Phenalen-1-One-Mediated Antimicrobial Photodynamic Therapy and Chlorhexidine Applied to a Novel Caries Biofilm Model

Wimmer, Fabian; Muehler, Denise; Thurnheer, Thomas; Belibasakis, Georgios N.; Hiller, Karl‐Anton; Maisch, Tim; Buchalla, Wolfgang

doi:10.1159/000487815

Cited by 20 publications

(14 citation statements)

References 45 publications

(53 reference statements)

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“…The concentration of 0.5% of HAP or silica, respectively, was chosen to mimic dilution effects as they may occur in the oral cavity after using a mouthwash with 5% HAP [18]. In contrast to previous works [34,35], we used no filter-sterilized saliva here to promote biofilm formation as salivary Ca 2+ ions (concentrations between 20 and 55 μg/ mL [11,[31][32][33], as described above), may have impeded Ca 2+ release measurements.…”

Section: Discussionmentioning

confidence: 99%

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

et al. 2020

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Background: Synthetic particulate hydroxyapatite (HAP; Ca 5 (PO 4 ) 3 (OH)) is used as ingredient in oral care products but its effects on cariogenic biofilms are not clear yet. The primary mode of action of HAP may be acting as a calcium phosphate reservoir when deposited in oral biofilms and release Ca 2+ and (hydrogen) phosphate ions upon bacterial acid challenge. The aim of this in vitro study was to test this hypothesis by investigating release of Ca 2+ ions and potential buffering effects from HAP upon bacterial acid challenge in planktonic cultures and biofilms of Streptococcus mutans. Methods: Planktonic cultures of S. mutans were grown in BHI broth with 1% sucrose or with additional 5% HAP or 5% silica for up to 48 h. Separately, biofilms of S. mutans were grown in BHI for 72 h in total. After 24 h of this biofilm culture, either BHI alone or BHI with additional 0.5% HAP or 0.5% silica was added. After 48 h, BHI with 1% sucrose was added to allow bacterial acid formation. Ca 2+ release was determined colorimetrically and pH measurements were performed using a pH electrode. For statistical analysis, non-parametrical procedures were applied (n ≥ 10; Mann-Whitney U test; α = 0.05).Results: Relevant release of Ca 2+ was only evident in planktonic cultures or biofilms with HAP but not in both other groups (p ≤ 0.001). In suspended biofilms with HAP, median pH was 4.77 after 72 h and about 0.5 pH units higher as compared to both other groups (4.28 or 4.32, respectively; p ≤ 0.001).Conclusions: Under the tested conditions, synthetic HAP releases Ca 2+ ions upon bacterial acid challenge and may also show some buffering capacity but further studies are needed to investigate whether the concentrations tested here can also be reached clinically in dental biofilms.

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Section: Discussionmentioning

confidence: 99%

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

et al. 2020

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“…The antimicrobial efficacy of CHX, CPC, and citrus extract was then further evaluated in a more complex polymicrobial biofilm model cultured from A. naeslundii , A. odontolyticus, and S. mutans , whose culture conditions have been described and extensively discussed recently (Cieplik et al., ). While biofilms grown in vitro from defined consortia can never mimic the vast microbial complexity found in the oral cavity (Dewhirst et al., ; Marsh & Zaura, ), this may not be a crucial point for testing antimicrobial efficacy of given compounds because it is well‐known that the enhanced tolerance of bacteria in sessile biofilm mode is mostly due to the protective role of the extracellular polymeric substance (EPS), which acts as a diffusion barrier for antimicrobial agents (Bowen, Burne, Wu, & Koo, ; Stewart & Costerton, ).…”

Section: Discussionmentioning

confidence: 99%

“…Polyspecies biofilms were cultured as it has been described in detail recently (Cieplik et al., ). Briefly, after discarding saliva, wells were filled with 200 μl of BCM containing A .…”

