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Direct transformation of solar energy into electrical energy by means of biological photosynthesis is considered as an attractive option for sustainable electrical energy production. Thylakoid membranes, the site of photosynthesis, are regarded as a promising biological material for the development of photoelectric biodevices, which produce electrical power consuming only light energy as oxygen evolves at photobioanode upon irradiation and biocathode converts it back to water. Therefore, in this work dual-feature photobioanode based on nanoimprinted gold substrates modified with thylakoids in combination with a capacitive part made of a planar gold substrate coated with a conductive polymer was designed and evaluated, providing open-circuit potential of -0.21 V vs. Ag vertical bar AgCl vertical bar KClsat and a capacitance of ca. 60 F m(-2) both at ambient light and artificial illumination of 400 W m(-2). Combination of thylakoid based dual-feature photobioanode with bilirubin oxidase modified transparent and capacitive indium tin oxide biocathode resulted in a photoelectric biosupercapacitor with remarkable characteristics at ambient light, viz. an open-circuit voltage as high as 0.74 V, which was stable upon charge-discharge cycles during ca. 2 h.

As the global energy demand continues to increase, the interest in photosynthetic energy conversion is growing accordingly. Chloroplasts, photosynthetic organelles present in plants and algae, are attractive candidates for construction of bio solar cells; however, they have been less studied because of their complex membrane system, which restricts electrochemical communication with an electrode surface. Nevertheless, in this work photobioanodes based on planar and nanoimprinted gold substrates modified with chloroplasts were designed and evaluated. Apparently, nanoimprint lithography contributed to higher photocurrent densities, not only owing to the enlarged real surface area, but also due to boosting electrochemical communication between the photosynthetic organelles and the electrode. Combining chloroplast-modified nanoimprinted gold electrodes with a capacitive part made of a planar gold substrate, coated with a conductive polymer, resulted in a dual-feature photobioanode providing a lower open-circuit potential, i. e., -0.11 V vs. Ag|AgCl|KClsat, and an enhanced capacitance of ca. 37 F m(-2) upon illumination of 400 W m(-2).

More sustainable ways to produce and store energy are urgently needed to reduce our dependence on fossil fuels, which are the principal drivers of global warming and pollution. Hydrogen may become ...

In the last few years, there have been an increasing number of reports where different energy harvesters are directly combined with charge storing devices, based on dual-function electrodes able to convert and store electrical energy in the same volume. This includes (bio)fuel cells harvesting chemical energy, (bio)solar cells harvesting solar energy, tribo- and piezoelectric devices harvesting mechanical energy, and thermoelectrics harvesting thermal energy, which now have been intimately combined with batteries and electrochemical capacitors. These new types of hybrid electric devices show great promise especially for the design of self-powered electronics where an integrated hybrid power system is preferable to separated ones, capable of scavenging ambient energy and simultaneously store it and in this way increasing the efficiency and enabling further miniaturization. This paper details the recent emergence of hybrid energy systems, reviewing the progress made using widely different energy harvesting techniques, which have so-far not been described in a single body of work.

Sweat is a promising biofluid in allowing for non-invasive sampling. Here, we investigate the use of a voltammetric electronic tongue, combining different metal electrodes, for the purpose of non-invasive sample assessment, specifically focusing on sweat. A wearable electronic tongue is presented by incorporating metal electrodes on a flexible circuit board and used to non-invasively monitor sweat on the body. The data obtained from the measurements were treated by multivariate data processing. Using principal component analysis to analyze the data collected by the wearable electronic tongue enabled differentiation of sweat samples of different chemical composition, and when combined with 1H-NMR sample differentiation could be attributed to changing analyte concentrations.

