Elucidating the Role of Oxidative Debris in the Antimicrobial Properties of Graphene Oxide

In this paper, we investigate, for the first time, how oxidative debris affects the antimicrobial activity of graphene oxide (GO). Besides the conventional definition of GO structure, our study demonstrates that GO is also composed of one additional component called oxidative debris, small and highly oxidized fragments adsorbed on the GO surface. After the removal of oxidative debris using an alkaline washing process, the toxicity of GO sheets to Escherichia coli cells significantly decreased. Raman spectroscopy measurements and acellular oxidation of glutathione indicated that oxidative debris increase the antimicrobial activity of GO sheets by improving their ability to promote bacteria inactivation via cell membrane damage and oxidative stress mechanisms. Given the influence of oxidative debris on the antimicrobial activity of GO, our findings emphasize the need to investigate the presence of oxidative debris before establishing correlations between physicochemical properties and the bioreactivity of GO sheets.