Wearable Colorimetric Biosensor Based on Copper Coordination Polymer Nanozymes for Noninvasive Monitoring of Ascorbic Acid.

Real-time monitoring of ascorbic acid (AA) in sweat is critical for evaluating oxidative stress and nutritional status. However, the practical application of current wearable sensors is often compromised by complex matrix interference and interfacial instability during physical activity. To address these challenges, we developed a high-performance wearable colorimetric sensing platform based on copper coordination polymer nanozymes (Cu-CPs). Through systematic screening, the Cu-CPs II system was identified for its superior peroxidase-like activity and stability. The patch enables a sensitive colorimetric transition from brilliant green to white upon AA detection, with a linear range of 0.05-1.3 mM, a limit of detection of 25 μM, and a response time of 15 min. To translate this material into a wearable device, we engineered a trilayer flexible patch with a "substrate-reaction-isolation" sandwich architecture. This design allows the sensor to be activated in situ by sweat, triggering a sensitive colorimetric transition from brilliant green to white upon AA detection, which can be instantly quantified via a smartphone. On-body trials confirmed that the patch exhibits excellent skin conformability and mechanical robustness, enabling precise, dynamic tracking of sweat AA fluctuations before and after exercise. This work presents a universal, cost-effective strategy for constructing highly stable, noninvasive wearable biosensors, holding great promise for personalized health management.