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Biofuel cells have recently gained popularity as a green and renewable energy source. Biofuel cells are unique devices of energy and are capable of converting the stored chemical energy from waste materials such as pollutants, organics and wastewater into reliable, renewable, pollution-free energy sources through the action of biocatalysts such as various microorganisms and enzymes. It is a promising technological device to treat waste to compensate for global warming and the energy crisis through the green energy production process. Due to their unique properties, various potential biocatalysts are attracting researchers to apply them to various microbial biofuel cells for improving electricity and power. Recent research in biofuel cells is focusing on the exploitation of different biocatalysts and how they are enhancing power generation for various applications in the field of environmental technology, and biomedical fields such as implantable devices, testing kits, and biosensors. This review focusing the importance of microbial fuel cells (MFCs) and enzymatic fuel cells (ECFs) and role of different types of biocatalysts and their mechanisms for improving biofuel cell efficiency gathered from recent reports. Finally, its multifaceted applications with special emphasis on environmental technology and biomedical field will be described, along with future perspectives. [ABSTRACT FROM AUTHOR]

An enzyme‐based biofuel cell (EBFC) is widely regarded as one of the most efficient power sources for bio‐friendly and implantable medical devices, capable of converting electrochemical reactions into electrical currents under physiological conditions. However, despite its potential, the practical and commercial use of EBFCs is limited by their low power output and operational instability. Therefore, significant research efforts have focused on increasing power output and stability by improving electron transfer between enzymes and host electrodes and developing efficient enzyme immobilization techniques. However, most EBFCs produced by current methods still deliver unsatisfactory performance. A promising approach to address these challenges is the use of conductive linkers that promote favorable interfacial interactions between adjacent enzymes and between enzymes and host electrodes. These linkers can facilitate electron transfer and ensure robust enzyme immobilization. In addition, designing the host electrode with a 3D structure and a large surface area can further improve the areal energy performance. This perspective reviews the working principles, types, and electron transfer mechanisms of EBFC electrodes and explores how conductive linkers and 3D host electrodes can enhance the performance of EBFC electrodes. Finally, recent advances in integrating EBFCs into biomedical devices are described. [ABSTRACT FROM AUTHOR]

Biofuel cells (BFCs) offer an eco‐friendly route to convert biochemical energy into electricity. However, their performance is hindered by insufficient enzyme immobilization as well as limited electron transfer within the enzymatic electrode. While the incorporation of redox mediators (RMs) into enzyme layers has been shown to improve BFC performance through enhanced electron transfer, progress has plateaued in the last decade. Herein, a major breakthrough is presented realized by a novel strategy that exploits electron transfer‐intensified RM layers. Metal nanoparticles covalently bridged between neighboring RMs facilitate electron transfer ubiquitously. Electron transfer characteristics are enhanced not only within the RM layers themselves, but also at the glucose oxidase (GOx)/host electrode and GOx/GOx interfaces. This leads to a remarkable performance boost in the enzymatic anode. A hybrid BFC constructed with innovative anode and Pt‐based cathode exhibits a striking combination of high power output (2.3 and 8.5 mW cm−2 at 10 and 300 mmol L−1 glucose, respectively) and exceptional operational stability (≈80% and 47% power retention after 10 days and 1 month, respectively), outperforming all previously reported BFCs by a significant margin. [ABSTRACT FROM AUTHOR]

Carbon‐based nanozymes have received considerable attention due to their superior biosafety, enhanced tolerance to extreme conditions, and ease of chemical modification. However, due to limited material diversity and unconfirmed molecular structure, carbon‐based nanozymes face challenges such as relatively low enzyme activity and unclear catalytic mechanisms. The development of materials with well‐defined structures and controllable properties is crucial for promoting the rapid progress of nanozymes. Herein, 3,4,9,10‐perylenetetracarboxylic dianhydride (PD) exhibits both glucose oxidase (GOx)‐like and catalase (CAT)‐like activities, which may be due to the fact that PD possesses the features of highly conjugated structure and high electron mobility. In addition, it is demonstrated that the enzymatic activity is related to the degree of PD aggregation via the characterization of its morphology and size. Based on the excellent GOx‐like and CAT‐like activities of PD, a self‐cascade catalytic system is constructed for application in biofuel cells (BFCs). It is worth mentioning that such BFC still maintains high stability after working for 30 days. Therefore, this study expands the enzyme‐like systems and discovers that nanomaterials with highly conjugated structures and high electron mobility can mimic enzymes. Additionally, the multi‐enzyme activities are utilized to construct self‐cascade systems, which can effectively improve the performance of BFCs. [ABSTRACT FROM AUTHOR]

