Magnetohydrodynamic Enhancement of Biofuel Cell Performance

Biofuel cells have become an interesting alternative for the design of sustainable energy conversion systems with multiple applications ranging from biosensing and bioelectronics to autonomously moving devices. However, as an electrochemical system, their performance is intimately related to mass transport conditions. In this work, the magnetohydrodynamic (MHD) effect is studied as an easy and straightforward alternative to enhance the performance of a biofuel cell based on the enzymes glucose oxidase (GOx) and bilirubin oxidase (BOD). The synergetic effect between the electric and ionic currents, produced by the enzymatic redox reactions, and a magnetic field orthogonal to the surface of the electrodes, leads to the formation of localized magnetohydrodynamic vortexes. Such an integrated convective regime generates an increase of the bioelectrocatalytic current and its concomitant power output in the presence of the external magnetic field. In addition, by fine-tuning the spatial arrangement of the anode and cathode, it is possible to benefit from the sum of anodic and cathodic MHD vortexes, leading to an enhanced power output of up to 300 %.

Recent advances in the role of biocatalyst in biofuel cells and its application: An overview

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.

Biological electricity generation system based on mitochondria-nanochannel-red blood cells

The high-efficiency energy conversion process in organisms is usually carried out by organelles, proteins and membrane systems. Inspired by the cellular aerobic respiration process, we present an artificial electricity generation device, aimed at sustainable and efficient energy conversion using biological components, to demonstrate the feasibility of bio-inspired energy generation for renewable energy solutions. This approach bridges biological mechanisms and technology, offering a pathway to sustainable, biocompatible energy sources. The device features a mitochondria anode and oxygen-carrying red blood cells (RBCs) cathode, alongside a sandwich-structured sulfonated poly(ether ether ketone) and polyimide composite nanochannel for efficient proton transportation, mimicking cellular respiration. Achieving significant performance with 40 wt% RBCs, it produced a current density of 6.42 mA cm-2 and a maximum power density of 1.21 mW cm-2, maintaining over 50% reactivity after 8 days. This research underscores the potential of bio-inspired systems for advancing sustainable energy technologies.

Photoswitchable Enzymatic Biofuel Cell Based on Fusion Protein with Natural Photoreceptor Vivid

Enzymatic biofuel cells (EBFCs) have increasingly been the subject of research, but the control of the EBFC output remains difficult. In this study, we fuse glucose 6-phosphate dehydrogenase (G6PDH) and diaphorase (DI) with the natural photoreceptor Vivid named "Mag". The output current and power density of EBFCs with the fusion protein exhibit a sensitive and efficient response to blue light. Following optimizations, the power density increases nearly 4-fold from 1.32 to 6.26 μW cm^-2, whereas the current rises from 5.9 to 10.8 μA after 20 min of illumination, dropping back within 30 min under dark conditions.

A review: Evolution of enzymatic biofuel cells

Ever-growing demands for energy, the unsustainability of fossil fuel due to its scarcity and massive impact on global economies and the environment, have encouraged the research on alternative power sources to work upon for the governments, companies, and scientists across the world. Enzymatic biofuel cells (eBFCs) is one category of fuel cell that can harvest energy from biological moieties and has the future to be used as an alternative source of energy. The aim of this review is to summarize the background and state-of-the-art in the field of eBFCs. This review article will be very beneficial for a wide audience including students and new researchers in the field. A part of the paper summarized the challenges in the preparation of anode and cathode and the involvement of nanomaterials and conducting polymers to construct the effective bioelectrodes. It will provide an insight for the researchers working in this challenging field. Furthermore, various applications of eBFCs in implantable power devices, tiny electronic gadgets, and self powered biosensors are reported. This review article explains the development in the area of eBFCs for several years from its origin to growth systematically. It reveals the strategies that have been taken for the improvements required for the better electrochemical performance and operational stability of eBFCs. It also mentions the challenges in this field that will require proper attention so that the eBFCs can be utilized commercially in the future. The review article is written and structurized in a way so that it can provide a decent background of eBFCs to its reader. It will definitely help in enhancing the interest of reader in eBFCs.