High-performance autotolerant bioelectrodes should be ideally suited to design implantable bioelectronic devices. Because of its high redox potential and ability to reduce oxygen directly to water, human ceruloplasmin, HCp, the only blue multicopper oxidase present in human plasma, appears to be the ultimate biocatalyst for oxygen biosensors and also biocathodes in biological power sources. In comparison to fungal and plant blue multicopper oxidases, e.g. Myrothecium verrucaria bilirubin oxidase and Rhus vernicifera laccase, respectively, the inflammatory response to HCp in human blood is significantly reduced. Partial purification of HCp allowed to preserve the native conformation of the enzyme and its biocatalytic activity. Therefore, electrochemical studies were carried out with the partially purified enzyme immobilised on nanostructured graphite electrodes at physiological pH and temperature. Amperometric investigations revealed low reductive current densities, i.e. about 1.65 µA cm−2 in oxygenated electrolyte and in the absence of any mediator, demonstrating nevertheless direct electron transfer based O2 bioelectroreduction by HCp for the first time. The reductive current density obtained in the mediated system was about 12 µA cm−2. Even though the inflammatory response of HCp is diminished in human blood, inadequate bioelectrocatalytic performance hinders its use as a cathodic bioelement in a biofuel cell. Swedish Knowledge Foundation 20170168 Ministerio de Economía y Competitividad BES-2015-071247

Background When compared to the general population, socioeconomically disadvantaged communities frequently experience compromised health. Monitoring the divide is challenging since in general, standardized biomedical tests are linguistically and culturally inappropriate. The aim of this study was to develop a novel healthcare technology for its usage in socioeconomically disadvantaged areas.Methods A unique mobile biomedical testbed based on non-invasive analysis, accompanied with the World Health Organization Quality of Life survey, was developed. This healthcare approach was used in Lindängen, a socioeconomically disadvantaged neighborhood in Malmö, which has been listed as one of the twelve most vulnerable neighborhoods in Sweden. Results The less intrusive biomedical approach, compared to conventional setups used, e.g., wrist blood pressure monitoring, bioimpedance analysis and cardiovascular diagnostics, non-invasive determination of blood bioanalytes, was highly appreciated by the participants, i.e., 39 female volunteers of Middle Eastern origin. Surprisingly, the collected biomedical data illustrated that the apparent health of the participants from Lindängen was comparable to the general Swedish population. The Quality of Life-BREF survey, used to gather information regarding subjective health perceptions within the cohort, combined with advanced statistical data analysis, revealed statistically significant correlations between perceived health and biomedical data. Even though the dependences found were complex, the recognition of which is essential in further research. Conclusions Our results validate the potential of non-invasive technologies in combination with advanced statistical analysis, especially when combined with linguistically and culturally appropriate healthcare methodologies, allowing participants to appreciate the significance of the different parameters to evaluate and monitor aspects of health.

Non-invasive healthcare technologies are an important part of research and development nowadays due to the low cost and convenience oered to both healthcare receivers and providers. This work overviews the recent advances in the field of non-invasive electrochemical biosensors operating in secreted human physiological fluids, viz. tears, sweat, saliva, and urine. Described electrochemical devices are based on dierent electrochemical techniques, viz. amperometry, coulometry, cyclic voltammetry, and impedance spectroscopy. Challenges that confront researchers in this exciting area and key requirements for biodevices are discussed. It is concluded that the field of non-invasive sensing of biomarkers in bodily fluid is highly convoluted. Nonetheless, if the drawbacks are appropriately addressed, and the pitfalls are adroitly circumvented, the approach will most certainly disrupt current clinical and self-monitoring practices.

Background: Citizens living in disadvantaged neighborhoods are susceptible to chronic diseases associated with factors such as physical inactivity and poor nutrition. Women are considered more vulnerable in these situations owing to lack of access to health promotional activities catering their needs. This study aimed at evaluating the effects of a participatory research informed physical activity intervention on the health and related behavior of women living in disadvantaged neighborhoods in Southern Sweden. Methods: Forty women were invited to participate in a participatory research informed physical activity intervention delivered by health promoters and health ambassadors over a 3-month period. Quality of life was assessed using the WHOQOL-BREF questionnaire and questions regarding behavioral factors including frequency of leisure time physical activity, everyday activities, intake of fruit, vegetable, fish and soda were assessed at three time points including t1, prior to intervention start, t2 immediately post-intervention and t3, 6-month post-intervention. Furthermore, biomedical outcomes such as hemoglobin, blood pressure, resting heart rate, blood flow rate, body mass index, fat mass index and muscle mass index were also assessed at the same three time points. Wilcoxon’s Sign Rank Test was used to compare pre- and post-test scores. Results: There was an increase in the scores of the different domains of health related quality of life at t2 immediately post-intervention (p

