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

Xiaoyue Liang,Huijuan Yin,Guohui Yan,Zhaohui Zou,Zheng Zou,Xiaoxi Dong,Changyi Li

doi:10.1142/s1793545820500224

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.

Highlights

Caries and its complications can cause tooth pain and even tooth loss, seriously a®ecting the oral and systemic health of patients
The main objective of this study is to evaluate the antibacterial e®ect of antibacterial photodynamic therapy on Streptococcus mutans (S. mutans) biolm model in vitro
Through antibacterial photodynamic therapy (aPDT) guided by LED light source, some scholars believe that in the antibacterialeld, in order to achieve e®ective sterilization e®ect, the energy density of aPDT should be above 30 J/cm[2] when LED light is used for irradiation.[18]

Summary

Introduction

Caries and its complications can cause tooth pain and even tooth loss, seriously a®ecting the oral and systemic health of patients. If antibiotics are used for a long time, the bacteria are prone to developing drug resistance, reducing their antibacterial e®ect and creating a vicious circle. While chemical oxidants such as high concentration of chlorhexidine and sodium hypochlorite have good e±cacy in killing bacteria and are not easy to cause bacteria to develop tolerance, due to the di±culty in controlling their application range, the drugs can spread from the local oral environment to other tissues, corroding the body and causing tissue in°ammation and damage.[4,5] a new method is urgently needed in clinic, which can achieve good antibacterial e®ect, and be safe and nontoxic to the body. With the development of the study of photochemotherapy, photodynamic therapy (PDT) has gradually come into people'seld of vision

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