A comparison of glucose oxidase and aldose dehydrogenase as mediated anodes in printed glucose/oxygen enzymatic fuel cells using ABTS/laccase cathodes

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

Monitoring glucose levels in physiological fluids can help prevent severe complications associated with hypo- and hyper-glycemic events. Current glucose-monitoring systems require a three-electrode setup and a power source to function, which can hamper the system miniaturization to the patient discomfort. Enzymatic fuel cells (EFCs) offer the opportunity to develop self-powered and minimally invasive glucose sensors by eliminating the need for an external power source. Nevertheless, practical applications demand for cost-effective and mass-manufacturable EFCs compatible with integration strategies. In this study, we explore for the first time the use of gold electrodes on a printed circuit board (PCB) for the development of an EFC and demonstrate its application in saliva. To increase the specific surface area, the PCB gold-plated electrodes were modified with porous gold films. At the anode, glucose oxidase is immobilized with an osmium redox polymer that serves as an electron-transfer mediator. At the cathode, bilirubin oxidase is adsorbed onto the porous gold surface with a blocking agent that prevents parasitic reactions while maintaining the enzyme catalytic activity. The resulting EFC showed a linear response to glucose in phosphate buffer within the range 50 μM to 1 mM, with a sensitivity of 14.13 μA cm-2 mM-1. The sensor was further characterized in saliva, showing the linear range of detection of 0.75 to 2 mM, which is within the physiological range, and sensitivity of 21.5 μA cm-2 mM-1. Overall, this work demonstrates that PCBs are suitable platforms for EFCs, paving the way for the development of fully integrated systems in a seamless and miniaturized device.

A single-liquid miniature biofuel cell with boosting power density via gas diffusion bioelectrodes

The low solubility of gas molecules in aqueous solutions has limited the power density output of enzymatic biofuel cells. Herein, a single-liquid miniature glucose-O2 fuel cell was constructed by using gas diffusion electrodes, which were prepared by immobilizing glucose oxidase (GOx) or laccase (Lac) modified on a porous structured carbon paper (CP). Due to the fast and direct O2 diffusion from air to the active sites of the immobilized enzyme through the pores of the CP anode/cathode with controlled wettability, the maximum power output densities dramatically increased to 9.64 μW cm-2 at 0.43 V and 53.0 μW cm-2 at 0.45 V for the cell in 5 mM glucose and after exposing the cell to air or O2 atmosphere, respectively. Interestingly, the resulting single-liquid cell could harvest power from human serum operating at a maximum power density of 49.0 μW cm-2 at 0.2 V. The biofuel cell fabricated by the gas diffusion electrodes displayed advantages such as high output power density, low cost and high 'on-chip' integrability and miniaturization, which suggest its great potential for implantable self-powered sensors and for many future applications.

Enzyme production ofd-gluconic acid and glucose oxidase: successful tales of cascade reactions

This review mainly focuses on the use of glucose oxidase in the production ofd-gluconic acid, which is a reactant of undoubtable interest in different industrial areas. As example of diverse enzymatic cascade reactions.

Study on an improved bio-electrode made with glucose oxidase immobilized mesoporous carbon in biofuel cells

Response surface methodology (RSM) was used for process optimization to immobilize glucose oxidase (GOx) on ordered mesoporous carbon (OMC).

A high-performance bioanode based on a nitrogen-doped short tubular carbon loaded Au nanoparticle co-immobilized mediator and glucose oxidase for glucose/O2 biofuel cells

A high-performance bioanode for glucose/O₂ biofuel cells based on N-STCs loaded Au NPs co-immobilized mediator and GOD was successfully developed.

Tuning Structural Changes in Glucose Oxidase for Enzyme Fuel Cell Applications

Stabilization and electrical contacting of redox enzymes with electrodes are fundamental requirements for bioelectronics devices, including biosensors and enzyme fuel cells (EFCs). In this study, we show increased glucose oxidase (GOx) stability by immobilization with Nafion. The immobilization process affected GOx conformation but was not detrimental to its activity, which was maintained for more than 120 days. The GOx/Nafion system was interfaced to a carbon cloth electrode and assembled in a prototypal EFC fed with glucose. Polarization and power density curves demonstrated that GOx/Nafion system was able to generate power, exploiting a Nafion-assisted electron transfer process to the electrode. Our findings are consistent with the onset of pH-dependent conformational equilibrium for the enzyme secondary structure and its active site. Significantly, the protective effect exerted by Nafion on the enzyme structure may be tuned by varying parameters such as the pH to fabricate durable EFCs with good electrocatalytic performance.

Design of a mediated enzymatic fuel cell to generate power from renewable fuel sources

The present work reported a compartment-less enzymatic fuel cell (EFC) based on newly synthesized Poly(pyrrole-2-carboxylic acid-co-3-thiophene acetic acid) film containing glucose oxidase and laccase effectively wired by p-benzoquinone incorporated into the copolymer structure. The resulting system generated a power density of 18.8 µW/cm(2) with 30 mM of glucose addition at +0.94 V at room temperature. Improvements to maximize the power output were ensured with step-by-step optimization of electrode fabrication design and operational parameters for operating the system with renewable fuel sources. We demonstrated that the improved fuel cell could easily harvest glucose produced during photosynthesis to produce electrical energy in a simple, renewable and sustainable way by generating a power density of 10 nW/cm(2) in the plant leaf within 2 min. An EFC for the first time was successfully operated in municipal wastewater which contained glycolytic substances to generate electrical energy with a power output of 3.3 µW/cm(2).

