Hierarchical spindle-structured carbon nanotube fiber as efficient enzyme-enriched reservoir for robust Biosensing...

Enzyme-based electrochemical fiber biosensors are attractive for wearable health monitoring but suffer from low sensitivity and limited stability due to restricted enzyme loading and enzyme loss during use or washing. Here, we report a one-step electrochemical morphology reconstruction strategy to fabricate spindle-structured carbon nanotube fibers (SS-CNTFs) that serve as enzyme-enriched reservoirs. The hierarchical multilayered nodules provide a >40-fold increase in electroactive surface area, enabling dense and protected enzyme immobilization. Using glucose oxidase as a model, the SS-CNTF biosensor achieved a sensitivity of 22.6 nA μM^-1, nearly 20-fold higher than intrinsic CNTF biosensor. The biosensor exhibited excellent linearity from 1 to 1000 μM (R² = 0.9997), retained >70 % of its sensitivity after three months, withstood 400 deformation cycles and 100 test cycles, and preserved >75 % sensitivity after 435 min of machine washing-durability rarely achieved in previous reports. Integrated into textiles with a wireless module, the sensor enabled real-time sweat glucose monitoring during exercise and sauna conditions, showing strong agreement with commercial assays. This work establishes a robust and washable fiber biosensor platform, advancing smart textiles beyond current state-of-the-art for personalized healthcare.