Antibacterial Effect Of Graphene Oxide Against Streptococcus Mutans

Objectives 1.To research the antibacterial effect of graphene oxide against planktonic S.mutans.2.To research the antibacterial effect of graphene oxide against S.mutans biofilms.Methods 1.To research the antibacterial effect of graphene oxide against planktonic S.mutans.S.mutans was selected as mode bacteria.After co-incubation with GO nanosheets for specific time,MTT reduction assay was applied to detect the metabolic activity of bacterial cells;Colony forming units(CFU)counting method was used to reveal the amount of live bacteria;Growth curve determination reflected the re-culture ability of bacteria after GO treated;Live/dead fluorescent staining assay was performed to show the live/dead status of bacteria in planktonic form;Transmission electron microscopy(TEM)was applied to reveal the morphological change of bacterial cells.2.To research the antibacterial effect of graphene oxide against S.mutans biofilms.S.mutans was selected as mode bacteria to construct the bacterial biofilm model.GO was added in biofilm developing system in different concentrations and at different biofilm formation stages.Crystal violet assay was used to detect the biomass of biofilm;CFU counting method was used to reveal the amount of live bacteria;MTT reduction assay was applied to show the metabolic activity of bacterial cells;Live/dead fluorescent staining assay was performed to show the live/dead status of bacteria in biofilm;Extracellular polymeric substances(EPS) fluorescent staining assay was performed to reveal the EPS amount of biofilm;Scanning electron microscopy(SEM)was applied to show the morphological change of bacterial biofilm.Result 1.After 20 ~ 80 μg/m L GO treated,planktonic S.mutans appeared to be lower metabolic activity,less amounts,slower growth status and increasing ratio of dead cells.It also would be seen that bacteria cells aggregated severely and cell integrity destroyed.2.At the early stage of bacterial biofilm formation,with 5 ~ 80 μg/m L GO treatment,S.mutans biofilm would be inhibited to some extent.Less amounts of biomass both live and dead cells,lower metabolic activity,decreasing ratio of live cells and EPS in biofilm can be found.It was prominent that the structure of bacteria biofilm disintegrated and even more,some cell integrity destroyed.Conclusion Graphene oxide nanosheets have excellent antibacterial effect against both planktonic bacteria and bacterial biofilm with limit of concentration and timing.Destroy of the cell membrane would be the resources of its antibacterial properties.Definitely,GO nanosheets would be a kind of promising nanomaterial that can be applied in dental care and therapy.