Photodynamic inactivation mediated by methylene blue or chlorin e6 against Streptococcus mutans biofilm

Author(s)

Nie, Min ; Deng, Dong Mei ; Wu, Yafei ; de Oliveira, Kleber Thiago ; Bagnato, Vanderlei Salvador ; Crielaard, Wim ; Rastelli, Alessandra Nara de Souza

• Document type: Journal article
• Source: Photodiagnosis and Photodynamic Therapy; v. 31, p. 7-pg., 2020-09-01.

Abstract

Background: An appropriate photosensitizer (PS) for photodynamic inactivation should have a pronounced antimicrobial efficacy but low dark toxicity. The aim of this study is to investigate the concentration-dependent antimicrobial efficacies of methylene blue (MB) and chlorin e6 (Ce6), against Streptococcus mutans biofilms and to compare the efficacies of these two PSs. Methods: The 48-h S. mutans UA159 biofilms, grown on glass coverslips, were subjected to MB or Ce6 at 25, 50, 100 and 200 mu M with or without irradiation by 660 nM LED light (L). Control groups (-PS-L and -PS + L) were also included. Viability of the biofilm was analyzed by CFU/biofilm and biofilm lactic acid production was quantified by an enzymatic assay. Results: With irradiation, MB under 25 mu M resulted in 2-log reduction in biofilm viability and 30-fold reduction in biofilm lactic acid production. However, this biofilm killing efficacy did not change with increasing MB concentration. The biofilm killing efficacy of Ce6 increased with increasing Ce6 concentrations and resulted in Slog reduction in biofilm viability. The lactic acid inhibitory effect of Ce6 was significantly lower than MB at 25 mu M (p < 0.01) but higher than MB at 200 mu M (p = 0.05), although the difference at 200 mu M did not reach statistical significance. No dark toxicity could be observed for MB whereas low dark toxicity could be seen for Ce6 when the concentration is above 50 mu M. Conclusion: Ce6 under 200 mu M showed to be a more powerful PS for photodynamic inactivation than MB. Both Ce6- and MB-based photodynamic inactivation are useful methods for biofilm control in caries prevention. (AU)

• FAPESP's process: 15/21183-1 - Antimicrobial photodynamic therapy and its effect over biofilm responsible by dental caries
• Grantee: Alessandra Nara de Souza Rastelli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/07276-1 - CEPOF - Optics and Photonic Research Center
• Grantee: Vanderlei Salvador Bagnato
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 18/00106-7 - Photocatalyzed Reactions by using porphyrins and continuous flow conditions: Arylations of heterocycles and activated olefins.
• Grantee: Kleber Thiago de Oliveira
• Support Opportunities: Regular Research Grants