Mussel-Bioinspired Edible Ca²⁺-Crosslinked Alginate Hydrogel Electrodes for Glucose Gastrointestinal Monitoring

A novel self-standing, edible polydopamine-based alginate-hydrogel electrode that intrinsically conducts ions and electrons is introduced, redefining the architecture of ingestible bioelectronics. The edible polydopamine-based alginate-hydrogel electrode are based on Ca²⁺-crosslinked alginate (3.5% w/v) plasticized with glycerol (5% w/v) and reinforced with polydopamine, silver nanoparticles, and food-grade glucose oxidase. The optimized formulation exhibits an electroactive surface area of 1.99 ± 0.07 cm², a double-layer capacitance of 10.1 ± 0.3 µF, and a charge-transfer resistance of 7.7 ± 0.6 kΩ. Structural characterization by SEM, TEM, AFM, WAXS, and FTIR confirms uniform dispersion of AgNPs, pDA domain formation, and stable enzyme incorporation, while rheology and DMA reveal enhanced viscoelasticity, tensile strength (14 MPa), and Young's modulus (65 MPa). Configured as a first-generation glucose biosensor operating in USP simulated intestinal fluid (pH 6.8), the electrode displays a linear response from 50 µm to 1.0 mm, a detection limit of 10.4 ± 0.8 µm, and an apparent K_M ^app of 0.35 ± 0.08 mm. The biosensor retains ≥95% activity during 20 h of continuous operation and 90% after 30 days storage, with negligible interference from physiological species. This edible platform establishes a robust route toward ingestible bioelectronics for non-invasive glucose monitoring and personalized metabolic management.