Simultaneous detection of multiple sweat biomarkers provides a non-invasive, real-time approach for monitoring physiological states, offering valuable insights into health, metabolic function, and personalized nutrition. We present novel touch-based electrochemical sensor platforms capable of measuring key biomarkers, including β-hydroxybutyrate (HB) & glucose, urea & ammonium, zinc ions (Zn(II)) & ascorbic acid (AA), from fingertip sweat. These "two-minute touch" systems feature a disposable dual-sensor array integrated with a porous poly(vinyl alcohol) (PVA) hydrogel, facilitating rapid sweat collection under resting conditions. The detection processes utilize screen-printed carbon electrodes (SPCEs) modified with biocatalytic or ion-selective layers, providing high sensitivity and specificity for each biomarker. The amperometric dual-sensor platform for HB and glucose incorporates an HB sensor using a β-hydroxybutyrate dehydrogenase (HBD) enzyme system for mediated detection of fluctuating ketone levels, alongside a glucose sensor employing glucose oxidase to catalyze the conversion of glucose to gluconic acid and hydrogen peroxide. The hydrogen peroxide is subsequently detected by mediated carbon on a screen-printed electrode. This system enables fast, accurate detection of dynamic HB changes, with strong correlation to capillary blood measurements, making it especially useful for individuals managing ketosis, such as those with diabetes or taking ketone supplements. For urea and ammonium detection, a potentiometric sensor based on urease and ion-selective electrodes is used. The hydrolysis of urea generates ammonium and bicarbonate, with the ammonium ions detected via a solid-contact ammonium-ion selective electrode. This indirect measurement of sweat urea correlates well with blood urea levels, making it a valuable tool for monitoring kidney function and hydration status. In addition, Zn(II) ions are measured using a bismuth/Nafion-modified screen-printed electrode with square-wave anodic stripping voltammetry (SWASV), while AA detection is based on open-circuit potential (OCP) changes at a tetrathiafulvalene-7,7,8,8 tetracyanoquinodimethane (TTF-TCNQ) modified electrode. This micronutrient sensing system enables rapid, real-time monitoring of Zn(II) and AA concentrations following supplementation, supporting personalized nutrition and immune health.

Sumeyye Seker

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