Recent scientific publications by Eccrine co-founder and Chief Science Officer, Jason Heikenfeld, and his co-authors at the University of Cincinnati demonstrate new breakthroughs in sweat sensing. The first article demonstrates the ability to increase biomarker concentrations in sweat, improving detection. The second article establishes feasibility for reliable integration of sweat stimulants within a wearable device for use periods of 24 h or more, expanding the reach of sweat sensing devices into applications involving sedentary populations.
Enhancing glucose flux into sweat by increasing paracellular permeability of the sweat gland
Andrew Jajack, Michael Brothers, Gerald Kasting, Jason Heikenfeld
July 16, 2018
Abstract: Non-invasive wearable biosensors provide real-time, continuous, and actionable health information. However, difficulties detecting diluted biomarkers in excreted biofluids limit practical applications. Most biomarkers of interest are transported paracellularly into excreted biofluids from biomarker-rich blood and interstitial fluid during normal modulation of cellular tight junctions. Calcium chelators are reversible tight junction modulators that have been shown to increase absorption across the intestinal epithelium. However, calcium chelators have not yet been shown to improve the extraction of biomarkers. Here we show that for glucose, a paracellularly transported biomarker, the flux into sweat can be increased by >10x using citrate, a calcium chelator, in combination with electroosmosis. Our results demonstrate a method of increasing glucose flux through the sweat gland epithelium, thereby increasing the concentration in sweat. Future work should examine if this method enhances flux for other paracellularly transported biomarkers to make it possible to detect more biomarkers with currently available biosensors... Full Research Article
Membrane isolation of repeated-use sweat stimulants for mitigating both direct dermal contact and sweat dilution
P. Simmers, Y. Yuan, Z. Sonner, and J. Heikenfeld
Abstract: With the device integration of sweat stimulation, sweat becomes a stronger candidate for non-invasive continuous biochemical sensing. However, sweat stimulants are cholinergenic agents and non-selective to just the sweat glands, and so, direct placement of sweat stimulants poses additional challenges in the possibility for uncontrollable transport of the stimulant into the body and challenges in contamination of the sweat sample. Reported here is membrane isolation of repeated-use sweat stimulants for mitigating direct dermal contact, dilution of the sweat stimulant, and contamination of the sweat sample. The membrane dramatically reduces passive diffusion of the sweat stimulant carbachol by roughly two orders of magnitude, while still allowing repeated sweat stimulation by iontophoretic delivery of the carbachol through the membrane and into the skin. Both in-vivo and in-vitro validation reveal feasibility for reliable integration of sweat stimulants within a wearable device for use periods of 24 h or more. In addition, advanced topics and confounding issues such as stimulant gel design, osmotic pressure, and ionic impurities are speculatively and theoretically discussed... Full Research Article