Tuning Structural Changes in Glucose Oxidase for Enzyme Fuel Cell Applications

Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction: Applications in Microbial Fuel Cells

Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a revolutionary answer to the global environmental challenges. Yet, one key factor that limits the implementation of larger scale MFCs is the high cost and low durability of current electrode materials, owing to the use of platinum at the cathode side. To address this issue, the scientific community has devoted its research efforts for identifying innovative and low cost materials and components to assemble lab-scale MFC prototypes, fed with wastewaters of different nature. This review work summarizes the state-of the-art of developing platinum group metal-free (PGM-free) catalysts for applications at the cathode side of MFCs. We address how different catalyst families boost oxygen reduction reaction (ORR) in neutral pH, as result of an interplay between surface chemistry and morphology on the efficiency of ORR active sites. We particularly review the properties, performance, and applicability of metal-free carbon-based materials, molecular catalysts based on metal macrocycles supported on carbon nanostructures, M-N-C catalysts activated via pyrolysis, metal oxide-based catalysts, and enzyme catalysts. We finally discuss recent progress on MFC cathode design, providing a guidance for improving cathode activity and stability under MFC operating conditions.

Enzyme production ofd-gluconic acid and glucose oxidase: successful tales of cascade reactions

This review mainly focuses on the use of glucose oxidase in the production ofd-gluconic acid, which is a reactant of undoubtable interest in different industrial areas. As example of diverse enzymatic cascade reactions.

Novel Composite Electrode of the Reduced Graphene Oxide Nanosheets with Gold Nanoparticles Modified by Glucose Oxidase for Electrochemical Reactions

Graphene-based composites have been widely explored for electrode and electrocatalyst materials for electrochemical energy systems. In this paper, a novel composite material of the reduced graphene oxide nanosheets (rGON) with gold nanoparticles (NPs) (rGON-AuNP) is synthesized, and its morphology, structure, and composition are characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopic (FTIR), Raman, and UV-Vis techniques. To confirm this material’s electrochemical activity, a glucose oxidase (GOD) is chosen as the target reagent to modify the rGON-AuNP layer to form GOD/rGON-AuNP/glassy carbon (GC) electrode. Two pairs of distinguishable redox peaks, corresponding to the redox processes of two different conformational GOD on AuNP, are observed on the cyclic voltammograms of GOD/rGON-AuNP/GC electrode. Both cyclic voltammetry and electrochemical impedance spectroscopy are employed to study the mechanism of direct electron transfer from GOD to GC electrode on the rGON-AuNP layer. In addition, this GOD/rGON-AuNP/GC electrode shows catalytic activity toward glucose oxidation reaction.

Novel grafted electrochemical interface for covalent glucose oxidase immobilization using reactive pentafluorophenyl methacrylate

One of the most important factors for the proper functioning of enzymatic electrochemical biosensors is the enzyme immobilization strategy. In this work, glucose oxidase was covalently immobilized using pentafluorophenyl methacrylate (PFM) by applying two different surface modification techniques (plasma polymerization and plasma-grafting). The grafted surface was specifically designed to covalently anchor enzyme molecules. It was observed using QCM-D measurements the PFM plasma-grafted surfaces were able to retain a higher number of active enzyme molecules than the PFM polymerized surfaces. An amperometric glucose biosensor using titanium dioxide nanotubes array (TiO₂NTAs) modified by PFM plasma-grafted surface was prepared. The resulting biosensor exhibited a fast response and short analysis time (approximately eight minutes per sample). Moreover, this biosensor achieved high sensitivity (9.76 μA mM^-1) with a linear range from 0.25 to 1.49 mM and a limit of detection (LOD) equal to 0.10 mM of glucose. In addition, the glucose content of 16 different food samples was successfully measured using the developed biosensor. The obtained results were compared with the respective HPLC value and a deviation smaller than 10% was obtained in all the cases. Therefore, the biosensor was able to overcome all possible interferences in the selected samples/matrices.

Induced-fit adsorption of diol-based porous organic polymers for tetracycline removal

Adsorption is recognized as one of the most efficient approaches for antibiotics removal from water. Inspired by the enzyme-substrate interaction model, we proposed induced-fit adsorption (IFA) model, and rationally designed and fabricated diol-based porous organic polymers (POPs) as adsorbents for tetracycline (TC) removal. For 2,3-naphthalenediol-based POP (NTdiol-POP), the preferable geometry of diol-groups contributed to the high binding energy with TC species and flexible methylene linkages between neighboring rigid naphthalene rings gave rise to precisely matching between TC species and adsorbents, that is, the induced-fit conformation change. As a result, NTdiol-POP exhibited a high saturated adsorption capacity of 155.8 mg g^-1. More importantly, NTdiol-POP exhibited excellent TC removal efficiencies in both concentrated solution (96% for 4 p.p.m) and trace level solution (97% for 250 p.p.b).

Effects of the surface chemistry and structure of carbon nanotubes on the coating of glucose oxidase and electrochemical biosensors performance

Glucose oxidase has been immobilized on multiwall and herringbone carbon nanotubes for glucose biosensing.

Conformational Changes of Enzymes and Aptamers Immobilized on Electrodes

Conformation constitutes a vital property of biomolecules, especially in the cases of enzymes and aptamers, and is essential in defining their molecular recognition ability. When biomolecules are immobilized on electrode surfaces, it is very important to have a control on all the possible conformational changes that may occur, either upon the recognition of their targets or by undesired alterations. Both enzymes and aptamers immobilized on electrodes are susceptible to conformational changes as a response to the nature of the charge of the surface and of the surrounding environment (pH, temperature, ionic strength, etc.). The main goal of this review is to analyze how the conformational changes of enzymes and aptamers immobilized on electrode surfaces have been treated in reports on biosensors and biofuel cells. This topic was selected due to insufficient information found on the actual conformational changes involved in the function of these bioelectrochemical devices despite its importance.