The Role And Mechanism Of Graphene Oxide In Bacterial Inactivation And Membrane Inhibition

Graphene oxide（GO）is a promising antibacterial agent,for its biocompatibility and persistent stress to bacteria,but the antibacterial mechanism remains to be studied.It has been reported that the effects of GO on different bacteria are different.There are significant differences in cell wall of Gram-positive bacteria and Gram-negative bacteria.Based on this,Staphylococcus aureus,Staphylococcus epidermidis represented Gram-positive bacteria and Pseudomonas aeruginosa,Escherichia coli represented Gram-negative bacteria were used in this study to explore the effects of GO on different bacteria.The achievements are not only beneficial for the understanding of the interaction between GO and bacteria,but also help for the antibacterial application of GO.The main results are as follow:（1）GO has a more efficient bactericidal effect on Gram-positive bacteria,4mg/L GO can kill 100%10⁸ CFU/mL Staphylococcus aureus and Staphylococcus epidermidis,but the maximum lethality of 0-10 mg/L GO against Pseudomonas aeruginosa and Escherichia coli was only 24%.Further analysis showed that GO combined with teichoic acid,a component of Gram-negative bacteria cell wall.And this combination interfered with regulation of autolysin activity,resulting in over expression of autolysin and degradation of peptidoglycan,which finally caused the death of bacteria.（2）The bactericidal effect of GO on Gram-negative bacteria is not significant,but GO could significantly inhibit the biofilm formation in short-term exposure.0-40 mg/L GO made no difference on Pseudomonas aeruginosa proliferation,but the biofilm biomass of bacteria treated with 40mg/L GO reduced by 62%.Further research showed that GO affects biofilm formation by adsorption of 3OC₁₂-HSL and protease;however,in long-term exposure,the bacteria could evolve for the adaptive response of quorum sensing.After 200 generations,both the 3OC₁₂-HSL and protease levels were restored and had no difference with wide type strain,the interference of biofilm was eliminated.