title: Porcine ear skin as a biological substrate for in vitro testing of sunscreen performance.
abstract: OBJECTIVE
  The purpose of the study was to examine the use of skin from porcine ears as a biological substrate for in vitro testing of sunscreens in order to overcome the shortcomings of the presently used polymethylmethacrylate (PMMA) plates that generally fail to yield a satisfactory correlation between sun protection factors (SPF) in vitro and in vivo.
  
  
  METHODS
  Trypsin-separated stratum corneum and heat-separated epidermis provided UV-transparent substrates that were laid on quartz or on PMMA plates. These were used to determine surface roughness by chromatic confocal imaging and to measure SPF in vitro of 2 sunscreens by diffuse transmission spectroscopy.
  
  
  RESULTS
  The recovered skin layers showed a lower roughness than full-thickness skin but yielded SPF in vitro values that more accurately reflected the SPF determined in vivo by a validated procedure than PMMA plates, although the latter had in part roughness values identical to those of intact skin. Combination of skin tissue with a high roughness PMMA plate also provided accurate SPF in vitro.
  
  
  CONCLUSIONS
  Besides roughness, the improved affinity of the sunscreen to the skin substrate compared to PMMA plates may explain the better in vitro prediction of SPF achieved with the use of a biological substrate.
authors.affiliation: Institute of Pharmaceutical Technology, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland.
authors.forename: Myriam
authors.initials: M
authors.lastname: Sohn
authors.forename: Verena
authors.initials: V
authors.lastname: Korn
authors.forename: Georgios
authors.initials: G
authors.lastname: Imanidis
mesh_terms: D000818:Animals; D004423:Ear; D004817:Epidermis / Q000378:metabolism* / Q000528:radiation effects; D066298:In Vitro Techniques; D019904:Polymethyl Methacrylate; D011791:Quartz; D013473:Sunscreening Agents / Q000494:pharmacology*; D013499:Surface Properties; D013552:Swine; D014466:Ultraviolet Rays
chemical_list: D013473:Sunscreening Agents; D011791:Quartz; D019904:Polymethyl Methacrylate