How the reduction of O2 on enzymes and/or redox mediators affects the calibration curve of “wired” glucose oxidase and glucose dehydrogenase biosensors

Glucose oxidation by osmium redox polymer mediated enzyme electrodes operating at low potential and in oxygen, for application to enzymatic fuel cells

“…This study thus targets research on using enzyme electrodes prepared by co-immobilisation in a similar matrix to that previously reported [20] but replacing the Os (dmbpy) 2 PVI redox polymer with a redox polymer, Os(dmobpy) 2 PVI, that has a lower redox potential, À0.02 V vs Ag/AgCl [21,24,25]. Verification of the electrochemical response of Os (dmobpy) 2 PVI was undertaken using cyclic voltammetry (CV) in the presence and absence of substrate in PBS at 37 C. The formal redox potential (E 0 ) for the Os(II/III) transition of the redox polymer, estimated from the midpoint between the oxidation and reduction peak potentials by CV recorded at 1 mV s À1 scan rate in the absence of substrate, is confirmed as À0.02 V AE 0.01 vs Ag/AgCl, which agrees well with the value reported for other enzyme electrodes prepared using this redox polymer [21,24,25]. Under the same conditions, the full width half maximum (FWHM) for oxidation of the enzyme electrode redox polymer is 0.110 AE 0.005 V vs Ag/AgCl, which is close to the predicted response of 0.09 V for an ideal surface-confined one electron redox system [31].…”

“…The Os (dmobpy) 2 PVI is selected as it has a lower reported redox potential, À0.02 V vs Ag/AgCl, compared to Os(dmbpy) 2 PVI previously used, 0.12 V vs Ag/AgCl [21,24,25]. This lower anode mediator redox potential can contribute to an overall increased difference in potential between anode and cathode of an assembled EFC leading to improved power output of the fuel cell.…”

“…Glucose oxidase, GOx, is a widely used glucose oxidising enzyme due to its commercial availability and high turnover rate, thus becoming a benchmark for comparison of glucose oxidising enzyme electrodes. The main disadvantage however is its sensitivity to oxygen [21,22], which can reduce the power output of EFCs [22,23] through oxygen competition for electrons [10]. As a result, oxygen-insensitive glucose oxidising enzymes, such as the glucose dehydrogenases, may be utilised to alleviate this issue.…”

Effect of Multi‐Walled Carbon Nanotubes on Glucose Oxidation by Glucose Oxidase or a Flavin‐Dependent Glucose Dehydrogenase in Redox‐Polymer‐Mediated Enzymatic Fuel Cell Anodes

“…[4,8,9] Synthetic polymers, such as poly(N-vinylimidazole) and poly(4-vinylpyridine), containing osmium pendant moieties have been the focus of much of this research, [9][10][11][12][13][14] owing to the ability to modulate the mediator redox potential of the central Os metal by using coordinating ligands, the relative stability of the resulting complexes in the reduced/oxidised states (Os II /Os III ), and because the hydrogel characteristics of enzymatic electrodes based on redox-polymer films permit rapid mass and charge transport, thus generating substantial current signals. [9,15,16] Matching the enzyme with mediator and immobilisation approach is important to provide the highest current signal, at an appropriate redox potential, to permit application of enzymatic electrodes as biosensors, or as electrodes in EFCs. Recent methods for improved integration of components of enzymatic electrodes to provide for increased current as a function of underlying geometric electrode area have focused on the addition of conductive particles to enzymatic electrode films.…”

“…These enzymatic electrodes were prepared by co-immobilisation on graphite of an {Os(4,4'-dimethyl-2,2'-bipyridine) 2 10 Cl}Cl redox polymer, because of its lower redox potential (0.12 V vs. Ag/AgCl), [25] thus providing the possibility of a higher cell voltage for an EFC assembled with it. GOx has been used as a benchmark for the performance of electrodes based on glucose-oxidising enzymes, owing to its high glucose turnover rate [9] and commercial availability, however, its main disadvantage is its sensitivity to oxygen, [16,26] which can affect the power output of an EFC. [26,27] Thus, we also compared the performances of enzymatic electrodes based on GOx and the oxygen-insensitive enzyme FADGDH.…”