title: Comparing methods for detecting and characterizing metal oxide nanoparticles in unmodified commercial sunscreens.
abstract: OBJECTIVE
  To determine if commercial sunscreens contain distinct nanoparticles and to evaluate analytical methods for their ability to detect and characterize nanoparticles in unmodified topical products using commercial sunscreens as a model.
  
  
  METHODS
  A total of 20 methods were evaluated for their ability to detect and characterize nanoparticles in unmodified commercial sunscreens.
  
  
  RESULTS
  Variable-pressure scanning-electron microscopy, atomic-force microscopy, laser-scanning confocal microscopy and X-ray diffraction were found to be viable and complementary methods for detecting and characterizing nanoparticles in sunscreens.
  
  
  CONCLUSIONS
  It was determined that several of the commercial sunscreens contained distinct nanoparticles. No one method was able to completely characterize nanoparticles in the unmodified products but the viable methods provided complementary information regarding the nanoparticles and how they were interacting with the sunscreen matrix.
authors.affiliation: Center for Drug Evaluation & Research, FDA, Silver Spring, MD 20993, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Tyner
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wokovich
authors.forename: William H
authors.initials: WH
authors.lastname: Doub
authors.forename: Lucinda F
authors.initials: LF
authors.lastname: Buhse
authors.forename: Li-Piin
authors.initials: LP
authors.lastname: Sung
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Watson
authors.forename: Nakissa
authors.initials: N
authors.lastname: Sadrieh
mesh_terms: D053768:Metal Nanoparticles / Q000032:analysis*; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000032:analysis*; D013473:Sunscreening Agents / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D010087:Oxides; D013473:Sunscreening Agents