Cutaneous delivery of α-tocopherol and lipoic acid using microemulsions: influence of composition and charge.
Issue Date
2013-06
Authors
Cichewicz, Allie*
Pacleb, Chelsea
Connors, Ashley
Hass, Martha A
Lopes, Luciana B
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Abstract
Objectives: 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.
Key findings: 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.
Citation
Cichewicz A, Pacleb C, Connors A, Hass MA, Lopes LB. Cutaneous delivery of α-tocopherol and lipoic acid using microemulsions: influence of composition and charge. J Pharm Pharmacol. 2013 Jun;65(6):817-26. doi: 10.1111/jphp.12045. Epub 2013 Feb 26. PMID: 23647675; PMCID: PMC3648887.
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R15 AR060008/AR/NIAMS NIH HHS/United States , 1R15AR060008-01A1/AR/NIAMS NIH HHS/United States