title: The effects of graphene oxide on green algae Raphidocelis subcapitata.
abstract: Graphene represents a new class of nanomaterials that has attracted great interest due to its unique electrical, thermal, and mechanical properties. Once disposed in the environment, graphene can interact with biological systems and is expected to exhibit toxicological effects. The ecotoxicity of graphene and its derivatives, viz.: graphene oxide (GO) depends on their physicochemical properties, including purity, diameter, length, surface charge, functionalization and aggregation state. In this study we evaluated the effects of graphene oxide (GO) on green algae Raphidocelis subcapitata. The algae were exposed to different concentrations of GO pre-equilibrated for 24h with oligotrophic freshwater medium (20ml) during incubation in a growth chamber under controlled conditions: 120μEm(-2)s(-1) illumination; 12:12h light dark cycle and constant temperature of 22±2°C. Algal growth was monitored daily for 96h by direct cell counting. Reactive oxygen species level (ROS), membrane damage (cell viability) and autofluorescence (chl-a fluorescence) were evaluated using fluorescent staining and further analyzed by flow cytometry. The toxic effects from GO, as observed in algal density and autofluorescence, started at concentrations from 20 and 10μgmL(-1), respectively. Such toxicity is probably the result of ROS generation and membrane damage (cell viability). The shading effect caused by GO agglomeration in culture medium may also contribute to reduce algal density. The results reported here provide knowledge regarding the GO toxicity on green algae, contributing to a better understanding of its environmental behavior and impacts.
authors.affiliation: Nanomedicine and Nanotoxicology Group, Physics Institute of São Carlos, São Paulo University, P.O. Box 369, Av. Trabalhador São-Carlense, 400, 13566-590, São Carlos, S.P., Brazil. Electronic address: pmayrink1@yahoo.com.br.
authors.forename: P F M
authors.initials: PF
authors.lastname: Nogueira
authors.affiliation: Nanomedicine and Nanotoxicology Group, Physics Institute of São Carlos, São Paulo University, P.O. Box 369, Av. Trabalhador São-Carlense, 400, 13566-590, São Carlos, S.P., Brazil.
authors.forename: D
authors.initials: D
authors.lastname: Nakabayashi
authors.affiliation: Nanomedicine and Nanotoxicology Group, Physics Institute of São Carlos, São Paulo University, P.O. Box 369, Av. Trabalhador São-Carlense, 400, 13566-590, São Carlos, S.P., Brazil.
authors.forename: V
authors.initials: V
authors.lastname: Zucolotto
mesh_terms: D002462:Cell Membrane / Q000187:drug effects; D000460:Chlorophyta / Q000187:drug effects*; D006108:Graphite / Q000633:toxicity*; D049329:Nanostructures / Q000633:toxicity; D010087:Oxides / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D010087:Oxides; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; D006108:Graphite
keywords: Alga; Aquatic environment; Graphene; Oxidative stress; Toxicity