Section: Methodsmentioning

confidence: 99%

“…Bacteria were grown and maintained on Columbia Agar plates (provided by the Institute for Microbiology and Hygiene, University Medical Center Regensburg, Germany) under anaerobic conditions (80% N 2 , 10% CO 2 , 10% H 2 ; microincubator MI23NK, SCHOLZEN Microbiology Systems, St. Margrethen, Switzerland). As a basal liquid medium, the modified Fluid Universal Medium (mFUM) was employed, supplemented with 67 mmol/L Sørensen's buffer (pH 7.2) and containing carbohydrate (0.15% (w/v) glucose and 0.15% (w/v) sucrose), as described earlier (Cieplik et al., ; Gmür & Guggenheim, ; Guggenheim, Giertsen, Schüpbach, & Shapiro, ). For the preparation of planktonic cultures, colonies were picked, suspended in 5 ml of mFUM with 0.5 ml fetal bovine serum (FBS; Gibco ® life technologies, Carlsbad, CA, USA) and cultured over‐night under anaerobic conditions in order to obtain bacteria in the stationary phase of growth.…”

Section: Methodsmentioning

confidence: 99%

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Antimicrobial efficacy of alternative compounds for use in oral care toward biofilms from caries‐associated bacteria in vitro

Kara¹,

Muehler²,

Enax

et al. 2018

MicrobiologyOpen

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For caries‐active patients, antimicrobial measures may be useful in addition to mechanical biofilm removal. The aim of this study was to investigate the antimicrobial efficacy of alternative compounds for use in oral care from two main categories (i.e., preservatives and natural compounds) toward biofilms from caries‐associated bacteria as compared to oral care gold‐standards chlorhexidine digluconate ( CHX ), cetylpyridinium chloride ( CPC ), and zinc. Compounds were screened in initial Streptococcus mutans biofilms. Then, the most effective compounds were further investigated in mature S. mutans and polymicrobial biofilms comprising Actinomyces naeslundii , Actinomyces odontolyticus, and S. mutans . Here, distinct treatment periods and concentrations were evaluated. Biofilms were visualized by scanning electron microscopy and bacterial membrane damage was evaluated by means of flow cytometry and staining with SYBR Green and propidium iodide. Citrus extract was the only compound exhibiting similar antimicrobial efficacy in initial S. mutans biofilms (>5 log 10 ) as compared to CHX and CPC , but its effect was clearly inferior in mature S. mutans and polymicrobial biofilms. Flow cytometric data suggested that the mechanism of antimicrobial action of citrus extract may be based on damage of bacterial membranes similar to CHX and CPC . From all alternative compounds investigated in this study, citrus extract exhibited the highest antimicrobial efficacy toward in vitro biofilms from caries‐associated bacteria, but still was less effective than oral care gold‐standard antiseptics CHX and CPC . Nevertheless, citrus extract may be a valuable antimicrobial compound for use in oral care for caries‐active patients.

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“…Phenalen-1-one-mediated aPDT has already shown its high antimicrobial potential and may be particularly advantageous since PS based on a phenalen-1-one structure nearly quantitatively react according to the type II mechanism (singlet oxygen quantum yields Φ Δ ≥ 0.85) ( Cieplik et al, 2013 , 2015 , 2016 , 2018 ; Späth et al, 2014 ; Tabenski et al, 2016 ). However, target structures of aPDT with this class of PS are still unknown.…”

Section: Introductionmentioning

confidence: 99%

Phenalen-1-one-Mediated Antimicrobial Photodynamic Therapy: Antimicrobial Efficacy in a Periodontal Biofilm Model and Flow Cytometric Evaluation of Cytoplasmic Membrane Damage

Steinwachs¹,

Muehler²,

Hiller³

et al. 2018

Front. Microbiol.

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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.

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Phenalen-1-One-Mediated Antimicrobial Photodynamic Therapy and Chlorhexidine Applied to a Novel Caries Biofilm Model

Cited by 20 publications

References 45 publications

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

Antimicrobial efficacy of alternative compounds for use in oral care toward biofilms from caries‐associated bacteria in vitro

Phenalen-1-one-Mediated Antimicrobial Photodynamic Therapy: Antimicrobial Efficacy in a Periodontal Biofilm Model and Flow Cytometric Evaluation of Cytoplasmic Membrane Damage

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