title: Measuring sunscreen protection against solar-simulated radiation-induced structural radical damage to skin using ESR/spin trapping: development of an ex vivo test method.
abstract: The in vitro star system used for sunscreen UVA-testing is not an absolute measure of skin protection being a ratio of the total integrated UVA/UVB absorption. The in vivo persistent-pigment-darkening method requires human volunteers. We investigated the use of the ESR-detectable DMPO protein radical-adduct in solar-simulator-irradiated skin substitutes for sunscreen testing. Sunscreens SPF rated 20+ with UVA protection, reduced this adduct by 40-65% when applied at 2 mg/cm(2).   SPF 15 Organic UVA-UVB (BMDBM-OMC) and TiO(2)-UVB filters and a novel UVA-TiO(2) filter reduced it by 21, 31 and 70% respectively. Conventional broad-spectrum sunscreens do not fully protect against protein radical-damage in skin due to possible visible-light contributions to damage or UVA-filter degradation. Anisotropic spectra of DMPO-trapped oxygen-centred radicals, proposed intermediates of lipid-oxidation, were detected in irradiated sunscreen and DMPO. Sunscreen protection might be improved by the consideration of visible-light protection and the design of filters to minimise radical leakage and lipid-oxidation.
authors.affiliation: RAFT Institute, Mount Vernon Hospital, Northwood, Middlesex, UK. haywoodr@raft.ac.uk
authors.forename: Rachel
authors.initials: R
authors.lastname: Haywood
authors.forename: Arsen
authors.initials: A
authors.lastname: Volkov
authors.forename: Carima
authors.initials: C
authors.lastname: Andrady
authors.forename: Robert
authors.initials: R
authors.lastname: Sayer
mesh_terms: D002478:Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects; D047188:Chalcones / Q000528:radiation effects; D002934:Cinnamates / Q000528:radiation effects; D003497:Cyclic N-Oxides; D018736:DNA Adducts; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D005347:Fibroblasts / Q000737:chemistry / Q000187:drug effects* / Q000528:radiation effects*; D005609:Free Radicals; D006801:Humans; D066298:In Vitro Techniques; D015603:Keratinocytes / Q000737:chemistry / Q000187:drug effects* / Q000528:radiation effects*; D008055:Lipids / Q000032:analysis / Q000528:radiation effects; D008297:Male; D018384:Oxidative Stress; D011427:Propiophenones; D011506:Proteins / Q000528:radiation effects; D012867:Skin / Q000166:cytology / Q000528:radiation effects*; D017768:Skin, Artificial; D013113:Spin Labels; D013473:Sunscreening Agents / Q000494:pharmacology* / Q000528:radiation effects; D014025:Titanium / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D047188:Chalcones; D002934:Cinnamates; D003497:Cyclic N-Oxides; D018736:DNA Adducts; D005609:Free Radicals; D008055:Lipids; D011427:Propiophenones; D011506:Proteins; D013113:Spin Labels; D013473:Sunscreening Agents; C009495:titanium dioxide; C118580:octylmethoxycinnamate; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D014025:Titanium; C049935:avobenzone