title: Nanoparticle coated submicron emulsions: sustained in-vitro release and improved dermal delivery of all-trans-retinol.
abstract: OBJECTIVE
  The aim of this research is to investigate the dermal delivery of all-trans-retinol from nanoparticle-coated submicron oil-in-water emulsions as a function of the initial emulsifier type, the loading phase of nanoparticles, and the interfacial structure of nanoparticle layers.
  
  
  METHODS
  The interfacial structure of emulsions was characterized using freeze-fracture-SEM. In-vitro release and skin penetration of all-trans-retinol were studied using Franz diffusion cells with cellulose acetate membrane, and excised porcine skin. The distribution profile was obtained by horizontal sectioning of the skin using microtome-cryostat and HPLC assay.
  
  
  RESULTS
  The steady-state flux of all-trans-retinol from silica-coated lecithin emulsions was decreased (up to 90%) and was highly dependent on the initial loading phase of nanoparticles; incorporation from the aqueous phase provided more pronounced sustained release. For oleylamine emulsions, sustained release effect was not affected by initial location of nanoparticles. The skin retention significantly (p < or = 0.05) increased and was higher for positive oleylamine-stabilised droplets. All-trans-retinol was mainly localized in the epidermis with deeper distribution to viable skin layers in the presence of nanoparticles, yet negligible permeation (approximately 1% of topically applied dose) through full-thickness skin.
  
  
  CONCLUSIONS
  Sustained release and targeted dermal delivery of all-trans-retinol from oil-in-water emulsions by inclusion of silica nanoparticles is demonstrated.
authors.affiliation: Ian Wark Research Institute, ARC Special Research Centre for Particle and Material Interfaces, University of South Australia, Adelaide, South Australia 5095, Australia. ghony001@students.unisa.edu.au
authors.forename: Nasrin
authors.initials: N
authors.lastname: Ghouchi Eskandar
authors.forename: Spomenka
authors.initials: S
authors.lastname: Simovic
authors.forename: Clive A
authors.initials: CA
authors.lastname: Prestidge
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D016503:Drug Delivery Systems / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D012822:Silicon Dioxide / Q000737:chemistry; D012869:Skin Absorption; D013552:Swine; D014801:Vitamin A / Q000008:administration & dosage* / Q000493:pharmacokinetics*
chemical_list: D004655:Emulsions; D014801:Vitamin A; D012822:Silicon Dioxide