Effect of 5-aminolevulinic Acid Photodynamics Therapy on Biofilm of Propionibacterium Acnes

Abstract

Objective To investigate the effect of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) on Propionibacterium acnes (P.acnes) biofilm. Methods P.acnes biofilms were constructed on a cell slide and treated with ALA-PDT.According to different light doses,the biofilms were divided into six groups:ALA-PDT group [ALA-PDT1 (50 J/cm2),ALA-PDT2 group (100 J/cm2),ALA-PDT3 group (200 J/cm2)],ALA-only group (ALA group),light-only group (LED),and a negative control group (ALA-PDT-group).The biofilm structure and the ratio of the dead bacteria/live bacteria were observed using a laser confocal microscope (CLSM).Biofilm viability was measured using the XTT assay. Results CLSM showed that the biofilm structures of ALA group and LED group were not significantly different from that of ALA-PDT-group,whereas the biofilm structure was more seriously damaged in ALA-PDT1 group,ALA-PDT2 group,and ALA-PDT3 group than in the ALA-PDT-group.The ratios of the dead/live bacteria in ALA-PDT-group,ALA group,LED group,ALA-PDT1 group,ALA-PDT2 group,and ALA-PDT3 group were 0.350±0.033, 0.305±0.046, 0.330±0.032, 1.525±0.439, 2.293±0.148 and 3.092±0.189,respectively.ALA group(md=0.003, P=1.000)and LED group(md=-0.025, P=1.000)did not significantly differ from the ALA-PDT-group.However,the ratio of dead/live bacteria in ALA-PDT-group was significantly lower than those in ALA-PDT1 group (md=-0.162, P<0.001),ALA-PDT2 group (md=-0.254, P<0.001),and ALA-PDT3 group (md=-0.352, P<0.001).The values of the XTT assay were were 0.462±0.028,0.465±0.044,0.437±0.047,0.301±0.040,0.207±0.001,and 0.110±0.007,respectively,in ALA-PDT-group,ALA group,LED group,ALA-PDT1 group,ALA-PDT2 group,and ALA-PDT3 group.Although the values of XTT assay in ALA(md=-0.044, P=1.000)and LED groups (md=-0.020, P=1.000)did not significantly differ from that in ALA-PDT-group,it was significantly higher in ALA-PDT-group than in ALA-PDT1 group (md=1.175, P<0.001),ALA-PDT2 group (md=1.942, P<0.001),and ALA-PDT3 group (md=-0.352, md=2.742, P<0.001). Conclusions ALA-PDT has an inhibitory effect on P.acnes biofilm.ALA-PDT destroys biofilm structure and inhibits biofilm viability.