A novel biofuel cell (BFC)-based self-powered electrochemical immunosensing platform was developed by integrating the target-induced biofuel release and biogate immunoassay for ultrasensitive 17β-estradiol (E2) detection. The carbon nanocages/gold nanoparticle composite was employed in the BFCs device as the electrode material, through which bilirubin oxidase and glucose oxidase were wired to form the biocathode and bioanode, respectively. Positively charged mesoporous silica nanoparticles (PMSN) were encapsulated with glucose molecules as biofuel and subsequently coated by the negatively charged AuNPs-labelled anti-E2 antibody (AuNPs-Ab) serving as a biogate. The biogate could be opened efficiently and the trapped glucose released once the target E2 was recognized and captured by AuNPs-Ab due to the decreased adhesion between the antigen–antibody complex and PMSN. Then, glucose oxidase oxidized the glucose to produce a large number of electrons, resulting in significantly increased open-circuit voltage (EOCV). Promisingly, the proposed BFC-based self-powered immunosensor demonstrated exceptional sensitivity for the detection of E2 in the concentration range from 1.0 pg mL−1 to 10.0 ng mL −1, with a detection limit of 0.32 pg mL−1 (S/N = 3). Furthermore, the prepared BFC-based self-powered homogeneous immunosensor showed significant potential for implementation as a viable prototype for a mobile and an on-site bioassay system in food and environmental safety applications. [ABSTRACT FROM AUTHOR]

Although fossil fuels are widely used to meet energy needs, intensive research has been carried out in recent years on hydrogen production from renewable sources due to their decrease over time and environmental pollution concerns. Biofuel cell technology is one of the promising current technologies. It has been proven that various microorganisms produce energy through their natural metabolism, and that energy production is produced in biofuel cells by exoelectrogenic microorganisms that can transfer electrons to an electrode surface. Although it has been stated that employing human cells to generate energy is feasible, it is unknown whether doing so would enable the production of hydrogen. Within the scope of this perspective article, the issue of hydrogen production in bioelectrolysis cells using human cells will be discussed for the first time. Optimizing hydrogen production in bioelectrolysis cells using human cells is important in terms of contributing to hydrogen technologies. Within the scope of the article, promising human cell lines for hydrogen production are emphasized and hydrogen production potentials in bioelectrolysis cells using these cell lines are discussed. In conclusion, some human cells can be used for hydrogen gas production in bioelectrolysis cells due to their bioelectrochemical and metabolic properties. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are sustainable energy recovery systems because they use organic waste as biofuel. Using critical raw materials (CRMs), like platinum-group metals, at the cathode side threatens MFC technology's sustainability and raises costs. By developing an efficient electrode design for MFC performance enhancement, CRM-based cathodic catalysts should be replaced with CRM-free materials. This work proposes developing and optimizing iron-based air cathodes for enhancing oxygen reduction in MFCs. By subjecting iron phthalocyanine and carbon black pearls to controlled thermal treatments, we obtained Fe-based electrocatalysts combining high surface area (628 m2 g−1) and catalytic activity for O2 reduction at near-neutral pH. The electrocatalysts were integrated on carbon cloth and carbon paper to obtain gas diffusion electrodes whose architecture was optimized to maximize MFC performance. Excellent cell performance was achieved with the carbon-paper-based cathode modified with the Fe-based electrocatalysts (maximum power density-PDmax = 1028 mWm−2) compared to a traditional electrode design based on carbon cloth (619 mWm−2), indicating the optimized cathodes as promising electrodes for energy recovery in an MFC application. [ABSTRACT FROM AUTHOR]

The adoption of microbial fuel cell (MFC) technology hinges on the development of efficient proton‐exchange membranes (PEMs), which significantly influences fuel cell performance and cost. PEMs have a critical role in preventing oxygen crossover, maintaining electrochemical neutrality, and supporting microorganisms within MFCs. Nafion, the current industry‐standard PEM, grapples with environmental, cost, and performance issues. Although improvements to Nafion have been reported using additives, immersion in heteropolyacids, different pretreatment methods, and UV irradiation, many of the challenges still remain. Herein, the recent developments in the area of alternative PEMs are reviewed and analyzed. Among them, sulfonated aromatic hydrocarbons, particularly sulfonated polyether ether ketone, have emerged as top contenders in terms of scale up and commercial viability. At the same time, membranes based on polyvinyl alcohol, ionic liquids, and natural materials are also being actively researched for various MFC applications. Since most studies are short term and lab scale, there is a need evaluate long‐term stability and economic cost of PEMs in terms of standardized parameters such as power‐to‐cost and normalized energy recovery. Additionally, for emerging low‐energy‐density MFC applications like biosensors and in vivo power sources, PEM properties and design need to be tailored carefully. [ABSTRACT FROM AUTHOR]

Quinones are electrochemical probes which are used for a large range of applications including bioenergetics. One electrochemical feature of quinones is their possible slow electron transfer kinetics. In this article we compared several quinones towards electron transfer kinetics and the ability of anodic pretreatment to increase electron transfer rate constant. Rotating disk electrode and chronoamperometry measurements were used to revisit their electrochemical behavior. Additionally, the number of electrons exchanged as a function of the characteristic time was used as a proxy to investigate kinetic limitations. A model was suggested to rationalize our results. Beyond a classification of quinones regarding the kinetic and thermodynamic ability of the hydroquinone form to be re‐oxidized, some intrinsic physicochemical properties were identified from our model (such as a time dependency of the exchanged number of electrons) to characterize such important redox mediators. [ABSTRACT FROM AUTHOR]

Environmental pollution is becoming ubiquitous; it has a negative impact on ecosystem diversity and worsens the quality of human life. This review discusses the possibility of applying the plant microbial fuel cells (PMFCs) technology for concurrent processes of electricity generation and the purification of water and soil ecosystems from organic pollutants, particularly from synthetic surfactants and heavy metals. The review describes PMFCs' functioning mechanisms and highlights the issues of PMFCs' environmental application. Generally, this work summarizes different approaches to PMFC development and to the potential usage of such hybrid bioelectrochemical systems for environmental protection. [ABSTRACT FROM AUTHOR]