Biomolecule Release from Alginate Composite Hydrogels Triggered by Logically Processed Signals

Alginate composite hydrogels that exhibit highly sensitive stimuli-responsive behavior were used for signal-stimulated release of pre-loaded insulin. The alginate pores, particularly located at the periphery, were blocked by interpenetration of polyvinyl alcohol (PVA) cross-linked with 1,3-benzenediboronic acid (IPN), thus, significantly reducing uncontrolled leakage of the entrapped biomolecules. The beads were loaded with insulin and various enzymes mimicking different Boolean logic gates (AND, OR, NOR, IMP, INHIB). The enzymes were activated with biologically relevant input signals applied in four logic combinations: 0,0; 1,0; 0,1; 1,1, having the production of H₂ O₂ as the result of the biocatalytic reactions. The "successful" combination of the input signals leading to the H₂ O₂ production was different for different logic gates, following the corresponding truth tables of the logic gates. When H₂ O₂ was produced, boronate ester bonds were oxidized and the IPN was irreversibly degraded, thus re-opening the original pores of the hydrogel. This process allowed release of insulin from the alginate beads. The smart soft material that we have developed tackled well-known limitations of these systems and it may prove valuable in future medical diagnostics or treatments.

Self-powered molecule release systems activated with chemical signals processed through reconfigurable Implication or Inhibition Boolean logic gates

The Implication (IMPLY) and Inhibition (INHIB) Boolean logic gates were realized using switchable chimeric pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH-Clamp) containing a fused affinity clamp unit recognizing a signal-peptide. The second component of the logic gate was the wild-type PQQ-glucose dehydrogenase working cooperatively with the PQQ-GDH-Clamp enzyme. The IMPLY and INHIB gates were realized using the same enzyme composition activated with differently defined input signals, thus representing reconfigurable logic systems. The logic gates were first tested while operating in a solution with optical analysis of the output signals. Then, the enzymes were immobilized on a buckypaper electrode for electrochemical transduction of the output signals. The switchable modified electrodes mimicking the IMPLY or INHIB logic gates were integrated with an oxygen-reducing electrode modified with bilirubin oxidase to operate as a biofuel cell activated/inhibited by various input signal combinations processed either by IMPLY or INHIB logic gates. The switchable biofuel cell was used as a self-powered device triggering molecule release function controlled by the logically processed molecule signals.

Anode-Driven Controlled Release of Cathodic Fuel via pH Response for Smart Enzymatic Biofuel Cell

Enzymatic biofuel cells (EBFCs) with or without a membrane to separate the anodic and cathodic compartments generally suffered from high internal resistance or interactive interference, both of which restricted the improvement of their performance. Herein, a smart membrane-less EBFC was engineered based on anode-driven controlled release of cathodic acceptor via pH-responsive metal-organic framework ([Fe(CN)6]3-@ZIF-8) nanocarriers. The glucose anodic oxidation would produce gluconic acid accompanied by the change in pH value from neutral to the acidic case, which could drive the degradation of [Fe(CN)6]3-@ZIF-8 nanocarriers and further realize the controlled release of cathodic acceptor [Fe(CN)6]3-. More importantly, compared with controlled EBFC with or without membrane, the power output of the as-proposed EBFC enhanced at least 700 times due to the seamless electronic communication. Therefore, the ingenious strategy not only realized the successful engineering of the membrane-less EBFC but also provided an appealing idea for constructing smart devices.

Enhancement of Biosensors by Implementing Photoelectrochemical Processes

Research on biosensors is growing in relevance, taking benefit from groundbreaking knowledge that allows for new biosensing strategies. Electrochemical biosensors can benefit from research on semiconducting materials for energy applications. This research seeks the optimization of the semiconductor-electrode interfaces including light-harvesting materials, among other improvements. Once that knowledge is acquired, it can be implemented with biological recognition elements, which are able to transfer a chemical signal to the photoelectrochemical system, yielding photo-biosensors. This has been a matter of research as it allows both a superior suppression of background electrochemical signals and the switching ON and OFF upon illumination. Effective electrode-semiconductor interfaces and their coupling with biorecognition units are reviewed in this work.

