Toxicity of a polymer–graphene oxide composite against bacterial planktonic cells, biofilms, and mammalian cells

It is critical to develop highly effective antimicrobial agents that are not harmful to humans and do not present adverse effects on the environment. Although antimicrobial studies of graphene-based nanomaterials are still quite limited, some researchers have paid particular attention to such nanocomposites as promising candidates for the next generation of antimicrobial agents. The polyvinyl-N-carbazole (PVK)-graphene oxide (GO) nanocomposite (PVK-GO), which contains only 3 wt% of GO well-dispersed in a 97 wt% PVK matrix, presents excellent antibacterial properties without significant cytotoxicity to mammalian cells. The high polymer content in this nanocomposite makes future large-scale material manufacturing possible in a high-yield process of adiabatic bulk polymerization. In this study, the toxicity of PVK-GO was assessed with planktonic microbial cells, biofilms, and NIH 3T3 fibroblast cells. The antibacterial effects were evaluated against two Gram-negative bacteria: Escherichia coli and Cupriavidus metallidurans; and two Gram-positive bacteria: Bacillus subtilis and Rhodococcus opacus. The results show that the PVK-GO nanocomposite presents higher antimicrobial effects than the pristine GO. The effectiveness of the PVK-GO in solution was demonstrated as the nanocomposite "encapsulated" the bacterial cells, which led to reduced microbial metabolic activity and cell death. The fact that the PVK-GO did not present significant cytotoxicity to fibroblast cells offers a great opportunity for potential applications in important biomedical and industrial fields.