Various sensors and electronic devices are recently developed to monitor human health in mechanically flexible or even stretchable forms for intimate contact with non‐flat curvilinear surfaces of the human body. For successful operation of these devices, finding a proper way to electrically power them is very important. In this work, glucose/oxygen fueled enzymatic biofuel cells (EBFCs) based on microfluidic structured elastomeric polydimethylsiloxane substrate with wrinkled gold (Au) electrodes are suggested for power supply. For doing that, firstly, bottom surface of microfluidic channel is covered with buckled Au electrodes for stretchability. By microfluidic design showing capillary imbibition through fluidic channels, loading of catalyts is promoted. Interestingly, buckled Au electrodes induce much better anodic and cathodic reaction rates than those of non‐buckled Au electrodes by 25% and 33%, respectively. This is because surface area and the amount of catalyst loading in electrodes increase by Au wrinkling. In evaluations of EBFCs using the buckled Au electrodes, maximum power density reaches 7.1 ± 0.64 µW cm−2, while they show decent performance of 5.4 ± 0.49 µW cm−2 even under external stretching. Taken together, it is corroborated that such proposed stretchable EBFCs are alternative for providing electrical power in wearable or implantable devices. [ABSTRACT FROM AUTHOR]

Abstract Quinones are electrochemical probes which are used for a large range of applications including bioenergetics. One electrochemical feature of quinones is their possible slow electron transfer kinetics. In this article we compared several quinones towards electron transfer kinetics and the ability of anodic pretreatment to increase electron transfer rate constant. Rotating disk electrode and chronoamperometry measurements were used to revisit their electrochemical behavior. Additionally, the number of electrons exchanged as a function of the characteristic time was used as a proxy to investigate kinetic limitations. A model was suggested to rationalize our results. Beyond a classification of quinones regarding the kinetic and thermodynamic ability of the hydroquinone form to be re‐oxidized, some intrinsic physicochemical properties were identified from our model (such as a time dependency of the exchanged number of electrons) to characterize such important redox mediators.

Quick and effective point-of-care (POC) devices have the chance to revolutionize healthcare in developed and developing countries since they can operate anywhere the patient is, with the possibility of obtaining and sending the results to the doctor without delay. In recent years, significant efforts have focused on developing new POC systems that can screen for biomarkers continuously and non-invasively in body fluids to prevent, diagnose, and manage diseases. However, one of the critical challenges left to address is how to power them effectively and sufficiently. In developing countries and rural and remote areas, where there are usually no well-established electricity grids or nearby medical facilities, and using batteries is unreliable or not cost-effective, alternative power sources are the most challenging issue for stand-alone and self-sustained POC devices. Here, we provide an overview of the techniques for used self-powering POC devices, where the sample is used to detect and simultaneously generate energy to power the system. Likewise, this paper introduced the state-of-the-art with a review of different research projects, patents, and commercial products for self-powered POCs from the mid-2010s until present day. [ABSTRACT FROM AUTHOR]

Chemical biomarkers in the central nervous system can provide valuable quantitative measures to gain insight into the etiology and pathogenesis of neurological diseases. Glutamate, one of the most important excitatory neurotransmitters in the brain, has been found to be upregulated in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, stroke, epilepsy, chronic pain, and migraines. However, quantitatively monitoring glutamate release in situ has been challenging. This work presents a novel class of flexible, miniaturized probes inspired by biofuel cells for monitoring synaptically released glutamate in the nervous system. The resulting sensors, with dimensions as low as 50 by 50 μm, can detect real‐time changes in glutamate within the biologically relevant concentration range. Experiments exploiting the hippocampal circuit in mice models demonstrate the capability of the sensors in monitoring glutamate release via electrical stimulation using acute brain slices. These advances could aid in basic neuroscience studies and translational engineering, as the sensors provide a diagnostic tool for neurological disorders. Additionally, adapting the biofuel cell design to other neurotransmitters can potentially enable the detailed study of the effect of neurotransmitter dysregulation on neuronal cell signaling pathways and revolutionize neuroscience. [ABSTRACT FROM AUTHOR]

Magnetically stimulated bio‐and electrochemical systems have gained increasing importance in recent years due to their enhanced sensitivity and selectivity, improved spatial control, and ability to operate in complex environments, offering significant advantages over conventional systems. Essentially, this review provides a comprehensive and informative survey about the state‐of‐art as well as the recent efforts and applications made in the past decade, with a focus on new functional magnetic materials and nano‐architectonic interfaces that have led to promising advances in biosensors, biofuel cells, and their integration into devices. Future directions and perspectives are also discussed. [ABSTRACT FROM AUTHOR]

The amalgamation of flexible electronics in biological systems has shaped the way health and medicine are administered. The growing field of flexible electrochemical bioelectronics enables the in situ quantification of a variety of chemical constituents present in the human body and holds great promise for personalized health monitoring owing to its unique advantages such as inherent wearability, high sensitivity, high selectivity, and low cost. It represents a promising alternative to probe biomarkers in the human body in a simpler method compared to conventional instrumental analytical techniques. Various bioanalytical technologies are employed in flexible electrochemical bioelectronics, including ion-selective potentiometry, enzymatic amperometry, potential sweep voltammetry, field-effect transistors, affinity-based biosensing, as well as biofuel cells. Recent key innovations in flexible electrochemical bioelectronics from electrochemical sensing modalities, materials, systems, fabrication, to applications are summarized and highlighted. The challenges and opportunities in this field moving forward toward future preventive and personalized medicine devices are also discussed.

