Search

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).

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).

International audience; Here we detail an optimized transparent capacitive glucose oxidizing bioanode, capable of supplying current densities of 10 mAcm¢2 at applied potentials of 0.1 V–0.2V versus saturated calomel electrode, when continuously performing in a simple phosphate buffer, pH 7.4 and artificial human tears, both with a glucose concentration of 0.05 mM only. When operating in pulsemode, the bioanode was able to deliver current densities as high as 21 mAcm¢2 at the beginning of the pulse with 571 mCcm¢2 total charges stored. The biogenic part of the enzymatic device was a recombinant glucose oxidase mutant from Penicillium amagasakiense with high catalytic efficiency towards glucose, up to 14.5·104 M¢1 s¢1. The non-biogenic part of the anodic system was based on a poly(3,4-ethylenedioxythiophene)-graphene nanocomposite, as a highly capacitive component with a capacitance density in the 1 mFcm¢2 range, multi-walled carbon nanotubes, as an additional nanostructuring element, anda conductive organic 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 enzymatic anode for hybrid electric power biodevices, energizing smart contact lenses.

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–saturated phosphate buffer solution, pH 7.4 (PB), and also in phosphate buffer solution containing redox–active blood components (BMB). The open circuit potential of the biocathode is 0.33 and 0.08 V vs. the saturated calomel electrode in PB and BMB, respectively; it is completely restored after at least three self-charge/discharge cycles with connection to resistors with different resistance. Bioelectrocatalytic current density of oxygen reduction 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, respectively.

Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved. (Less)

We have developed and synthesized nanobiocomposite materials based on graphene, poly(3,4-ethylenedioxythiophene), and glucose oxidase immobilized on the surface of various nanomaterials (gold nanoparticles and multi-walled carbon nanotubes) of different sizes (carbon nanotubes of different diameters). Comparative studies of the possible influence of the nanomaterials nature on the bioelectrocatalytic characteristics of glucose-oxidizing bioanodes in a neutral phosphate buffer solution demonstrated that the bioelectrocatalytic current densities of nanocomposite-based bioanodes are only weakly dependent on the size of the nanomaterial and are primarily defined by its nature. The developed nanobiocomposites are promising materials for new bioelectronic devices due to the ease in adjusting their capacitive and bioelectrocatalytic characteristics, which allows one to use them for the production of dual-function electrodes: i.e., electrodes which are capable of generating and storing electric power simultaneously.