Direct Enzymatic Glucose/O2 Biofuel Cell based on Poly-Thiophene Carboxylic Acid alongside Gold Nanostructures Substrates Derived through Bipolar Electrochemistry

Glucose-based biofuel cells and their applications in medical implants: A review

In glucose biofuel cells (G-BFCs), glucose oxidation at the anode and oxygen reduction at the cathode yield electrons, which generate electric energy that can power a wide range of electronic devices. Research associated with the development of G-BFCs has increased in popularity among researchers because of the eco-friendly nature of G-BFCs (as related to their construction) and their evolution from inexpensive bio-based materials. In addition, their excellent specificity towards glucose as an energy source, and other properties, such as small size and weight, make them attractive within various demanding applied environments. For example, G-BFCs have received much attention as implanted devices, especially for uses related to cardiac activities. Envisioned pacemakers and defibrillators powered by G-BFCs would not be required to have conventional lithium batteries exchanged every 5-10 years. However, future research is needed to develop G-BFCs demonstrating more stable power consistency and improved lifespan, as well as solving the challenges in converting laboratory-made implantable G-BFCs into implanted devices in the human body. The categorization of G-BFCs as a subcategory of different biofuel cells and their performance is reviewed in this article.

Fabrication and characterization of electrically conducting electrochemically synthesized polypyrrole-based enzymatic biofuel cell anode with biocompatible redox mediator vitamin K3

Enzymatic biofuel cells (EBFCs) hold tremendous potential to power biomedical devices, biosensors, and bioelectronics. Unlike conventional toxic batteries, these electrochemical devices are biocompatible, harnessing energy from physiological fluids and producing usable electrical energy. But the commercialization of EBFCs is limited by the low operational stability, limited power output and poor electron transport efficiency of the enzymatic electrodes. In this study, a novel bioanode exhibiting a high electron transfer ability and long-term stability was fabricated. For the preparation of the anode, surfactant-assisted polypyrrole (PPy) was electrochemically co-deposited on a platinum wire with the simultaneous entrapment of vitamin K3 (VK3) and GOx (glucose oxidase) in the PPy matrix. Herein, conducting PPy acts as an electron transfer enhancer and provides appropriate electrical communication between the active site of the enzyme glucose oxidase (GOx) and the electrode surface. Biocompatible redox mediator vitamin K3 was employed as an electron transfer mediator to shuttle electrons between the oxidized fuel glucose and surface of the electrode in the electrochemical cell. The electrical conductivity of PPy was measured using the four-probe technique of conductivity measurement of semiconductors. The morphological characterization of as-synthesized anode (PPy/CTAB/VK3/GOx) was performed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical characterization was studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. It was observed that the room-temperature conductivity of PPy lies in the semiconducting range and it also shows good stability on exposure to laboratory air, making it a promising material to provide electrical contact. The study developed a bioanode producing a modest current density of 6.35 mA cm-2 in 20 mM glucose solution. The stability, current output and ease of manufacturing process of the electrode make it particularly suitable for employment in biofuel cell applications.

A one-pot rotational DC-bipolar approach for fabricating artistic metallic carpets

This is a brief report on the fabrication of concentric multi-element metallic carpets through a one-pot rotational bipolar electro-engineering procedure. A suspended piece of nickel foam as a bipolar electrode (BPE) is rotated in an aqueous solution containing a ternary mixture of metal ions when sufficient DC potential is applied to driving electrodes. The customizable tools of this art are potential gradient, rotation, and concentration/kinetic polarizations. Creating the multi-element radial gradient is typically tested in a one-pot artistic jewelry electroplating.

Development of GO/Co/Chitosan-Based Nano-Biosensor for Real-Time Detection of D-Glucose

Electrochemical nano-biosensor systems are popular in the industrial field, along with evaluations of medical, agricultural, environmental and sports analysis, because they can simultaneously perform qualitative and quantitative analyses with high sensitivity. However, real-time detection using an electrochemical nano-biosensor is greatly affected by the surrounding environment with the performance of the electron transport materials. Therefore, many researchers are trying to find good factors for real-time detection. In this work, it was found that a composite composed of graphite oxide/cobalt/chitosan had strong stability and electron transfer capability and was applied to a bioelectrochemical nano-biosensor with high sensitivity and stability. As a mediator-modified electrode, the GO/Co/chitosan composite was electrically deposited onto an Au film electrode by covalent boding, while glucose oxidase as a receptor was immobilized on the end of the GO/Co/chitosan composite. It was confirmed that the electron transfer ability of the GO/Co/chitosan composite was excellent, as shown with power density analysis. In addition, the real-time detection of D-glucose could be successfully performed by the developed nano-biosensor with a high range of detected concentrations from 1.0 to 15.0 mM. Furthermore, the slope value composed of the current, per the concentration of D-glucose as a detection response, was significantly maintained even after 14 days.

