Non-invasive monitoring of interstitial fluid lactate through an epidermal iontophoretic device

The development of a non-invasive sensing technology that allows collection of interstitial fluid (ISF) lactate and its subsequent analysis without exertion requirement, could enable lactate monitoring from rested individuals. Here, we describe a wearable, soft epidermal adhesive patch that integrates a reverse iontophoretic (RI) system, and an amperometric lactate biosensor placed on the anodic electrode with a porous hydrogel reservoir, for simultaneous ISF lactate extraction and quantification via electrochemical sensing, respectively. The iontophoretic system includes agarose hydrogels for preventing skin electrocution, while a porous polyvinyl alcohol-based hydrogel facilitates the effective transport of lactate from skin to the biosensor. The flexible skin-worn device tested on healthy individuals at rest showed rapid lactate collection from the ISF after 10 min of reverse iontophoresis with no evidence of discomfort or irritation to the skin. Detailed characterization of the enzymatic biosensor before and during on-body trials along with relevant control experiments confirmed the efficient extraction and selective detection of ISF lactate. Such an epidermal technology represents the first demonstration of an all-in-one platform that integrates non-invasive collection and subsequent analysis of lactate from iontophoretically extracted ISF toward point-of-care operation.