The interest in energy producing devices based on biocatalysts increased notably in the last few years. Either enzymes or microorganisms can be used to catalyse the reactions in the anode or/and cathode compartment of a biofuel cell. Multicopper oxidases like laccases or bilirubin oxidase can catalyse the 4 e^- reduction of oxygen to water at the cathode side. Their efficient and stable immobilisation on the electrode surface conco­mitantly designing optimized electron-transfer pathways between enzyme and electrode is crucial for long-term stability and maximum power output of the envisaged biofuel cell.

One possible approach is the integration of laccases or bilirubin oxidase into an Os-complex modified polymer matrix on top of an appropriate electrode surface. The re­dox potential and the electron transfer characteristics of the Os-complex modified polymer need to be adapted to the chosen enzyme for providing an optimized operation of the biofuel cell. Thus, a specific design of the polymer-linked Os-complexes with respect to their redox potential as well as the properties of the polymer itself is of crucial importance. The redox potential of the polymer-bound Os-complexes can be tailored by variations in their ligand sphere while the properties of the polymer back­bone can be modulated by choosing different types of the polymer-forming monomers. As a matter of fact, by variation of all these parameters libraries of redox polymers are obtained which have to be investigated together with the different enzymes. Thus, fast screening of these multi-parameter systems is essential. In this communication, we will describe the application of redox competition mode SECM (RC-SECM) for monitoring local biocatalytic O₂ reduction activity of enzyme/redox polymer spotsin dependence of enzyme-to-polymer ratio and nature of the used enzyme and/or Os-complex modi­fied polymer. A piezo-microdispenser in combination with a high-accuracy positioning unit was used for automated and reproducible formation of enzyme/redox polymer spot arrays, which were then further investigated using RC-SECM. For a more in depth evaluation of the obtained biofuel cell cathodes, pH and longterm stability was automatically evaluated using an electrochemical robotic system. The enzyme/redox polymer films are automatically formed and fuel cell power and potential curves are automatically obtained using slow-scan linear sweep voltammetry. Results concerning the straight forward and automatic optimization of biofuel cell cathodes by combining RC-SECM and electrochemical robotics will be presented.

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