Dual-light photodynamic therapy administered daily provides a sustained antibacterial effect on biofilm and prevents Streptococcus mutans adaptation

Abstract

Antibacterial photodynamic therapy (aPDT) and antibacterial blue light (aBL) are emerging treatment methods auxiliary to mechanical debridement for periodontitis. APDT provided with near-infrared (NIR) light in conjunction with an indocyanine green (ICG) photosensitizer has shown efficacy in several dental in-office-treatment protocols. In this study, we tested Streptococcus mutans biofilm sensitivity to either aPDT, aBL or their combination dual-light aPDT (simultaneous aPDT and aBL) exposure. Biofilm was cultured by pipetting diluted Streptococcus mutans suspension with growth medium on the bottom of well plates. Either aPDT (810 nm) or aBL (405 nm) or a dual-light aPDT (simultaneous 810 nm aPDT and 405 nm aBL) was applied with an ICG photosensitizer in cases of aPDT or dual-light, while keeping the total given radiant exposure constant at 100 J/cm 2. Single-dose light exposures were given after one-day or four-day biofilm incubations. Also, a model of daily treatment was provided by repeating the same light dose daily on four-day and fourteen-day biofilm incubations. Finally, the antibacterial action of the dual-light aPDT with different energy ratios of 810 nm and 405 nm of light were examined on the single-day and four-day biofilm protocols. At the end of each experiment the bacterial viability was assessed by colonyforming unit method. Separate samples were prepared for confocal 3D biofilm imaging. On a one-day biofilm, the dual-light aPDT was significantly more efficient than aBL or aPDT, although all modalities were bactericidal. On a four-day biofilm, a single exposure of aPDT or dual-light aPDT was more efficient than aBL, resulting in a four logarithmic scale reduction in bacterial counts. Surprisingly, when the same amount of aPDT was repeated daily on a four-day or a fourteen-day biofilm, bacterial viability improved significantly. A similar improvement in bacterial viability was observed after repetitive aBL application. This viability improvement was eliminated when dual-light aPDT was applied. By changing the 405 nm to

Indocyanine Green-Assisted and LED-Light-Activated Antibacterial Photodynamic Therapy Reduces Dental Plaque

“…The photosensitizer initiates an electron transfer reaction, activating nearby oxygen molecules to form reactive oxygen species (ROS). The ROS action is eventually bactericidal [ 7 ]. Streptococcal species lack catalase enzyme, which is the most important intracellular enzyme in the protection against ROS, rendering the species especially vulnerable [ 24 ].…”

“…In the presence of oxygen, it releases energy in the form of singlet oxygen and heat that destroy bacteria, fungi, and viruses [ 6 ]. Research concerning aPDT have demonstrated its potent efficacy against dental pathogens, and the relative effectiveness against streptococci makes the approach very appealing [ 7 ]. However, aPDT use in clinical dentistry has been limited to in-office treatment [ 8 ], and home-use appliances are not readily available.…”

Microbial biofilm: A matter of grave concern for human health and food industry

“…Recently, bacteriophage-based treatments are proposed to eradicate biofilms and one can design effective phage-based strategies upon understanding phage-biofilms interactions [182]. Photodynamic therapy is yet another strategy that has been proven as effective in inhibiting biofilm in wounds and also eradicating planktonic cells [183,184].…”

Assessment and Characterization of Some New Photosensitizers for Antimicrobial Photodynamic Therapy (aPDT)

“…Several studies have shown that oral bacteria are sensitive to PDT in planktonic cultures. Recent studies have reported that PDT induced bacterial cell destruction and reduced bacterial counts by more than 10-fold in biofilms of Streptococcus mutants [ 22 , 23 , 24 , 25 , 26 ], Streptococcus sobrinus and Streptococcus sanguinis , using toluidine blue or erythrosine as a photosensitizer [ 2 , 27 , 28 ], silver nanoclusters/rose Bengal nanocomposite [ 22 ], curcumin and methylene blue [ 24 ].…”