Highlights Screen-printable functional nanocomposite inks are engineered for flexible, single-enzyme-based energy-harvesting, and self-powered biosensing devices. A BFC powered by the same biosubstrate (glucose) is developed to harvest energy in a biofluid model and act as a self-powered electrochemical glucose. Customized inks are advantageous in terms of integrating with flexible materials, which can be integrated with a wide range of wearables and soft bioelectronics.

The extraordinary potential of hydrogen as a clean and sustainable fuel has sparked the interest of the scientific community to find environmentally friendly methods for its production. Biological catalysts are the most attractive solution, as they usually operate under mild conditions and do not produce carbon-containing byproducts. Hydrogenases promote reversible proton reduction to hydrogen in a variety of anoxic bacteria and algae, displaying unparallel catalytic performances. Attempts to use these sophisticated enzymes in scalable hydrogen production have been hampered by limitations associated with their production and stability. Inspired by nature, significant efforts have been made in the development of artificial systems able to promote the hydrogen evolution reaction, via either electrochemical or light-driven catalysis. Starting from small-molecule coordination compounds, peptide- and protein-based architectures have been constructed around the catalytic center with the aim of reproducing hydrogenase function into robust, efficient, and cost-effective catalysts. In this review, we first provide an overview of the structural and functional properties of hydrogenases, along with their integration in devices for hydrogen and energy production. Then, we describe the most recent advances in the development of homogeneous hydrogen evolution catalysts envisioned to mimic hydrogenases. [ABSTRACT FROM AUTHOR]

Environmental pollution is becoming ubiquitous; it has a negative impact on ecosystem diversity and worsens the quality of human life. This review discusses the possibility of applying the plant microbial fuel cells (PMFCs) technology for concurrent processes of electricity generation and the purification of water and soil ecosystems from organic pollutants, particularly from synthetic surfactants and heavy metals. The review describes PMFCs’ functioning mechanisms and highlights the issues of PMFCs’ environmental application. Generally, this work summarizes different approaches to PMFC development and to the potential usage of such hybrid bioelectrochemical systems for environmental protection.

Highlights: Screen-printable functional nanocomposite inks are engineered for flexible, single-enzyme-based energy-harvesting, and self-powered biosensing devices. A BFC powered by the same biosubstrate (glucose) is developed to harvest energy in a biofluid model and act as a self-powered electrochemical glucose. Customized inks are advantageous in terms of integrating with flexible materials, which can be integrated with a wide range of wearables and soft bioelectronics. Developing flexible bioelectronics is essential to the realization of artificial intelligence devices and biomedical applications, such as wearables, but their potential is limited by sustainable energy supply. An enzymatic biofuel cell (BFC) is promising for power supply, but its use is limited by the challenges of incorporating multiple enzymes and rigid platforms. This paper shows the first example of screen-printable nanocomposite inks engineered for a single-enzyme-based energy-harvesting device and a self-powered biosensor driven by glucose on bioanode and biocathode. The anode ink is modified with naphthoquinone and multiwalled carbon nanotubes (MWCNTs), whereas the cathode ink is modified with Prussian blue/MWCNT hybrid before immobilizing with glucose oxidase. The flexible bioanode and the biocathode consume glucose. This BFC yields an open circuit voltage of 0.45 V and a maximum power density of 266 μW cm−2. The wearable device coupled with a wireless portable system can convert chemical energy into electric energy and detect glucose in artificial sweat. The self-powered sensor can detect glucose concentrations up to 10 mM. Common interfering substances, including lactate, uric acid, ascorbic acid, and creatinine, have no effect on this self-powered biosensor. Additionally, the device can endure multiple mechanical deformations. New advances in ink development and flexible platforms enable a wide range of applications, including on-body electronics, self-sustainable applications, and smart fabrics. [ABSTRACT FROM AUTHOR]

