title: Effect of preparation and processing conditions on UV absorbing properties of hydroxyapatite-Fe2O3sunscreen.
abstract: The development of innovative, safe and non-photocatalytic sunscreens is urgently needed, as it is essential to have sunscreen filters offering appropriate UV protection without damaging the environment and/or generating free radicals when in contact with the skin. Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) when substituted with iron has UV protection properties and is not photocatalytic; HAp was used to make a sunscreen filter by treating cod fish bones in an iron-containing solution, and then calcining them at 700°C. Here we present a systematic and advanced study on this material, to obtain a sunscreen with improved UV absorbing properties. Bones were treated with three different iron salts - Fe(II) chloride, Fe(II) lactate and Fe(III) nitrate - under various pH conditions. Results showed that Fe(II) chloride in basic pH led to the most effective iron inclusion. High energy ball milling or ultrasound were investigated to increase surface area and corresponding UV absorption; high energy ball milling treatment led to the best optical properties. The optimum powders were used to formulate UV protection creams, which showed Sun Protection Factor (SPF) values significantly superior to the control cream (up to 4.1). Moreover the critical wavelength (λcrit) was >370nm (388-389nm) and UVA/UVB ratios were very close to 1. With these properties these sunscreens can be classified as broad UV protectors. Results also showed that combining these powders with other sunscreens (i.e. titanium dioxide), a synergic effect between the different components was also observed. This investigation showed that HAp-based sunscreens of marine origin are a valid alternative to commercial products, safe for the health of the customers and, being non-photocatalytic, do not pose a threat to the environment.
authors.affiliation: Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior Biotecnologia, Porto, Portugal.
authors.forename: M A
authors.initials: MA
authors.lastname: C Teixeira
authors.affiliation: Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior Biotecnologia, Porto, Portugal. Electronic address: cpiccirillo@porto.ucp.pt.
authors.forename: C
authors.initials: C
authors.lastname: Piccirillo
authors.affiliation: Department of Engineering of Materials and Ceramics/CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal.
authors.forename: D M
authors.initials: DM
authors.lastname: Tobaldi
authors.affiliation: Department of Engineering of Materials and Ceramics/CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal.
authors.forename: R C
authors.initials: RC
authors.lastname: Pullar
authors.affiliation: Department of Engineering of Materials and Ceramics/CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal.
authors.forename: J A
authors.initials: JA
authors.lastname: Labrincha
authors.affiliation: Inovapotek, Pharmaceutical Research and Development, Porto, Portugal.
authors.forename: M O
authors.initials: MO
authors.lastname: Ferreira
authors.affiliation: Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior Biotecnologia, Porto, Portugal.
authors.forename: P M
authors.initials: PM
authors.lastname: L Castro
authors.affiliation: Universidade Católica Portuguesa, CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior Biotecnologia, Porto, Portugal.
authors.forename: M M
authors.initials: MM
authors.lastname: E Pintado
mesh_terms: D017886:Durapatite / Q000737:chemistry*; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013473:Sunscreening Agents / Q000138:chemical synthesis* / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D005290:Ferric Compounds; D013473:Sunscreening Agents; C000499:ferric oxide; D017886:Durapatite
keywords: Critical wavelength; Hydroxyapatite; Iron oxide; Sun Protection Factor; Sunscreen; UVA/UVB