Mild heat and mild ultrasound for five minutes significantly enhances absorption of ascorbic acid into the deep layers of the skin

  • In this study it was found that just five minutes of 36º heat and 20mW of low frequency ultrasound significantly enhanced the absorption of ascorbic acid through the epidermis, dermis and deeper layers of the skin.
  • This adds to the large body of research about sonoporation, an electromesotherapy and corroborates the findings of our daily practice for the last six years, whereby radiofrequency (heat at 41º) and low frequency ultrasound (35W) increases absorption of actives in our treatment creams by 500%.
  • 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-labeled LAA aqueous solution. After 15 min post-exposure, radioactivity was measured in tape-striped stratum corneum (TS-SC), epidermis, dermis, and receptor fluid. Since 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: 5 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 ultrasound/heat treatment, compared to the results of Franz cell model. CONCLUSION: 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 response 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.

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