Ruthenium‐based Conjugated Polymer and Metal‐organic Framework Nanocomposites for Glucose Sensing

Enzymatic bioelectrodes based on ferrocene-modified metal-organic layers for electrochemical glucose detection

Metal-organic frameworks (MOFs) are often applied for enzyme immobilization, while they are limited for bioelectrochemical applications due to poor electronic conductivity. Two-dimensional (2D) metal-organic layers (MOLs) with an ultra-thin lamellar structure can effectively shorten the electron transport path and improve the electron transfer rate. In this study, ferrocene as an electron mediator is covalently bound to a 2D-MOL (Fc-NH2-Hf-BTB-MOL) to accelerate electron transfer between the electrode surface and enzyme. Glucose oxidase (GOx) is immobilized on the electrode modified with Fc-NH2-Hf-BTB-MOL with the addition of chitosan and carboxylated carbon nanotubes. Electrochemical tests such as cyclic voltammetry are carried out on the glucose biosensor, which shows linear detection ranges of 5 ~ 400 μM and 3 ~ 9 mM, with a detection limit of 3.9 μM (S/N = 3). Therefore, this strategy of construction of an enzyme electrode based on 2D-MOLs with enhanced electron transfer results in a biosensor with excellent specificity and activity for practical glucose detection.

A Self-Powered Enzymatic Glucose Sensor Utilizing Bimetallic Nanoparticle Composites Modified Pencil Graphite Electrodes as Cathode

Enzymatic biofuel cells (EBFC) are promising sources of green energy owing to the benefits of using renewable biofuels, eco-friendly biocatalysts, and moderate operating conditions. In this study, a simple and effective EBFC was presented using an enzymatic composite material-based anode and a nonenzymatic bimetallic nanoparticle-based cathode respectively. The anode was constructed from a glassy carbon electrode (GCE) modified with a multi-walled carbon nanotube (MWCNT) and ferrocene (Fc) as a conductive layer coupled with the enzyme glucose oxidase (GOx) as a sensitive detection layer for glucose. A chitosan layer was also applied to the electrode as a protective layer to complete the composite anode. Chronoamperometry (CA) results show that the MWCNT-Fc-GOx/GCE electrode has a linear relationship between current and glucose concentration, which varied from 1 to 10 mM. The LOD and LOQ were calculated for anode as 0.26 mM and 0.87 mM glucose, respectively. Also the sensitivity of the proposed sensor was calculated as 25.71 μ A/mM. Moreover, the studies of some potential interferants show that there is no significant interference for anode in the determination of glucose except ascorbic acid (AA), uric acid (UA), and dopamine (DA). On the other hand, the cathode consisted of a disposable pencil graphite electrode (PGE) modified with platinum-palladium bimetallic nanoparticles (Nps) which exhibit excellent conductivity and electron transfer rate for the oxygen reduction reaction (ORR). The constructed EBFC was optimized and characterized using various electroanalytical techniques. The EBFC consisting of MWCNT-Fc-GOx/GCE anode and Pt-PdNps/PGE cathode exhibits an open circuit potential of 285.0 mV and a maximum power density of 32.25 µW cm-2 under optimized conditions. The results show that the proposed EBFC consisting of an enzymatic composite-based anode and bimetallic nanozyme-based cathode is a unique design and a promising candidate for detecting glucose while harvesting power from glucose-containing natural or artificial fluids.

Metal-Organic Framework for the Immobilization of Oxidoreductase Enzymes: Scopes and Perspectives

Oxidoreductases are a wide class of enzymes that can catalyze biological oxidation and reduction reactions. Nowadays, oxidoreductases play a vital part in most bioenergetic metabolic pathways, which have important applications in biodegradation, bioremediation, environmental applications, as well as biosensors. However, free oxidoreductases are not stable and hard to be recycled. In addition, cofactors are needed in most oxidoreductases catalyze reactions, which are so expensive and unstable that it hinders their industrial applications. Enzyme immobilization is a feasible strategy that can overcome these problems. Recently, metal-organic frameworks (MOFs) have shown great potential as support materials for immobilizing enzymes due to their unique properties, such as high surface-area-to-volume ratio, chemical stability, functional designability, and tunable pore size. This review discussed the application of MOFs and their composites as immobilized carriers of oxidoreductase, as well as the application of MOFs as catalysts and immobilized carriers in redox reactions in the perspective of the function of MOFs materials. The paper also focuses on the potential of MOF carrier-based oxidoreductase immobilization for designing an enzyme cascade reaction system.

