Mechanism of Antibacterial Activity of Photochemically Transformed Graphene Oxide

Abstract

This work examined the mechanism behind the antibacterial activity of graphene oxide (GO) before and after phototransformation in sunlight conditions Our previous research has shown that GO can be phototransformed under simulated sunlight exposure forming products with progressively reduced sizes and oxygen-containing functionalities Depending on the phototransformation conditions GO could become more toxic while the toxicity was negated after phototransformation in the presence of H2O2 (i e indirect photolysis) While the finding is interesting and could aid in assessing the ecological impact of GO the mechanism is not completely clear This is the motivation of this study New techniques including the antibacterial test of GO materials deposited on surfaces cell morphology membrane integrity using fluorescence dyes and antioxidant effect and reactive oxygen species (ROS) detection were developed and used to shed mechanistic light on the altered toxicity after phototransformation The results indicate that bacteria incubated with phototransformed GO deposited on surfaces showed increased growth inhibition The enhanced toxicity could be attributed to the reduced functional groups and/or sizes of GO after phototransformation Greater cell deformation and increased membrane permeability correlated with larger extent of GO phototransformation The growth of bacteria incubated with GO materials and antioxidants including natural organic matter (NOM) increased indicating that oxidative stress likely plays a role Collectively the results indicate that phototransformation enhanced antibacterial activity is associated with oxidative stress that increases with the degree of phototransformation

Date of Award	2016 Sept 1
Original language	English
Supervisor	Wen-Che Hou (Supervisor)