Nanoemulsion-based patch for the dermal delivery of ascorbic acid

Photo-aging is caused mainly by sun radiations, which consist mainly of the ultraviolet radiation (UVA and UVB). Ascorbic acid (AA) has been widely used in the cosmetic field as an anti-wrinkle, anti-pigmentary, and antioxidant agents, however, its cosmetic application is limited due to its poor penetration across the skin, rapid oxidation, and instability of the formulation. The objective of the present study was to utilize a nanoemulsion as a nanocarrier strategy to deliver AA dermally and stabilize it. A concentration of 80 mg/mL AA was loaded into oil-in-water (O/W) nanoemulsion and characterized in terms of droplet size, zeta potential, thermodynamic stability, and morphology. Patches were then prepared using hydroxypropyl methylcellulose (HPMC) and sodium carboxymethyl cellulose (NaCMC), AA nanoemulsion, and plasticizers (PEG 400 in Formulation 1, F1, and isopropanol in Formulation 2, F2) and evaluated in terms of stability, in vitro release, and ex vivo permeation study. The mean droplet size of the AA nanoemulsion was 14.4 +/- 1.9 nm, zeta potential was close to zero. The AA nanoemulsion was physically stable showing no phase separation or turbidity after centrifugation and heating/cooling tests. The cumulative amount per area of AA permeated across Strat-M (R) membrane was 602.2 +/- 57.9 mu g/cm(2). The ex vivo permeation profile showed a controlled-release profile of AA within 24 h, achieving a maximum amount of 414 mu g permeated across the stratum corneum. The release fitted the Higuchi model with a correlation coefficient of 0.995. Nanoemulsion-based patches could serve a potential system for the dermal delivery of unstable hydrophilic compound