Carbon nanotubes: a powerful bridge for conductivity and flexibility in electrochemical glucose sensors

The utilization of nanomaterials in the biosensor field has garnered substantial attention in recent years. Initially, the emphasis was on enhancing the sensor current rather than material interactions. However, carbon nanotubes (CNTs) have gained prominence in glucose sensors due to their high aspect ratio, remarkable chemical stability, and notable optical and electronic attributes. The diverse nanostructures and metal surface designs of CNTs, coupled with their exceptional physical and chemical properties, have led to diverse applications in electrochemical glucose sensor research. Substantial progress has been achieved, particularly in constructing flexible interfaces based on CNTs. This review focuses on CNT-based sensor design, manufacturing advancements, material synergy effects, and minimally invasive/noninvasive glucose monitoring devices. The review also discusses the trend toward simultaneous detection of multiple markers in glucose sensors and the pivotal role played by CNTs in this trend. Furthermore, the latest applications of CNTs in electrochemical glucose sensors are explored, accompanied by an overview of the current status, challenges, and future prospects of CNT-based sensors and their potential applications.

Development of a highly sensitive glucose nanocomposite biosensor based on recombinant enzyme from corn

BACKGROUND

Enzymes are biocatalysts that play a vital role in the production of biomolecules. Plants can be a valuable and cost-effective source for producing well-structured recombinant enzymes. Glucose is one of the most important biological molecules, providing energy to most living systems. An electrochemical method for immobilization of enzyme is promising because it is economic, generates less component waste, improves the signal-to-noise ratio, leads to a lower limit of detection, and stabilizes and protects the enzyme structure.

RESULTS

A glucose biosensor was constructed using polyaniline (PANI) and a recombinant enzyme from corn, plant-produced manganese peroxidase (PPMP), with polymerization of aniline as a monomer in the presence of gold nanoparticles (AuNPs)-glucose oxidase (GOx), and bovine serum albumin. Using linear sweep voltammetry and cyclic voltammetry techniques, PANI-AuNPs-GOx-PPMP/Au electrode exhibited a superior sensing property with a wider linear range of 0.005-16.0 mm, and a lower detection limit of 0.001 mm compared to PANI-GOx-PPMP/Au electrode and PANI-GOx-PPMP/AuNPs/Au electrode. The biosensor selectivity was assessed by determining glucose concentrations in the presence of ascorbic acid, dopamine, aspartame, and caffeine.

CONCLUSION

We conclude that a plant-produced Mn peroxidase enzyme combined with conductive polymers and AuNPs results in a promising nanocomposite biosensor for detecting glucose. The use of such devices for quality control in the food industry can have a significant economic impact. © 2022 Society of Chemical Industry.

Review of the Design of Ruthenium-Based Nanomaterials and Their Sensing Applications in Electrochemistry

In this review, ruthenium nanoparticles (Ru NPs)-based functional nanomaterials have attractive electrocatalytic characteristics and they offer considerable potential in a number of fields. Ru-based binary or multimetallic NPs are widely utilized for electrode modification because of their unique electrocatalytic properties, enhanced surface-area-to-volume ratio, and synergistic effect between two metals provides as an effective improved electrode sensor. This perspective review suggests the current research and development of Ru-based nanomaterials as a platform for electrochemical (EC) sensing of harmful substances, biomolecules, insecticides, pharmaceuticals, and environmental pollutants. The advantages and limitations of mono-, bi-, and multimetallic Ru-based nanocomposites for EC sensors are discussed. Besides, the relevant EC properties and analyte sensing approaches are also presented. On the basis of these insights, we highlighted recent results for synthesizing techniques and EC environmental pollutant sensors from the perspectives of diverse supports, including graphene, carbon nanotubes, silica, semiconductors, metal sulfides, and polymers. Finally, this work overviews the modern improvements in the utilization of Ru-based nanocomposites on the basis for electroanalytical sensors as well as suggestions for the field's future development.

