A physical method to enhance transdermal delivery of a tissue optical clearing agent: combination of microneedling and sonophoresis.

BACKGROUND AND OBJECTIVES Various physical methods, such as microneedling, laser ablation, sonophoresis, and sandpaper, have been widely studied to enhance the transdermal delivery of tissue optical clearing (TOC) agents. A previous study demonstrated that the microneedling method could effectively enhance the permeability of a TOC agent through the skin barrier. STUDY DESIGN/MATERIALS AND METHODS In this study, we introduce a new physical combination method which utilizes both microneedling and sonophoresis to further enhance the transdermal delivery of a TOC agent, glycerol. Porcine skin samples were divided into a control group treated only with the microneedle roller and a test group treated with both the microneedle roller and sonophoresis. Glycerol was applied topically after microneedling. The optimal concentration and transdermal delivery efficacy of glycerol were quantitatively evaluated. RESULTS A 70% glycerol solution was determined to be the optimal concentration for the combination method. The combination method resulted in approximately a 2.3-fold higher transdermal diffusion rate of glycerol when compared to the microneedling method alone. CONCLUSION The combination method and optimal glycerol concentration effectively enhanced transdermal delivery of glycerol by accelerating the diffusion rate through the skin barrier.