Switchable Bioelectrocatalysis Controlled by pH Changes

Cooperative Control of Bioelectrocatalytic Activity for Thermo- and Photo-Switchable Cup-Stacked Carbon Nanofiber Electrodes Modified with Phase Transition Polymer and Heme Peptide

Empowering biocatalyst-modified electrodes with the ability to both enforce and perceive will enable the development of intrinsically switchable bioelectrode systems, which exhibit autonomous and heteronomous actions specific to living organisms. However, the electrocatalytic activity of switchable bioelectrodes reported so far has been controlled by changes in the rate of substrate transport to biocatalysts. Here, we prepared a cup-stacked carbon nanofiber (CSCNF) electrode modified with a thermoresponsive N-isopropylacrylamide-based polymer containing peroxidase model compounds (HP). As CSCNFs worked as a converter from near-infrared (NIR) light to heat, bioelectrocatalytic activity of the electrode to H2O2 reduction was reversibly controlled by changes in the amount of electroactive HP, based on expanded and contracted states of the polymers induced by not only environmental temperature changes but also external NIR light irradiation. This intrinsically switchable bioelectrode technique would hold promise for adding new performances in electrochemical biosensors and biofuel cells, for example, autonomous and heteronomous tunable sensitivity and capacity.

Control of Allosteric Protein Electrochemical Switches with Biomolecular and Electronic Signals

The construction of allosteric protein switches is a key goal of synthetic biology. Such switches can be compiled into signaling systems mimicking information and energy processing systems of living organisms. Here we demonstrate construction of a biocatalytic electrode functionalized with a recombinant chimeric protein between pyrroloquinoline quinone-dependent glucose dehydrogenase and calmodulin. This electrode could be activated by calmodulin-binding peptide and showed a high bioelectrocatalytic current (ca. 300 μA) due to efficient direct electron transfer. In order to expand the types of inputs that can be used to activate the developed electrode, we constructed a caged version of calmodulin-binding peptide that could be proteolytically uncaged using a protease of choice. Finally, the complexity of the switchable bioelectrochemical system was further increased by the use of almost any kind of molecule/biomolecule or electronic signal, unequivocally proving the orthogonality of the aforementioned system.

PQQ-GDH - Structure, function and application in bioelectrochemistry

This review summarizes the basic features of the PQQ-GDH enzyme as one of the sugar converting biocatalysts. Focus is on the membrane -bound and the soluble form. Furthermore, the main principles of enzymatic catalysis as well as studies on the physiological importance are reviewed. A short overview is given on developments in protein engineering. The major part, however, deals with the different fields of application in bioelectrochemistry. This includes approaches for enzyme-electrode communication such as direct electron transfer, mediator-based systems, redox polymers or conducting polymers and holoenzyme reconstitution, and covers applied areas such as biosensing, biofuel cells, recycling schemes, enzyme competition, light-directed sensing, switchable detection schemes, logical operations by enzyme electrodes and immune sensing.

Multiple stimuli-switchable electrocatalysis and logic gates of rutin based on semi-interpenetrating polymer network hydrogel films

The switching properties of PAA–PDEA films polymerized as a semi-IPN were studied with rutin as a probe and a logic gate was constructed.

Polymers and biopolymers at interfaces

This review updates recent progress in the understanding of the behaviour of polymers at surfaces and interfaces, highlighting examples in the areas of wetting, dewetting, crystallization, and 'smart' materials. Recent developments in analysis tools have yielded a large increase in the study of biological systems, and some of these will also be discussed, focussing on areas where surfaces are important. These areas include molecular binding events and protein adsorption as well as the mapping of the surfaces of cells. Important techniques commonly used for the analysis of surfaces and interfaces are discussed separately to aid the understanding of their application.

A Stimuli-Responsive Biosensor of Glucose on Layer-by-Layer Films Assembled through Specific Lectin-Glycoenzyme Recognition

The research on intelligent bioelectrocatalysis based on stimuli-responsive materials or interfaces is of great significance for biosensors and other bioelectronic devices. In the present work, lectin protein concanavalin A (Con A) and glycoenzyme glucose oxidase (GOD) were assembled into {Con A/GOD}n layer-by-layer (LbL) films by taking advantage of the biospecific lectin-glycoenzyme affinity between them. These film electrodes possess stimuli-responsive properties toward electroactive probes such as ferrocenedicarboxylic acid (Fc(COOH)₂) by modulating the surrounding pH. The CV peak currents of Fc(COOH)₂ were quite large at pH 4.0 but significantly suppressed at pH 8.0, demonstrating reversible stimuli-responsive on-off behavior. The mechanism of stimuli-responsive property of the films was explored by comparative experiments and attributed to the different electrostatic interaction between the films and the probes at different pH. This stimuli-responsive films could be used to realize active/inactive electrocatalytic oxidation of glucose by GOD in the films and mediated by Fc(COOH)₂ in solution, which may establish a foundation for fabricating novel stimuli-responsive electrochemical biosensors based on bioelectrocatalysis with immobilized enzymes.