Analysis of ultrasonically extracted interstitial fluid as a predictor of blood glucose levels

Transdermal extraction of clinically relevant analytes offers a potentially noninvasive method of diagnostics. However, development of such a method i s limited by the low permeability of skin. In this paper, we present a pote ntial method for noninvasive diagnostics based on ultrasonic skin permeabil ization and subsequent extraction of interstitial fluid (TSF) across the sk in using vacuum. TSF extracted by this method was collected and analyzed fo r glucose and other analytes. Glucose concentration in the extracted fluid correlates well with blood glucose concentration over a range of 50-250 mg/ dl. A mathematical model describing vacuum-induced transport of ISF through ultrasonically permeabilized skin is presented as well. The model accounts for convective, as well as diffusive, transport processes across blood cap illaries, epidermis, and the stratum corneum. The overall predictions of th e model compare favorably with the experimental observations.