Detailed impedance and voltammetric studies of hexameric octaheme nitrite reductase immobilized on carbon-based nanomaterials, specifically nanotubes and nanoparticles, were performed. Well-pronounced bioelectrocatalytic reduction of nitrite on enzyme-modified electrodes was obtained. Analysis of the impedance data indicated the absence of long-lived intermediates involved in the nitrite reduction. Cyclic voltammograms of biomodified electrodes had a bi-sigmoidal shape, which pointed to the presence of two enzyme orientations on carbon supports. The maximum (limiting) catalytic currents were determined and, by applying the correction by the mixed kinetics equation, the Tafel dependences were plotted for each catalytic wave/each enzyme orientation. Finally, two schemes for the rate-limiting processes during bioelectrocatalysis were proposed, viz. for low- and high-potential orientations.

Background Despite numerous interventions aiming to improve physical activity in socially disadvantaged populations, physical inactivity remains to be a rising challenge to public health globally, as well as, in Sweden. In an effort to address this challenge, a community-based participatory intervention was developed through active community engagement and implemented in a socially disadvantaged neighborhood in Sweden. The current study aims to present the development and initial evaluation of a participatory research driven physical activity intervention. Methods Fifteen participants (11 females and 4 males) aged 17–59 years volunteered to participate in the physical activity intervention program. The intervention program was evaluated using a longitudinal mixed methods design measuring health impact changes over time through focus group discussions and quality of life surveys. Further additional biomedical health parameters such as levels of glycosylated hemoglobin, blood pressure, levels of oxygen saturation and body mass index were monitored before and after the intervention. Focus group data were analyzed using content analysis with an inductive approach. The pre-and post-test scores from the survey-based quality of life domains, as well as the health parameters were compared using non-parametric and parametric statistics. Results Four themes emerged from the analysis of the focus group discussions including sense of fellowship, striving for inclusion and equity, changing the learner perspective and health beyond illness. The scores for the domains Physical Health, Psychological Health, Social Relationships and Health Satisfaction where significantly higher after participation in the physical activity intervention program compared to the pre-test scores (p Conclusion The focus group discussions and results from the surveys and biomedical measures reveal important findings to understand and further develop the intervention program to promote health equity among citizens in disadvantaged areas. Evaluating the feasibility of such an intervention using multiple approaches contributes to effective implementation of it for larger communities in need.

We present a transparent and flexible self-charging biosupercapacitor based on an optimised mediator- and membrane-free enzymatic glucose/oxygen biofuel cell. Indium tin oxide (ITO) nanoparticles were spray-coated on transparent conducting ITO supports resulting in a flocculent, porous and nanostructured electrode surface. By this, high capacitive currents caused by an increased electrochemical double layer as well as enhanced catalytic currents due to a higher number of immobilised enzyme molecules were obtained. After a chemical pre-treatment with a silane derivative, bilirubin oxidase from Myrothecium verrucaria was immobilized onto the ITO nanostructured electrode surface under formation of a biocathode, while bioanodes were obtained by either immobilisation of cellobiose dehydrogenase from Corynascus thermophilus or soluble PQQ-dependent glucose dehydrogenase from Acinetobacter calcoaceticus. The latter showed a lower apparent KM value for glucose conversion and higher catalytic currents at µM glucose concentrations. Applying the optimised device as a biosupercapacitor in a discontinuous charge/discharge mode led to a generated power output of 0.030mW/cm2 at 50µM glucose, simulating the glucose concentration in human tears. This represents an enhancement by a factor of 350 compared to the power density obtained from the continuously operating biofuel cell with a maximum power output of 0.086µW/cm2 under the same conditions. After 17h of charging/discharging cycles a remarkable current enhancement was still measured. The entire device was transferred to flexible materials and applied for powering a flexible display showing its potential applicability as an intermittent power source in smart contact lenses.

