Abstract
In light of increasing resistance toward conventional antibiotics and antiseptics, antimicrobial photodynamic therapy (aPDT) may be a valuable alternative, especially for use in dentistry. In this regard, photosensitizers (PS) based on a phenalen-1-one structure seem to be especially favorable due to their high singlet oxygen quantum yield. However, the actual target structures of phenalen-1-one-mediated aPDT are still unclear. The aim of the present study was to investigate the antimicrobial efficacy of aPDT mediated by phenalen-1-one derivatives SAPYR and SAGUA for inactivation of a polymicrobial biofilm consisting of three putative periodontal pathogens in vitro and to get first insights in the mechanism of action of phenalen-1-one-mediated aPDT by assessing damage of cytoplasmic membranes. aPDT with SAPYR exhibited identical antimicrobial efficacy as compared to chlorhexidine (CHX) [4.4–6.1 log10 reduction of colony forming units (CFUs) depending on bacterial species] while aPDT with SAGUA was less effective (2.0–2.8 log10). Flow cytometric analysis combined with propidium iodide (PI) staining revealed no damage of cytoplasmic membranes after aPDT with both phenalen-1-one derivatives, which was confirmed by spectroscopic measurements for release of nucleic acids after treatment. Spectrophotometric PS-uptake measurements showed no uptake of SAPYR by bacterial cells. Despite the inability to pinpoint the actual target of phenalen-1-one-mediated aPDT, this study shows the high antimicrobial potential of phenalen-1-on mediated aPDT (especially when using SAPYR) and represents a first step for getting insights in the mechanism and damage patterns of aPDT with this class of PS.
Highlights
Periodontal disease is among the most prevalent diseases worldwide according to the most recent Global Burden of Disease study (1990–2015) affecting more than 537 million adults (GBD 2015 Disease and Injury Incidence and Prevalence Collaborators, 2016) and it is known to be the major cause for tooth loss (Tonetti et al, 2017)
Antimicrobial photodynamic therapy with SAPYR reduced colony forming units (CFUs) of A. naeslundii and F. nucleatum by 6.0 and 6.1 log10 and P. gingivalis by 4.4 log10
APDT with SAGUA led to reductions of 2.8 log10 against A. naeslundii, 2.4 log10 against F. nucleatum and 2.0 log10 against P. gingivalis only
Summary
Periodontal disease is among the most prevalent diseases worldwide according to the most recent Global Burden of Disease study (1990–2015) affecting more than 537 million adults (GBD 2015 Disease and Injury Incidence and Prevalence Collaborators, 2016) and it is known to be the major cause for tooth loss (Tonetti et al, 2017). For patients suffering from aggressive periodontitis or severe or refractory forms of chronic periodontitis, it is common clinical practice to prescribe antibiotics (i.e., amoxicillin and metronidazole) adjunctively to subgingival debridement (van Winkelhoff et al, 1996; Zandbergen et al, 2013). This attracts critical voices nowadays (Preus et al, 2014), as more periodontal pathogens increasingly exhibit resistance toward these antibiotics (Rams et al, 2014). It has been recommended that its use should be limited to the applications “with a clear patient benefit” (i.e., in intensive care patients) in order to reduce the risk of inducing acquired resistances to CHX in pathogens (Kampf, 2016)
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