Chitosan-based enzyme ink for screen-printed bioanodes

Abstract

In this study, magnesium oxide (MgO)-templated mesoporous carbon (MgOC) and chitosan cross-linked with genipin (chitosan–genipin) were considered bio-composite inks for screen-printed bioanodes. The fabrication processes were optimized using rheological and structural data, and a bioanode ink containing glucose oxidase (GOx) and 1,2-naphthoquinone (1,2-NQ) was successfully developed. The optimal bioanode-ink contained MgOC pre-treated by washing to achieve a hydrophilic and neutral surface, which helped maintain enzyme activity and resulted in a highly porous electrode structure, which is essential for the accessibility of glucose to GOx. A bioanode fabricated using this ink showed a linear response current dependency up to 8 mM glucose with a sensitivity of 25.83 μA cm⁻² mM⁻¹. Combined with a conventional biocathode, an electromotive force of 0.54 V and a maximal power density of 96 μW cm⁻² were achieved. These results show that this bio-composite ink can be used to replace the multi-step process of printing with conventional ink followed by drop-casting enzyme and mediator with a one-step printing process.