The Antibacterial Effect Of Photodynamic Therapy On The Biofilm Of P.gingivalis And T.forsythia

Objective:Bacterial infection plays the most important role in dental implant failure.The most common microorganism associated with implant failure is gram-negative anaerobic bacteria.The traditional treatment of peri-implantitis is mainly mechanical treatment and drug treatment.Photodynamic therapy（PDT）is mainly used in the early treatment of tumors,oral leukoplakia,skin acne and other diseases.In recent years,the anti microbial effect of photodynamic therapy has been gradually found.Therefore,it has a broad application prospect to explore suitable photosensitizers to control peri-implantitis.The aim of this study was to investigate the antibacterial activity of a new photosensitizer NHS-BODIPY-Br against P.gingivalis and T.forsythia in vitro.Methods:Synthesis of photosensitizer NHS-BODIPY-Br in laboratory.The biocompatibility of photosensitizer NHS-BODIPY-Br was detected by CCK8.P.gingivalis and T.forsythia were cultured in anaerobic condition（10%CO₂,10%H₂,80%N₂）for 48h to form a biofilm and then treated with antibacterial photodynamic therapy.The photosensitizer concentration was 5mg/L,10mg/L,15mg/L and the laser intensity was 15J/cm² and 30J/cm².After treatment,bacterial activity,residual LPS and laser confocal analysis were performed to determine the optimal treatment combination.Results:（1）Compared with the control group,NHS-BODIPY-Br had no significant effect on cell proliferation（P>0.05）.（2）when the concentration of NHS-BODIPY-Br was 10mg/L and the laser intensity was 15J/cm²,the decrease rate of bacterial biofilm was about98%.（3）When the concentration of NHS-BODIPY-Br was 10 mg/L and the laser intensity was 15J/cm²,there was no significant difference in the level of residual lipopolysaccharide between the two groups（P>0.05）.（4）when the concentration of NHS-BODIPY-Br was 10 mg/L and the laser intensity was 15J/cm²,red fluorescence was abundant,and there was no viable bacterial colony in the whole biofilm.Conclusion:This study shows that the NHS-BODIPY-Br-mediated photodynamic therapy can effectively inhibit the biofilm of P.gingivalis and T.forsythia.when the concentration of NHS-BODIPY-Br was 10 mg/L and the laser intensity was 15J/cm²,the decrease rate of bacterial biofilm was about 98%.