title: Antibacterial activity of graphite, graphite oxide, graphene oxide, and reduced graphene oxide: membrane and oxidative stress.
abstract: Health and environmental impacts of graphene-based materials need to be thoroughly evaluated before their potential applications. Graphene has strong cytotoxicity toward bacteria. To better understand its antimicrobial mechanism, we compared the antibacterial activity of four types of graphene-based materials (graphite (Gt), graphite oxide (GtO), graphene oxide (GO), and reduced graphene oxide (rGO)) toward a bacterial model-Escherichia coli. Under similar concentration and incubation conditions, GO dispersion shows the highest antibacterial activity, sequentially followed by rGO, Gt, and GtO. Scanning electron microscope (SEM) and dynamic light scattering analyses show that GO aggregates have the smallest average size among the four types of materials. SEM images display that the direct contacts with graphene nanosheets disrupt cell membrane. No superoxide anion (O(2)(•-)) induced reactive oxygen species (ROS) production is detected. However, the four types of materials can oxidize glutathione, which serves as redox state mediator in bacteria. Conductive rGO and Gt have higher oxidation capacities than insulating GO and GtO. Results suggest that antimicrobial actions are contributed by both membrane and oxidation stress. We propose that a three-step antimicrobial mechanism, previously used for carbon nanotubes, is applicable to graphene-based materials. It includes initial cell deposition on graphene-based materials, membrane stress caused by direct contact with sharp nanosheets, and the ensuing superoxide anion-independent oxidation. We envision that physicochemical properties of graphene-based materials, such as density of functional groups, size, and conductivity, can be precisely tailored to either reducing their health and environmental risks or increasing their application potentials.
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459.
authors.forename: Shaobin
authors.initials: S
authors.lastname: Liu
authors.forename: Tingying Helen
authors.initials: TH
authors.lastname: Zeng
authors.forename: Mario
authors.initials: M
authors.lastname: Hofmann
authors.forename: Ehdi
authors.initials: E
authors.lastname: Burcombe
authors.forename: Jun
authors.initials: J
authors.lastname: Wei
authors.forename: Rongrong
authors.initials: R
authors.lastname: Jiang
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D006108:Graphite / Q000494:pharmacology*; D008027:Light; D008855:Microscopy, Electron, Scanning; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012542:Scattering, Radiation
chemical_list: D000900:Anti-Bacterial Agents; D017382:Reactive Oxygen Species; D006108:Graphite; D005978:Glutathione