Organic transdermal iontophoresis patch with built-in biofuel cell.

A completely organic iontophoresis patch is reported. A built-in biofuel cell is mounted on the patch that generates transdermal iontophoretic administration of compounds into the skin. The amplitude of transdermal current is tuned by integrating a conducting polymer-based stretchable resistor of predetermined resistance.

Surfactant-assisted direct electron transfer between multi-copper oxidases and carbon nanotube-based porous electrodes.

The effects of pre-treatment with surfactants on the electrocatalytic reaction of multi-copper oxidases were quantitatively evaluated using a well-structured carbon nanotube forest electrode. It was found that both the charge polarity of the head group and the aromatics in the tail part of the surfactants affect the efficiency of enzymatic electrocatalysis.

Flexible, layered biofuel cells.

Similar to conventional electrolyte batteries, biofuel cells often need to be stacked in order to boost their single cell voltage (<1 V) up to a practical level. Here, we report a laminated stack of biofuel cells that is composed of bioanode fabrics for fructose oxidation, hydrogel sheets containing electrolyte and fuel (fructose), and O(2)-diffusion biocathode fabrics. The anode and cathode fabrics were prepared by modifying fructose dehydrogenase and bilirubin oxidase, respectively, on carbon nanotubes-decorated carbon fiber fabrics. The total thickness of the single set of anode/gel/cathode sheets is just 1.1mm. The laminated triple-layer stack produces an open-circuit voltage of 2.09 V, which is a 2.8-fold increase over that of a single set cell (0.74 V). The present layered cell (5 mm × 5 mm) produces a maximum power of 0.64 mW at 1.21 V, a level that is sufficient to drive light-emitting diodes.

Self-regulating enzyme-nanotube ensemble films and their application as flexible electrodes for biofuel cells.

Nanostructured carbons have been widely used for fabricating enzyme-modified electrodes due to their large specific surface area. However, because they are random aggregates of particular or tubular nanocarbons, the postmodification of enzymes to their intrananospace is generally hard to control. Here, we describe a free-standing film of carbon nanotube forest (CNTF) that can form a hybrid ensemble with enzymes through liquid-induced shrinkage. This provides in situ regulation of its intrananospace (inter-CNT pitch) to the size of enzymes and eventually serves as a highly active electrode. The CNTF ensemble with fructose dehydrogenase (FDH) showed the oxidation current density of 16 mA cm(-2) in stirred 200 mM fructose solution. The power density of a biofuel cell using the FDH-CNTF anode and the Laccase-CNTF cathode reached 1.8 mW cm(-2) (at 0.45 V) in the stirred oxygenic fructose solution, more than 80% of which could be maintained after continuous operation for 24 h. Application of the free-standing, flexible character of the enzyme-CNTF ensemble electrodes is demonstrated via their use in the patch or wound form.

Novel high-affinity Aß-binding peptides identified by an advanced in vitro evolution, progressive library method.

Recent studies have been supporting that the generation of Aß42 oligomers is responsible for Alzheimer's disease. Therefore, those peptides which bind to Aß42 are scientifically interesting and can be possible candidates for the diagnosis and therapy of Alzheimer's disease. A systemic in vitro evolution, developed recently and the designated progressive library method (PLM), was applied to obtain Ab42-binding aptamers peptides. As a result, high affinity peptide aptamers made of 8 or 9 amino acids could be identified by this approach, endorsing the methodological effectiveness. Namely, the selection products from the secondary library of diversified peptides, which was constructed based on the information obtained from the primary library selection, were confirmed to be superior to those selected from the primary library as had been reported previously. The affinities of those peptides measured by SPR (surface plasmon resonance) were comparable to or higher than that of those peptides so far reported (K(d) of 10⁻7). The other peptides selected were confirmed of their binding by a novel mode of gel shift assay (fluorescence enhancement caused by the binding). Thus, novel Aß42-binding peptides with high affinity were provided for the future Alzheimer's disease study. The demonstration of the effectiveness of the systemic in vitro evolution of PLM is very encouraging for the study of identifying novel functional peptides.

Automatic, sequential power generation for prolonging the net lifetime of a miniature biofuel cell stack.

A sequential power generation system for prolonging the net lifetime of a miniature biofuel cell stack has been developed. The system consists of layered chambers of enzyme fuel cells designed to be exposed sequentially to fuel solution by automatically switched fuel flow. The cell chambers were initially separated by magnetized plastic covers sealed with a degradable glue, poly(lactic-co-glycolic acid) (PLGA). The time that the cover was opened by attraction with an external magnet, thereby activating the following cell, was adjustable from a few hours to a few weeks by controlling the weight ratio of Fe(3)O(4) in the covers and the molecular weight of PLGA. By using sequential power generation in this way, the power output of the system was stable for longer periods, and therefore the net lifetime of the stack has been extended as compared with that of a single biofuel cell.