Glucose oxidase and polyacrylic acid based water swellable enzyme-polymer conjugates for promoting glucose detection

Mussel-inspired Self-assembly into Polymer Coatings of Different Molecular Weight Electrolytes for Enhanced Self-healing and Corrosion Properties

Self-healing coatings offer tremendous application prospects in the field of preventing metal corrosion because of their superior functionality. The coordination of barrier performance and self-healing ability, however, continues to be difficult. Herein, a polymer coating based on polyethyleneimine (PEI) and polyacrylic acid (PAA) with self-repairing and barrier ability was designed. Introducing the catechol group into the anti-corrosion coating increases the adhesion and self-healing efficiency of the coating, providing a guarantee for the long-term stable bonding between the anti-corrosion coating and the metal substrate. Small molecular weight PAA polymers are added to polymer coatings to increase their self-healing capabilities and corrosion resistance. Because layer-by-layer assembly creates reversible hydrogen bonds and electrostatic bonds that help the coating repair itself when it is damaged, and because the traction of small molecular weight polyacrylic acid speeds up this process. When polyacrylic acid (PAA) with a molecular weight of 2000 was present in the coating at a concentration of 1.5 mg/mL, the coating's self-healing capability and corrosion resistance were at their peak. The PEI-C/PAA45W -PAA2000 coating completed the self-healing within 10 min, and the corrosion resistance efficiency (Pe ) was as high as 90.1 %. The polarization resistance (Rp ) was maintained at 7.67×104  Ω cm2 after immersion for more than 240 h. It was better than other samples in this work. The polymer provides a new idea for the prevention of metal corrosion.

Electrospun nanofiber-based glucose sensors for glucose detection

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.

The response regularity of biohydrogen production by anthracite H2-producing bacteria consortium to six conventional veterinary antibiotics

The impact of antibiotics on H₂-producing bacteria must be considered in the industrialization of biological H₂ production using livestock manure as raw resources. However, whether antibiotics that may be contained in excreta will threaten the safety of biohydrogen production needs to be researched. This study explored the impact characteristics and mechanism of six single antibiotics and three groups of compound antibiotics on H₂ production. Experiments confirmed that most antibiotics have different degrees of H₂ production inhibition, while some antibiotics, which like Penicillin G, Streptomycin Sulfate, and their compound antibiotics, could promote the growth of Ethanoligenens sp. and improve H₂ yield on the contrary. Comprehensive analysis shows that the main inhibitory mechanisms were: (1) board-spectrum inhibition, (2) partial inhibition, (3) H₂ consumption enhancement; and the enhancement mechanisms were: (1) enhance the growth of H₂-producing bacteria, (2) enhanced starch hydrolysis, (3) inhibitory H₂ consumption or release of acid inhibition. Meanwhile, experiment found that the effect of antibiotics on H₂ producing was not only related to type, but also to dosage. Even one kind of antibiotic may have completely opposite effects on H₂-producing bacteria under different dosage conditions. Inhibition of H₂ yield was highest with Levofloxacin at 6.15 mg/L, gas production was reduced by 88.77%; and enhancement of H₂ yield was highest with Penicillin G at 7.20 mg/L, the gas production increased by 72.90%. In the selection of raw material, the type and content of antibiotics demand a detailed investigation and analysis to ensure that the sustainability of H₂ yield.

Cheap and Sustainable Biosensor Fabrication by Enzyme Immobilization in Commercial Polyacrylic Acid/Carbon Nanotube Films

Novel glucose biosensors were constructed by loading glucose oxidase (GOx) into the nanopores of homogenous carbon nanotube (CNT) films on the surface of Pt disk electrodes and trapping the enzyme by subsequent deposition of polyacrylic acid (PAA), forming PAA/GOx-CNT-modified Pt disks. In amperometric biosensing with anodic hydrogen peroxide (H₂O₂) detection at a potential of +600 mV, increasing electrolyte glucose concentrations produced instantaneous steps in the H₂O₂ oxidation current. Glucose biosensor amperometry was feasible down to 10 μM, with a sensitivity of about 34 μA mM^-1 cm^-2 and linear current response up to 5 mM. The biosensors reliably determined glucose concentrations in human serum and a beverage. Successful trials with PAA/GOx-CNT-modified screen-printed Pt electrode disks demonstrated the potential of this means of enzyme fixation in biosensor mass fabrication, which offers a unique combination of cheap availability of the two matrix constituents and sensor layer formation through simple drop-and-dry steps. PAA/GOx-CNT/Pt biosensors are green and user-friendly bioanalytical tools that do not need large budgets, special skills, or laboratory amenities for their production. Any user, from industrial, university, or school laboratories, even if inexperienced in biosensor construction, can prepare functional biosensors with GOx, as in these proof-of-principle studies, or with other redox enzymes, for clinical, environmental, pharmaceutical, or food sample analysis.

Microfluidic fabrication of tunable alginate-based microfibers for the stable immobilization of enzymes

Immobilized enzymes have drawn extensive attention due to their enhanced stability, easy separation from reaction mixture, and prominent recyclability. Nevertheless, it is still an ongoing challenge to develop potent immobilization techniques which are capable of stable enzyme encapsulation, minimal loss of activity, and modulability for various enzymes and applications. Here, microfibers with tunable size and composition were fabricated using a home-made microfluidic device. These microfibers were able to efficiently encapsulate bovine serum albumin (BSA), glucose oxidase (GOx), and horseradish peroxidase (HRP). But the physically adsorbed enzymes readily diffused into the catalytic reaction system. The leakage of enzymes could be substantially inhibited by conjugating to polyacrylic acid (PAA) and incorporating into alginate-based microfibers, enabling stable immobilization, improved recyclability, and enhanced thermostability. In addition, GOx and HRP-loaded microfibers were fabricated under the optimized conditions for the visual detection of glucose using the cascade reaction of these enzymes, showing sensitive color change to glucose with concentration range of 0-2 mM. Due to the tunability and versatility, this microfluidic-based microfiber platform may provide a valuable approach to the enzyme immobilization for the cascade catalysis and diagnoses with multiple clinical markers. This article is protected by copyright. All rights reserved.