The interface between protein and material surface is of great research interest in applications varying from implants, tissue engineering to bioelectronics. Maintaining functionality of bioelements depends greatly on the immobilization process. In the present study direct electron transfer of cellobiose dehydrogenase from Humicola insolens ( Hi CDH), adsorbed on four different self-assembled monolayers (SAMs) formed by 5–6 chain length carbon thiols varying in terminal group structure was investigated. By using a combination of quartz crystal microbalance with dissipation, ellipsometry and electrochemistry the formation and function of the Hi CDH film was studied. It was found that the presence of charged pyridinium groups was needed to successfully establish direct electron contact between the enzyme and electrode. SAMs formed from hydrophilic charged thiols achieved nearly two times higher current densities compared to hydrophobic charged thiols. Additionally, the results also indicated proportionality between Hi CDH catalytic constant and water content of the enzyme film. Enzyme films on charged pyridine thiols had smaller variations in water content and viscoelastic properties than films adsorbed on the more hydrophobic thiols. This work highlights several perspectives on the underlying factors affecting performance of immobilized Hi CDH.

An intrinsic self-charging biosupercapacitor built on a unique concept for the fabrication of biodevices based on redox polymers is presented. The biosupercapacitor consists of a high-potential redox polymer based bioanode and a low-potential redox polymer based biocathode in which the potentials of the electrodes in the discharged state show an apparent potential mismatch E

Specific wiring of biocatalysts par excellence, viz. redox enzymes, to an electrode can be exploited in the fabrication of high-performance bioelectronic devices. Here we report oxygen electroreduction catalysed by Didymocrea sp. J6 laccase wired to gold nanoparticles via the trinuclear copper cluster. Bypassing the intramolecular electron transfer, which under certain conditions is the rate-limiting step of oxygen bioelectroreduction, has resulted in the fabrication of a high current density biocathode based on high-redox-potential laccase, which is able to operate in electrolytes with a broad pH range in the presence of high fluoride concentrations.

Here we report on an entirely new kind of bioelectronic device – a solar biosupercapacitor, which is built from a dual-feature photobioanode combined with a double-function enzymatic cathode. The self-charging biodevice, based on transparent nanostructured indium tin oxide electrodes modified with biological catalysts, i.e. thylakoid membranes and bilirubin oxidase, is able to capacitively store electricity produced by direct conversion of radiant energy into electric energy. When self-charged during 10 min, using ambient light only, the biosupercapacitor provided a maximum of 6 mW m−2 at 0.20 V. Keywords: Solar biosupercapacitor, Thylakoid, Bilirubin oxidase, Indium tin oxide, Nanoparticle

Electron and proton transfer reactions in enzymes are enigmatic and have attracted a great deal of theoretical, experimental, and practical attention. The oxidoreductases provide model systems for testing theoretical predictions, applying experimental techniques to gain insight into catalytic mechanisms, and creating industrially important bio(electro)conversion processes. Most previous and ongoing research on enzymatic electron transfer has exploited a theoretically and practically sound but limited approach that uses a series of structurally similar (“homologous”) substrates, measures reaction rate constants and Gibbs free energies of reactions, and analyses trends predicted by electron transfer theory. This approach, proposed half a century ago, is based on a hitherto unproved hypothesis that pre-exponential factors of rate constants are similar for homologous substrates. Here, we propose a novel approach to investigating electron and proton transfer catalysed by oxidoreductases. We demonstrate the validity of this new approach for elucidating the kinetics of oxidation of “non-homologous” substrates catalysed by compound II of Coprinopsis cinerea and Armoracia rusticana peroxidases. This study – using the Marcus theory – demonstrates that reactions are not only limited by electron transfer, but a proton is transferred after the electron transfer event and thus both events control the reaction rate of peroxidase-catalysed oxidation of substrates.

