Enzyme Immobilization and Mediation with Osmium Redox Polymers for Anodes and Cathodes

Enzymatic electrodes are becoming increasingly common for energy production and sensing applications. Research over the past several decades has addressed a major issue that can occur when using these biocatalysts, i.e., slow heterogeneous electron transfer, by incorporation of a redox active species to act as an electron shuttle. There are several advantages to immobilizing both the enzyme and mediator at the electrode surface, including increased electron transfer rates, decreased electron leaching, and minimized diffusion limitations. Redox polymers consisting of a redox active center attached to a polymer backbone are a particularly attractive option because they have high self-exchange rates for electron transfer and tunable redox potential. Osmium polymers are the most well-studied of this type of polymer for bioelectrocatalysis. Here, we describe the methods to synthesize one of the most common Os redox polymers and how it can be used to fabricate enzymes electrodes. Procedures are also outlined for evaluating enzyme anodes and cathodes separately and combined in a biofuel cell.