Flexible Fiber Sensors for Real‐Time Monitoring of Redox Signaling Molecules in Exercise‐Mimicking Engineered Skeletal Muscle

Abstract Real‐time monitoring of reactive oxygen and nitrogen species (RONS) in skeletal muscle provides crucial insights into the cause‐and‐effect relationships between physical activity and health benefits. However, the dynamic production of exercise‐induced RONS remains poorly explored, due to the lack of sensing tools that can conform to soft skeletal muscle while monitor RONS release during exercise. Here we introduce dual flexible sensors via twisting carbon nanotubes into helical bundles of fibers and subsequent assembling electrochemical sensing components. These flexible sensors exhibit low bending stiffness, excellent H 2 O 2 and NO sensing abilities, outstanding biocompatibility and compliance with engineered skeletal muscle tissue. This allows real‐time and simultaneous monitoring of H 2 O 2 and NO release from engineered skeletal muscle in response to different exercise‐mimicking stretches, which reveals that warm‐up activities before high‐intensity exercise may enhance adaptive responses by down‐regulating H 2 O 2 and up‐regulating NO production. The proposed sensing strategy demonstrates great versatility in monitoring multiple biomarkers of soft tissue and organs.