Magnetic field-assisted surface engineering technology for active regulation of Fe3O4 medium to enable the laccase electrochemical biosensing of catechol with visible stripe patterns

BACKGROUND

Catechol (CC), a prevalent phenolic compound, is a byproduct in various agricultural, chemical, and industrial processes. CC detection is crucial for safeguarding water quality and plays a pivotal role in enhancing the overall quality of life of individuals. Electrochemical biosensors exhibit rapid responses, have small sizes, and can be used for real-time monitoring. Therefore, the development of a fast and sensitive electrochemical biosensor for CC detection is crucial.

RESULT

In this study, a laccase-based electrochemical biosensor for detection of CC is successfully developed using Fe3O4 nanoparticles as medium and optimized by applying a magnetic field. This research proposes a unique strategy for biosensor enhancement by actively controlling the distribution of magnetic materials on the electrode surface through the application of a magnetic field, resulting in a visibly alternating stripe pattern. This approach effectively disperses magnetic particles, preventing their aggregation and reducing the boundary layer thickness, enhancing the electrochemical response of the biosensor. After fabrication condition optimization, CC is successfully detected using this biosensor. The fabricated sensor exhibits excellent performance with a wide linear detection range of 10-1000 μM, a low detection limit of 1.25 μM, and a sensitivity of 7.9 μA/mM. The fabricated sensor exhibits good selectivity and reliable detection in real water samples. In addition, the laccase-based sensor has the potential for the fast and accurate monitoring of CC in olive oil.

SIGNIFICANCE

The magnetic field optimization in this study significantly improved the performance of the electrochemical biosensor for detecting CC in environmental samples. Overall, the sensor developed in this study has the potential for fast and accurate monitoring of CC in environmental samples, highlighting the potential importance of a magnetic field environment in improving the performance of catechol electrochemical biosensors.

Fast, Multiple-Use Optical Biosensor for Point-of-Care Glucose Detection with Mobile Devices Based on Bienzyme Cascade Supported on Polyamide 6 Microparticles

Non-invasive glucose determination provides major advantages in health monitoring and protection. It enables widespread point-of-care testing, which is affordable, sensitive, specific, rapid and equipment-free. This work reports on the development and analytical performance of a colorimetric biosensor in detecting glucose in human urine. Highly porous polyamide microparticles were synthesized as the support for the glucose oxidase (GOx) and horseradish peroxidase (HRP) dyad, which was immobilized randomly or consecutively-first HRP and then GOx. The latter system was superior, as GH@PA-C showed much higher activity than the random system, and it was used to prepare the biosensor, along with the 3,3',5,5'-tetramethylbenzidine chromogen. When in contact with urine, the biosensor displayed a strict linear correlation between the color difference and the glucose concentration in urine in the range of 0.01-3.0 mM, as established by the CIELab image processing algorithm and UV-VIS measurements. The biosensor acted in 20 s and had a detection limit of 30.7 µM in urine, high operational activity at pH = 4-8 and unchanged detection performance after 30 days of storage. Its unique feature is the possibility of multiple consecutive uses without the serious deterioration of the recovery and dispersion values. These characteristics can open the way for new routines in non-invasive personal diabetes detection.

Polymer/Enzyme Composite Materials—Versatile Catalysts with Multiple Applications

A significant interest was granted lately to enzymes, which are versatile catalysts characterized by natural origin, with high specificity and selectivity for particular substrates. Additionally, some enzymes are involved in the production of high-valuable products, such as antibiotics, while others are known for their ability to transform emerging contaminates, such as dyes and pesticides, to simpler molecules with a lower environmental impact. Nevertheless, the use of enzymes in industrial applications is limited by their reduced stability in extreme conditions and by their difficult recovery and reusability. Rationally, enzyme immobilization on organic or inorganic matrices proved to be one of the most successful innovative approaches to increase the stability of enzymatic catalysts. By the immobilization of enzymes on support materials, composite biocatalysts are obtained that pose an improved stability, preserving the enzymatic activity and some of the support material’s properties. Of high interest are the polymer/enzyme composites, which are obtained by the chemical or physical attachment of enzymes on polymer matrices. This review highlights some of the latest findings in the field of polymer/enzyme composites, classified according to the morphology of the resulting materials, following their most important applications.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Advanced Optical Sensing of Phenolic Compounds for Environmental Applications

Phenolic compounds are particularly dangerous due to their ability to remain in the environment for a long period of time and their toxic effects. They enter in the environment in different ways, such as waste from paper manufacturing, agriculture (pesticides, insecticides, herbicides), pharmaceuticals, the petrochemical industry, and coal processing. Conventional methods for phenolic compounds detection present some disadvantages, such as cumbersome sample preparation, complex and time-consuming procedures, and need of expensive equipment. Therefore, there is a very large interest in developing sensors and new sensing schemes for fast and easy-to-use methods for detecting and monitoring the phenolic compound concentration in the environment, with special attention to water. Good analytical properties, reliability, and adaptability are required for the developed sensors. The present paper aims at revising the most generally used optical methods for designing and fabricating biosensors and sensors for phenolic compounds. Some selected examples of the most interesting applications of these techniques are also proposed.

Magnetically Responsive PA6 Microparticles with Immobilized Laccase Show High Catalytic Efficiency in the Enzymatic Treatment of Catechol

Herewith we report the first attempt towards non-covalent immobilization of Trametes versicolor laccase on neat and magnetically responsive highly porous polyamide 6 (PA6) microparticles and their application for catechol oxidation. Four polyamide supports, namely neat PA6 and such carrying Fe, phosphate-coated Fe and Fe3O4 cores were synthesized in suspension by activated anionic ring-opening polymerization (AAROP) of ε-caprolactam (ECL). Enzyme adsorption efficiency up to 92% was achieved in the immobilization process. All empty supports and PA6 laccase complexes were characterized by spectral and synchrotron WAXS/SAXS analyses. The activity of the immobilized laccase was evaluated using 2,2’-Azino-bis-(3- ethylbenzothiazoline-6-sulfonic acid (ABTS) and compared to the native enzyme. The PA6 laccase conjugates displayed up to 105% relative activity at room temperature, pH 4, 40 °C and 20 mM ionic strength (citrate buffer). The kinetic parameters of the ABTS oxidation were also determined. The reusability of the immobilized laccase-conjugates was proven for five consecutive oxidation cycles of catechol.