title: Determination of wavelength-specific UV protection factors of sunscreens in intact skin by EPR measurement of UV-induced reactive melanin radical.
abstract: There remains an unmet need for skin tissue-based assays for the measurement of the UVA protection and efficacy of sunscreens. Here we describe development of a novel electron paramagnetic resonance assay that uses the photogeneration of reactive melanin radical as a measure of UV light penetration to melanocytes in situ in skin. We have used areas of focal melanocytic hyperplasia in the skin of Monodelphis domestica to model the human nevus. We show that we are able to use this assay to determine the monochromatic protection factors (mPF) of research and commercial sunscreens at specific narrow wavebands of UVB, UVA and blue visible light. Both commercial sunscreens, a sun protection factor (SPF) 4 and an SPF 30 product, had mPFs in the UVB range that correlated well with their claimed SPF. However, their mPF in the UVA ranges were only about one-third of claimed SPF. This technique can be used to design and assay sunscreens with optimally balanced UVA and UVB protection.
authors.affiliation: College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
authors.forename: Leslie
authors.initials: L
authors.lastname: Lund
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Ley
authors.forename: Linda A
authors.initials: LA
authors.lastname: Felton
authors.forename: Graham S
authors.initials: GS
authors.lastname: Timmins
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D008543:Melanins / Q000378:metabolism*; D000090204:Mesothelin; D051379:Mice; D023421:Models, Animal; D012867:Skin / Q000378:metabolism / Q000528:radiation effects*; D013473:Sunscreening Agents; D014466:Ultraviolet Rays
chemical_list: D008543:Melanins; C000715528:Msln protein, mouse; D013473:Sunscreening Agents; D000090204:Mesothelin