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Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca(2+) -induced changes in the immobilized enzyme we employ surface-enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca(2+) ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca(2+) to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials.

The development of O2 tolerant glucose sensors based on the highly active and robust enzyme glucose oxidase is still a major challenge because of the competition between the natural electron acceptor O2 and free‐diffusing or polymer‐bound artificial electron acceptors. We report the fabrication of a glucose oxidase based bioanode that operates under ambient conditions. Combination of this bioanode with a bilirubin oxidase based biocathode enabled the fabrication of a glucose/O2 powered biofuel cell as integrated power source for a self‐powered device. Glucose oxidase at the anode was electrically wired via a low‐potential redox polymer, i. e. a Toluidine Blue‐modified poly(methacrylate) based polymer, that ensures a high open‐circuit voltage of the biofuel cell but also catalytically reduces O2 and hence requires a protection shield for measurements under ambient conditions. The sensing layer was deposited by means of potential pulse‐assisted co‐deposition of glucose oxidase within the redox polymer and was protected from O2 by a newly proposed lactate oxidase/catalase based O2 removal layer that was immobilized within a hydrophilic redox‐silent polymer on top of the sensing layer. The protection layer was powered by lactate, a natural component in human blood. The biofuel cell exhibited an OCV of ca. 650 mV and the power output was dependent on the glucose concentration without any interference from oxygen providing that lactate was available in the analyte solution.

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