title: Development and stability of innovative semisolid formulations containing nanoencapsulated lipoic acid for topical use.
abstract: BACKGROUND
  The cosmetic benefit obtained from the use of lipoic acid in the treatment of different skin disorders related to oxidative stress is compromised by its chemical instability, which complicates the preparation of cosmetic formulations suitable for topical use. Considering that nanoencapsulation increases the stability of lipoic acid, the aim of this study was to develop different semisolid formulations, based on innovative cosmetic ingredients and containing lipoic acid-loaded nanocapsules.
  
  
  METHODS
  Lipoic acid-loaded nanocapsules (5.0 mg/mL) were prepared by interfacial deposition of the pre-formed polymer and the thickening agents Aristoflex AVC and DC RM2051, used alone or in combination. The formulations were characterized in terms of resistance to centrifugation, pH, lipoic acid content, rheological characteristics and optical parameters determined by multiple light scattering. Also, their stability when subjected to cycles of thermal heating and freezing was evaluated.
  
  
  CONCLUSIONS
  The semisolid formulations presented suitable properties for cutaneous administration, with enhanced physicochemical stability, considering the drug content and resistance to centrifugation, being observed for the formulations containing nanocapsules. All of the proposed formulations showed pseudoplastic flow behavior. The nanoencapsulation leads to an increase in the flow indexes. After the stress cycles an improvement in the consistency, particularly for the formulations containing nanocapsules, was observed. According to the results of multiple light scattering analysis, the formulations can be considered stable.
  
  
  CONCLUSIONS
  The use of new cosmetic ingredients, unlike traditional hydrogels, represents a differentiated platform for preparation of stable semisolid formulations containing polymeric nanocapsules, presenting physicochemical properties suitable for topical use.
authors: Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, 90610-000, Rio Grande do Sul, Brasil.
authors: Irene C
authors: IC
authors: Külkamp-Guerreiro
authors: Thatiana F
authors: TF
authors: Terroso
authors: Evelise R
authors: ER
authors: Assumpção
authors: Simone J
authors: SJ
authors: Berlitz
authors: Renata V
authors: RV
authors: Contri
authors: Adriana R
authors: AR
authors: Pohlmann
authors: Silvia S
authors: SS
authors: Guterres
mesh_terms: D000287:Administration, Topical; D002626:Chemistry, Pharmaceutical; D004339:Drug Compounding; D006863:Hydrogen-Ion Concentration; D036103:Nanotechnology; D012212:Rheology; D008063:Thioctic Acid / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D008063:Thioctic Acid