Flexible glucose biosensor via co-electrodeposition of methylene blue and glucose oxidase on carbon nanotube yarns

In this study, we report a flexible and highly sensitive glucose sensor (CNTYs-MB/GOx) for the first time based on methylene blue (MB) and glucose oxidase (GOx) co-electrodeposited onto carbon nanotube yarns (CNTYs). Unlike conventional MB/GOx coatings on planar carbon electrodes, the three-dimensional CNTY network provides a large electroactive surface area and efficient electron transport pathways, enabling dense and uniform immobilization of the MB/GOx complex. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) confirmed the effective capture and stabilization of GOx by MB and its homogeneous distribution on the CNTYs. This co-deposition strategy increased the active surface area 1.3-fold compared with physically adsorbed MB/GOx, resulting in significantly enhanced electrocatalytic activity. The sensor achieved a low detection limit of 25.2 μM, a wide linear range of 0.1–65 mM, excellent repeatability (RSD = 4.12 %), high selectivity (interference <5.4 %), and good long-term stability (86 % signal retention after 15 days). Moreover, it maintained a stable current response (RSD = 1.22 %) under repeated bending and mechanical deformation. In comparison of sequential electrodeposition and physical adsorption methods, this one-step co-electrodeposition enables MB and GOx to assemble synergistically on the CNTY surface, improving enzyme retention, increasing electroactive surface area, and facilitating efficient electron transfer. These results highlight the advantages of the CNTY-based co-electrodeposition approach and its potential for developing flexible, wearable glucose monitoring devices beyond traditional MB/GOx platforms.