This work demonstrates a continuous, noninvasive wearable sensor for the measurement of inflammation in sweat via disease-specific and general markers Calprotectin and Interleukin-6 (IL-6), respectively. 12 subjects wore the sensor over a two-day period, during which their Calprotectin and IL-6 levels were measured continuously from sweat expired passively at the skin surface, according to Figure 1, a schematic of the sensor’s mechanism of detection which utilizes electrochemical impedance spectroscopy (EIS). Target markers Calprotectin and IL-6 bind to antibody-functionalized electrodes at the sensor surface, thereby creating a measurable impedance change. Sensor impedance was recorded continuously with a sampling rate of 1-1.5 minutes for a period of 40 hours. Sensor stability was demonstrated through continuous relative humidity and temperature measurements of the sensor-skin interface over the study period. Measurements were validated by comparison to synchronously collected salivary measurements.
Calprotectin and IL-6 were measured in sweat and saliva of 2 chronically inflamed subjects and 10 healthy subjects over a two-day period. Temporal 40-hour continuous tracking of sweat Calprotectin demonstrated higher basal Calprotectin in chronically inflamed subjects over a healthy subject. Between sweat and saliva, Calprotectin and IL-6 demonstrated a strong linear relationship (R²>0.7) and strong to moderate linear relationships between Calprotectin and IL-6 in sweat and saliva, respectively. Bland-Altman analysis and Deming regression analysis determined low incidence of outliers and similar ranges of Calprotectin and IL-6 expression between sweat and saliva. Diurnal observations of Calprotectin expression demonstrated significantly higher sweat Calprotectin and higher median Calprotectin measured in the morning-afternoon than measured in the evening among inflamed and healthy subjects, respectively.

Figure 1. Overview of the wearable inflammation sensor and device design.

Professor Shalini Prasad PhD

Professor, University of Texas, Dallas

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