A Primary Study On Antibacterial Activity Of Temporary Stopping Containing Graphene Oxide On E. Coli

Objectives:The aim of the study was to investigate the antibacterial activity of the graphene-oxide-containing temporary stoppings on Escherichia coli(E.coli).Methods:The temporary stoppings were heated to80℃. Then the graphene oxide was added to the temporary stoppings with certain proportion. The commercial temporary stoppings and the temporary stoppings containing graphene oxide (0.5-,1-,2-,3wt%) were taken as test groups while the sterile glass slides were controls. All the samples were made into disc with lmm thickness and10mm diameter. Plate count method and fluorescence microscopy were adopted for the antibacterial test.1. Plate count method:1.1samples were placed in the bacterial suspension (initial concentration:1106CFU/mL). After incubation in the swing bed for18h (37℃,220rpm),50μL of each bacterial suspension (diluted106times) was cultured on an agar plate. After incubation at37℃for24h, the number of colonies were counted to compute the final bacterial concentration.1.2The bacterial suspension with two initial concentrations (1106CFU/mL and1105CFU/mL) was introduced onto samples with a density of60μL/cm2and then, they were incubated for24h. The dissociated bacteria were collected. Afterwards, a50μL of collected bacterial solution (diluted100times) was inoculated onto a standard agar culture medium. After incubation at37℃for24h, the culture plates with active bacteria were photographed.2. Fluorescence microscopy observation:After incubation in the bacterial suspension (initial concentration:1106CFU/mL) for18h, samples were stained by SYTO9/PI (LIVE/DEAD BacLightTM Bacterial Viability Kit, L1304567,) for10min and then were observed by fluorescence microscopy.Results:1. With the adopted Plate Count method1.1, no obvious differences in colony counting were observed among groups. The final concentrations of all groups were calculated as109CFU/mL.2. With the adopted Plate Count method1.2, the colonies were distinctly decreased after the24h-incubation of the inoculated bacterial micro-solution on all test samples (0G0,0.5GO,1GO,2GO,3GO), as compared with slides. In particular, the bacterial progress on3GO was distinctly declined.3. Fluorescence microscopy showed that uncultured temporary stoppings with SYTO9staining demonstrated bacteria-like fluorescence imaging, whereas no presence of bacteria-like fluorescence imaging with PI staining. After PI staining, all samples revealed the bacteria-like fluorescence imaging, which was considered as dead bacteria. Samples with higher concentrations of GO (2%and3%) revealed more dead bacteria on the surface.Conclusions:In our experiment, the graphene-oxide-containing temporary stoppings were observed to suppress E.coli to a minor degree.