Microbial Activity And Community Ecosystem In Saliva Exposures To Graphene Oxide-based Nanomaterials

Purpose1.To study the antibacterial property of Graphene oxide(GO)and Graphene oxide-silver Nanocomposite(GO-AgNPs)on human salivary bacteria.2.To study the effects of Graphene oxide and Graphene oxide-silver Nanocomposite on human salivary bacterial community.Methods1.The antibacterial property of GO and GO-AgNPs on salivary bacteria.The oral saliva samples collected from volunteers were tested by MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide,MTT)assay to detect the metabolism of bacteria;after labeling the bacteria treated with nanomaterials by live/dead fluorescent staining,Flow Cytometry was performed to explore the ratio of Gram-negative bacteria and Gram-positive bacteria;Confocal Laser Scanning Microscopy was applied to observe the live and dead cells;Transmission Eelectron Microscope was used to observe the changes of morphology of bacteria.2.effects of Graphene oxide and Graphene oxide-silver Nanocomposite on human salivary microbial community.Collect samples from saliva of volunteers,deal with a high affinity photoreactive DNA binding dye Propidium monoazide(PMA).High-throughput sequencing then used to explore the changes of composition,biodiversity,relative abundance and the ratio of gram-negative bacteria and gram-positive bacteria etc.Result1.GO and GO-AgNPs have different degree of antibacterial properties for salivary bacteria.After the treatment of GO and GO-AgNPs,metabolism of bacteria decreased,the proportion of dead cells relatively increased and bacteria gatheredthemselves together,the integrity of bacteria was destroyed.Both MTT assay and flow cytometry experiment showed that from GO=20 ?g/mL and GO-AgNPs=2.5?g/mL,the bacteria died significantly.Flow cytometry experiment also showed that from GO=40 ? g/mL and GO-AgNPs=10 ? g/mL,less than half of bacteria survived.Confocal laser scanning microscopy showed that when GO=80 ?/mL and GO-AgNPs=15 ? g/mL,most of the bacteria died equivalently.Transmission electron microscopy showed that after dealing with GO and GO-AgNPs,the bacterial cells were damaged,and the integrity of the cells was seriously damaged,and the GO-AgNPs was more damaging to them.2.GO and GO-AgNPs have great influences in the structure of bacteria,the results of high-throughput sequencing showed that after the treatment of GO and GO-AgNPs,the composition and relative abundance of salivary bacteria had changed,and the proportion of gram-negative bacteria have decreased.ConclusionGO and GO-AgNPs has a excellent antibacterial properties on salivary bacteria,and can cause the changes of composition and relative abundance.The proportion of gram-negative bacteria of also have decreased after treated by GO and GO-AgNPs,which means such nanomaterials may have great potential in oral clinical treatment.