The Impact of Glucose Oxidase Immobilization on Dendritic Gold Nanostructures on the Performance of Glucose Biosensors

In recent years, many efforts have been made to develop rapid, sensitive and user-friendly glucose biosensors for monitoring blood glucose concentration in patients. In this study, the electrochemical glucose biosensors based on graphite rod (GR) electrode electrochemically modified with dendritic gold nanostructures (DGNs) and glucose oxidase (GOx) were developed. Phenazine methosulfate was used as a soluble redox mediator. Three GOx immobilization methods: adsorption on DGNs and cross-linking with glutaraldehyde (GA) vapour (GA-GOx/DGNs/GR), covalent immobilization on DGNs modified with 11-mercaptoundecanoic acid self-assembled monolayer (SAM) (GOx-SAM/DGNs/GR) and covalent immobilization on SAM with additional cross-linking with GA vapour (GA-GOx-SAM/DGNs/GR), were used. It was determined that GA significantly improved the stability of the enzyme layer. The difference of maximal current generated during the enzymatic reaction (ΔI_max) equal to 272.06 ± 8.69 µA was obtained using a biosensor based on GA-GOx/DGNs/GR electrodes. However, the highest ΔI_max equal to 384.20 ± 16.06 µA was obtained using GA-GOx-SAM/DGNs/GR electrode. ΔI_max for biosensors based on the GA-GOx-SAM/DGNs/GR electrode was 1.41 times higher than for the GA-GOx/DGNs/GR, whereas the linear dynamic range from 0.1 to 10 mM was the same using all three GOx immobilization methods. The limit of detection using GA-GOx-SAM/DGNs/GR and GA-GOx/DGNs/GR electrodes was 0.019 and 0.022 mM, respectively. The ability to detect glucose in the serum by developed biosensors was evaluated.

Bipolar (Bio)electroanalysis

This contribution reviews a selection of the most recent studies on the use of bipolar electrochemistry in the framework of analytical chemistry. Despite the fact that the concept is not new, with several important studies dating back to the middle of the last century, completely novel and very original approaches have emerged over the last decade. This current revival illustrates that scientists still (re)discover some exciting virtues of this approach, which are useful in many different areas, especially for tackling analytical challenges in an unconventional way. In several cases, this "wireless" electrochemistry strategy enables carrying out measurements that are simply not possible with classic electrochemical approaches. This review will hopefully stimulate new ideas and trigger scientists to integrate some aspects of bipolar electrochemistry in their work in order to drive the topic into yet unexplored and eventually completely unexpected directions.

Direct Electrochemical Enzyme Electron Transfer on Electrodes Modified by Self-Assembled Molecular Monolayers

Self-assembled molecular monolayers (SAMs) have long been recognized as crucial “bridges” between redox enzymes and solid electrode surfaces, on which the enzymes undergo direct electron transfer (DET)—for example, in enzymatic biofuel cells (EBFCs) and biosensors. SAMs possess a wide range of terminal groups that enable productive enzyme adsorption and fine-tuning in favorable orientations on the electrode. The tunneling distance and SAM chain length, and the contacting terminal SAM groups, are the most significant controlling factors in DET-type bioelectrocatalysis. In particular, SAM-modified nanostructured electrode materials have recently been extensively explored to improve the catalytic activity and stability of redox proteins immobilized on electrochemical surfaces. In this report, we present an overview of recent investigations of electrochemical enzyme DET processes on SAMs with a focus on single-crystal and nanoporous gold electrodes. Specifically, we consider the preparation and characterization methods of SAMs, as well as SAM applications in promoting interfacial electrochemical electron transfer of redox proteins and enzymes. The strategic selection of SAMs to accord with the properties of the core redox protein/enzymes is also highlighted.

Transition-Metal-Doped Molybdenum Diselenides with Defects and Abundant Active Sites for Efficient Performances of Enzymatic Biofuel Cell and Supercapacitor Applications

We have demonstrated the synthesis of defect-rich Ni-doped MoSe₂ nanoplates (NiMoSe₂) and their application as an efficient electrocatalyst for enzymatic biofuel cells and electrochemical pseudocapacitors. In this study, a new type of interpretation is proposed that a defective surface facilitates the effective entrapment of enzymes (glucose oxidase (GOD), laccase) for biofuel cells and additional ion diffusion for Faradic charge-discharge reaction. The transmission electron microscopy and UV-vis spectroscopy techniques scrutinized the formation of defects/distortions and the resultant successful entrapment of enzymes. The performed electrochemical characterizations of enzyme-immobilized NiMoSe₂/nickel foam (NF) bioanode (NiMoSe₂/GOD/NF) and biocathode (NiMoSe₂/laccase/NF) exhibited better direct charge conductive behavior at the interface of enzymes and electrode material. Herein, the assembled biofuel cells exhibited an open-circuit voltage ( V_OC = 0.6 V) and a short-circuit current density ( J_SC = 8.629 mA cm^-2) with a maximum power density ( P_max) of 1.2 mW cm^-2. For the electrochemical pseudocapacitor application, the proposed NiMoSe₂/NF exhibited excellent specific capacitance (535.74 F g^-1), with 86.7% rate performance. Finally, this work suggests new insights into both enzymatic biofuel cell and supercapacitor applications.