Effect of antibacterial photodynamic therapy on Streptococcus mutans plaque biofilm in vitro

Abstract

The main objective of this study is to evaluate the antibacterial effect of antibacterial photodynamic therapy (aPDT) on Streptococcus mutans (S. mutans) biofilm model in vitro. The selection of photosensitizers is the key step for the efficacy of photodynamic therapy (PDT). However, no studies have been conducted in the oral field to compare the functional characteristics and application effects of PDT mediated by various photosensitizers. In this research, the antibacterial effect of Methylene blue (MB)/650[Formula: see text]nm laser and Hematoporphyrin monomethyl ether (HMME)/532[Formula: see text]nm laser on S. mutans biofilm was compared under different energy densities to provide experimental reference for the clinical application of the two PDT. The yield of lactic acid was analyzed by Colony forming unit (CFU) and spectrophotometry, and the complete biofilm activity was measured by Confocal Laser Scanning Microscopy (CLSM) to evaluate the bactericidal effect on each group. Based on the results of CFU, the bacterial colonies formed by 30.4[Formula: see text]J/cm2 532[Formula: see text]nm MB-aPDT group and 30.4[Formula: see text]J/cm2 532[Formula: see text]nm HMME-aPDT group were significantly less than those in other groups, and the bacterial colonies in HMME-aPDT group were less than those in HMME-aPDT group. Lactic acid production in all treatment groups except the photosensitizer group was statistically lower than that in the normal saline control group. The activity of bacterial plaque biofilm was significantly decreased in the two groups treated with 30.4[Formula: see text]J/cm2 aPDT. Therefore, aPDT suitable for energy measurement can kill S. mutans plaque biofilm, and MB-aPDT is better than HMME-aPDT.

Natural Photosensitizers in Antimicrobial Photodynamic Therapy

“…Paramanantham et al reported that APDT with the PS malachite green inhibits the growth of S. aureus biofilms by up to 80% [ 27 ]. Streptococcus mutans , which is responsible for forming dental biofilms, is also effectively suppressed by APDT [ 31 ]. E. faecalis, which causes endodontic infections, is another example of the use of APDT against Gram-positive bacteria [ 32 ].…”

Theranostic nanoplatforms of emodin-chitosan with blue laser light on enhancing the anti-biofilm activity of photodynamic therapy against Streptococcus mutans biofilms on the enamel surface

“…As previously mentioned, the tooth enamel demineralization and dental caries is initiated through the production of organic acids such as lactic acid by microbial plaques. aPDT can reduce and inhibit the tooth enamel demineralization and dental caries via suppuration of the lactic acid production capacity in S. mutans biofilms [ 59 , 60 ]. In this study, lactate dehydrogenase calorimetry was employed to assay the lactate concentration.…”

Photodynamic Therapy (PDT) in Prosthodontics: Disinfection of Human Teeth Exposed to Streptococcus mutans and the Effect on the Adhesion of Full Ceramic Veneers, Crowns, and Inlays: An In Vitro Study

“…The carious potential of this bacterium is accentuated by the ability to secrete glucan (which promotes bacterial adhesion and biofilm formation) and lactic acid, also by its acid tolerance mechanism [ 19 ]. Previous studies evaluated PDT’s efficacy on S. mutans biofilms incubated for 5 days [ 4 , 7 ], 3 days [ 20 ], 48 h [ 21 ], respectively, while others [ 22 ] used a 7-day old biofilm. Our streptococcal biofilm also visibly developed on prepared teeth after 8 days.…”

“…The selection of the photosensitizer (MB) and laser power (100 mW) was based on previous works that demonstrated their efficacy [ 4 , 21 , 30 ]. MB had also a higher sterilizing effect [ 20 ] when compared with hematoporphyrin monomethyl ether (HMME). Post-PDT SEM images revealed a significant bacterial reduction; our results are in consensus with the antibacterial effect reported by other studies [ 4 , 6 , 20 , 21 , 31 , 32 ].…”

“…MB had also a higher sterilizing effect [ 20 ] when compared with hematoporphyrin monomethyl ether (HMME). Post-PDT SEM images revealed a significant bacterial reduction; our results are in consensus with the antibacterial effect reported by other studies [ 4 , 6 , 20 , 21 , 31 , 32 ].…”