The Chemistry and Applications of Metal-Organic Frameworks (MOFs) as Industrial Enzyme Immobilization Systems

Enzymatic biocatalysis is a sustainable technology. Enzymes are versatile and highly efficient biocatalysts, and have been widely employed due to their biodegradable nature. However, because the three-dimensional structure of these enzymes is predominantly maintained by weaker non-covalent interactions, external conditions, such as temperature and pH variations, as well as the presence of chemical compounds, can modify or even neutralize their biological activity. The enablement of this category of processes is the result of the several advances in the areas of molecular biology and biotechnology achieved over the past two decades. In this scenario, metal–organic frameworks (MOFs) are highlighted as efficient supports for enzyme immobilization. They can be used to ‘house’ a specific enzyme, providing it with protection from environmental influences. This review discusses MOFs as structures; emphasizes their synthesis strategies, properties, and applications; explores the existing methods of using immobilization processes of various enzymes; and lists their possible chemical modifications and combinations with other compounds to formulate the ideal supports for a given application.

Research Progress of UiO-66-Based Electrochemical Biosensors

UiO-66, as a member of the MOFs families, is widely employed in sensing, drug release, separation, and adsorption due to its large specific surface area, uniform pore size, easy functionalization, and excellent stability. Especially in electrochemical biosensors, UiO-66 has demonstrated excellent adsorption capacity and response signal, which significantly improves the sensitivity and specificity of detection. However, the existing application research remains in its infancy, lacking systematic methods, and recycling utilization and exclusive sensing of UiO-66 still require further improvement. Therefore, one of the present research objectives is to explore the breakthrough point of existing technologies and optimize the performance of UiO-66-based electrochemical biosensors (UiO-66-EBs). In this work, we summarized current experimental methods and detection mechanisms of UiO-66-EBs in environmental detection, food safety, and disease diagnosis, analyzed the existing problems, and proposed some suggestions to provide new ideas for future research.

Fully integrated flexible biosensor for wearable continuous glucose monitoring

Continuous physiological monitoring is a promising alternative to current chronic disease management for obtaining big data sets to help individualized therapy. Here, we present a continuous glucose monitoring platform consisting of a screen-printed electrochemical biosensor and a fully integrated wireless electrochemical analysis system. A biocompatible conjugated polymer (poly (N-phenylglycine)) was employed as the support material for enzyme immobilization. Specifically, a polyurethane outer layer was decorated onto the working electrode of the biosensor to construct a diffusion limiting membrane and improve the linear range of the glucose sensor. We optimized the fabricated glucose sensor so that it achieves a linear range of 1-30 mM and a sensitivity of 12.69 μA mM^-1·cm^-2 in vitro. The long-term stability is up to 30 days by storing in PBS solution at 4°C. The overall system design was very small (0.8 × 1.8 cm) and consisted of a signal conditioning part, a programmable electrochemical chip, and a wireless connection using Bluetooth Low Energy with a smartphone. Finally, we carried out biocompatibility tests and animal experiments to demonstrate the device can successfully monitor blood glucose in vivo.

Sensitive Electrochemical Detection of Bioactive Molecules (Hydrogen Peroxide, Glucose, Dopamine) with Perovskites-Based Sensors

Perovskite-modified electrodes have received increasing attention in the last decade, due to their electrocatalytic properties to undergo the sensitive and selective detection of bioactive molecules, such as hydrogen peroxide, glucose, and dopamine. In this review paper, different types of perovskites involved for their electrocatalytic properties are described, and the proposed mechanism of detection is presented. The analytical performances obtained for different electroactive molecules are listed and compared with those in terms of the type of perovskite used, its nanostructuration, and its association with other conductive nanomaterials. The analytical performance obtained with perovskites is shown to be better than those of Ni and Co oxide-based electrochemical sensors. Main trends and future challenges for enlarging and improving the use of perovskite-based electrochemical sensors are then discussed.