title: Evaluation of anti-microbial activities of ZnO, citric acid and a mixture of both against Propionibacterium acnes.
abstract: OBJECTIVE
  In this study, anti-microbial activities of ZnO of three different particle sizes of citric acid (CA) and of mixtures of ZnO and CA were confirmed against Propionibacterium acnes.
  
  
  METHODS
  ZnO with the smallest particle size showed relatively high anti-microbial activity by disc diffusion assay and broth macrodilution assay. The mixtures of ZnO and CA also showed relatively high anti-microbial activity when the particle size of ZnO was the smallest. Furthermore, anti-microbial activities of ZnO, CA and the mixtures of ZnO and CA were compared through the checkerboard assay.
  
  
  RESULTS
  The results indicated that a 1 : 1 ratio of ZnO and CA resulted in the highest anti-microbial activity. The substances were confirmed to have synergic anti-microbial effects. With the time-kill curve assay, the mixture of ZnO-containing CA reduced the surviving microbial content the most after 24 h.
  
  
  CONCLUSIONS
  The results of our study suggest that ZnO may not only be an anti-microbial ingredient for the prevention of and treatment of acne. The results of our study suggest that ZnO may be an anti-microbial ingredient for the prevention of and treatment of acne when mixed with CA.
authors.affiliation: Department of Fine Chemistry, Cosmetic R&D Center, College of Energy and Biotechnology, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul, 139-743, Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Bae
authors.affiliation: Department of Fine Chemistry, Cosmetic R&D Center, College of Energy and Biotechnology, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul, 139-743, Korea.
authors.forename: S N
authors.initials: SN
authors.lastname: Park
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D019343:Citric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D011425:Propionibacterium acnes / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D017382:Reactive Oxygen Species; D019343:Citric Acid; D015034:Zinc Oxide
keywords: 
  Propionibacterium acnes
  ; FBC index; anti-microbial; citric acid; zinc oxide