title: Melatonin-based pickering emulsion for skin's photoprotection.
abstract: BACKGROUND
  Based on its antioxidant activity, melatonin was recently found to have a protection effect against photocarcinogenesis.
  
  
  OBJECTIVE
  This work aimed to develop an innovative sunscreen formulation based on the Pickering emulsions concept, stabilized by physical UV filters, modified starch and natural oils associated to melatonin as a key strategy for prevention against UV-induced skin damage.
  
  
  METHODS
  For this purpose, melatonin was incorporated in Pickering emulsions that were characterized using physicochemical, in vitro and in vivo testing. Physicochemical studies included physical and chemical stability by a thorough pharmaceutical control. The possible protective effects of melatonin against UV-induced cell damage in HaCaT cell lines were investigated in vitro. The safety assessment and the in vivo biological properties of the final formulations, including Human Repeat Insult Patch Test and sunscreen water resistance tests were also evaluated.
  
  
  CONCLUSIONS
  These studies demonstrated that melatonin sunscreen Pickering emulsion was beneficial and presented a powerful protection against UVB-induced damage in HaCat cells, including inhibition of apoptosis. The inclusion of zinc oxide, titanium dioxide, green coffee oil and starch ensured a high SPF (50+) against UVA and UVB.
  
  
  CONCLUSIONS
  The combination of melatonin, multifunctional solid particles and green coffee oil, contributed to achieve a stable, effective and innovative sunscreen with a meaningful synergistic protection against oxidative stress.
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Joana
authors.initials: J
authors.lastname: Marto
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Andreia
authors.initials: A
authors.lastname: Ascenso
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Lídia M
authors.initials: LM
authors.lastname: Gonçalves
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Luís F
authors.initials: LF
authors.lastname: Gouveia
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Manteigas
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Pedro
authors.initials: P
authors.lastname: Pinto
authors.affiliation: b Laboratórios Atral S.A , Castanheira Do Ribatejo , Portugal.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Oliveira
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: António J
authors.initials: AJ
authors.lastname: Almeida
authors.affiliation: a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon , Portugal and.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Ribeiro
mesh_terms: D004655:Emulsions / Q000008:administration & dosage* / Q000737:chemistry*; D006801:Humans; D008550:Melatonin / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D009821:Oils / Q000008:administration & dosage* / Q000737:chemistry; D018384:Oxidative Stress / Q000187:drug effects*; D012867:Skin; D013213:Starch; D013473:Sunscreening Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D004655:Emulsions; D009821:Oils; D013473:Sunscreening Agents; C009495:titanium dioxide; D013213:Starch; D014025:Titanium; D008550:Melatonin; D015034:Zinc Oxide
keywords: Antioxidant; melatonin; photodamage; pickering emulsion; topical delivery