Longitudinal tracking of chronic inflammation through Calprotectin and Interleukin-6 using a sweat wearable device

Abstract

This work demonstrates a continuous, noninvasive two-plex electrochemical biosensor for the measurement of inflammation in sweat via disease-specific and general markers Calprotectin and Interleukin-6 (IL-6), respectively. Sensor functionalization and sensor stability was characterized through Fourier Transform Infrared (FTIR) spectroscopy. Sensor stability was characterized through open circuit potential and electrochemical impedance spectroscopy (EIS). On-body stability was demonstrated through relative humidity and temperature measurements of the sensor-skin interface.

Calprotectin and IL-6 were measured in sweat over 2 days from 2 chronically inflamed subjects and 10 healthy subjects to characterize dual sweat expression of the markers and investigate diurnal patterns of expression across the two groups. Sweat Calprotectin was continuously tracked over a 40-h period for chronically inflamed and healthy subjects with different inflammatory activity and treatments. Sensor measurements were recorded continuously with a sampling rate of 1–1.5 min.

Significantly higher sweat Calprotectin and higher median sweat Calprotectin expression was observed in the morning-afternoon than in the evening among inflamed and healthy subjects, respectively. Higher median sweat IL-6 was observed in inflamed individuals in the morning-afternoon, while higher median sweat IL-6 was observed in healthy individuals in the evening. Temporal results of sweat Calprotectin tracking demonstrate higher basal Calprotectin in an unmedicated over a medicated inflamed subject, and higher basal Calprotectin of inflamed subjects over a healthy subject.

Calprotectin and IL-6 demonstrated a strong positive linear relationship in sweat. Diurnal patterns were observed in the sweat of inflamed and healthy individuals, and continuous tracking of disease-specific inflammation through sweat Calprotectin was demonstrated.