title: Cutaneous delivery of α-tocopherol and lipoic acid using microemulsions: influence of composition and charge.
abstract: OBJECTIVE
  To assess whether the composition and charge of microemulsions affect their ability to simultaneously deliver α-tocopherol and lipoic acid into viable skin layers.
  
  
  METHODS
  α-Tocopherol and lipoic acid were added (1.1 and 0.5% w/w, respectively) to decylglucoside-based microemulsions containing mono-dicaprylin. Microemulsions containing surfactant : oil : water (w/w/w) at 60 : 30 : 10 (ME-O) and 46 : 23 : 31 (ME-W), as well as a cationic form of ME-W containing 1% phytosphingosine (ME-Wphy) were characterized, and their ability to disrupt the skin barrier and deliver the antioxidants in vitro in the skin was evaluated. Antioxidant activity in ME-Wphy-treated skin was assessed using the thiobarbituric acid-reactive substances (TBARS) assay.
  
  
  RESULTS
  The internal phase diameters of microemulsions ranged between 42 and 55 nm; phytosphingosine addition and pH adjustment to 5.0 increased zeta potential from -4.3 to +29.1 mV. ME-O displayed w/o structure, whereas ME-W and ME-Wphy were consistent with o/w. Microemulsions affected skin electrical resistance and transepidermal water loss, but did not affect lipoic acid penetration. α-Tocopherol delivery increased following the order ME-O < ME-W < ME-Wphy. ME-Wphy presented suitable short-term stability. The antioxidants delivered by ME-Wphy decreased TBARS cutaneous levels.
  
  
  CONCLUSIONS
  Even though microemulsion structure only affected tocopherol penetration, delivered levels of both antioxidants were sufficient for a decrease in TBARS, supporting their use for enhanced protection.
authors: Department of Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA.
authors: Allie
authors: A
authors: Cichewicz
authors: Chelsea
authors: C
authors: Pacleb
authors: Ashley
authors: A
authors: Connors
authors: Martha A
authors: MA
authors: Hass
authors: Luciana B
authors: LB
authors: Lopes
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods; D004655:Emulsions / Q000008:administration & dosage / Q000737:chemistry; D005960:Glucosides / Q000008:administration & dosage / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009821:Oils / Q000737:chemistry; D010539:Permeability; D012867:Skin / Q000378:metabolism; D012869:Skin Absorption; D013110:Sphingosine / Q000031:analogs & derivatives / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D013552:Swine; D008063:Thioctic Acid / Q000008:administration & dosage* / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D024502:alpha-Tocopherol / Q000008:administration & dosage* / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D004655:Emulsions; D005960:Glucosides; D009821:Oils; D013501:Surface-Active Agents; D014867:Water; D008063:Thioctic Acid; C012491:phytosphingosine; D024502:alpha-Tocopherol; D013110:Sphingosine
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