title: Phototoxicity is not associated with photochemical tissue bonding of skin.
abstract: OBJECTIVE
  We have developed a light-activated method called photochemical tissue bonding (PTB) for closing wounds using green light and a photosensitizing dye (Rose Bengal-RB) to initiate photochemical crosslinking of wound surface proteins. These studies were designed to determine whether RB causes phototoxicity during closure of skin incisions with PTB.
  
  
  METHODS
  RB phototoxicity was evaluated after sealing incisions in porcine skin ex vivo and rabbit skin in vivo using PTB (1 mM RB, 100 J/cm(2), 532 nm, 0.3 or 0.5 W/cm(2).) Dead cells were identified by pyknotic nuclei and eosinophilic cytoplasm on H&E-stained sections. The influence on RB phototoxicity of penetration of RB into the wound wall (by confocal microscopy), RB concentration in the tissue (by extraction), and fluence of 532 nm reaching depths in skin (calculated from skin optical properties) were investigated.
  
  
  RESULTS
  No significant differences were found in the percent dead cells in PTB-treated and control incisions in porcine skin at 24 hours or in rabbit skin at 2 hours and 3 and 7 days after surgery. RB was retained in a approximately 100 microm wide band next to the wound wall. The mean RB concentration within this band was 0.42+/-0.03 mM. Monte Carlo modeling of light distribution indicated that the fluence rate decreased from the subsurface peak to 0.5 W/cm(2) in the mid-dermis (approximately 350 microm.) In vitro RB phototoxicity to dermal fibroblasts yielded an LD(50) of 0.50+/-0.09 J/cm(2) when the cells contained 0.46 mM RB.
  
  
  CONCLUSIONS
  PTB does not cause phototoxicity when used to repair skin wounds even though the RB concentration and 532 nm fluence in the mid-dermis during PTB are much greater than the LD(50) for RB phototoxicity in vitro. These results indicate that phototoxicity is not a concern when using PTB for tissue repair.
authors.affiliation: Harvard-MIT Health Sciences Technology Program, Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.forename: Anna
authors.initials: A
authors.lastname: Yaroslavsky
authors.forename: Frank P
authors.initials: FP
authors.lastname: Henry
authors.forename: Robert W
authors.initials: RW
authors.lastname: Redmond
authors.forename: Irene E
authors.initials: IE
authors.lastname: Kochevar
mesh_terms: D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D017484:Dermatitis, Phototoxic / Q000503:physiopathology*; D062109:Dermatologic Surgical Procedures; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts; D007150:Immunohistochemistry; D028022:Low-Level Light Therapy; D008297:Male; D009010:Monte Carlo Method; D017319:Photosensitizing Agents / Q000494:pharmacology / Q000633:toxicity; D011817:Rabbits; D011897:Random Allocation; D012016:Reference Values; D012307:Risk Factors; D012395:Rose Bengal / Q000494:pharmacology*; D012867:Skin / Q000473:pathology; D012869:Skin Absorption / Q000187:drug effects / Q000528:radiation effects; D013552:Swine; D014014:Tissue Adhesives / Q000494:pharmacology*; D014945:Wound Healing / Q000502:physiology*
chemical_list: D017319:Photosensitizing Agents; D014014:Tissue Adhesives; D012395:Rose Bengal