Passive, Electromagnetic-Responsive Hydrogel Immunosensor for Exercise Intensity Monitoring Based on Sweat C-Reactive Protein.

Although moderate exercise benefits health, excessive amounts of prolonged, high-intensity exercise may damage tissues and cause inflammation-related diseases. There is a growing interest in exercise-related health monitoring and tracking; however, a handy, noninvasive, and accurate method for wearable detection of exercise-induced inflammation still lacks. Here, this work reports a wireless and passive immunosensor for the noninvasive, low-cost, and simple monitoring of C-reactive protein (CRP) in sweat as an inflammatory marker to evaluate exercise-induced inflammation. The sensor has a sandwich structure, in which the middle layer is an immuno-sensitive hydrogel whose internal network structure cracks with the entry of CRP. A pair of coils converts the change of hydrogel into a shift of radio frequency (RF). The limit of detection (LoD) is as low as pg mL-1, covering the concentration range of human sweat CRP. The sensor can be used in direct detection for sweat samples from subjects, demonstrating a correlation between exercise-induced inflammation and exercise intensity. By tracking daily sweat CRP, the wearable passive immunosensor provides a methodology to quantify exercise intensity in terms of inflammation and has potential in customizing personal exercise protocols.