Integrating photosynthetic cell components with nanostructured materials can facilitate the conversion of solar energy into electric power for creating sustainable carbon-neutral energy sources. With the aim at exploring efficient photoinduced biocatalytic energy conversion systems, we have used an amidated carbon nanotube (aCNT) networked matrix to integrate thylakoid membranes (TMs) for construction of a direct electron transfer-driven biosolar cell. We have evaluated the resulting photobioelectrochemical cells systematically. Compared to the carboxylated CNT (cCNT)-TMs system, the aCNT-TMs system enabled a 1.5-fold enhancement in photocurrent density. This system offers more advantages including a reduced charge-transfer resistance, a lower open-circuit potential, and an improved cell stability. More remarkably, the average power density of the optimized cells was 250 times higher than that of reported analogue systems. Our results suggest the significance of physical and electronic interactions between the photosynthetic components and the support nanomaterials and may offer new clues for designing improved biosolar cells.

The concept of supercapacitive photo-bioanode and biosolar cell (photo-biosupercapacitor) for simultaneous solar energy conversion and storage is demonstrated for the first time. Exploiting the capacitive component significantly improves the electron transfer processes and allows the achievement of a current density of 280 µA cm−2 in the pulse mode.

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 neg. values. Concomitantly, at the biocathode the redn. of O2 by means of bilirubin oxidase embedded in the same redox polymer leads to the oxidn. 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 d. is obtained for a short time exceeding the steady state power of a corresponding biofuel cell by a factor of 8.

Here we report an enzymic fuel cell in a vein replica that generates sustained electricity, enough to power an e-​ink display, in an authentic human blood stream. We also detail a simple and safe approach for fuel cell evaluation under homeostatic conditions. Our results demonstrate proof-​of-​principle operation of a biocompatible and safe biodevice that could be implanted in superficial human veins, which we anticipate to be a starting point for more sophisticated investigations of personal sources of electricity.

A review. 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 electroredn. and bioelectroredn. processes. To addnl. distinguish 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 electroredn. 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 biol. catalysts, esp. 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, esp. when these electrodes operate in complex electrolytes, such as physiol. fluids, e.g. human blood.

A potentially implantable biocathode with the function of charge accumulation based on a nanobiocomposite including multiwall carbon nanotubes, polyaniline, and bilirubin oxidase is developed. The regularities of the functioning of the obtained electrode are studied in air-​satd. phosphate buffer soln., pH 7.4 (PB)​, and also in phosphate buffer soln. contg. redox-​active blood components (BMB)​. The open circuit potential of the biocathode is 0.33 and 0.08 V vs. the SCE in PB and BMB, resp.; it is completely restored after at least three self-​charge​/discharge cycles with connection to resistors with different resistance. Bioelectrocatalytic c.d. of oxygen redn. is 0.50 and 0.42 mA cm-​2 with the residual activity of 78 and 60​% of the initial value after 12 h of continuous operation in PB at 25°C and in BMB at 37°C, resp.

The thesis is focused on an entirely new class of electric power biodevices –self-charging biosupercapacitors, or in other words, charge-storing biofuelcells. The power generating segments of these biodevices rely on differentredox enzymes electrically wired to electrode surfaces. Planar electrodes wereadditionally nanostructured by gold nanoparticles to increase the real surfacearea/enhance enzyme loading. Bilirubin oxidase was used as a cathodicbiocatalyst responsible for oxygen electroreduction, whereas cellobiosedehydrogenase and glucose dehydrogenase were exploited as anodicbioelements catalyzing electrooxidation of glucose. The charge-storingsegments of biosupercapacitors were based on different electroconductingpolymers, including carbon nanotube based nanocomposites, and osmiummodified redox hydrogels. The particular bioelectrodes were characterized indetail using scanning electron and atomic force microscopies, as well asvarious electrochemical techniques. Self-charging biosupercapacitors wereassembled and basic parameters of the biodevices, viz. open-circuit voltages,power and charge densities, and stability, were studied in continuous andpulse operating modes.

A review. This work provides an overview of the recent advances in the field of tear-​based wearable electrochem. biodevices, including non-​invasive biosensors, biol. 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 the authors detail an optimized transparent capacitive glucose oxidizing bioanode, capable of supplying current densities of 10 μA cm-​2 at applied potentials of 0.1 V-​0.2 V vs. SCE, when continuously performing in a simple phosphate buffer, pH 7.4 and artificial human tears, both with a glucose concn. of 0.05 mM only. When operating in pulse mode, the bioanode was able to deliver current densities ≤21 μA cm-​2 at the beginning of the pulse with 571 μC cm-​2 total charges stored. The biogenic part of the enzymic device was a recombinant glucose oxidase mutant from Penicillium amagasakiense with high catalytic efficiency towards glucose, up to 14.5x104 M-​1 s-​1. The nonbiogenic part of the anodic system was based on a poly(3,​4-​ethylenedioxythiophene)​-​graphene nanocomposite, as a highly capacitive component with a capacitance d. in the 1 mF cm-​2 range, multi-​walled carbon nanotubes, as an addnl. nanostructuring element, and a conductive org. complex, as an electron shuttle between the redox enzyme and the electrode surface. The bioanode could potentially serve as a prototype of a double-​function enzymic anode for hybrid elec. power biodevices, energizing smart contact lenses.

A direct electron transfer (DET) based sulphite/oxygen biofuel cell is reported that utilises human sulphite oxidase (hSOx) and Myrothecium verrucaria bilirubin oxidase (MvBOx) and nanostructured gold electrodes. For bioanode construction, the nanostructured gold microelectrodes were further modified with 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester) to which polyethylene imine was covalently attached. hSOx was adsorbed onto this chemically modified nanostructured electrode with high surface loading of electroactive enzyme and in presence of sulphite high anodic bioelectrocatalytic currents were generated with an onset potential of 0.05 V vs. NHE. The biocathode contained MvBOx directly adsorbed to the deposited gold nanoparticles for cathodic oxygen reduction starting at 0.71 V vs. NHE. Both enzyme electrodes were integrated to a DET-type biofuel cell. Power densities of 8 and 1 μW cm−2 were achieved at 0.15 V and 0.45 V of cell voltages, respectively, with the membrane based biodevices under aerobic conditions.