, transportation to residential sites, trigger of defense system, etc. On the other hand, proteins adsorbed onto ENM surface may passivate their high surface activity and prevent generation of free radicals, the main source of nanotoxicity, but at the expense of possible conformational and activity alteration to the bound proteins. By hypothesizing the direct link between protein-nanomaterial interaction and the behavior of ENM in biological systems, we propose to analyze the formation of protein corona, sort out its dependence on the physical properties of ENM, and initiate the exploration of potential effects of binding to ENM on proteins. We have developed effective tools for the interaction study, including flow-field flow fractionation for isolation of proteins of high affinity and capillary electrophoresis for binding affinity measurement. With these tools, we will screen for proteins in human plasma or cell lysate having high affinity to the selected ENM (Specific Aim 1). This study will reveal proteins present in the corona after ENM entering our body or invading cells. These proteins should play important roles in governing the ENM behaviors in their biological hosts and the host response to ENM entry. In the meanwhile, these proteins will be the most possible targets being affected by ENM because of the close contact. Secondly, we will study the interactions between a representative group of proteins and the selected nanomaterials in details (Specific Aim 2), aiming to obtain better understanding on the general dependence of interaction to the ENM properties, such as core materials, size, shape, and surface functionalization. Last, we will assess outcomes of protein-nanomaterial interaction from the aspect of alteration of enzyme activities (Specific Aim 3). Our study will lead to better understanding of the biological effects of nanomaterials and the general dependence of interaction on the ENM properties, which can guide the design of nanomedicines as well as ensure safe implementation of nanomaterials. PUBLIC HEALTH RELEVANCE: We propose experiments to test our hypothesis that the biological behavior of nanomaterials may be carried out via strong interactions with plasma and cellular proteins. Such interactions could alter the protein conformation and thus protein function. The outcome of the propose research may shed light on how the nanomaterials behave inside the biological host, knowledge required by nanomedicine design and nanomaterials exposure control.