Glucose oxidase (GOx)-based electrodes are important for bioelectronics, such as glucose sensors. It is challenging to effectively link GOx with nanomaterial-modified electrodes while preserving enzyme activity in a biocompatible environment. To date, no reports have used biocompatible food-based materials, such as egg white proteins, combined with GOx, redox molecules, and nanoparticles to create the biorecognition layer for biosensors and biofuel cells. This article demonstrates the interface of GOx integrated with egg white proteins on a 5 nm gold nanoparticle (AuNP) functionalized with a 1,4-naphthoquinone (NQ) and conjugated with a screen-printed flexible conductive carbon nanotube (CNT)-modified electrode. Egg white proteins containing ovalbumin can form three-dimensional scaffolds to accommodate immobilized enzymes and adjust the analytical performance. The structure of this biointerface prevents the escape of enzymes and provides a suitable microenvironment for the effective reaction. The bioelectrode's performance and kinetics were evaluated. Using redox-mediated molecules with the AuNPs and the three-dimensional matrix made of egg white proteins improves the transfer of electrons between the electrode and the redox center. By engineering the layer of egg white proteins on the GOx-NQ-AuNPs-mediated CNT-functionalized electrodes, we can modulate analytical performances such as sensitivity and linear range. The bioelectrodes demonstrate high sensitivity and can prolong the stability by more than 85% after 6 h of continuous operation. The use of food-based proteins with redox molecule-modified AuNPs and printed electrodes demonstrates advantages for biosensors and energy devices due to their small size, large surface area, and ease of modification. This concept holds a promise for creating biocompatible electrodes for biosensors and self-sustaining energy devices. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are crystalline materials that are formed by self-assembling organic linkers and metal ions with large specific areas and pore volumes. Their chemical tunability, structural diversity, and tailor-ability make them adaptive to decorate many substrate materials, such as biomass-derived carbon materials, and competitive in many environmental biosystems, such as biofuel cells, bioelectrocatalysts, microbial metal reduction, and fermentation systems. In this review, we surmised the recent progress of MOFs and MOF-derived materials and their applications in environmental biosystems. The behavior of MOFs and MOF-derived materials in different environmental biosystems and their influences on performance are described. The inherent mechanisms will guide the rational design of MOF-related materials and lead to a better understanding of their interaction with biocomponents. [ABSTRACT FROM AUTHOR]

Biofuel cells have been in the spotlight for the past century because of their potential and promise as a unique platform for sustainable energy harvesting from the human body and the environment. Because biofuel cells are typically developed in a small platform serving as a primary battery with limited fuel or as a rechargeable battery with repeated refueling, they have been interchangeably named biobatteries. Despite continuous advancements and creative proof-of-concept, however, the technique has been mired in its infancy for the past 100 years, which has provoked increasing doubts about its commercial viability. Low performance, instability, difficulties in operation, and unreliable and inconsistent power generation question the sustainable development of biofuel cells. However, the advancement in bioelectrocatalysis revolutionizes the electricity-producing capability of biofuel cells, promising an attractive, practical technique for specific applications. This perspective article will identify the misconceptions about biofuel cells that have led us in the wrong development direction and revisit their potential applications that can be realizable soon. Then, it will discuss the critical challenges that need to be immediately addressed for the commercialization of the selected applications. Finally, potential solutions will be provided. The article is intended to inspire the community so that fruitful commercial products can be developed soon. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) with their high pore volumes and chemically‐diverse pore environments have emerged as components of catalytic electrodes for biosensors, biofuel cells, and bioreactors. MOFs are widely exploited for gas capture, separations, and catalysis, but their integration at electrodes with biocatalysts for (bio)electrocatalysis is a niche topic that remains largely unexplored. This review focuses on recent advances in MOF and MOF‐derived carbon electrodes for bioelectrochemical applications. A range of MOF materials and their integration into devices with enzymes and microbes are reported. Key properties and performance characteristics are considered and opportunities facing MOFs for (bio)electrochemical applications are discussed. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the efficiency of a biofuel cell technology (BFC) based on the commercial biological product “Doctor Robik 109” in the utilization of some nitrogen-containing components of wastewater (urea, ammonium nitrogen, and peptone). The following electrochemical parameters were measured during the BFC operation with “Doctor Robik 109”: voltage, current strength, power, and redox potential of the anolyte. The nitrogen-containing substrates were determined using photometric methods. The number of microorganisms was calculated by Koch’s method. It was shown that “Doctor Robik 109” generated an electric current in the BFC upon the usage of urea (0.5 g/L), ammonium nitrogen (0.5 g/L of NH4+ ions), and peptone (0.5 g/L) as substrates. The current generation by microorganisms of “Doctor Robik 109” in the BFC was accompanied by an increase in the number of cells of microorganisms, a depletion of the tested substrates, and a decrease in the redox potential of the anolyte. In the BFC containing model wastewater with the addition of 0.5 g/L of urea, “Doctor Robik 109” generated an open-circuit voltage of up to 332 mV (for 5 days). With 0.5 g/L NH4+ and 0.5 g/L peptone, this value was higher – up to 483 mV (for 1 day) and up to 520 mV (for 10 days), respectively. The current strength (in the short-circuit mode) in the BFC with urea reached 519 μA, and in the BFC with peptone it was more than two times higher (up to 1248 μA). Based on the data obtained, with an account of the breadth of the substrate specificity of microorganisms of “Doctor Robik 109”, its low cost and ease of use, recommendations were given for the use of this biological product in BFC for waste disposal and treatment of various types of wastewater with simultaneous generation of electric current.

Abstract Electrochemical oxygen reduced reaction (ORR) is a critical element in clean energy development. Despite efforts to enhance gas transfer to the reaction interface, the low solubility of O2 molecules and slow diffusion rate in liquid electrolyte is still a significant challenge. Herein, we design an artificial outer membrane on microalgal cells, which consists of a carbon dots/bilirubin oxidase (CDs/BOD) ORR catalyst layer and a L‐cystine/Au nanoporous O2 supply layer. O2 generated by photosynthesis from microalgal cells then can be directly transported to the CDs/BOD catalytic interfaces, overcoming the sluggish gas transfer in the electrolyte. Thus, the cathode constructed by the fabricated microalgal cells realizes an ORR current density of 655.2 μA/cm2 with fast ORR kinetics, which is 2.68 times higher than that of a BOD cathode fed with pure O2. A membrane‐less glucose/O2 biofuel cell is further developed using the hybrid artificial cells as the cathode, and the power density is 2.39 times higher than that of a BOD cathode biofuel cell in O2 saturated solution. This biomimetic design supplies O2 directly to the carbon dots/BOD catalyst layer from the microalgae membrane through a nanoporous L‐cys/Au layer, providing an alternative solution for the transfer barrier of O2 in the electrolyte.

