Photodynamic Inactivation of Periopathogens With the use of Titanium Dioxide-based, Blue Light Sensitive Photosensitizer

Objectives: Introducing photosensitizers activated by the blue light for the use in periodontal antimicrobial photodynamic therapy arouses much interest. The key periopathogens are sensitive to this spectral range of light as their cell wall contains protoporphyrin IX characterized by the absorption maximum in the range of 430-450 nm. Thus, the aim of the study was to evaluate the effectiveness of new, blue-light sensitive hybrid nanocrystalline material based on TiO₂ in the photodynamic inactivation of selected periopathogens.
Methods: Following referential strains were studied: Porphyromonas gingivalis ATCC 33277, Aggregatibacter actinomycetemcomitans ATCC 33384 and Fusobacterium nucleatum ATCC 10953. The photosensitizer used was TiO₂ sensitized to visible light by a colored compound (bromopirogallol red). It was applied in the concentration ranging from 0.004 to 0.1 mg/mL. The non-laser blue light source was used (l = 450 – 470 nm, 3700 – 4000 mW/cm²). Irradiation times of 30, 60 and 120 seconds were applied. Bacteria were irradiated in the planktonic phase mixed with the solution of photosensitizer. Following cultivation, colony forming units were counted.
Results: The sole application of blue light in the highest dose reduced the viability of P. gingivalis and F. nucleatum by 1.59 and 2.14 log₁₀ respectively. Upon the application of the same light dose in the presence of photosensitizer in the most effective concentration (i.e. 0.02 mg/mL) the viability reductions amounted 4.02 log₁₀ for P. gingivalis and 3.97 log₁₀ for F. nucleatum. No photokilling effect was observed for A. actinomycetemcomitans, either when blue light was used alone or in the presence of photosensitizer.
Conclusions: The new TiO₂-based photosensitizer enables significant reductions of the viability of periopathogens associated with biofilm formation (F. nucleatum) and chronic periodontitis (P. gingivalis). The lethal effect of sole blue light on the two above mentioned strains should set the path in the future research on photosensitizers for the use in periodontology.