Development of Flexible, Conductive and Biocompatible Chitosan-Based Miniaturized Bioelectrodes for Enzymatic Glucose Biofuel Cells

The need for new clean energy sources for portable devices in biomedical, agro-food industry and environmental related sectors boosts scientists towards the development of new strategies for energy harvesting for their application in biodevices development. In this sense, enzymatic biofuel cells (BFCs) have gained much attention in the last years. This work faces the challenge of develop new generation of BFCs able to be adapted to remote and personal monitoring devices within the framework of wearable technologies. To this aim, one of the main challenges consists of the development of conductive and biocompatible electrodes, which constitute a challenge itself due to the non-conductive capabilities of most of the biocompatible supports. Additionally, bioelectrodes may achieve good mechanical properties and resilience in order to be suitable for the envisioned application, which involves exposure to deformation during long-term use. Furthermore, it is desirable that the systems developed are versatile enough to be adapted to miniaturized supports for new personal wearable devices development. In the present work, self-standing chitosan-carbon black membranes have been synthesized and modified with suitable enzymes for the assembly of an enzymatic glucose BFC. The membranes have been adapted to be integrated in miniaturized interdigitated gold electrodes as the step forward to miniaturized systems, modified with enzymes and metallic particles clusters and tested for energy harvesting from glucose solutions. The miniaturized system produces a power density of 0.64 µW/cm2 that is enhanced to 2.75 µW/cm2 in the presence of the metallic clusters, which constitute a 76% incensement. Such preliminary demonstrations highlight the good response of metals in bioelectrode configuration. However, energy harvesting real application of the developed miniaturized electrodes need still improvements but pave the way for the use of BFC as an energy source in wearable technologies due to their good mechanical, electrical and biocompatible properties.

In Silico Analysis of Glucose Oxidase H516r and H516d Mutations for an Enzymatic Fuel Cell

Glucose oxidase (GOx) is an oxido-reductase enzyme that catalyzes glucose into hydrogen peroxide and glucono delta-lactone (GDL). GOx has the potential to be used in the medical field. Numerous research concerning the usage of GOx to create enzymatic biofuel cells have been done, nevertheless the results obtained have not been optimal. This research aims to increase the Km values of GOx in order to increase its potential as a material for an enzymatic fuel cell. The amino acid histidine in position 516 is a residue in the active site that plays an important part in the process of glucose oxidation. In this research we mutated H516 by in silico twice resulting in the mutants R516 and D516. The mutations resulted in a change of the docking area for both mutants and in the docking affinity for H516D resulting in higher Km values. This shows that the H516 residue plays an important part in the functions of glucose oxidase and mutation into aspartate could improve glucose oxidase based enzymatic fuel cells.

Phototrophs in alternative energy

The role of phototrophs is examined in alternative energy, with the main emphasis on unicellular algae. Particular attention is paid to the use of phototrophs for generating electricity using biofuel cells (plant and enzymatic biofuel cells are discussed). This study focuses on microbial fuel cells (MFC), which, along with electric power, allow obtaining biofuels and biohydrogen. This article explains the factors limiting the MFC power, and ways of overcoming them. For example, it seems promising to develop various photobioreactors in order to reduce the loss of MFC power due to overvoltage. The use of microphototrophs in MFC has led to the development of photosynthetic MFC (or PhotoMFC) through the design of autotrophic photobioreactors with forced illumination. They allow generating oxygen through photosynthesis, both in situ and ex situ, by recirculating oxygen from the photobioreactor to the cathode chamber. Artificial redox mediators can be used here, transferring electrons directly from the non-catalytic cathode to O2, formed as a result of the photosynthetic activity of algae. Biologically catalyzed cathodes have been proven to generate less power than chemical catalysts. It is noted, that the MFC installations with the micro-algae allow utilizing a wider circle of different connections – the components of effluents and withdrawals: organic acids, sugar, alcohols, fats and other substrata. The use of phototrophs for the production of biofuels is of special interest. Several different types of renewable biofuels can be produced from microalgae, the production of which can be combined with wastewater treatment, CO2 capture and production of various compounds.

Research Progress and Prospects of Nanozyme-Based Glucose Biofuel Cells

The appearance and evolution of biofuel cells can be categorized into three groups: microbial biofuel cells (MBFCs), enzymatic biofuel cells (EBFCs), and enzyme-like nanomaterial (nanozyme)-based biofuel cells (NBFCs). MBFCs can produce electricity from waste; however, they have significantly low power output as well as difficulty in controlling electron transfer and microbial growth. EBFCs are more productive in generating electricity with the assistance of natural enzymes, but their vulnerability under diverse environmental conditions has critically hindered practical applications. In contrast, because of the intrinsic advantages of nanozymes, such as high stability and robustness even in harsh conditions, low synthesis cost through facile scale-up, and tunable catalytic activity, NBFCs have attracted attention, particularly for developing wearable and implantable devices to generate electricity from glucose in the physiological fluids of plants, animals, and humans. In this review, recent studies on NBFCs, including the synthetic strategies and catalytic activities of metal and metal oxide-based nanozymes, the mechanism of electricity generation from glucose, and representative studies are reviewed and discussed. Current challenges and prospects for the utilization of nanozymes in glucose biofuel cells are also discussed.