Transdermal extraction of analytes using low-frequency ultrasound

Purpose. Transdermal extraction of clinically relevant analytes offers a potentially non-invasive method of diagnostics. However, development of such a method is limited by the low skin permeability. In this paper, we report a potential method for non-invasive diagnostics based on ultrasonic skin permeabilization and subsequent extraction of interstitial fluid (ISF) across the skin. Methods. In vivo experiments were performed using Sprague Dawley rats to assess ultrasound-induced skin permeabilization and subsequent extraction of various analytes. Serum and ISF concentrations of various analytes were measured. Results. Application of low-frequency ultrasound rapidly increased skin permeability. Skin remained in a state of high permeability for at least three hours. During this period, application of vacuum extracted ISF across rat skin in vivo at a rate of 25.7 μl/cm²/hr. We measured concentrations of various analytes including glucose, albumin, calcium, urea, triglycerides, lactate, and dextran in transdermally extracted fluid. The composition of the fluid extracted transdermally is similar to that of ISF. Conclusions. Application of low-frequency ultrasound allows skin permeabilization and extraction of ISF across the skin.