Design of Experiments Approach to Provide Enhanced Glucose‐oxidising Enzyme Electrode for Membrane‐less Enzymatic Fuel Cells Operating in Human Physiological Fluids

Abstract

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.

An Oxygen Insensitive Amperometric Glucose Biosensor Based on An Engineered Cellobiose Dehydrogenase: Direct versus Mediated Electron Transfer Responses

“…The peak current varies linearly with the square root of scan rate at higher scan rates when semi‐infinite diffusion within the film limits the current response [34] . The surface coverage (Γ os ) of the redox polymer, estimated by integrating the area under the peak for CVs recorded at slow scan rate in the absence of glucose, is 144±3 nmol cm −2 , which confirms multi‐layer formation, similar to results obtained by others for the co‐immobilization of enzymes and osmium‐based redox polymers [35–38] . On addition of glucose to the electrochemical cell, sigmoidal shaped responses characteristic of an electrocatalytic (EC’) process are observed.…”

Self-Powered Detection of Glucose by Enzymatic Glucose/Oxygen Fuel Cells on Printed Circuit Boards

“…The amounts of enzyme, osmium-based redox polymer, and PEGDGE solution were chosen based on previous research. 26 Two microliters of this stock solution was then drop-cast onto the hPG/Au electrodes and allowed to evaporate at room temperature for 1 h. The surface coverage of the Os polymer onto the hPG/Au electrode was estimated according to eq 1 where Q (C) is the charge required for either the reduction or oxidation of the Os polymer; n is the number of electrons involved; F (96,486 C mol –1 ) is the Faraday constant, and A (cm 2 ) is the geometric surface area of the electrode. The charge of the electrodes was calculated by cycling the potential of the electrode in 0.1 M phosphate buffer, pH 7.4, at a scan rate of 10 mV s –1 versus Ag/AgCl.…”

“…The amounts of enzyme, osmium-based redox polymer, and PEGDGE solution were chosen based on previous research. 26 Two microliters of this stock solution was then drop-cast onto the hPG/Au electrodes and allowed to evaporate at room temperature for 1 h. The surface coverage of the Os polymer onto the hPG/Au electrode was estimated according to eq 1…”

“…A stock solution was prepared by mixing 8 μL of 5 mg mL –1 osmium polymer with 8 μL of 5 mg mL –1 GOx and 4 μL of 15 mg mL –1 PEGDGE solution. The amounts of enzyme, osmium-based redox polymer, and PEGDGE solution were chosen based on previous research . Two microliters of this stock solution was then drop-cast onto the hPG/Au electrodes and allowed to evaporate at room temperature for 1 h. The surface coverage of the Os polymer onto the hPG/Au electrode was estimated according to eq where Q (C) is the charge required for either the reduction or oxidation of the Os polymer; n is the number of electrons involved; F (96,486 C mol –1 ) is the Faraday constant, and A (cm 2 ) is the geometric surface area of the electrode.…”

Glucose biosensor based on open-source wireless microfluidic potentiostat

“…While glucose oxidase (GOx) is the most reported enzyme for this application, Flavin adenine dinucleotide-dependent glucose dehydrogenase (FADGDH) is more suitable than GOx due to its lack of reactivity with molecular oxygen. Previous work reported by us has demonstrated the improved suitability of FADGDH over GOx for such applications [46,47]. The combination of redox polymer films with enzymes on electrode surfaces to mediate electron transfer between active site and electrode surface has been widely demonstrated.…”