Flexible electrochemical aptasensor for non-invasive potassium detection in human sweat

This study presents a flexible electrochemical aptasensor designed for non-invasive potassium ion detection in human sweat, enabling real-time assessment during physical exertion. A gold thin-film electrode was functionalized with a thiolated, guanine-rich DNA aptamer bearing a ferrocene label, which produced a signal-on response upon K⁺ binding. Morphological (SEM, AFM) and chemical (XPS) analyses confirmed successful surface modification and aptamer immobilization. Electrochemical characterization using cyclic voltammetry and impedance spectroscopy revealed a marked increase in charge transfer resistance following aptamer assembly (from 520 Ω to 3960 Ω), with partial recovery (to 2410 Ω) after K⁺ exposure. Square wave voltammetry exhibited a linear detection range from 0.5 nM to 100 µM (R² = 0.996), a sensitivity of 1.73 µA per log[K⁺], and a detection limit of 0.12 nM. Selectivity studies showed over 85 % signal suppression for interfering ions (Na⁺, Ca²⁺, Mg²⁺, Zn²⁺, NH₄⁺). Human sweat validation demonstrated recovery rates between 96.2 % and 103.0 %, with RSDs under 4.1 %. Mechanical and environmental durability tests confirmed 89.6 % signal retention after 7 days of ambient storage and 6.3 % signal drift over 5 h of continuous operation. These findings highlight the sensor’s robustness, specificity, and practical suitability for wearable bioelectronic platforms.