2. Academic Validation
  3. Photodynamic inactivation mediated by methylene blue or chlorin e6 against Streptococcus mutans biofilm

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

  • Photodiagnosis Photodyn Ther. 2020 Sep:31:101817. doi: 10.1016/j.pdpdt.2020.101817.
Min Nie 1,  Dong Mei Deng 2,  Yafei Wu 3,  Kleber Thiago de Oliveira 4,  Vanderlei Salvador Bagnato 5,  Wim Crielaard 2,  Alessandra Nara de Souza Rastelli 6
Affiliations

Affiliations

  • 1 State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Key Lab of Oral Diseases of Gansu Province, Northwest Minzu University, Lanzhou, China.
  • 2 Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
  • 3 State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
  • 4 Federal University of São Carlos - UFSCar, Department of Chemistry, São Carlos, São Paulo, Brazil.
  • 5 University of São Paulo - USP, Physics Institute of São Carlos - IFSC, Optical Group, Campus São Carlos, São Carlos, São Paulo, Brazil.
  • 6 University of São Paulo State - UNESP, Araraquara, School of Dentistry, Department of Restorative Dentistry, Campus Araraquara, Araraquara, São Paulo, Brazil. Electronic address: alessandra.nara-souza-rastelli@unesp.br.
PMID: 32407890 DOI: 10.1016/j.pdpdt.2020.101817
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 μM 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 μM 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 5-log reduction in biofilm viability. The lactic acid inhibitory effect of Ce6 was significantly lower than MB at 25 μM (p<0.01) but higher than MB at 200 μM (p=0.05), although the difference at 200 μM 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 μM.

Conclusion: Ce6 under 200 μM 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.

Keywords

Biofilm; Chlorin e6; Lactic acid production; Methylene blue; Photodynamic inactivation; Streptococcus mutans.

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