Chlorin-based photosensitizer under blue or red-light irradiation against multi-species biofilms related to periodontitis

In our previous study, Chlorin-e6 (Ce6) demonstrated a significant reduction of microorganisms' viability against single-species biofilm related to periodontitis once irradiated by red light (660 nm). Also, higher bacteria elimination was observed under blue light (450 nm) irradiation. However, the use of blue light irradiation of Ce6 for antimicrobial administration is poorly explored. This study evaluated the effect of chlorin-e6-mediated antimicrobial photodynamic therapy (aPDT) using different wavelengths (450 or 660 nm) against multi-species biofilms related to periodontitis. Streptococcus oralis, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans composed the mature biofilm developed under proper conditions for five days. aPDT was performed using different concentrations of Ce6 (100 and 200 μM), wavelengths (450 or 660 nm), and comparisons were made after qPCR assay and confocal laser scanning microscopy (CLSM) analysis. The greatest bacterial elimination was observed in the groups where Ce6 was used with blue light, for S. orallis (2.05 Log10 GeQ mL-1, p < 0.0001) and P. gingivalis (1.4 Log10 GeQ mL-1, p < 0.0001), aPDT with red light showed significant bacteria reduction only for S. orallis. aPDT with blue light demonstrated statistically higher elimination in comparison with aPDT with red light. The aPDT did not show a statistically significant effect when tested against A. actinomycetemcomitans and F. nucleatum (p=0.776 and 0.988, respectively). The aPDT using blue light showed a promising higher photobiological effect, encouraging researchers to consider it in the irradiation of Ce6 for further investigations.