Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland.
Koite Health Oy, Espoo, Finland.
PLoS One. 2020 May 6;15(5):e0232775. doi: 10.1371/journal.pone.0232775. eCollection 2020.
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/cm2. 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 colony-forming 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 810 nm radiant exposure ratio in dual-light aPDT, the increase in aBL improved the antibacterial action when the biofilm was older. In conclusion, when aPDT is administered repeatedly to S. mutans biofilm, a single wavelength-based aBL or aPDT leads to a significant biofilm adaptation and increased S. mutans viability. The combined use of aBL light in synchrony with aPDT arrests the adaptation and provides significantly improved and sustained antibacterial efficacy.
抗菌光动力疗法（aPDT）和抗菌蓝光（aBL）是牙周炎机械清创的辅助新兴治疗方法。结合近红外（NIR）光和吲哚菁绿（ICG）光敏剂的 aPDT 在几种牙科门诊治疗方案中显示出了疗效。在这项研究中，我们测试了变形链球菌生物膜对 aPDT、aBL 或联合双光 aPDT（同时进行 aPDT 和 aBL）暴露的敏感性。通过在底部有生长培养基的微孔板上用移液器将稀释的变形链球菌悬浮液转移到生物膜中进行培养。在 aPDT 或双光的情况下，使用 ICG 光敏剂进行 aPDT 或双光 aPDT（同时进行 810nm aPDT 和 405nm aBL），同时将总给定辐射暴露保持在 100 J/cm2。在一天或四天的生物膜孵育后，单次光照射。此外，通过在四天和十四天的生物膜孵育中每天重复相同的光剂量，提供了每日治疗的模型。最后，在一天和四天的生物膜方案中，检查了不同的 810nm 和 405nm 光能量比的双光 aPDT 的抗菌作用。在每个实验结束时，通过平板计数法评估细菌活力。为共聚焦 3D 生物膜成像准备了单独的样本。在一天的生物膜中，双光 aPDT 明显比 aBL 或 aPDT 更有效，尽管所有方式都具有杀菌作用。在四天的生物膜中，aPDT 或双光 aPDT 的单次照射比 aBL 更有效，导致细菌计数减少四个对数级。令人惊讶的是，当在四天或十四天的生物膜上每天重复相同量的 aPDT 时，细菌活力显著提高。在重复应用 aBL 时也观察到了类似的细菌活力提高。当应用双光 aPDT 时，这种活力提高被消除了。通过改变双光 aPDT 中的 405nm 到 810nm 辐射暴露比，当生物膜老化时，增加 aBL 提高了抗菌作用。总之，当反复向变形链球菌生物膜中给予 aPDT 时，基于单波长的 aBL 或 aPDT 会导致生物膜适应并增加变形链球菌的活力。aBL 光与 aPDT 同步使用可阻止适应并提供显著改善和持续的抗菌效果。