Weaving Enzymes with Polymeric Shells for Biomedical Applications

Enzyme therapeutics have received increasing attention due to their high biological specificity, outstanding catalytic efficiency, and impressive therapeutic outcomes. Protecting and delivering enzymes into target cells while retaining enzyme catalytic efficiency is a big challenge. Wrapping of enzymes with rational designed polymer shells, rather than trapping them into large nanoparticles such as liposomes, have been widely explored because they can protect the folded state of the enzyme and make post-functionalization easier. In this review, the methods for wrapping up enzymes with protective polymer shells are mainly focused on. It is aimed to provide a toolbox for the rational design of polymeric enzymes by introducing methods for the preparation of polymeric enzymes including physical adsorption and chemical conjugation with specific examples of these conjugates/hybrid applications. Finally, a conclusion is drawn and key points are emphasized.

New Biocatalyst Including a 4-Nitrobenzoic Acid Mediator Embedded by the Cross-Linking of Chitosan and Genipin and Its Use in an Energy Device

A new anodic catalyst consisting of carbon nanotube, 4-nitrobenzoic acid, chitosan, genipin, and glucose oxidase (GOx) (CNT/4-NBA/[Chit/GOx/GP]) is suggested to promote the glucose oxidation reaction (GOR) and the performance of enzymatic biofuel cell (EBC). In this catalyst, through the cross-linked structure of chitosan and genipin and the proper distribution of amine groups within chitosan, many GOx molecules are maximally captured, their leaching out is suppressed, and the GOR is improved upon. In addition, 4-nitrobenzoic acid plays the role of mediator well. The effect induced by the cross-linked structure is evaluated by ultraviolet-visible (UV-vis) spectroscopy, pH measurements, and electrochemical characterizations. According to the characterizations, the new CNT/4-NBA/[Chit/GOx/GP] catalyst contains a large amount of GOx (17.8 mg/mL) and produces a high anodic current (331 μA/cm² at 0.3 V vs Ag/AgCl) with a low onset potential (0.05 V vs Ag/AgCl) because its catalytic activity follows the desirable reaction pathway that minimizes creation of a protonated amine group that interferes with GOR. When the performance of EBC using this catalyst as an anodic electrode is measured, the EBC shows a high open-circuit voltage of 0.54 V and a maximum power density of 38 μW/cm².

Multicomponent bionanocomposites based on clay nanoarchitectures for electrochemical devices

Based on the unique ability of defibrillated sepiolite (SEP) to form stable and homogeneous colloidal dispersions of diverse types of nanoparticles in aqueous media under ultrasonication, multicomponent conductive nanoarchitectured materials integrating halloysite nanotubes (HNTs), graphene nanoplatelets (GNPs) and chitosan (CHI) have been developed. The resulting nanohybrid suspensions could be easily formed into films or foams, where each individual component plays a critical role in the biocomposite: HNTs act as nanocontainers for bioactive species, GNPs provide electrical conductivity (enhanced by doping with MWCNTs) and, the CHI polymer matrix introduces mechanical and membrane properties that are of key significance for the development of electrochemical devices. The resulting characteristics allow for a possible application of these active elements as integrated multicomponent materials for advanced electrochemical devices such as biosensors and enzymatic biofuel cells. This strategy can be regarded as an "a la carte" menu, where the selection of the nanocomponents exhibiting different properties will determine a functional set of predetermined utility with SEP maintaining stable colloidal dispersions of different nanoparticles and polymers in water.

Hydrodynamic Layer-by-Layer Assembly of Transferable Enzymatic Conductive Nanonetworks for Enzyme-Sticker-Based Contact Printing of Electrochemical Biosensors

Realizing high-performance electrochemical biosensors in a simple contact-printing-based approach significantly increases the applicability of integrated flexible biosensors. Herein, an enzyme-sticker-based approach that enables flexible and multielectrochemical sensors via simple contact-transfer printing is reported. The enzyme sticker consists of an enzymatic conductive network film and a polymeric support. The enzyme-incorporated nanostructured conductive network showing an efficient electrical coupling was assembled via the hydrodynamic layer-by-layer assembly of redox enzymes, polyelectrolytes, single-walled carbon nanotubes, and a biological glue material, M13 phage. The enzymatic conductive network on a polymeric membrane support was facilely wet contact-transfer printed onto integrated electrode systems by exploiting varying degrees of hydrophilicity displayed by the enzymatic electronic film, polymeric support, and receiving electrodes of the sensor system. The glucose sensors fabricated using the enzyme sticker detected glucose at a concentration of as low as 35 μM and showed high selectivity and stability. Furthermore, a flexible dual-sensor array capable of detecting both glucose and lactate was demonstrated using the versatile enzyme sticker concept. This work presents a new route toward assembling and integrating hybrid nanomaterials with efficient electrochemical coupling for high-performance biosensors and health-monitoring devices as well as for emerging bioelectronics and electrochemical devices.