Fungal high-redox-potential laccases (HRPLs) are multicopper oxidases with a relaxed substrate specificity that is highly dependent on their binding affinity and redox potential of the T1Cu site (ET1). In this study, we combined computational design with directed evolution to tailor an HRPL variant with increased ET1 and activity toward high-redox-potential mediators as well as enhanced stability. Laccase mutant libraries were screened in vitro using synthetic high-redox-potential mediators with different oxidation routes and chemical natures, while computer-aided evolution experiments were run in parallel to guide benchtop mutagenesis, without compromising protein stability. Through this strategy, the ET1 of the evolved HRPL increased from 740 to 790 mV, with a concomitant improvement in thermal and acidic pH stability. The kinetic constants for high-redox-potential mediators were markedly improved and were then successfully tested within laccase mediator systems (LMSs). Two hydrophobic substitutions surrounding the T1Cu site appeared to underlie these effects, and they were rationalized at the atomic level. Together, this study represents a proof-of-concept of the joint elevation of the ET1, redox mediator activity, and stability in an HRPL, making this versatile biocatalyst a promising candidate for future LMS applications and for the development of bioelectrochemical devices., This work was supported by the European Union project Bioenergy-FP7-PEOPLE-2013-ITN-607793, the COST Action [CM1303 Systems Biocatalysis],the Swedish Energy Agency (44707-1), the Knowledge Foundation (20170168), and the Spanish Government [BIO2016-79106-R-Lignolution and CTQ2016-79138-R]., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

There is a growing interest in the design and engineering of operational biofuel cells that can be implanted. This review highlights the recent progress in the electrochemistry of biofuel cell technologies, but with a particular emphasis on the medical and physiological aspects that impact the biocompatibility of biofuel cells operating inside a living body. We discuss the challenge of supplying power to implantable medical devices, with regard to the limitations of lithium battery technology and why implantable biofuel cells can be a promising alternative to provide the levels of power required for medical devices. In addition to the challenge of designing a biofuel cell that provides a stable level of sufficient power, the review highlights the biocompatibility and biofouling problems of implanting a biofuel cell that have a major impact on the availability of the substrates inside body that provide fuel for the biofuel cell. These physiological challenges and associated ethical considerations are essential to consider for biofuel cells that are designed to be implanted for long-term operation inside a living animal and eventually to human clinical applications. (C) 2018 The Authors. Published by Elsevier B.V.

We propose the very first “Nernstian biosupercapacitor”, a biodevice based on only one redox polymer: poly(vinyl imidazole‐co‐allylamine)[Os(bpy)2Cl], and two biocatalysts. At the bioanode PQQ‐dependent glucose dehydrogenase reduces the Os3+ moieties at the polymer to Os2+ shifting the Nernst potential of the Os3+/Os2+ redox couple to negative values. Concomitantly, at the biocathode the reduction of O2 by means of bilirubin oxidase embedded in the same redox polymer leads to the oxidation of Os2+ to Os3+ shifting the Nernst potential to higher values. Despite the use of just one redox polymer an open circuit voltage of more than 0.45 V was obtained during charging and the charge is stored in the redox polymer at both the bioanode and the biocathode. By connecting both electrodes via a predefined resistor a high power density is obtained for a short time exceeding the steady state power of a corresponding biofuel cell by a factor of 8.

Wir stellen hier einen “Nernst-Biosuperkondensator” vor, der auf nur einem Redoxpolymer, Poly(vinylimidazol-co-allylamin)-Os(bpy)2Cl] und zwei Biokatalysatoren beruht. Wahrend des Ladevorgangs des Biosuperkondensators sind Bioanode und Biokathode elektrisch voneinander getrennt. An der Bioanode werden die am Redoxpolymer gebundenen Os3+-Komplexe uber die Oxidation von Glukose an der PQQ-abhangigen Glukosedehydrogenase zu Os2+ reduziert, sodass das Nernst-Potential des Os3+/Os2+-Redoxpaars zu negativen Werten verschoben wird. Die gleichzeitige durch Bilirubinoxidase katalysierte Reduktion von O2 an der Biokathode fuhrt zur Oxidation der polymergebundenen Os-Komplexe und damit zu einer Verschiebung des Nernst-Potentials zu positiveren Werten. Trotz der Nutzung nur eines Redoxpolymers wurde wahrend des Ladevorgangs eine Leerlaufspannung groser 0.45 V erreicht, wobei die Ladung im Redoxpolymer an Bioanode und Biokathode gespeichert wird. Nach Kontaktieren der beiden Elektroden uber einen Widerstand vordefinierter Grose wurde uber einen kurzen Zeitraum eine hohe Energiedichte erreicht, welche die Energiedichte einer entsprechenden kontinuierlich betriebenen Biobrennstoffzelle um den Faktor 8 ubertrifft.

