title: Flow cytometric assessment of Streptococcus mutans viability after exposure to blue light-activated curcumin.
abstract: BACKGROUND
  Streptococcus mutans biofilms are considered as primary causative agents of dental caries. Photodynamic antimicrobial chemotherapy (PACT) has been recently proposed as a strategy for inactivating dental biofilms. This study aimed to investigate the effect of blue light-activated curcumin on S. mutans viability and to explore its potential as a new anti-caries therapeutic agent. The effect of different concentrations and incubation times of photo-activated curcumin on the survival of S. mutans in planktonic and biofilm models of growth was assessed by flow cytometry.
  
  
  METHODS
  Streptococcus mutans in planktonic suspensions or biofilms formed on hydroxyapatite disks were incubated for 5 or 10min with curcumin prior to blue light activation. Bacteria were labeled with SYTO 9 and propidium iodide before viability was assessed by flow cytometry. Results were statistically analyzed using one-way ANOVA and Tukey multiple comparison intervals (α=0.05).
  
  
  RESULTS
  For planktonic cultures, 0.2μM of light-activated curcumin significantly reduced S. mutans viability (p<0.05). For biofilm cultures, light-activated curcumin at concentration of 40-60μM only suppressed viability by 50% (p<0.05). Independently of the mode of growth, incubation time has no significant effect on PACT efficiency.
  
  
  CONCLUSIONS
  This study indicates that blue light-activated curcumin can efficiently inactivate planktonic cultures of S. mutans whereas biofilms were more resistant to treatment. Flow cytometry allowed the detection of bacteria with damaged membranes that were unable to replicate and grow after cell sorting. Further studies seem warranted to optimize the efficacy of light-activated curcumin against S. mutans biofilms.
authors: Endodontics Unit, Section of Dental Medicine, University of Geneva, 19 rue Barthelemy Menn, CH-1205 Geneva, Switzerland. Electronic address: dcmanoil@gmail.com.
authors: Daniel
authors: D
authors: Manoil
authors: Endodontics Unit, Section of Dental Medicine, University of Geneva, 19 rue Barthelemy Menn, CH-1205 Geneva, Switzerland. Electronic address: Anna.Filieri@unige.ch.
authors: Anna
authors: A
authors: Filieri
authors: Flow Cytometry Facility, Faculty of Medecine, University of Geneva, Rue Michel-Servet 1, CH-1211 Geneva 4, Switzerland. Electronic address: Cecile.Gameiro@unige.ch.
authors: Cécile
authors: C
authors: Gameiro
authors: Department of Pharmaceutics and Biopharmaceutics, School of Pharmaceutical Sciences, University of Geneva, Quai Ernest Ansermet 30, CH-1211, Geneva 4, Switzerland. Electronic address: Norbert.Lange@unige.ch.
authors: Norbert
authors: N
authors: Lange
authors: Service of Infectious Diseases, University Hospitals of Geneva, Rue Micheli-du-Crest 24, CH-1205 Geneva, Switzerland. Electronic address: Jacques.Schrenzel@unige.ch.
authors: Jacques
authors: J
authors: Schrenzel
authors: Department of Restorative Dentistry, University of Washington, Box 357456, 1959 NE Pacific Street, Seattle, WA 98195-7456, USA. Electronic address: jwataha@gmail.com.
authors: John C
authors: JC
authors: Wataha
authors: Endodontics Unit, Section of Dental Medicine, University of Geneva, 19 rue Barthelemy Menn, CH-1205 Geneva, Switzerland. Electronic address: Serge.Bouillaguet@unige.ch.
authors: Serge
authors: S
authors: Bouillaguet
mesh_terms: D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D003116:Color; D003474:Curcumin / Q000528:radiation effects*; D005434:Flow Cytometry / Q000379:methods*; D008027:Light; D010775:Photic Stimulation / Q000379:methods*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000528:radiation effects; D011829:Radiation Dosage; D013295:Streptococcus mutans / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology
chemical_list: D017319:Photosensitizing Agents; D003474:Curcumin
keywords: BacLight; Biofilm; Dentistry; Flow cytometry; PDT