Quick and effective point-of-care (POC) devices have the chance to revolutionize healthcare in developed and developing countries since they can operate anywhere the patient is, with the possibility of obtaining and sending the results to the doctor without delay. In recent years, significant efforts have focused on developing new POC systems that can screen for biomarkers continuously and non-invasively in body fluids to prevent, diagnose, and manage diseases. However, one of the critical challenges left to address is how to power them effectively and sufficiently. In developing countries and rural and remote areas, where there are usually no well-established electricity grids or nearby medical facilities, and using batteries is unreliable or not cost-effective, alternative power sources are the most challenging issue for stand-alone and self-sustained POC devices. Here, we provide an overview of the techniques for used self-powering POC devices, where the sample is used to detect and simultaneously generate energy to power the system. Likewise, this paper introduced the state-of-the-art with a review of different research projects, patents, and commercial products for self-powered POCs from the mid-2010s until present day.

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme's catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification. [ABSTRACT FROM AUTHOR]

Wearable biofuel cells (BFCs) technologies have the potential to address the challenge of on‐body energy supply of wearable electronics. However, previous wearable BFCs primarily focus on "worn‐on‐skin" sweat ones, which can hardly directly generate steady and nonintermittent electricity under certain but almost ineluctable wearable circumstances (e.g., intermittent sweating, perspiration biofuel concentration fluctuation, and dynamic contact between wearable BFCs and epidermal sweat). Here, in an alternative "worn‐close to‐skin" manner, the first example of a flexible BFC‐in‐a‐tube (named iezTube) as an entirely self‐contained wearable BFC (ESW‐BFC) for wearable energy generation by integrating a single‐layer fluff pulp (FP)‐based microfluidic module for the efficient sampling/utilization of biofuel fluids and the steady contact between biofuel fluids and wearable BFC with a flexible nano‐engineered BFC‐based BFC module for real‐time bio‐energy generation, along with an air‐breathing module that is based on a breathable and waterproof non‐woven tapes covered centrifuge tube‐based for continuous oxidizer supply, is reported. Through the seamless system integration, effective series‐connection pattern, and diverse readily accessible biofuel fluids pre‐collection, the iezTube demonstrates an exceptional capability to steadily and nonintermittently power wearable electronics under some certain but nearly ineluctable wearable circumstances and holds considerable and inimitable prospects as an ESW‐BFC for wearable electronics. [ABSTRACT FROM AUTHOR]

Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller—particularly in point‐of‐care (POC) devices and wearable platforms—it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self‐powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme‐based systems, battery‐based systems, and ion‐selective electrode‐based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them. [ABSTRACT FROM AUTHOR]

Flap endonuclease 1 (FEN1) is a structure-specific endonuclease that plays a critical role in the maintenance of genome integrity. In this work, we demonstrate a novel self-powered electrochemical FEN1 biosensor for potential applications in molecular diagnosis. Porous Fe 3 O 4 nanoparticles are first prepared, and single-strand DNA probes are absorbed on the surface of the nanoparticles. Thus, electrochemical species of [Fe(CN) 6 ] 3- can be encapsulated inside the porous nanoparticles with the molecular gate of negatively charged DNA. On the other hand, a dumbbell structured DNA probe with 5' flap is designed. FEN1 is able to cleave the flap and activate the CRISPR/Cas system for the digestion of single-stranded DNA around Fe 3 O 4 nanoparticles. As a result, the leakage of [Fe(CN) 6 ] 3- contributes to an enhanced electrochemical response, which can be used to reveal the level of FEN1. The high sensitivity of this biosensor is due to the application of porous nanomaterials and Mn 2+ accelerated CRISPR/Cas cleavage. It succeeds in detection of biological samples and screening of FEN1 inhibitors. Therefore, this proposed method has potential applications in the early diagnosis of diseases and drug discovery.

Wearable sensor technology is a key to sustainable healthcare systems because of its unique capability to assess a wearer's state of wellbeing. We must continue to explore the sensible integration of sensors into wearable and energy-sustainable systems. This article reveals a new example of self-powered bioelectronics on a mask for continuously monitoring glucose by leveraging printed biofuel-cell-based carbon-nanotube-modified bioelectronics. The bioanode relies on the oxidation of glucose with the assistance of glucose oxidase and tetrathiafulvalene functionalized on the polyaniline-modified electrode, whereas the cathode, with the assistance of platinum-poly(3,4-ethylenedioxythiophene) materials, utilizes oxygen reduction reaction. The developed flexible electrodes show enhanced capacitance and favorable biocatalytic performances. This mask biodevice yields an open circuit voltage (OCV) of 0.37 V and achieves a maximum output density of 14 μW cm−2. The applicability to glucose detection shows that the self-powered analytical signal is proportional to the glucose concentration up to 10.00 mM with the limit of detection of 0.22 mM. This self-powered biosensor is also not affected by common interfering agents, such as lactic acid, uric acid, ascorbic acid, and creatinine. It is envisioned that this platform would further improve a wide range of digital e-health diagnostic and physiological monitoring applications.

