Graphene and Graphene Oxide Toxicity and the Impact to Environmental Microorganisms
In natural and engineered environments, such as landfills and wastewater treatment plants, microorganisms are responsible for cleaning the environment by digesting and biodegrading contaminants. Antimicrobial pollutants can seriously hinder the functionality of native microbial populations leading to ineffective removals of biological and chemical wastes. Additionally, microorganisms can have deleterious effects to society through diseases and food spoilage. Therefore, it is essential to understand the effect of these nanomaterials on microbial populations as well as their role in hindering microbial activities, such as biological wastewater treatment and antimicrobial properties, to keep the environment balanced and to develop safe antimicrobial applications. This study presents the effects of graphene (G) and graphene oxide (GO) to fungi and bacteria to identify their impact to the environment and antimicrobial properties for potential applications. These nanomaterials were shown to inhibit significantly fungal growth and their mechanisms of inactivation involved apoptosis of the fungal hyphae. Acute and chronic toxicity to bacterial communities was also investigated in wastewater. The presence of high concentrations of these nanomaterials in the acute assays affected the carbon, nitrogen and phosphorus biogeochemical cycles significantly. While the chronic assay, showed that the bacterial population shifted differently in the presence of G or GO. Overall, GO was shown to have a more pronounced toxicity than G to the microbial communities in activated sludge. The antimicrobial properties of these nanomaterials were further explored for application as antimicrobial coatings with polymeric adhesives. The coatings with polymeric adhesives were effective against a wide range of bacteria and did not present cytotoxicity to human corneal epithelial cells, which implied these coatings are promising for biomedical applications.