How Oxygen-Containing Groups on Graphene Influence the Antibacterial Behaviors

Graphene can be obtained with the reduction of graphene oxide (GO). Various reduction methods will result in different varieties and amounts of oxygen-containing groups on the reduced graphene oxide (rGO) with diverse properties. In this work, rGO is fabricated on the titanium surfaces by the reduction process of GO through three types of reduction methods, for example, vacuum thermal annealing, hydrazine hydrate, and sodium borohydride chemical reduction. Results show that thermal annealing can remove carboxyl entirely at 600 degrees C for 1 h, and hydrazine hydrate can eliminate the oxygen functionalities, especially for epoxide. For sodium borohydride, it can dispose of carbonyl by converting carbonyl into hydroxyl. The rGO with different reduction process exhibits different responses for bacteria with higher numbers of carboxyl and hydroxyl/epoxide showing more effective antibacterial activities. It is concluded that carboxyl can inhibit the adhesion of bacteria on rGO surfaces by electrostatic repulsion and kill the bacteria with oxidative pressure mediated with the production of reactive oxygen species which is closely related with hydroxyl/epoxide. Furthermore, GO and rGO all exhibit excellent biocompatibility with no cytotoxicity.