Abstract Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller—particularly in point‐of‐care (POC) devices and wearable platforms—it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self‐powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme‐based systems, battery‐based systems, and ion‐selective electrode‐based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them.

Effective wound management has the potential to reduce both the duration and cost of wound healing. However, traditional methods often rely on direct observation or complex and expensive biological testing to monitor and evaluate the invasive damage caused by wound healing, which can be time-consuming. Biosensors offer the advantage of precise and real-time monitoring, but existing devices are not suitable for integration with sensitive wound tissue due to their external dimensions. Here, we have designed a self-powered biosensing suture (SPBS) based on biofuel cells to accurately monitor glucose concentration at the wound site and promote wound healing. The anode of the SPBS consists of carbon nanotubes-modified carbon fibers, tetrathiafulvalene (TTF), and glucose oxidase (GOx), while the cathode is composed of Ag 2 O and carbon nanotubes modified nanotubes modified carbon fibers. It was observed that SPBS exhibited excellent physical and chemical stability in vitro. Regardless of different bending degrees or pH values, the maximum power density of SPBS remained above 92%, which is conducive to long-term dynamic evaluation. Furthermore, the voltage generated by SPBS reflects blood glucose concentration, and measurements at wound sites are consistent with those obtained using a commercially available blood glucose meter. SPBS achieves the healing effect of traditional medical sutures after complete healing within 14 days. It offers valuable insights for intelligent devices dedicated to real-time wound monitoring. [ABSTRACT FROM AUTHOR]

Electrochemical oxygen reduced reaction (ORR) is a critical element in clean energy development. Despite efforts to enhance gas transfer to the reaction interface, the low solubility of O2 molecules and slow diffusion rate in liquid electrolyte is still a significant challenge. Herein, we design an artificial outer membrane on microalgal cells, which consists of a carbon dots/bilirubin oxidase (CDs/BOD) ORR catalyst layer and a L‐cystine/Au nanoporous O2 supply layer. O2 generated by photosynthesis from microalgal cells then can be directly transported to the CDs/BOD catalytic interfaces, overcoming the sluggish gas transfer in the electrolyte. Thus, the cathode constructed by the fabricated microalgal cells realizes an ORR current density of 655.2 μA/cm2 with fast ORR kinetics, which is 2.68 times higher than that of a BOD cathode fed with pure O2. A membrane‐less glucose/O2 biofuel cell is further developed using the hybrid artificial cells as the cathode, and the power density is 2.39 times higher than that of a BOD cathode biofuel cell in O2 saturated solution. This biomimetic design supplies O2 directly to the carbon dots/BOD catalyst layer from the microalgae membrane through a nanoporous L‐cys/Au layer, providing an alternative solution for the transfer barrier of O2 in the electrolyte. [ABSTRACT FROM AUTHOR]

Biofuel cell (BFC) that transfers chemical energy into electricity is a promising candidate as an energy‐harvesting device for implantable electronics. However, there still remain major challenges for implantable BFCs, including bulky and rigid device structure mismatching with soft tissues such as the brain, and the power output decreases due to the fouling process in a biological environment. Here, a flexible and anti‐biofouling fiber BFC working in the brain chronically is developed. The fiber BFC is based on a carbon nanotube fiber electrode to possess small size and flexibility. A hydrophilic zwitterionic anti‐biofouling polydopamine‐2‐methacryloyloxyethyl phosphorylcholine layer is designed on the surface of fiber BFC to resist the nonspecific protein adsorption in a complex biological environment. After implantation, the fiber BFC can achieve a stable device/tissue interface, along with a negligible immune response. The fiber BFC has first realized power generation in the mouse brain for over a month, exhibiting its promising prospect as an energy‐harvesting device in vivo. [ABSTRACT FROM AUTHOR]

Highly stretchable textile-based biofuel cells (BFCs), acting as effective self-powered sensors, have been fabricated using screen-printing of customized stress-enduring inks. Due to synergistic effects of nanomaterial-based engineered inks and the serpentine designs, these printable bioelectronic devices endure severe mechanical deformations, e.g., stretching, indentation, or torsional twisting. Glucose and lactate BFCs with the single enzyme and membrane-free configurations generated the maximum power density of 160 and 250 µW cm-2 with the open circuit voltages of 0.44 and 0.46 V, respectively. The textile-BFCs were able to withstand repeated severe mechanical deformations with minimal impact on its structural integrity, as was indicated from their stable power output after 100 cycles of 100% stretching. By providing power signals proportional to the sweat fuel concentration, these stretchable devices act as highly selective and stable self-powered textile sensors. Applicability to sock-based BFC and self-powered biosensor and mechanically compliant operations was demonstrated on human subjects. These stretchable skin-worn "scavenge-sense-display" devices are expected to contribute to the development of skin-worn energy harvesting systems, advanced non-invasive self-powered sensors and wearable electronics on a stretchable garment.