Construction of Multiple Switchable Sensors and Logic Gates Based on Carboxylated Multi-Walled Carbon Nanotubes/Poly(N,N-Diethylacrylamide)

In this work, binary hydrogel films based on carboxylated multi-walled carbon nanotubes/poly(N,N-diethylacrylamide) (c-MWCNTs/PDEA) were successfully polymerized and assembled on a glassy carbon (GC) electrode surface. The electroactive drug probes matrine and sophoridine in solution showed reversible thermal-, salt-, methanol- and pH-responsive switchable cyclic voltammetric (CV) behaviors at the film electrodes. The control experiments showed that the pH-responsive property of the system could be ascribed to the drug components of the solutions, whereas the thermal-, salt- and methanol-sensitive behaviors were attributed to the PDEA constituent of the films. The CV signals particularly, of matrine and sophoridine were significantly amplified by the electrocatalysis of c-MWCNTs in the films at 1.02 V and 0.91 V, respectively. Moreover, the addition of esterase, urease, ethyl butyrate, and urea to the solution also changed the pH of the system, and produced similar CV peaks as with dilution by HCl or NaOH. Based on these experiments, a 6-input/5-output logic gate system and 2-to-1 encoder were successfully constructed. The present system may lead to the development of novel types of molecular computing systems.

Enzyme-based logic gates and circuits-analytical applications and interfacing with electronics

The paper is an overview of enzyme-based logic gates and their short circuits, with specific examples of Boolean AND and OR gates, and concatenated logic gates composed of multi-step enzyme-biocatalyzed reactions. Noise formation in the biocatalytic reactions and its decrease by adding a "filter" system, converting convex to sigmoid response function, are discussed. Despite the fact that the enzyme-based logic gates are primarily considered as components of future biomolecular computing systems, their biosensing applications are promising for immediate practical use. Analytical use of the enzyme logic systems in biomedical and forensic applications is discussed and exemplified with the logic analysis of biomarkers of various injuries, e.g., liver injury, and with analysis of biomarkers characteristic of different ethnicity found in blood samples on a crime scene. Interfacing of enzyme logic systems with modified electrodes and semiconductor devices is discussed, giving particular attention to the interfaces functionalized with signal-responsive materials. Future perspectives in the design of the biomolecular logic systems and their applications are discussed in the conclusion. Graphical Abstract Various applications and signal-transduction methods are reviewed for enzyme-based logic systems.

Enzyme-based logic systems interfaced with signal-responsive materials and electrodes

Enzyme-based biocomputing systems were interfaced with signal-responsive membranes and electrodes resulting in bioelectronic devices switchable by logically processed biomolecular signals. "Smart" membranes, electrodes, biofuel cells, memristors and substance-releasing systems were activated by various combinations of biomolecular signals in the pre-programmed way implemented in biocatalytic cascades mimicking logic networks.

Programming the quorum sensing-based AND gate in Shewanella oneidensis for logic gated-microbial fuel cells

A modularly structured, flexible, and reprogrammable AND logic gate gene circuit-controlled microbial fuel cell.

Activation of a biocatalytic electrode by removing glucose oxidase from the surface--application to signal triggered drug release

A biocatalytic electrode activated by pH signals was prepared with a multilayered nanostructured interface including PQQ-dependent glucose dehydrogenase (PQQ-GDH) directly associated with the conducting support and glucose oxidase (GOx) located on the external interface. GOx was immobilized through a pH-signal-cleavable linker composed of an iminobiotin/avidin complex. In the presence of GOx, glucose was intercepted at the external interface and biocatalytically oxidized without current generation, thus keeping the electrode in its nonactive state. When the pH value was lowered from pH 7.5 to 4.5 the iminobiotin/avidin complex was cleaved and GOx was removed from the interface allowing glucose penetration to the electrode surface where it was oxidized by PQQ-GDH yielding a bioelectrocatalytic current, thus switching the electrode to its active state. This process was used to trigger a drug-mimicking release process from another connected electrode. Furthermore, the pH-switchable electrode can be activated by biochemical signals logically processed by biocatalytic systems mimicking various Boolean gates. Therefore, the developed switchable electrode can interface biomolecular computing/sensing systems with drug-release processes.

