title: Formulation and characterization of liquid crystal systems containing azelaic acid for topical delivery.
abstract: OBJECTIVE
  The aim of this study is to prepare and characterize azelaic acid (AzA) containing liquid crystal (LC) drug delivery systems for topical use.
  
  
  METHODS
  Two ternary phase diagrams, containing liquid paraffin as the oil component and a mixture of two nonionic surfactants (Brij 721P and Brij 72), were constructed. Formulations chosen from the phase diagrams were characterized by polarized light microscopy, rheological analyses, differential scanning calorimetry (DSC), and small angle x-ray scattering spectroscopy.
  
  
  RESULTS
  Polarized light microscopy proved that except the oil/water emulsion (O/W E), other formulations showed lamellar LC structure. In vitro release studies indicated that the fastest release was achieved by the Lamellar LC (LLC) and O/W E systems, whereas slower release was obtained from the emulsion containing lamellar LC (E-LLC) and distorted lamellar LC (D-LLC) systems. Results of rheological measurements both supported the results of in vitro release studies and showed that the emulsion containing the LC (E-LLC) system had the most stable structure. The formulations and their effect on stratum corneum (SC) were evaluated by DSC studies. The lamellar LC (LLC), emulsion containing lamellar liquid crystal (E-LLC), and O/W E formulations had an effect on both lipid and protein components of SC, whereas distorted lamellar liquid crystal (D-LLC) system had an effect on only the lipid components of SC.
  
  
  CONCLUSIONS
  LLC systems could be considered promising for the topical delivery of AzA.
authors.affiliation: Department of Pharmaceutical Technology, Hacettepe University, Faculty of Pharmacy, Ankara, Turkey.
authors.forename: Merve
authors.initials: M
authors.lastname: Aytekin
authors.forename: R Neslihan
authors.initials: RN
authors.lastname: Gursoy
authors.forename: Semra
authors.initials: S
authors.lastname: Ide
authors.forename: Elif H
authors.initials: EH
authors.lastname: Soylu
authors.forename: Sueda
authors.initials: S
authors.lastname: Hekimoglu
mesh_terms: D000287:Administration, Topical; D003879:Dermatologic Agents / Q000008:administration & dosage / Q000737:chemistry*; D003998:Dicarboxylic Acids / Q000008:administration & dosage / Q000737:chemistry*; D016503:Drug Delivery Systems; D004655:Emulsions / Q000008:administration & dosage / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry*
chemical_list: D003879:Dermatologic Agents; D003998:Dicarboxylic Acids; D004655:Emulsions; C010038:azelaic acid