title: The influence of microemulsion structure on their skin irritation and phototoxicity potential.
abstract: The purpose of this study was to examine skin irritation and phototoxicity potentials of several microemulsions (ME), all comprising approximately the same percentage of surfactant mixture, but varying oil/water content and consequently inner structure being either droplet-like (o/w ME, o/w ME carbomer, w/o ME and w/o ME white wax) or lamellar (gel-like ME). Two different in vitro methods were used: MTT assay (performed either on reconstructed human epidermis (RHE) or NCTC 2544 cells) and pig ear test. Neither assay revealed the difference among ME with droplet-like structure. Then again, pig ear test and MTT assay performed on RHE indicated that gel-like ME is more irritant compared to other tested ME, whereas no difference among formulations were observed by MTT assay on NCTC 2544 cells. The reasonable explanation is destruction and consequently uniform structure of ME upon dilution that is inevitable for testing on cell cultures. The results of phototoxicity test again indicated the increased potential of gel-like ME to cause adverse effects on skin. It can be concluded that for ME consisting of the same amount of identical surfactants but having different structure the latter represent a crucial factor that determines their dermal toxicity.
authors.affiliation: Faculty of pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia.
authors.forename: Branka
authors.initials: B
authors.lastname: Rozman
authors.affiliation: Faculty of pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Gosenca
authors.affiliation: Laboratoire de Recherche et Développement de Pharmacie Galénique Industrielle, EA 4169 Fonctions physiologiques et pathologiques de la barrière cutanée, Faculté de Pharmacie, Université Claude Bernard Lyon I, 8 Avenue Rockefeller, F-69373 Lyon Cedex 08, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Falson
authors.affiliation: Faculty of pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia. Electronic address: mirjana.gasperlin@ffa.uni-lj.si.
authors.forename: Mirjana
authors.initials: M
authors.lastname: Gašperlin
mesh_terms: D000818:Animals; D002460:Cell Line; D002626:Chemistry, Pharmaceutical / Q000379:methods; D017484:Dermatitis, Phototoxic / Q000209:etiology*; D004655:Emulsions; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D023422:Skin Irritancy Tests; D013501:Surface-Active Agents / Q000737:chemistry*; D013552:Swine
chemical_list: D004655:Emulsions; D013501:Surface-Active Agents
keywords: Keratinocyte cell cultures; Microemulsion; Phototoxicity; RHE; Skin irritation; Structure