Being inspired by a very recent review entitled: “Electrocatalysis and bioelectrocatalysis – Distinction without a difference” and following the general approach employed by Prof. Dr. Schuhmann, in the current work we point to the similarities and differences between oxygen electroreduction and bioelectroreduction processes. To additionally distinct our paper from the recent review we touch on different bioelements, such as redox proteins and living cells, but we still keep a special emphasis on oxidoreductases, biocatalysts par excellence. Moreover, we also exclusively focus on oxygen electroreduction based on direct electron transfer reactions. On the one hand, we corroborate the previously made conclusion regarding intrinsically high activity of the active sites of biological catalysts, especially redox enzymes, which results in mass transfer and heterogeneous electron transfer limited currents from oxygen reducing bioelectrodes. On the other hand, we disagree with the statements regarding the exceptionality of precious metal catalysts, and the notion of a huge trade-off between high activity and stability of non-precious metal catalysts and bioelements. We show that the activity and stability of noble metal based cathodes is very far from perfect, especially when these electrodes operate in complex electrolytes, such as physiological fluids, e.g. human blood.

The multicopper oxidase Trametes hirsuta laccase (ThLc) served as a bioelectrocatalyst on nanostructured cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reductionwere as high as 0.5 mA/cm2 and 0.7 mA/cm2, which were recorded under direct and mediated electron transfer regimes, respectively. The experimental data were fitted to mathematical models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rateliming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5-8 nmsize Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets. © 2015 Elsevier B.V., This work was funded by the Seventh Framework Programme (BIOENERGY FP7-PEOPLE-2013-607793 project).

This work provides an overview of the recent advances in the field of tear-based wearable electrochemical biodevices, including non-invasive biosensors, biological fuel cells and biosupercapacitors. Contact lenses are attractive platforms for fabricating non-invasive self-contained gadgets for different applications, starting from devices with casual or mundane purposes only, like personalized smart lenses with direct (invisible for others) displays, and ending with biomedical devices for continuous fitness status and/or health care monitoring. Key requirements and challenges that confront researchers in this exciting area are discussed.

Here we report on an entirely new kind of bioelectronic device – a conventional biosupercapacitor, which is built from copper containing redox proteins. Prior to biodevice fabrication, detailed spectroelectrochemical studies of the protein, viz. Acidithiobacillus ferrooxidans rusticyanin, in solution and in adsorbed state, were performed, including estimation of the redox potential of the T1 site (0.62 V vs. NHE), protein midpoint potential when adsorbed on a self-assembled monolayer (0.34 V vs. NHE), as well as biocapacitance of rusticyanin modified gold electrodes (115 μF cm−2). The symmetrical biosupercapacitor based on two identical gold electrodes modified with rusticyanin is able to capacitively store electricity and deliver electric power accumulated mostly in the form of biopseudocapacitance, when charged and discharged externally. When charged during just 5 s, the biosupercapacitor with a total capacitance of about 73 μF cm−2 provided a maximum of 4 μA cm−2 peak current at 0.40 V. The biodevice, which can be charged and discharged at least 50 times without a significant loss of ability to store electric energy, had a low leakage current below 50 nA cm−2. The work was financially supported in part by the Swedish Energy Agency (project 44707-1).

