Ahmet Tezel1, Ashley Sens, Samir Mitragotri. 1. Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, USA.
Abstract
PURPOSE: Application of low-frequency ultrasound has been shown to increase skin permeability, thereby facilitating delivery of macromolecules (low-frequency sonophoresis). In this study, we seek to determine the dependence of transport pathways during low-frequency sonophoresis on ultrasound parameters. METHODS: Pig skin is exposed to low-frequency ultrasound over a range of frequencies to achieve different skin resistivities. The porous pathway model is used to study the dependence of average pore size, porosity, and tortuosity on ultrasound parameters. Imaging experiments are also carried out to visualize the transport pathways created by ultrasound. RESULTS: The data show that the average pore size, determined from the porous pathway model, does not depend on application frequency. Both in the presence and absence of ultrasound the average pore size determined from mannitol delivery is the same (28 +/- 12 A). With the application of ultrasound the skin porosity could be increased by up to 1700-fold. The effect of ultrasound on skin is heterogeneous thereby creating localized transport pathways (LTP). The porosity of these transport pathways is of the same order of magnitude as that of the dermis. CONCLUSIONS: With this study it is shown that low-frequency ultrasound increases skin permeability by increasing skin porosity rather than by increasing the size of the pores that are responsible for permeant delivery.
PURPOSE: Application of low-frequency ultrasound has been shown to increase skin permeability, thereby facilitating delivery of macromolecules (low-frequency sonophoresis). In this study, we seek to determine the dependence of transport pathways during low-frequency sonophoresis on ultrasound parameters. METHODS:Pig skin is exposed to low-frequency ultrasound over a range of frequencies to achieve different skin resistivities. The porous pathway model is used to study the dependence of average pore size, porosity, and tortuosity on ultrasound parameters. Imaging experiments are also carried out to visualize the transport pathways created by ultrasound. RESULTS: The data show that the average pore size, determined from the porous pathway model, does not depend on application frequency. Both in the presence and absence of ultrasound the average pore size determined from mannitol delivery is the same (28 +/- 12 A). With the application of ultrasound the skin porosity could be increased by up to 1700-fold. The effect of ultrasound on skin is heterogeneous thereby creating localized transport pathways (LTP). The porosity of these transport pathways is of the same order of magnitude as that of the dermis. CONCLUSIONS: With this study it is shown that low-frequency ultrasound increases skin permeability by increasing skin porosity rather than by increasing the size of the pores that are responsible for permeant delivery.
Authors: Jennifer E Seto; Baris E Polat; Renata F V Lopez; Daniel Blankschtein; Robert Langer Journal: J Control Release Date: 2010-03-25 Impact factor: 9.776
Authors: Baris E Polat; Shangchao Lin; Jonathan D Mendenhall; Brett VanVeller; Robert Langer; Daniel Blankschtein Journal: J Phys Chem B Date: 2011-01-11 Impact factor: 2.991