Redox enzymes can work as efficient electrocatalysts. The coupling of redox enzymatic reactions with electrode reactions is called enzymatic bioelectrocatalysis, which imparts high reaction specificity to electrode reactions with nonspecific characteristics. The key factors required for bioelectrocatalysis are hydride ion/electron transfer characteristics and low specificity for either substrate in redox enzymes. Several theoretical features of steady-state responses are introduced to understand bioelectrocatalysis and to extend the performance of bioelectrocatalytic systems. Applications of the coupling concept to bioelectrochemical devices are also summarized with emphasis on the achievements recorded in the research group of the author. [ABSTRACT FROM AUTHOR]

A spider nest shaped multi-scale three-dimensional substrate consisting of reduced graphene oxide (RGO) and nickel foam is fabricated for enzymatic electrodes and biofuel cells. According to the excellent conductivity and large electroactive surface area of this special structure, the enzymatic electrodes show large enzymatic loading density, low electron transfer resistance and high electrocatalytic efficiency. The strong forces in the spider nest shaped structure and the excellent enzymatic embedding method ensure the stability of the glucose oxidase bioanodes and laccase biocathodes. The Michaelis–Menten constant value for the bioanodes to glucose is calculated to be 2.24 mM, which is close to the Michaelis–Menten constant for free glucose oxidase, implying a remarkably high enzymatic activity. Employed the obtained bioelectrodes with great properties, the relative glucose/oxygen biofuel cell has an open-circuit voltage of 0.70 V, with a high output power performance, and a maximum output power of 7.05 ± 0.05 mW cm−2, owe to the high enzyme loading and low electron transfer resistance of the electrode based on the spider nest shaped structure. After 60 days of periodic storage experiments, the performance of the biofuel cell still maintained 84.2%, showing a good long-term stability. A unique spider nest shaped multi-scale three-dimensional substrate with extremely large specific surface area and excellent conductivity is employed to fabricate glucose/oxygen biofuel cells with remarkable electrocatalytic efficiency, great output power density and good stability. [Display omitted] • A unique spider nest shaped multi-scale three-dimensional substrate is fabricated. • The bioelectrodes show high enzymatic loading density and catalytic efficiency. • The glucose oxidase on bioanodes shows great enzymatic activity. • High power output and good stability of the biofuel cell is obtained. [ABSTRACT FROM AUTHOR]

Biofuel cells have been in the spotlight for the past century because of their potential and promise as a unique platform for sustainable energy harvesting from the human body and the environment. Because biofuel cells are typically developed in a small platform serving as a primary battery with limited fuel or as a rechargeable battery with repeated refueling, they have been interchangeably named biobatteries. Despite continuous advancements and creative proof-of-concept, however, the technique has been mired in its infancy for the past 100 years, which has provoked increasing doubts about its commercial viability. Low performance, instability, difficulties in operation, and unreliable and inconsistent power generation question the sustainable development of biofuel cells. However, the advancement in bioelectrocatalysis revolutionizes the electricity-producing capability of biofuel cells, promising an attractive, practical technique for specific applications. This perspective article will identify the misconceptions about biofuel cells that have led us in the wrong development direction and revisit their potential applications that can be realizable soon. Then, it will discuss the critical challenges that need to be immediately addressed for the commercialization of the selected applications. Finally, potential solutions will be provided. The article is intended to inspire the community so that fruitful commercial products can be developed soon.

Expert Systems are interactive and reliable computer-based decisionmaking systems that use both facts and heuristics for solving complex decision-making problems. Generally, the cyclic voltammetry (CV) experiments are executed a random number of times (cycles) to get a stable production of power. However, presently there are not many algorithms or models for predicting the power generation stable criteria in microbial fuel cells. For stability analysis of Medicinal herbs' CV profiles, an expert system driven by the augmented K-means clustering algorithm is proposed. Our approach requires a dataset that contains voltage-current relationships from CV experiments on the related subjects (plants/herbs). This new approach uses feature engineering and augmented K-means clustering techniques to determine the cycle number beyond which the CV curve stabilizes. We obtain an excellent estimate of the required CV cycles for getting a stable Voltage versus Current curve in this approach. Moreover, this expert system would reduce the time needed and the money spent on running additional and superfluous CV experiments cycles. Thus, it would streamline the process of Bacterial Fuel Cells production using the CV of medicinal herbs. [ABSTRACT FROM AUTHOR]

Thanks to rapid technological innovation over the last decade, a wide range of wearable devices have emerged, playing an inspiring role in healthcare, diagnostics, and sports monitoring. This review summarizes recent progress in the development and application of electrochemical (EC) sweat sensors and self-powered systems for wearable applications. Presented here are the most common types of EC sweat sensors, namely potentiometric ion-selective electrodes, amperometric enzymatic and non-enzymatic sensors, as well as differential pulse voltammetric sensors. The sensing principle and novel functional nanomaterials that are used to enhance the performance of wearable sweat sensors and their applications are summarized. The recent advancement of battery-free wearable devices is presented, including self-powered biofuel cells (BFC), energy harvesting from novel materials and its strategy, are also discussed. The challenges in, and opportunities for, the development of sweat sensor-based wearable systems moving forward are reviewed, with the aim of shedding some light on future directions. [ABSTRACT FROM AUTHOR]