Here we present the modification of fluorinated tin oxide electrodes with In2S3, an n-type semiconductor chalcogenide that absorbs visible light (λ ≤600 nm), and its further use as an active scaffold for laccase-catalyzed oxidation of water. Illumination of an FTO-In2S3- laccase electrode yields O2 production at much lower applied potential in comparison to the previous example using the same laccase, where only electric energy was applied. The present system allows a diversification of the energy applied to accomplish the water splitting, taking a portion of it from the sun. This work is the first example where an enzyme other than PSII has been used in combination with visible light to biocatalyze O2 evolution., This work was funded by the Spanish MINECO/FEDER projects CTQ2015-71290-R and ENE2013-46624-C4-1-R, by the CSIC PIE 201560I018 project, and by the European Commission project “Bioenergy” FP7-PEOPLE-2013-ITN-607793. A scholarship for C.T. was funded by the Spanish MINECO contract BES-2013-064099.

We detail a mediator- and membrane-free enzymatic glucose/oxygen biofuel cell based on transparent and nanostructured conducting supports. Chemically modified indium tin oxide nanoparticle modified electrodes were used to substantially increase the active surface area without significantly compromising transparency. Two different procedures for surface nanostructuring were employed, viz. spray-coating and drop-coating. The spray-coated biodevice showed superior characteristics as compared to the drop-coated enzymatic fuel cell, as a result of the higher nanostructured surface area as confirmed by electrochemical characterisation, as well as scanning electron and atomic force microscopy. Subsequent chemical modification with silanes, followed by the immobilisation of either cellobiose dehydrogenase from Corynascus thermophiles or bilirubin oxidase from Myrothecium verrucaria, were performed to obtain the bioanodes and biocathodes, respectively. The optimised biodevice exhibited an OCV of 0.67 V and power output of up to 1.4 µW/cm2 at an operating voltage of 0.35 V. This is considered a significant step forward in the field of glucose/oxygen membrane- and mediator-free, transparent enzymatic fuel cells., This work was supported in part by the European Commission through the Marie-Curie Project “Bioenergy” (PITN-GA-2013-607793), by the Swedish Research Council (621-2013-6006), and by the Cluster of Excellence RESOLV (EXC 1069) funded by the Deutsche Forschungsgemeinschaft (DFG).

An infrared spectroelectrochemical study of Trametes hirsuta laccase and Magnaporthe oryzae bilirubin oxidase has been performed using azide, an inhibitor of multicopper oxidases, as an active infrared probe incorporated into the T2/T3 copper cluster of the enzymes. The redox potential-controlled measurements indicate that N3 − stretching IR bands of azide ion bound to the T2/T3 cluster are only detected for the oxidized enzymes, confirming that azide only binds to Cu2+. Moreover, the process of binding/dissociation of azide ion is shown to be reversible. The interaction of halide anions, which also inhibit multicopper oxidases, with the active site of the enzymes was studied by measuring the changes in the azide FTIR bands. Enzymes inhibited by azide respond differently upon addition of fluoride or chloride ions to the sample solution inhibited by azide. Fluoride ions compete with azide for binding at one of the T2/T3 Cu ions, whereas competition from chloride ions is much less evident., This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under Grant agreement BIOENERGY FP7-PEOPLE-2013-607793.

We present data on operation of a miniature membrane-less, direct electron transfer based enzymatic fuel cell in human sweat and saliva. The enzymatic fuel cell was fabricated following our previous reports on miniature biofuel cells, utilizing gold nanoparticle modified gold microwires with immobilized cellobiose dehydrogenase and bilirubin oxidase. The following average characteristics of miniature glucose/oxygen biodevices operating in human sweat and saliva, respectively, were registered: 580 and 560 mV open-circuit voltage, 0.26 and 0.1 μW cm–2 power density at a cell voltage of 0.5 V, with up to ten times higher power output at 0.2 V. When saliva collected after meal ingestion was used, roughly a two-fold increase in power output was obtained, with a further two-fold increase by addition of 500 μM glucose. Likewise, the power generated in sweat at 0.5 V increased two-fold by addition of 500 μM glucose.

