Study Of Inhibition Induced By Rose Bengal-mediated Photodynamic Therapy On Porphyromonas Gingivalis

Objective：The three main factors of PDT are: photosensitizer, light source, and reactiveoxygen species (ROS). Several photosensi-tizers have been shown to be effectiveagainst target microorganisms without inducing damage to the host tissues. This studyevaluated in vitro the photodynamic effect of RB in combination with an LED lightsource on Porphyromonas gingivalis (P.g).The study will preliminary test and observthe RB-mediated PDT on P.g.Thus providing theoretical and experimental basis forclinical application of dental caries and periodontitis.Method：（1）This part was to evaluate specific effects of PDT on P.g Suspensions.Suspensions containing P.g concentration were prepared and divided into2groups:Control group (0.9%sodium chloride) and PDT group (inoculums,differentconcentration of RB for5min and LED for3min). Tenfold serial dilutions werecarried and aliquots seeded in MRS Medium Base which were then incubated for48h.Then the numbers colony-forming units per milliliter and analyzed statistically.（2）Using96-well culture plate to establish the model of bacterial biofilm.MTTassay was then used to compare the antimicrobial activities of RB-PDT group（50μM）, lighting group(LED for3min), RB group(RB for5min) and control group(0.9%sodium chloride).Then the OD values were measured with microplate reader.（3）Mature biofilm of P.g forned on glass slides for48h. Then biofilm weredivided into4group:RB-PDT group（50μM）, lighting group, RB group and controlgroup.The treated biofilmwas stained by SYT09/PI and Confocal laser scanningmicroscopy (CLSM) was used to observe each group to observe the bacreria stainingand bacterial activity.Result：（1）For both strains, the RB-PDT groups (with different concentration of RB,)presented a significant decrease in the CFU counts (p<0.05) compared with theControl group.And to compare the five different RB-PDT groups,it shows that colony count increased with the increase of concentration of RB decrease;（2）Determined by MTT test results show that RB-PDT group presented asignificant decrease in the OD values compared with the Control group,lighting groupand RB group.Comparison among the Control group,lighting group and RB group,the OD values between the three groups were no statistical significance.（3）The image of the biofilm treated by the Control group,lighting group andRB group show that the most bacterial was stained green fluorescence,just a littlebacterial was stained red fluorescence and the superposition graph was green. ThenRB-PDT group show that the vast majority of the microscope field of view was redstaining bacterial,only a small amount of green fluorescence, and the superpositiongraph was red.Conclusion：（1）It can be concluded that PDT was effective in reducing the numbers of P.gin vitro,and the inhibitory effect of PDT has solubility dependence.（2）The antibiofilm effect of the Control group,lighting group and RB groupwere not achieve under the experimental conditions.