(338f) Unraveling the Role of Nitrogen in the Biological Activity of Nitrogen-Doped Graphene

For decades, the nanotechnology community has grappled with the balance of advancing applications and considerations of potential human health and environmental implications of engineered nanomaterials (ENMs). Research on the biological implications of metal and non-metal ENMs has put into perspective with the relative magnitude of inherent hazard of different ENMs, environmental considerations that influence ENM behavior and toxicity, and the ability to manipulate properties to influence interactions at the bio-interface. Despite significant advancements in our understanding of ENM implications, we still lack the ability to translate governing principles between and within classes of ENMs, particularly carbon-based nanomaterials. The recent and rapid emergence of graphene has motivated our research to uncover the governing mechanisms of graphene interactions at the bio-interface and further, establish design guidelines to tailor graphene properties. Building on our previous research findings for graphene oxide, the current project focuses on nitrogen doped graphene (N-graphene). While nitrogen doping is an important approach to modulate the electronic and chemical properties of graphene intended to broaden its applications, very little is known about the influence of this heteroatom on the biological activity of graphene. This work investigates the biological activity of a N-graphene material suite systematically prepared using facile and ecofriendly synthesis methods. The degree of nitrogen doping and chemical state of nitrogen (i.e., pyridinic, pyrrolic, graphitic, and oxidized N) in doped graphene is tailored by thermal annealing under different temperatures and quantified using X-ray photoelectron spectroscopy. The bioactivity of the prepared materials is quantified as the inactivation of a bacterial model organism and the propensity to oxidize the intracellular antioxidant, glutathione. Given the importance of oxidative stress and electron transfer in mechanisms of toxicity, the materials electronic properties are evaluated using electrochemical techniques that enable the investigation of oxygen adsorption, reactive oxygen species production, and heterogeneous electron transfer. Several complementary characterization techniques are employed to evaluate the consequential properties after nitrogen doping such as sheet dimensions, aggregation state, surface area, and structural defects.