Nanomachine Networks: Functional All-Enzyme Hydrogels from Photochemical Cross-Linking of Glucose Oxidase.

Enzymes are attractive as catalysts due to their specificity and biocompatibility; however, their use in industrial and biomedical applications is limited by stability. Here, we present a facile approach for enzyme immobilization within "all-enzyme" hydrogels by forming photochemical covalent cross-links between the enzyme glucose oxidase. We demonstrate that the mechanical properties of the enzyme hydrogel can be tuned with enzyme concentration and the data suggests that the dimeric nature of glucose oxidase results in unusual gel formation behavior which suggests a degree of forced induced dimer dissociation and unfolding. We confirm and quantify the enzyme activity of the hydrogel using the Trinder assay and a 1D modeling approach and show that 50% enzymatic activity is retained upon hydrogel formation. These observed effects may be due to the forces experienced by the individual nanoscale enzymes during mesoscale network formation. We have therefore demonstrated that photochemical cross-linking can be readily employed to produce functional all-enzyme glucose oxidase hydrogels with easily tunable mechanical properties and specific catalytic activity. This approach provides enormous potential for producing biocatalytic materials with tunable mechanical properties, responsive biological functionality and high volumetric productivity which may inform the future design of biomedical devices with enhanced sensitivity and activity.