A Redox Hydrogel Protects the O sub(2)-Sensitive [FeFe]-Hydrogenase from Chlamydomonas reinhardtii from Oxidative Damage

The integration of sensitive catalysts in redox matrices opens up the possibility for their protection from deactivating molecules such as O sub(2). [FeFe]-hydrogenases are enzymes catalyzing H sub(2) oxidation/production which are irreversibly deactivated by O sub(2). Therefore, their use under aerobic conditions has never been achieved. Integration of such hydrogenases in viologen-modified hydrogel films allows the enzyme to maintain catalytic current for H sub(2) oxidation in the presence of O sub(2), demonstrating a protection mechanism independent of reactivation processes. Within the hydrogel, electrons from the hydrogenase-catalyzed H sub(2) oxidation are shuttled to the hydrogel-solution interface for O sub(2) reduction. Hence, the harmful O sub(2) molecules do not reach the hydrogenase. We illustrate the potential applications of this protection concept with a biofuel cell under H sub(2)/O sub(2) mixed feed. Reactivation is optional: [FeFe]-hydrogenase in a redox hydrogel can be exposed to O sub(2) under turnover conditions for H sub(2) oxidation. A stable catalytic current is maintained, which indicates that the protection mechanism is based only on O sub(2) reduction at the hydrogel surface.