Recent progress in oxygen-reducing laccase biocathodes for enzymatic biofuel cells

This review summarizes different approaches and breakthroughs in the development of laccase-based biocathodes for bioelectrocatalytic oxygen reduction. The use of advanced electrode materials, such as nanoparticles and nanowires is underlined. The applications of recently developed laccase electrodes for enzymatic biofuel cells are reviewed with an emphasis on in vivo application of biofuel cells.

Development and operation of gold and cobalt oxide nanoparticles containing polypropylene based enzymatic fuel cell for renewable fuels

Newly synthesized gold and cobalt oxide nanoparticle embedded Polypropylene-g-Polyethylene glycol was used for a compartment-less enzymatic fuel cell. Glucose oxidase and bilirubin oxidase were selected as anodic and cathodic enzymes, respectively. Electrode fabrication and EFC operation parameters were optimized to achieve high power output. Maximum power density of 23.5 µW cm(-2) was generated at a cell voltage of +560 mV vs Ag/AgCl, in 100mM PBS pH 7.4 with the addition of 20mM of synthetic glucose solution. 20 µg of polymer amount with 185 µg of glucose oxidase and 356 µg of bilirubin oxidase was sufficient to get maximum performance. The working electrodes could harvest glucose, produced during photosynthesis reaction of Carpobrotus Acinaciformis plant, and readily found in real domestic wastewater of Zonguldak City in Turkey.

Hydrogen peroxide produced by glucose oxidase affects the performance of laccase cathodes in glucose/oxygen fuel cells: FAD-dependent glucose dehydrogenase as a replacement

Hydrogen peroxide production by glucose oxidase (GOx) and its negative effect on laccase performance have been studied. Simultaneously, FAD-dependent glucose dehydrogenase (FAD-GDH), an O2-insensitive enzyme, has been evaluated as a substitute. Experiments focused on determining the effect of the side reaction of GOx between its natural electron acceptor O2 (consumed) and hydrogen peroxide (produced) in the electrolyte. Firstly, oxygen consumption was investigated by both GOx and FAD-GDH in the presence of substrate. Relatively high electrocatalytic currents were obtained with both enzymes. O2 consumption was observed with immobilized GOx only, whilst O2 concentration remained stable for the FAD-GDH. Dissolved oxygen depletion effects on laccase electrode performances were investigated with both an oxidizing and a reducing electrode immersed in a single compartment. In the presence of glucose, dramatic decreases in cathodic currents were recorded when laccase electrodes were combined with a GOx-based electrode only. Furthermore, it appeared that the major loss of performance of the cathode was due to the increase of H2O2 concentration in the bulk solution induced laccase inhibition. 24 h stability experiments suggest that the use of O2-insensitive FAD-GDH as to obviate in situ peroxide production by GOx is effective. Open-circuit potentials of 0.66 ± 0.03 V and power densities of 122.2 ± 5.8 μW cm(-2) were observed for FAD-GDH/laccase biofuel cells.

Membraneless glucose/O2 microfluidic enzymatic biofuel cell using pyrolyzed photoresist film electrodes

Biofuel cells typically yield lower power and are more difficult to fabricate than conventional fuel cells using inorganic catalysts. This work presents a glucose/O2 microfluidic biofuel cell (MBFC) featuring pyrolyzed photoresist film (PPF) electrodes made on silicon wafers using a rapid thermal process, and subsequently encapsulated by rapid prototyping techniques into a double-Y-shaped microchannel made entirely of plastic. A ferrocenium-based polyethyleneimine polymer linked to glucose oxidase (GOx/Fc-C6-LPEI) was used in the anode, while the cathode contained a mixture of laccase, anthracene-modified multi-walled carbon nanotubes, and tetrabutylammonium bromide-modified Nafion (MWCNTs/laccase/TBAB-Nafion). The cell performance was studied under different flow-rates, obtaining a maximum open circuit voltage of 0.54 ± 0.04 V and a maximum current density of 290 ± 28 μA cm(-2) at room temperature under a flow rate of 70 μL min(-1) representing a maximum power density of 64 ± 5 μW cm(-2). Although there is room for improvement, this is the best performance reported to date for a bioelectrode-based microfluidic enzymatic biofuel cell, and its materials and fabrication are amenable to mass production.

Cross-linked glucose oxidase clusters for biofuel cell anode catalysts

The efficient localization of increased levels of active enzymes onto conducting scaffolds is important for the development of enzyme-based biofuel cells. Cross-linked enzyme clusters (CEC) of glucose oxidase (GOx) constrained to functionalized carbon nanotubes (CEC-CNTs) were generated in order to evaluate the potential of using CECs for developing GOx-based bioanodes functioning via direct electron transfer from the GOx active site to the CNT scaffold. CEC-CNTs generated from several weight-to-weight ratios of GOx:CNT were examined for comparable catalytic activity to free GOx into the solution, with CEC-CNTs generated from a 100% GOx solution displaying the greatest enzymatic activity. Scanning transmission electron microscopic analysis of CEC-CNTs generated from 100% GOx to CNT (wt/wt) ratios revealed that CEC clusters of ∼78 µm2 localized to the CNT surface. Electrochemical analysis indicates that the enzyme is engaged in direct electron transfer, and biofuel cells generated using GOx CEC-CNT bioanodes were observed to have a peak power density of ∼180 µW cm(-2). These data indicate that the generation of nano-to-micro-sized active enzyme clusters is an attractive option for the design of enzyme-specific biofuel cell powered implantable devices.