title: Human skin penetration of sunscreen nanoparticles: in-vitro assessment of a novel micronized zinc oxide formulation.
abstract: The extent to which topically applied solid nanoparticles can penetrate the stratum corneum and access the underlying viable epidermis and the rest of the body is a great potential safety concern. Therefore, human epidermal penetration of a novel, transparent, nanoparticulate zinc oxide sunscreen formulation was determined using Franz-type diffusion cells, 24-hour exposure and an electron microscopy to verify the location of nanoparticles in exposed membranes. Less than 0.03% of the applied zinc content penetrated the epidermis (not significantly more than the zinc detected in receptor phase following application of a placebo formulation). No particles could be detected in the lower stratum corneum or viable epidermis by electron microscopy, suggesting that minimal nanoparticle penetration occurs through the human epidermis.
authors.affiliation: Therapeutics Research Unit, Southern Clinical Division, Department of Medicine, University of Queensland, Princess Alexandra Hospital, Woolloongabba, Australia. shereec@soms.uq.edu.au
authors.forename: Sheree E
authors.initials: SE
authors.lastname: Cross
authors.forename: Brian
authors.initials: B
authors.lastname: Innes
authors.forename: Michael S
authors.initials: MS
authors.lastname: Roberts
authors.forename: Takuya
authors.initials: T
authors.lastname: Tsuzuki
authors.forename: Terry A
authors.initials: TA
authors.lastname: Robertson
authors.forename: Paul
authors.initials: P
authors.lastname: McCormick
mesh_terms: D000279:Administration, Cutaneous; D002626:Chemistry, Pharmaceutical; D015194:Diffusion Chambers, Culture; D004817:Epidermis / Q000378:metabolism; D005260:Female; D006801:Humans; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D009924:Organ Culture Techniques; D010316:Particle Size; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D013678:Technology, Pharmaceutical / Q000379:methods; D013997:Time Factors; D015034:Zinc Oxide / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013473:Sunscreening Agents; D015034:Zinc Oxide