Photoinactivating periodontopathogens by a halogen lamp and novel Ruthenium-complexes

Methods: The PDD was applied against the periodontopathogens Porphyromonas gingivalis and Fusobacterium nucleatum. A halogen lamp (350–550 nm) activated three Ruthenium-based photosensitizers (RD3–CL, RSD3, RBY–CL). 100 µL of bacterial suspension (OD 0.6) were incubated with 100 µL of various photosensitizer concentrations for 15 min. After this period the cells were divided into two groups (washed/unwashed) and were irradiated for 0-30 seconds (fluence rate up to 13.2 J/cm²). After being plated on brain heart infusion agar (100 µL/plate), the cells were incubated anaerobically at 37°C for 8 and 4 days, respectively for P. gingivalis and F. nucleatum and the colony forming units were counted (cfu/ml).

Results: We have gained a 4–log10 viability reduction of Fusobacterium nucleatum and a complete elimination of Porphyromonas gingivalis when 25 µM of the photosensitizer RD3-CL were incubated for 15 min with the bacterial cells, washed off and then irradiated for 30 s (13.2 J/cm²) and 20 s (8.8 J/cm²) accordingly. Increases in drug concentration produced significantly higher killing (p = 0.021) that plateaued at 25 µM.

Conclusion: We were able to show that light from a common halogen lamp, such as those used in dentistry for polymerisation of composites, in the presence of 25 µM of RD3–CL yielded photoinactivation of P. gingivalis and F. nucleatum, after 20 s (8.8 J/cm²) and 30 s (13.2 J/cm²) respectively.