title: Diode laser activated indocyanine green selectively kills bacteria.
abstract: OBJECTIVE
  Commercially available photodynamic therapy for periodontal diseases utilizes methylene blue as a photosensitizer. Here we propose a novel photosensitizer dye, indocyanine green (ICG), because it can be readily activated by commercially available dental 810 nm diode lasers and has an established safety record as an intravascular agent in cardiac imaging and ophthalmologic photodynamic therapy. Therefore, we aim to characterize ICG uptake and killing of key periodontal pathogens to explore its potential as a periodontal photodynamic therapy agent.
  
  
  METHODS
  We tested ICG uptake by spectroscopy in Porphyromonas gingivalis 381 and Aggregatibacter actinomycetemcomitans, in addition to Escherichia coli DH5alpha and a human gingival epithelial cell line, HepG, in relation to ICG dose and exposure time. We then measured killing of bacteria by determining viable bacteria counts before and after exposure to ICG and 810 nm diode laser light (0-0.5 W output settings, 0-5 seconds). ICG was also applied to extracted, restored teeth, and the teeth inspected visually for staining after rinsing with saline.
  
  
  RESULTS
  We found rapid and significant uptake of indocyanine green into P. gingivalis 381 and A. actinomycetemcomitans 67, compared to E. coli DH5alpha and HepG gingival cell line. This correlated with significant killing of strains 381 and 67 compared to E.coli, with less than 10% survival. ICG does not appear to stain tooth surfaces and materials except calculus.
  
  
  CONCLUSIONS
  ICG combined with an 810 nm diode laser may be useful as a photodynamic adjunct for reduction of bacterial load in periodontal pockets.
authors.affiliation: College of Dental Medicine, Western University of Health Sciences, 309 East Second Street, Pomona, CA 91766, USA. tboehm@westernu.edu
authors.forename: Tobias K
authors.initials: TK
authors.lastname: Boehm
authors.forename: Sebastian G
authors.initials: SG
authors.lastname: Ciancio
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects* / Q000378:metabolism; D000704:Analysis of Variance; D002460:Cell Line; D055113:Chronic Periodontitis / Q000188:drug therapy / Q000382:microbiology; D004847:Epithelial Cells; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005881:Gingiva / Q000166:cytology; D006801:Humans; D007208:Indocyanine Green / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D054023:Lasers, Semiconductor; D010514:Periodontal Pocket / Q000382:microbiology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D007208:Indocyanine Green