Rational Design of Enzymatic Electrodes: Impact of Carbon Nanomaterial Types on the Electrode Performance.

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm-2 in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support.

Induction of a proton gradient across a gold-supported biomimetic membrane by electroenzymatic H2 oxidation.

Energy-transduction mechanisms in living organisms, such as photosynthesis and respiration, store light and chemical energy in the form of an electrochemical gradient created across a lipid bilayer. Herein we show that the proton concentration at an electrode/phospholipid-bilayer interface can be controlled and monitored electrochemically by immobilizing a membrane-bound hydrogenase. Thus, the energy derived from the electroenzymatic oxidation of H2 can be used to generate a proton gradient across the supported biomimetic membrane.

Multi-Substrate Biofuel Cell Utilizing Glucose, Fructose and Sucrose as the Anode Fuels.

A significant problem still exists with the low power output and durability of the bioelectrochemical fuel cells. We constructed a fuel cell with an enzymatic cascade at the anode for efficient energy conversion. The construction involved fabrication of the flow-through cell by three-dimensional printing. Gold nanoparticles with covalently bound naphthoquinone moieties deposited on cellulose/polypyrrole (CPPy) paper allowed us to significantly improve the catalysis rate, both at the anode and cathode of the fuel cell. The enzymatic cascade on the anode consisted of invertase, mutarotase, Flavine Adenine Dinucleotide (FAD)-dependent glucose dehydrogenase and fructose dehydrogenase. The multi-substrate anode utilized glucose, fructose, sucrose, or a combination of them, as the anode fuel and molecular oxygen were the oxidant at the laccase-based cathode. Laccase was adsorbed on the same type of naphthoquinone modified gold nanoparticles. Interestingly, the naphthoquinone modified gold nanoparticles acted as the enzyme orienting units and not as mediators since the catalyzed oxygen reduction occurred at the potential where direct electron transfer takes place. Thanks to the good catalytic and capacitive properties of the modified electrodes, the power density of the sucrose/oxygen enzymatic fuel cells (EFC) reached 0.81 mW cm-2, which is beneficial for a cell composed of a single cathode and anode.

Carbon-Based Nanobiohybrid Thin Film for Amperometric Glucose Sensing.

This pioneering study involved the fabrication of a new class of nanohybrid-based electrochemical glucose biosensor. First, three-dimensional (3D) graphene was fabricated as a platform of multiwalled carbon nanotube (MWCNT). Then, it was used to immobilize glucose oxidase (GOD) on nanohybrid thin film via the entrapment technique. The modified glucose biosensor indicated excellent biocatalytic activity toward the glucose measurment with a sensitivity of up to 49.58 µA mM-1 cm-2 and a wide linear dynamic range up to 16 mM. The fabricated biosensor shows an excellent stability of 87.8%, with its current diminishing after 3 months. This facile and simple electrochemical method for glucose monitoring using a modified glassy carbon electrode (GCE) by 3DG-MWCNT-GOD could open new avenues in producing of a inexpensive and sensitive glucose nanobiosensors.

Enzyme orientation for direct electron transfer in an enzymatic fuel cell with alcohol oxidase and laccase electrodes.

A new full enzymatic fuel cell was built and characterized. Both enzymatic electrodes were molecularly oriented to enhance the direct electron transfer between the enzyme active site and the electrode surface. The anode consisted in immobilized alcohol oxidase on functionalized carbon nanotubes with 4-azidoaniline, which acts as active-site ligand to orientate the enzyme molecule. The cathode consisted of immobilized laccase on functionalized graphite electrode with 4-(2-aminoethyl) benzoic acid. The enzymatic fuel cell reaches 0.5 V at open circuit voltage with both, ethanol and methanol, while in short circuit the highest current intensity of 250 µA cm(-2) was obtained with methanol. Concerning the power density, the methanol was the best substrate reaching 60 µW cm(-2), while with ethanol 40 µW cm(-2) was obtained.