Direct electron transfer (DET) between cellobiose dehydrogenase from Humicola insolens ascomycete (HiCDH) and gold nanoparticles (AuNPs) was achieved by modifying AuNPs with a novel, positively charged thiol N-(6-mercapto)hexylpyridinium (MHP). The DET enabled the use of the HiCDH enzyme as an anodic biocatalyst in the design of a mediatorless carbohydrate/oxygen enzymatic fuel cell (EFC). A biocathode of the EFC was based on bilirubin oxidase from Myrothecium verrucaria (MvBOx) directly immobilised on the surface of AuNPs. The following parameters of the EFC based on Au/AuNP/MHP/HiCDH bioanode and Au/AuNP/MvBOx biocathode were obtained in quiescent air saturated PBS, pH 7.4, containing: (i) 5 mM glucose-open-circuit voltage (OCV) of 0.65 ± 0.011 V and the maximal power density of 4.77 ± 1.34 μW cm−2 at operating voltage of 0.50 V; or (ii) 10 mM lactose-OCV of 0.67 ± 0.006 V and the maximal power density of 8.64 ± 1.91 μW cm−2 at operating voltage of 0.50 V. The half-life operation times of the EFC were estimated to be at least 13 and 44 h in air saturated PBS containing 5 mM glucose and 10 mM lactose, respectively. Among advantages of HiCDH/MvBOx FCs are (i) simplified construction, (ii) relatively high power output with glucose as biofuel, and (iii) the absence of the inhibition of the HiCDH based bioanode by lactose, when compared with the best previously reported CDH based bioanode.

Hybrid electric power biodevices, a new type of electric-power-producing device, are a combination of an electrochemical capacitor and a biofuel cell. In this Minireview, we summarise existing knowledge on double-function bioelectrodes, that is, single electrodes concurrently manifesting bio-electrocatalytic and charge-storage features, and describe important historical aspects and achievements in this area. We also discuss a recently proposed method for concomitant electric power generation and storage, which is exemplified by fabricated and characterised self-charging bio-supercapacitors, also termed charge-storing biofuel cells. The electric power in these hybrid devices is uninterruptedly generated by direct transformation of chemical energy into electric energy, as occurs in biofuel cells. The power is simultaneously and directly stored within a single device, relying on different types of capacitance based on reversible charge-transfer reactions (pseudocapacitance) and/or electric double-layer capacitance, as in electrochemical capacitors. We also present some unpublished results on both dual-feature electrodes and hybrid biodevices and briefly highlight the prospects for their application.

Bioelectrocatalytic reduction of oxygen to water at electrodes modified with gold nanoparticles and a new laccase from Trichaptum abietinum (TaLc) was studied. The bioelectrocatalytic current was found to be much higher at TaLc modified electrodes than at similarly prepared electrodes modified with a broadly used laccase from Trametes hirsuta (ThLc). To explain this difference the bioelectrocatalysis was described in terms of kinetic rate constants based on simultaneous cyclic voltammetry and quartz crystal microbalance measurements. From analysis of the rate constants both laccases appeared to possess similar rates (k0) of direct electron transfer. However, the enzyme turnover (kcat) was about three-fold higher for gold nanoparticle bound TaLc than for ThLc, calculated using surface concentration of enzyme established by QCM-D. Near reversible potential-induced reorientation of adsorbed proteins was observed by surface enhanced Raman spectroscopy.

Here we present the very first study of an enzymatic fuel cell (EFC) in a cell culture. An EFC with Corynascus thermophilus cellobiose dehydrogenase (CDH) based bioanode and Myrothecium verrucaria bilirubin oxidase (BOx) based biocathode was constructed at the bottom of a medusa cell culture plate. The constructed EFC had a power density of up to 25 μW cm(-2) at 0.5 V potential in simple buffer solution and in cell culturing medium. L929 murine fibroblast cells were seeded on top of the EFC and possible effects of the EFC on the cells and vice versa were studied. It was shown that on average the power of the EFC drops by about 70% under a nearly confluent layer of cells. The EFC appeared to have a toxic effect on the L929 cell line. It was concluded that the bioanode, consisting of CDH, produced hydrogen peroxide at toxic concentrations. However, the toxic effect was circumvented by co-immobilizing catalase on the bioanode.