Bioelectrochemistry – A growing community with broad diversity

Abstract

In our ever-changing and evolving world, disciplines in natural sciences are rarely able to solve complex research questions on their own anymore. Interdisciplinary research has become crucial to allow humanity to adapt to rapidly developing challenges, such as climate change, emerging diseases, an aging society, and growing socioeconomic inequalities. As one of the most rapidly growing interdisciplinary fields, bioelectrochemistry connects researchers all around the world, aiming to approach questions at the interface of biology, microbiology, chemistry, physics, and engineering from a new perspective. What started as a small community has developed over the last 2 decades into a diverse research society that provides remarkable insights into disease mechanisms, biomarker discovery, and bio-energy-related technology, such as microbial fuel cells.

This special collection presents research papers of exceptional bioelectrochemical studies, showcasing advances in point-of-care biosensor development, mechanistic bioelectrochemical research as well as biological energy harvesting and conversion. Articles are dedicated to understanding complex biological systems related to illnesses and answering questions in medical research, biosynthesis, and sustainable energy applications by bioelectrochemistry that require a multi-disciplinary knowledge base and interdisciplinary technologies.

The importance of the development of point-of-care sensors cannot be overstated, as biosensors are crucially needed to tackle emerging pathogens and to advance treatment strategies for other illnesses. The detection of disease biomarkers by electrochemistry has received tremendous attention over the last decade. Diagnostic studies for neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, infectious diseases, heart disease, and sepsis are only a few examples of ample contributions within this field of research. A wonderful example of successful immunosensing of a biomarker related to various illnesses, including angiogenesis, atherosclerosis, heart failure, and sepsis, is the contribution by Campuzano. In this publication, growth arrest-specific 6 (GAS6) protein is detected in human plasma and cell secretomes at screen-printed electrodes. Using the electrochemistry of the hydroquinone system, GAS6 is detected at antibody-modified magnetic micro-particles and further recognized by streptavidin-horseradish peroxidase. The use of screen-printed electrodes and an analysis time of about 75 min carries a great potential for the implementation of this sensing assay to be further developed into a clinical diagnostic device. Biodegradable electrodes are an emerging type of biosensors, highly applicable to clinical settings. Vadgama presents an interesting approach for chronic wound monitoring through albumin-collagen cross-linked membranes. This study demonstrates that diffusion barrier membranes can be made from protein mats, selective for H₂O₂, ascorbate, and glucose, and calls for future explorations of diffusion barriers for other clinical applications. A rather new type of biosensor is the photoelectrochemical (PEC) biosensor. These sensors operate based on the principle of photon-induced promotion of electrons to the conduction band within a semiconductor. The promoted electron can reduce an analyte or the formed valence band hole can oxidize an analyte. This principle is applied by Schöning, reporting a PEC enzymatic penicillin biosensor. The detection of penicillin was realized in this study through the enzyme penicillinase, immobilized on TiO₂ electrodes. The recognition of H⁺ ions, which are generated by penicillinase, opens the possibility to transfer this method to other analytes, enabling the application of this sensor to multi-analyte detection, as proposed by the authors. The detection of antibiotics in the environment is of great interest because the contamination of water and food sources with antimicrobials promotes the spread of drug resistance among microorganisms. Drug resistance has been declared a leading cause of death worldwide, and innovative strategies to counter this threat are crucial.

The development of biosensors would not be possible without bioelectrochemical studies to understand important cellular processes in healthy organisms, but also involved in disease initiation and progression. The importance of the formation of metal complexes in complex biological systems is explored in the contribution by Martic. The regulation of antioxidants and reactive oxygen species often depends on metal complex formation and is directly linked to cell death, cancer onset and development, neurodegeneration, and other pathologies. Martic and co-workers explore specifically the reactivity of quercetin and metallo-quercetin with superoxide and molecular oxygen. A mechanistic understanding of processes involved, helps to mimic biological functions, and aids to discover approaches to interfere with disease progression.

Biological systems are further known to be efficient in energy conversion. Coupling biological systems with electrochemistry can allow valorizing this efficiency. Contributions by Etienne and Schumann highlight how hydrogen can be used by bioelectrochemistry for both biosynthesis and the development of biofuel cells. In the contribution by Etienne, the authors show that the bioelectrochemical transfer of electrons from the synthetic energy source, hydrogen, to the biological energy carrier, NADH, can be used to drive ensuing enzymatic reactions, for which otherwise quantitative amounts of NADH would be necessary. Schuhmann used hydrogen as an energy source in bioanodes, using [NiFe] hydrogenase embedded within a novel viologen-modified polymer film to optimize charge transfer. Such hydrogen bioanodes are ultimately applicable in hydrogen biofuel cells. Finally, Katz showed how a combination of dehydrogenases and hexokinase can compete for substrate inputs, leading to an input-dependent response in the release of molecules. This can be considered as a Boolean logic gate with chemical inputs and outputs, that allow control of biofuel cells. Clearly, these contributions demonstrate a variety of highly innovative approaches to exploring the potential of biological processes to harvest and convert energy.

I hope you will enjoy reading the collective contributions to this special issue and appreciate the diversity within our growing community of bioelectrochemists. As we are adding experts to this field, the impact of research will further advance towards a more healthy and sustainable future.

The author declares that they have no conflict of interest.