Design of an Os Complex‐Modified Hydrogel with Optimized Redox Potential for Biosensors and Biofuel Cells

Abstract

Multistep synthesis and electrochemical characterization of an Os complex-modified redox hydrogel exhibiting a redox potential ≈+30 mV (vs. Ag/AgCl 3 M KCl) is demonstrated. The careful selection of bipyridine-based ligands bearing N,N-dimethylamino moieties and an amino-linker for the covalent attachment to the polymer backbone ensures the formation of a stable redox polymer with an envisaged redox potential close to 0 V. Most importantly, the formation of an octahedral N6-coordination sphere around the Os central atoms provides improved stability concomitantly with the low formal potential, a low reorganization energy during the Os(3+/2+) redox conversion and a negligible impact on oxygen reduction. By wiring a variety of enzymes such as pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase, flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase and the FAD-dependent dehydrogenase domain of cellobiose dehydrogenase, low-potential glucose biosensors could be obtained with negligible co-oxidation of common interfering compounds such as uric acid or ascorbic acid. In combination with a bilirubin oxidase-based biocathode, enzymatic biofuel cells with open-circuit voltages of up to 0.54 V were obtained.

Electrosynthesis of Pyrenediones on Carbon Nanotube Electrodes for Efficient Electron Transfer with FAD‐dependent Glucose Dehydrogenase in Biofuel Cell Anodes

“…[5] In this case, electron shuttles, called redox mediators have to be employed, even when a loss of the final cell voltage has to be taken into account. [6][7] Beside the optimization of electrocatalyic currents and open circuit potential (OCPs), the stability of operational mediator-enzyme assembly is an important criterion for enzymatic glucose biofuel cell research since the operational lifetime of such power generators is the principal drawback for realistic applications. [6] They are mostly based on quinone derivatives [4] or redox tunable Osmium complexes.…”

“…[6] They are mostly based on quinone derivatives [4] or redox tunable Osmium complexes. [6][7] Beside the optimization of electrocatalyic currents and open circuit potential (OCPs), the stability of operational mediator-enzyme assembly is an important criterion for enzymatic glucose biofuel cell research since the operational lifetime of such power generators is the principal drawback for realistic applications.…”

Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors

“…For the further development and performance improvement of bioelectrochemical devices, selection of a suitable mediator is critical. A mediator that has a low redox potential, but exhibits high electron transfer activity, is desired for high-power biofuel cells and for highly sensitive biosensors which is not affected by interfering substances such as uric acid or ascorbic acid [7,8,9]. …”

“…Osmium complex-type mediators are useful because, in addition to maintaining high kinetic constants through their efficient self-exchange electron transfer capabilities, they make it possible to control the potential at which the reaction proceeds solely by replacing the ligand [7,12,13,14,15,16]. However, Os complexes are expensive and non-sustainable, rendering them impractical for use in low-cost and disposable FAD-GDH-based electrodes.…”

Introducing Pseudocapacitive Bioelectrodes into a Biofuel Cell/Biosupercapacitor Hybrid Device for Optimized Open Circuit Voltage

“…Os‐complex modified polymers were used as electron relays for various enzymes and also proved to be suitable to act as charge storing matrix in BSCs ,,. Moreover, a rational ligand design for the polymer bound Os‐complexes allows fine tuning of the redox potential, e. g. by introduction of electron‐withdrawing (shift to more positive potentials) or electron‐donating groups (shift to more negative potentials) into the ligand sphere …”