Antibacterial Activity of Reduced Graphene Oxide

Figure 4

Fluorescent staining to assess cell viability in E. coli RGO systems (3 h, 37°C). The upper panel shows total cell population (both viable and dead cells) stained in green (Syto 9 staining), and the lower panel shows dead cells stained in red (propidium iodide staining) (). Note that for the 10 and 50 μg/mL RGO systems, the fluorescence staining seemed to reveal more live cells (relative to the cell-only control after exposure) when compared to those given by the agar colony counting method. This indicates presence of live but nonproliferating cells in the RGO systems, with the colony counting method only detecting live proliferating cells. It is also apparent that there were less cells present in the 200 and 400 μg/mL RGO systems (relative to the control after exposure), which could be due to physical piercing of the cells by RGO, with the noticeable presence of cellular debris (white circle).