Journal Article

Erythrosine is a potential photosensitizer for the photodynamic therapy of oral plaque biofilms

Simon Wood, Daniel Metcalf, Deirdre Devine and Colin Robinson

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 57, issue 4, pages 680-684
Published in print April 2006 | ISSN: 0305-7453
Published online February 2006 | e-ISSN: 1460-2091 | DOI:
Erythrosine is a potential photosensitizer for the photodynamic therapy of oral plaque biofilms

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  • Medical Oncology
  • Critical Care


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Objectives: The purpose of this study was to evaluate the clinical plaque disclosing agent erythrosine as a photosensitizer in the photodynamic killing of the oral bacterium Streptococcus mutans grown as a biofilm.

Methods: S. mutans biofilms of 200 μm thickness were grown in a constant-depth film fermenter. In addition to determining localization of the photosensitizer within biofilms using confocal laser scanning microscopy (CLSM), we compared the bacterial killing efficacy of erythrosine with that of two well-characterized photosensitizers, methylene blue (MB) and photofrin. Incubations were carried out with each photosensitizer (22 μM), and irradiation was for 15 min using a 400 W white light source.

Results: The CLSM results showed that erythrosine is taken up into S. mutans biofilms, where it is associated with the biomass of the biofilm rather than the fluid-filled channels and voids. Comparison of the cell killing efficacy of erythrosine in S. mutans biofilms of different ages showed that erythrosine was 1–2 log10 more effective at killing biofilm bacteria than photofrin and 0.5–1 log10 more effective than MB. The results were statistically significant (P < 0.01). Photodynamic therapy (PDT) with all three photosensitizers was increasingly effective as biofilm age increased, suggesting that temporal changes in biofilm architecture and composition affect susceptibility to PDT.

Conclusions: PDT using erythrosine as photosensitizer shows excellent potential as a treatment for oral plaque biofilms.

Keywords: PDT; photofrin; methylene blue; Streptococcus mutans

Journal Article.  3394 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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