title: Analysis of Riboflavin Compounds in the Rabbit Cornea In Vivo.
abstract: To investigate the composition and concentration of individual riboflavin compounds in the corneal stroma in vivo after soaking with various commercially available riboflavin formulations.
  
  
  
  Experiments were performed in 26 rabbit corneas in vivo: 24 corneas were soaked with riboflavin formulations for 30 minutes or with 0.9% NaCl for control (n = 2). After treatment, corneas were excised and prepared for ultra-high-pressure liquid chromatography (UHPLC) analysis. Additionally, computational chemical analysis of riboflavin compounds and keratan sulfate were performed.
  
  
  
  The amount of riboflavin and riboflavin phosphate isomers in cornea decreased by a factor of 10 to 100, when compared to the amount in riboflavin formulations. In particular, we found an inverse relationship in the ratio of riboflavin to riboflavin phosphate isomer concentration between formulations and cornea. The electronegativity and ionization potential of riboflavin and phosphate isomers are different.
  
  
  
  The inverse relationship observed might be explained by a stronger electronegativity of the phosphate isomers, leading to a stronger repulsion by corneal proteoglycans. Indicating the individual concentration of riboflavin compounds in formulations is more representative than the total riboflavin concentration. Riboflavin formulations and CXL protocols might be improved considering the differences in diffusion and ionization potentials of the different riboflavin compounds.
authors.affiliation: a Laboratory for Ocular Cell Biology , University of Geneva , Geneva , Switzerland.
authors.forename: Arthur
authors.initials: A
authors.lastname: Hammer
authors.affiliation: b School of Pharmaceutical Sciences , University of Geneva , Geneva , Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Rudaz
authors.affiliation: b School of Pharmaceutical Sciences , University of Geneva , Geneva , Switzerland.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Guinchard
authors.affiliation: a Laboratory for Ocular Cell Biology , University of Geneva , Geneva , Switzerland.|c Center for Applied Biotechnology and Molecular Medicine (CABMM) , University of Zurich , Zurich , Switzerland.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kling
authors.affiliation: a Laboratory for Ocular Cell Biology , University of Geneva , Geneva , Switzerland.|d Cathedral Eye Clinic Ltd. , University of Ulster , Belfast , Ireland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Richoz
authors.affiliation: a Laboratory for Ocular Cell Biology , University of Geneva , Geneva , Switzerland.|c Center for Applied Biotechnology and Molecular Medicine (CABMM) , University of Zurich , Zurich , Switzerland.|e ELZA Institute , Dietikon/Zurich , Switzerland.|f Department of Ophthalmology , University of Southern California , Los Angeles , CA , USA.
authors.forename: Farhad
authors.initials: F
authors.lastname: Hafezi
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000494:pharmacology; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D003432:Cross-Linking Reagents / Q000493:pharmacokinetics*; D004195:Disease Models, Animal; D007640:Keratoconus / Q000175:diagnosis / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D017319:Photosensitizing Agents / Q000493:pharmacokinetics; D011817:Rabbits; D012256:Riboflavin / Q000493:pharmacokinetics*; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: CXL; Corneal collagen cross-linking; UHPLC; riboflavin