The addition of multi‐walled carbon nanotubes (MWCNTs) to enzymatic electrodes based on either glucose oxidase (GOx), or an oxygen‐insensitive flavin adenine dinucleotide‐dependent glucose dehydrogenase (FADGDH), increases the amount of {Os(4,4′‐dimethyl‐2,2′‐bipyridine)2[poly(vinylimidazole)]10Cl}Cl redox polymer at the electrode surface, indicating that MWCNTs provide a surface for the immobilisation of film components. Glucose oxidation is highest for films with 68 % (w/w) MWCNTs, and a decrease is observed with larger amounts; this decrease is related to a decrease in retained enzyme activity. Enzymatic electrodes provide 4.2 mA cm−2 current density at 0.12 V versus Ag/AgCl, for GOx‐based electrodes, compared to 2.7 mA cm−2 for FADGDH‐based electrodes in 50 mM phosphate‐buffered saline containing 150 mM NaCl at 37 °C. Current densities of 0.52 and 1.1 mA cm−2 are obtained for FADGDH and GOx‐based electrodes, respectively, operating at physiologically relevant 5 mM glucose concentrations. These enzymatic electrodes, thus, show promise for application as anodes in enzymatic fuel cells for in vivo or ex vivo power generation.

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Graphite electrodes are modified with a redox polymer, [Os(4,4′‐dimethoxy‐2,2′‐bipyridine)2(polyvinylimidazole)10Cl]+ (E°′=−0.02 V vs Ag/AgCl (3 M KCl), crosslinked with a flavin adenine dinucleotide glucose dehydrogenase and multi‐walled carbon nanotubes for electrocatalytic oxidation of glucose. The enzyme electrodes provide 52 % higher current density, 1.22±0.10 mA cm−2 in 50 mM phosphate‐buffered saline at 37 °C containing 5 mM glucose, when component amounts are optimised using a design of experiments approach compared to one‐factor‐at‐a‐time. Current densities of 0.84±0.15 mA cm−2 were achieved in the presence of oxygen for these enzyme electrodes. Further analysis of the model allowed for altering of the electrode components while maintaining similar current densities, 0.78±0.11 mA cm−2 with 34 % less enzyme. Application of the cost‐effective anodes in membrane‐less enzymatic fuel cells is demonstrated by connection to cathodes prepared by co‐immobilisation of [Os(2,2′‐bipyridine)2(polyvinylimidazole)10Cl+] redox polymer, Myrothecium verrucaria bilirubin oxidase and multi‐walled carbon nanotubes on graphite electrodes. Power densities of up to 285 μW cm−2, 146 μW cm−2 and 60 μW cm−2 are achieved in pseudo‐physiological buffer, artificial plasma and human plasma respectively, showing promise for in vivo or ex vivo power generation under these conditions.

Biophotovoltaic devices modified with immobilized polymeric osmium/azine redox-mediators exhibited a considerable electrical output enhancement (64/43-fold under light/dark conditions, respectively). More importantly, the systems exhibited uninterrupted current generation at same magnitude levels during day/night cycles, paving the way toward solar energy conversion bio-panels that will not require energy storage peripherals.