Chitosan/sodium alginate-based electroconductive hydrogels for motion monitoring and photothermal therapy

Natural conductive hydrogels are regarded as desirable materials for motion monitoring owing to their outstanding biocompatibility and degradability. It has been reported that the occurrence rate of injuries in the final 30 % of the activity is closely associated with fatigue-induced changes in neuromuscular control. However, most hydrogels are designed solely for motion state and electromyography (EMG) detection and do not provide the capability to alleviate muscle fatigue. The development of conductive hydrogels that integrate motion monitoring with fatigue alleviation could enable simultaneous fatigue detection and on-demand fatigue relief, thereby reducing the risk of sports-related injuries. Photothermal therapy has been proven to be an effective method for relieving muscle fatigue. In this study, a double-network hydrogel composed of chitosan and sodium alginate was prepared, which incorporates lignin‑silver nanoparticles (NPs) and melanin NPs to achieve effective motion monitoring and photothermal therapy. A physical cross-linking network formed via electrostatic interactions between chitosan and sodium alginate was reinforced with a Genipin-mediated chemical cross-linking network. The addition of lignin‑silver NPs enhanced the hydrogel's conductivity and mechanical integrity, whereas melanin NPs improved adhesion and conferred photothermal responsiveness. The resulting hydrogel enabled reliable motion monitoring and real-time identification of exercise-induced fatigue through EMG. Upon fatigue detection, the photothermal properties of the hydrogel facilitated rapid fatigue alleviation.