title: The efficiency of cross-linking methods in eradication of bacteria is influenced by the riboflavin concentration and the irradiation time of ultraviolet light.
abstract: OBJECTIVE
  To determine bacterial eradication using numerous riboflavin concentrations and different ultraviolet light A (UVA) radiant and exposure time in an experimental model.
  
  
  METHODS
  Dilutions of Staphylococcus epidermidis were mixed with riboflavin at varying concentrations (0.007–0.09%). Effects on bacterial growth were evaluated after 0, 3, 6, 30 and 60 min of UVA exposure (irradiance 30 and 3 mW/cm2). Standard settings of UVA were compared with high-power UVA approach. Different fluid thicknesses of the exposed dilutions were also examined to improve the model.
  
  
  RESULTS
  Bacterial eradication (%) was increased after 60 compared with 30 min of UVA exposure for concentrations of 0.03–0.07% but not for 0.09% riboflavin.There was a significant difference between the efficacy between 0.03 and 0.09% and eradication dropped from 80%to 50%(p = 0.01).A correlation could be calculated for the amount of riboflavin at 60 min of UVA and the ability to kill bacteria(p = 0.01). The antibacterial effect was more pronounced when the tested bacterial suspension thickness was reduced. High-power UVA method was less potent in microbial elimination, eradicating only 60%of bacteria after 6 min versus 97–99%after 60 min in the low-power setting, compared with respective controls (p = 0.02).
  
  
  CONCLUSIONS
  In these in vitro experiments, a longer UVA exposure time in combination with lower riboflavin levels were found to be favourable in killing bacteria as compared to the standard cross-linking settings. Further studies are needed to evaluate the clinical relevance of these findings.
authors.forename: Anders
authors.initials: A
authors.lastname: Bäckman
authors.forename: Karim
authors.initials: K
authors.lastname: Makdoumi
authors.forename: Jes
authors.initials: J
authors.lastname: Mortensen
authors.forename: Sven
authors.initials: S
authors.lastname: Crafoord
mesh_terms: D015169:Colony Count, Microbial; D003131:Combined Modality Therapy; D003432:Cross-Linking Reagents; D006801:Humans; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D012256:Riboflavin / Q000008:administration & dosage*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control* / Q000532:radiotherapy; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000254:growth & development / Q000528:radiation effects*; D013997:Time Factors; D016896:Treatment Outcome; D014466:Ultraviolet Rays; D014467:Ultraviolet Therapy
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D012256:Riboflavin