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Bivalve Responses to Graphene Oxide Nanomaterial Exposures
Citation:
Khan, B., A. Adeleye, R. Burgess, R. Smolowitz, S. Russo, AND K. Ho. Bivalve Responses to Graphene Oxide Nanomaterial Exposures. Society of Environmental Toxicology and Chemistry North America (SETAC-NA) 39th Annual Meeting, Sacramento, CA, November 04 - 08, 2018.
Impact/Purpose:
The overall goal of this work is to evaluate responses of marine organisms to environmental exposures to carbon-based nanoparticles such as graphene oxide (GO). Given the increasing usage of graphene family nanomaterials in the field of electronics, material coatings, and biomedicine, it is likely that GO nanoparticles will make their way into aquatic ecosystems. Our knowledge of the environmental effects of such nanoparticles is very limited and incomplete. This research aims at understanding the impacts and toxicity of GO exposures using Eastern oysters as a model organism.
Description:
Graphene is a two-dimensional nanomaterial composed of sp2 hybridized carbon atoms. Due to its unique mechanical, thermal, electrical, and optical properties, the use of graphene family nanomaterials (GFNs) in electronics, biomedicine, surface coatings, filtration devices, and composite materials is rapidly growing. It is inevitable that with widespread use, GFNs will make their way to aquatic ecosystems. However, current information on fate and toxicity of GFNs, such as graphene oxide (GO), and their environmental impacts is scarce. Filter-feeding bivalves, such as Crassostrea virginica (Eastern oysters), are good models to study the effects of GO exposures on aquatic organisms. The goal of this pilot study is to evaluate effects of in vivo GO exposures on oysters using a static renewal design. Each oyster was placed in a beaker with 1 L of 0.22 µm filtered natural seawater that contained 0, 1, or 10 mg/L GO. Oysters were fed a mixed algal diet and three renewals were performed daily. For every renewal, a GO suspension was prepared in seawater and sonicated before its addition to the beakers. Water samples were analyzed for GO concentration and effective diameter after each renewal. After 72 hours of exposure, oysters were placed in clean seawater for 3 hours prior to harvesting gill and digestive gland tissues. Tissues were analyzed for lipid peroxidation, a marker of oxidative damage, and for activity of glutathione-s-transferase (GST), a detoxification enzyme that also participates in oxidative stress and cell signaling pathways. Additionally, gill tissues were fixed for histopathological analyses. Elevated lipid peroxidation in GO exposed oysters was found. No significant changes in GST activity were observed, but reduced total protein levels were noted in exposed oysters. Loss of mucous cells, hemocytic infiltration, and vacuolation were also observed in gill tissues. Results indicate that short-term GO exposures can induce oxidative stress, gill epithelial inflammation, and adversely affect overall health in oysters. Evaluation of sublethal effects of exposures to an emerging contaminant, such as GO, is critical to understanding the risks associated with increasing commercial usage of nanomaterials. Current long-term analyses of exposure effects are aimed at identification of molecular initiating events and subsequent key events that can contribute to the development of adverse outcome pathways (AOPs) for nanomaterials.