Carbon-encapsulated iron nanoparticles as ferromagnetic matrix for oxygen reduction in absence and presence of immobilized laccase

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.

Carbon-Encapsulated Iron Nanoparticles as a Magnetic Modifier of Bioanode and Biocathode in a Biofuel Cell and Biobattery

This work demonstrates the application of magnetic carbon-encapsulated iron nanoparticles (CEINs) for the construction of bioelectrodes in a biobattery and a biofuel cell. It has been shown that carbon-encapsulated iron nanoparticles are a suitable material for the immobilization of laccase (Lc) and 1,4-naphthoquinone (NQ) and fructose dehydrogenase (FDH). The system is stable; no leaching of the enzyme and mediator from the surface of the modified electrode was observed. The onset of the catalytic reduction of oxygen to water was at 0.55 V, and catalytic fructose oxidation started at −0.15 V. A biobattery was developed in which a zinc plate served as the anode, and the cathode was a glassy carbon electrode modified with carbon-encapsulated iron nanoparticles, laccase in the Nafion (Nf) layer. The maximum power of the cell was ca. 7 mW/cm2 at 0.71 V and under external resistance of 1 kΩ. The open-circuit voltage (OCV) for this system was 1.51 V. In the biofuel cell, magnetic nanoparticles were used both on the bioanode and biocathode to immobilize the enzymes. The glassy carbon bioanode was coated with carbon-encapsulated iron nanoparticles, 1,4-naphthoquinone, fructose dehydrogenase, and Nafion. The cathode was modified with carbon-encapsulated magnetic nanoparticles and laccase in the Nafion layer. The biofuel cell parameters were as follows: maximum power of 78 µW/cm2 at the voltage of 0.33 V and under 20 kΩ resistance, and the open-circuit voltage was 0.49 V. These enzymes worked effectively in the biofuel cell, and laccase also effectively worked in the biobattery.

Conformational control of human transferrin covalently anchored to carbon-coated iron nanoparticles in presence of a magnetic field

The control of the interactions of proteins with the support matrix plays a key role in medicine, drug delivery systems and diagnostics. Herein, we report that covalent anchoring of human transferrin to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field results in its conformational integrity and electroactivity. We have found that, the direct contact of human transferrin with Fe@C-COOH Nps does not lead to release of iron and in consequence to the irreversible conformational changes of the protein. Moreover, the examination of the direct electron transfer between Tf molecules from the conjugate and the electrode surface was possible. The quartz crystal microbalance with dissipation (QCM-D)- and thermogravimetric data (TGA) showed that under such conditions, in addition to a monolayer, an adlayer of the protein can be formed on Fe@C-COOH Nps at constant pH.

STATEMENT OF SIGNIFICANCE

To our best knowledge this is the first paper that reports on covalent anchoring of human transferrin (Tf) to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field, which results in its conformational integrity and electroactivity. We showed that it is possible to attach, without changing pH, more than one single layer of transferrin to the Fe@C-COOH Nps. This is a very rare phenomenon in the case of proteins. We proved, using various experimental techniques, that the proposed methodology does not lead to release of iron from Tf molecules, what was the major problem so far. We believe that this finding opens new possibilities in targeting drug delivery systems and medical diagnostics.