Laccase-based biocathodes: Comparison of chitosan and Nafion

A graphitized carbon@boron carbide-mediated laccase-based amperometric biosensor for epinephrine detection

The development of novel electron transfer mediator is important for laccase-based electrochemical biosensors. Here, graphitized carbon coated boron carbide (GC@B4C) was first used as the mediator to transfer electrons from laccase (Lac) to nickel foam (NF) electrode. The GC shell of GC@B4C particles was characterized and confirmed by HRTEM, XRD and Raman spectroscopy. The fabricated Lac/GC@B4C/NF electrode was applied for amperometric detection of epinephrine (EP). Detection results indicated Lac/GC@B4C/NF electrode has wide linear range (0.1 µM-2.6 mM), low detection limit (40 nM), high sensitivity (76.05 µA mM-1), strong anti-interference ability and favorable stability for EP detection. This work opened up the use of nonmetallic carbide as the mediator for enzyme-based electrochemical biosensors.

Conductive Polymers and Their Nanocomposites: Application Features in Biosensors and Biofuel Cells

Conductive polymers and their composites are excellent materials for coupling biological materials and electrodes in bioelectrochemical systems. It is assumed that their relevance and introduction to the field of bioelectrochemical devices will only grow due to their tunable conductivity, easy modification, and biocompatibility. This review analyzes the main trends and trends in the development of the methodology for the application of conductive polymers and their use in biosensors and biofuel elements, as well as describes their future prospects. Approaches to the synthesis of such materials and the peculiarities of obtaining their nanocomposites are presented. Special emphasis is placed on the features of the interfaces of such materials with biological objects.

Glucose Fuel Cells and Membranes: A Brief Overview and Literature Analysis

Glucose is a ubiquitous source of energy for nearly all living things, and glucose fuel cells (GFCs) are regarded as a sustainable power source because glucose is renewable, easily available, cheap, abundant, non-toxic and easy-to-store. Numerous efforts have been devoted to developing and improving GFC performance; however, there is still no commercially viable devices on the market. Membranes play an essential role in GFCs for the establishment of a suitable local microenvironment, selective ion conducting and prevention of substrate crossover. However, our knowledge on them is still limited, especially on how to achieve comparable efficacy with that of a biological system. This review article provides the first brief overview on these aspects, particularly keeping in sight the research trends, current challenges, and the future prospects. We aim to bring together literature analysis and technological discussion on GFCs and membranes by using bibliometrics, and provide new ideas for researchers in this field to overcome challenges on developing high-performance GFCs.

Hydration and Ionic Conductivity of Model Cation and Anion-Conducting Ionomers in Buffer Solutions (Phosphate, Acetate, Citrate)

We studied the gravimetric and volumetric water uptake and ionic conductivity of two model ionomers, cation-conducting sulfonated poly(ether ether ketone) (SPEEK) and anion-conducting polysulfone-trimethylammonium chloride (PSU-TMA), after immersion in phosphate, acetate, and citrate buffer solutions. The equilibrium swelling of SPEEK and PSU-TMA ionomer networks was determined as a function of the pH and buffer composition. The hydration data can be interpreted using the osmotic swelling pressure dependence on the ion-exchange capacity of the ionomers and the concentration of the electrolyte solutions. In the case of SPEEK, anisotropic swelling is observed in diluted buffer solutions, where the swelling pressure is higher. The large water uptake observed for citrate ions is due to the large hydration of this bulky anion. The ionic conductivity is related to the conducting ions and, in the case of SPEEK, to sorbed excess electrolyte. The highest ionic conductivity is observed after immersion in phosphate buffers. Ionic cross-linking is, for the first time, observed in the case of an anion-conducting ionomer in the presence of divalent citrate ions, which limits the volumetric swelling and decreases the ionic conductivity of PSU-TMA.

A self-powered glucose biosensor based on pyrolloquinoline quinone glucose dehydrogenase and bilirubin oxidase operating under physiological conditions

A novel biosensing system capable of simultaneously sensing glucose and powering portable electronic devices such as a digital glucometer is described. The biosensing system consists of enzymatic glucose biofuel cell bioelectrodes functionalized with pyrolloquinoline quinone glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOD) at the bioanode and biocathode, respectively. A dual-stage power amplification circuit is integrated with the single biofuel cell to amplify the electrical power generated. In addition, a capacitor circuit was incorporated to serve as the transducer for sensing glucose. The open circuit voltage of the optimized biofuel cell reached 0.55 V, and the maximum power density achieved was 0.23 mW/ cm² at 0.29 V. The biofuel cell exhibited a sensitivity of 0.312 mW/mM.cm² with a linear dynamic range of 3 mM - 20 mM glucose. The overall self-powered glucose biosensor is capable of selectively screening against common interfering species, such as ascorbate and urate and exhibited an operational stability of over 53 days, while maintaining 90 % of its activity. These results demonstrate the system's potential to replace the current glucose monitoring devices that rely on external power supply, such as a battery.