Design of experiments approach to provide enhanced glucose-oxidising enzyme electrode for membrane-less enzymatic fuel cells operating in human physiological fluids

Graphite electrodes are modified with a redox polymer, [Os(4,4-dimethoxy-2,2-bipyridine)(2)(polyvinylimidazole)(10)Cl](+) (E degrees=-0.02V vs Ag/AgCl (3M 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 +/- 0.10mAcm(-2) in 50mM phosphate-buffered saline at 37 degrees C containing 5mM glucose, when component amounts are optimised using a design of experiments approach compared to one-factor-at-a-time. Current densities of 0.84 +/- 0.15mAcm(-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 +/- 0.11mAcm(-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)(10)Cl+] redox polymer, Myrothecium verrucaria bilirubin oxidase and multi-walled carbon nanotubes on graphite electrodes. Power densities of up to 285Wcm(-2), 146Wcm(-2) and 60Wcm(-2) are achieved in pseudo-physiological buffer, artificial plasma and human plasma respectively, showing promise for invivo or ex vivo power generation under these conditions.RB acknowledges support through an NUI Galway College of Science fellowship and an Irish Research Council postgraduate scholarship. IO acknowledges support through an NUI Galway College of Science fellowship. RK acknowledges support from the Earth and Natural Science Doctoral Studies Programme funded by the Higher Education Authority (HEA) through the Programme for Research at Third‐Level Institutions, Cycle 5 (PRTLI‐5) and co‐funded by the European Regional Development Fund (ERDF). POC acknowledges support through a Science Foundation Ireland Technology Innovation Development Award.peer-reviewed2019-03-3