Enzyme Immobilization on Functionalized Graphene Oxide Nanosheets: Efficient and Robust Biocatalysts

Enzymes are used as biocatalysts for analytical purposes in diagnostics and preparative purposes in large-scale industrial processes. Despite perfect catalytic properties of enzymes, their industrial applications are limited due to the drawbacks regarding the lack of long-term stability under process conditions. The difficulties associated with recycling have to be resolved before enzyme implementation at industrial scale. Enzyme immobilization, as a novel approach, can improve the half-life, stability, catalytic activity, and reusability of enzymes. Graphene-based nanomaterials, as nanoscaled and thermostable inorganic carriers, are nontoxic materials and selective modulators for enzyme activity. Herein, we have concentrated on strategies for preparing graphene-based nanocomposites for enzyme immobilization. Nanostructures of graphene, hybrid graphene, and their derivatives with adjustable surface chemistry, caused them to be excellent candidates for immobilization of enzymes. For instance, the synthesis and functionalization of Fe3O4-graphene oxide (GO) hybrids were improved recently, in our research group, using cyanuric chloride and polyethylene glycol bis-amine for the immobilization of xylanase and glucoamylase enzymes, via physical and covalent attachments. Decorating GO nanosheets with Fe3O4 nanoparticles has facilitated the reusability of enzymes and increased the surface area for enzyme loading. The use of these hydrophilic crosslinkers may change the microenvironment of the immobilized enzymes that could result in the enhancement of their catalytic activity. As a result of the fascinating properties of graphene-based nanocarriers, with respect to structures that can be oriented and surfaces that can be modified, in our opinion, they offer some important advantages for biotechnological applications, especially in the areas of enzyme immobilization and medicine.