Enzyme Ink Formulation with Water-Based Binders Retains Enzymatic Activity for Biofuel Cells

Wearable enzymatic biofuel cells (EBFCs) are promising self-powered energy sources for real-time biosensing, enabling continuous physiological monitoring without external power supplies. Here, we report aqueous enzyme ink formulations incorporating water-based binders that preserve enzymatic activity and allow direct one-step screen printing of both bioanodes and biocathodes onto paper substrates. The inks consisted of MgO-templated mesoporous carbon, specific redox mediators, target enzymes (lactate oxidase, bilirubin oxidase, or flavin adenine dinucleotide-dependent glucose dehydrogenase), and polysaccharide-based thickeners, all dispersed in aqueous binder solutions. Electrochemical characterization revealed that the printed electrodes exhibited higher catalytic current densities, improved operational stability, and reduced mediator/enzyme leaching compared to conventional drop-casting methods. A lactate/oxygen EBFC assembled using the optimized inks achieved a maximum power density of 165 μW cm–2 with an open-circuit voltage of 0.63 V, maintaining high activity over prolonged chronoamperometric operation. Long-term storage at 5 °C under vacuum preserved enzymatic activity most effectively. These results demonstrate that aqueous enzyme inks enable scalable, reproducible, and high-performance EBFC fabrication, offering strong potential for integration into wearable self-powered biosensing platforms.