Effective control of bioelectricity generation from a microbial fuel cell by logical combinations of pH and temperature

In this study, a microbial fuel cell (MFC) with switchable power release is designed, which can be logically controlled by combinations of the most physiologically important parameters such as "temperature" and "pH." Changes in voltage output in response to temperature and pH changes were significant in which voltage output decreased sharply when temperature was lowered from 30°C to 10°C or pH was decreased from 7.0 to 5.0. The switchability of the MFC comes from the microbial anode whose activity is affected by the combined medium temperature and pH. Changes in temperature and pH cause reversible activation-inactivation of the bioanode, thus affecting the activity of the entire MFC. With temperature and pH as input signals, an AND logic operation is constructed for the MFC whose power density is controlled. The developed system has the potential to meet the requirement of power supplies producing electrical power on-demand for self-powered biosensors or biomedical devices.

Biocomputing, Biosensing and Bioactuation Based on Enzyme Biocatalyzed Reactions

The focus of this review paper is on the design and implementation of smart ‘Sense-and-Treat’ systems using enzyme-biocatalytic systems. These systems were used to perform biomolecular computing and they were functionally integrated with signal responsive materials aiming towards their biomedical use. Electrode interfaces, functionalized with signal-responsive materials, find applications in biocomputing, biosensing, and, specifically, triggered release of bioactive substances. ‘Sense-and-Treat’ systems require multiple components working together, including biosensors, actuators, and filters, in order to achieve closed-loop and autonomous operation. In general, biochemical logic networks were developed to process single biochemical or chemical inputs as well as multiple inputs, responding to nonphysiological (for concept demonstration purposes) and physiological signals (for injury detection or diagnosis). Actuation of drug-mimicking release was performed using the responsive material iron-cross-linked alginate with entrapped biomolecular species, responding to physical, chemical or biochemical signals.

ON/OFF states of a microbial fuel cell controlled by an optical switching system

An optical switching system was developed to control the ON/OFF state of a microbial fuel cell.

Responsive interface switchable by logically processed physiological signals: toward "smart" actuators for signal amplification and drug delivery

Biomarkers characteristic of liver injury, alanine transaminase and lactate dehydrogenase, were processed by an enzyme-based system functioning as a logic AND gate. The NAD+ output signal produced by the system upon its activation in the presence of both biomarkers was then biocatalytically converted to a decrease in pH. The acidic pH value biocatalytically produced by the system as a response to the biomarkers triggered the restructuring of a polymer-modified electrode interface. This allowed a soluble redox species to approach the electrode surface, thus switching the electrochemical reaction ON. The redox transformations activated by the biochemical signals resulted in an amplification of signals. This system represents the first example of an integrated sensing-actuating chemical device with the implemented AND Boolean logic for processing natural biomarkers at their physiologically relevant concentrations.

Electric field-guided neuron migration: a novel approach in neurogenesis

Effective directional neuron migration is crucial in development of the central nervous system and for neurogenesis. Endogenous electrical signals are present in many developing systems and crucial cellular behaviors such as neuronal cell division, cell migration, and cell differentiation are all under the influence of such endogenous electrical cues. Preclinical in vivo studies have used electric fields (EFs) to attempt to enhance regrowth of damaged spinal cord axons with some success. Recent evidence shows that small EFs not only guide axonal growth, but also direct the earlier events of neuronal migration and neuronal cell division. This raises the possibility that applied or endogenous EFs, perhaps in combination, may direct transplanted neural stem cells, or regenerating neurons, to the desired site after brain injury or neuron degeneration. The high complexity of both structure and function of the nervous system, however, poses significant challenges to techniques for applying EFs to promote neurogenesis. The evolution of functional biomaterials and nanotechnology may provide promising solutions for the application of EFs in guiding neuron migration and neurogenesis within the central nervous system.