title: Evaluating in vivo delivery of riboflavin with coulomb-controlled iontophoresis for corneal collagen cross-linking: a pilot study.
abstract: OBJECTIVE
  To evaluate the efficacy of coulomb-controlled iontophoresis (CCI) for delivery of riboflavin prior to corneal collagen cross-linking (CXL).
  
  
  METHODS
  The eyes of 20 8-week-old Lewis rats, subject to epithelium-ON (epi-ON, n = 20 eyes) or epithelium-OFF (epi-OFF, n = 20 eyes) conditions, were used to evaluate the in vivo delivery of two riboflavin solutions: 0.1% riboflavin-20% dextran T500 solution (riboflavin-dextran) and 0.1% riboflavin 5'-phosphate (riboflavin-phosphate). After systemic intramuscular anesthesia, 0.25 mL of the photosensitizing agent was delivered by either instillation or CCI (2.11 mA/cm(2) for 4 or 10 minutes) into either epithelial condition. The CCI probe on the eye without current served as control. Confocal microscopy of flat-mounted corneas was used to analyze intracorneal penetration and fluorometry was used to quantify riboflavin in the aqueous within 30 minutes of treatment.
  
  
  RESULTS
  Instillation and CCI allowed for uniform delivery of riboflavin-dextran throughout the stroma after epithelial debridement. Transepithelial delivery of riboflavin-dextran was not efficacious. Riboflavin-phosphate was successfully delivered in both epithelium conditions. Complete saturation of the cornea was achieved using CCI after removing the epithelium, the epi-ON case allowed for limited diffusion. Increasing the time from 4 to 10 minutes greatly increased the amount of riboflavin detected in the cornea and aqueous humor.
  
  
  CONCLUSIONS
  Coulomb-controlled iontophoresis is an effective technique for transepithelial delivery of riboflavin-phosphate into the cornea. This drug delivery method would allow clinicians to significantly shorten the time required for the CXL procedure, with or without epithelial debridement. Whether efficient crosslinking can be achieved through an intact epithelium remains to be demonstrated.
authors.affiliation: Ophthalmic Biophysics Center, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Arboleda
authors.forename: Laura
authors.initials: L
authors.lastname: Kowalczuk
authors.forename: Michèle
authors.initials: M
authors.lastname: Savoldelli
authors.forename: Christophe
authors.initials: C
authors.lastname: Klein
authors.forename: Sophia
authors.initials: S
authors.lastname: Ladraa
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Naud
authors.forename: Mariela C
authors.initials: MC
authors.lastname: Aguilar
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Parel
authors.forename: Francine
authors.initials: F
authors.lastname: Behar-Cohen
mesh_terms: D000818:Animals; D003094:Collagen / Q000187:drug effects / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D003432:Cross-Linking Reagents; D004195:Disease Models, Animal; D016503:Drug Delivery Systems; D007478:Iontophoresis / Q000379:methods*; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D017319:Photosensitizing Agents / Q000008:administration & dosage; D010865:Pilot Projects; D051381:Rats; D011917:Rats, Inbred Lew; D012256:Riboflavin / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: collagen cross-linking; drug delivery; iontophoresis; keratoconus; riboflavin