Passively Addressable Ultra-Low Volume Sweat Chloride Sensor

Abstract

This work demonstrates a novel electrochemical biosensor for the detection of chloride ion levels in ultra-low volumes (1–3 microliters) of passively expressed human sweat. We present here a hydration monitor that the pediatric, geriatric, and other immune-compromised or physically inactive/sedentary population cohort can utilize, for whom the current methods of chloride quantification of active stimulation of sweat glands through iontophoresis or treadmill runs are unsuitable. In this work, non-faradaic electroanalysis using gold microelectrodes deposited on a flexible nanoporous substrate, for high nanoscale surface area to volume enhancement, was leveraged to operate in ultra-low sweat volumes of <3 µL eluted at natural rates. The specific chloride ionophore-based affinity of chloride ions resulted in the modulation of charge transfer within the electrical double layer at the electrode–sweat buffer interface, which was transduced using electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Linear calibration dose responses with R-squared values of 0.9746 and 0.9403 for EIS and CA respectively were obtained for a dynamic range of 10–100 mM. The surface charge and the binding chemistry of the capture probe were studied using zeta potential studies and UV-Vis. The dynamic sweat chloride-tracking capability of the sensor was evaluated for a duration of 180 min. Studies were conducted to probe the efficacy of the developed sensor for passive ultra-low sweat chloride assessment on human subjects (n = 3).

Sweating Out the Circadian Rhythm: A Technical Review

“…Many studies have leveraged this in detecting biomolecules in the characterization of disease states. Examples include detecting Cl – ions in the characterization of cystic fibrosis, Neuropeptide-Y (NPY) in the characterization of major depressive disorder, cortisol for stress monitoring, and DHEA, a biomarker relevant for circadian rhythm monitoring . In addition, the ability to couple sweat easily with microprocessor technologies to create low-powered, economic wearable devices that can be used for self-monitoring makes sweat a more lucrative biofluid to be considered in the design of a wearable sensor device …”

Next-Generation Continuous Metabolite Sensing toward Emerging Sensor Needs

“…Further, electrochemical biosensing provides a continuous-valued direct electrical readout which allows for high sampling rates for tracking subtle changes for real-time sensing and miniaturization and mass-production opportunities. Our group has contributed in this realm by proposing wearable schemes focusing on lifestyle monitors quantifying metabolites such as alcohol, , glucose, , lactate, − and chloride , to name a few.…”

Potentiometric ion-selective sensors based on UV-ozone irradiated laser-induced graphene electrode

“…In recent years, electrochemical sensors have emerged as a popular device for real-time analysis and non-invasive monitoring of human body fluids such as urine, blood, sweat, tears, saliva and interstitial fluid [1][2][3][4]. It is important to detect and quantify the concentration of biomarkers such as metabolites, proteins, antibodies, electrolytes, ions and hormones which can provide crucial information about health and physical status of a person [2,[4][5][6][7][8].…”