title: Effect of ultrasound and heat on percutaneous absorption of l-ascorbic acid: human in vitro studies on Franz cell and Petri dish systems.
abstract: OBJECTIVE
  Percutaneous absorption of l-ascorbic acid (LAA) is limited due to its high hydrophilicity and low stability. Here, we investigated the effect of post-dosing sonophoresis (329 kHz, 20 mW cm-2) and heat (36°C) on transdermal delivery of LAA.
  
  
  METHODS
  Ultrasound/heat, heat and control treatments were applied on skin surface for 2 and 5 min after topical application of C14-labelled LAA aqueous solution. After 15 min post-exposure, radioactivity was measured in tape-striped stratum corneum (TS-SC), epidermis, dermis and receptor fluid. As Franz diffusion cell model may have different acoustic response than in vivo human tissues, a novel Petri dish model was developed and compared with Franz cell model on the effects of ultrasound/heat treatment on the skin permeability.
  
  
  RESULTS
  Five-min ultrasound/heat treatment significantly accelerated skin absorption/penetration of LAA; 2-min treatment showed no enhancement effect on Franz diffusion cell model at the end of experiment. The use of Petri dish model significantly increased LAA concentrations in epidermis after 5 min of ultrasound/heat treatment, compared to the results of Franz cell model.
  
  
  CONCLUSIONS
  Combination of ultrasound (329 kHz, 20 mW cm-2) and heat (36°C) significantly enhanced LAA transdermal penetration, when the time of treatment was sufficient (5 min). As Petri dish model was designed to simulate acoustic respond of dense human tissue to ultrasound, the difference between Franz cell and Petri dish models suggests that the enhancement effect of ultrasound/heat on skin penetration in vivo may be greater than that determined on in vitro Franz cell model.
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Jung
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Skin & Cosmetic Research Department, Shanghai Skin Disease Hospital, Shanghai, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Zou
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Elmahdy
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: X
authors.initials: X
authors.lastname: Hui
authors.affiliation: Department of Dermatology, University of California San Francisco, 90 Medical Center Way, Surge 110, San Francisco, CA, USA.
authors.forename: H I
authors.initials: HI
authors.lastname: Maibach
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D018929:Cell Culture Techniques; D006358:Hot Temperature; D006801:Humans; D066298:In Vitro Techniques; D014465:Ultrasonics
chemical_list: D001205:Ascorbic Acid
keywords: l-ascorbic acid; percutaneous penetration; skin barrier; skin structure; sonophoresis