Assessment of Salt Stress to Arabidopsis Based on the Detection of Hydrogen Peroxide Released by Leaves Using an Electrochemical Sensor

Salt stress will have a serious inhibitory effect on various metabolic processes of plant cells, this will lead to the excessive accumulation of reactive oxygen species (ROS). Hydrogen peroxide (H2O2) is a type of ROS that can severely damage plant cells in large amounts. Existing methods for assessing the content of H2O2 released from leaves under salt stress will cause irreversible damage to plant leaves and are unable to detect H2O2 production in real time. In this study, on the strength of a series of physiological indicators to verify the occurrence of salt stress, an electrochemical sensor for the detection of H2O2 released from leaves under salt stress was constructed. The sensor was prepared by using multi-walled carbon nanotube-titanium carbide-palladium (MWCNT-Ti3C2Tx-Pd) nanocomposite as substrate material and showed a linear response to H2O2 detection in the range 0.05-18 mM with a detection limit of 3.83 μM. Moreover, we measured the determination of H2O2 released from Arabidopsis leaves at different times of salt stress by the sensor, which was consistent with conventional method. This study demonstrates that electrochemical sensing is a desirable technology for the dynamic determination of H2O2 released by leaves and the assessment of salt stress to plants.

An Electrochemical Sensor Based on Chalcogenide Molybdenum Disulfide-Gold-Silver Nanocomposite for Detection of Hydrogen Peroxide Released by Cancer Cells

Hydrogen peroxide (H₂O₂) as a crucial signal molecule plays a vital part in the growth and development of various cells under normal physiological conditions. The development of H₂O₂ sensors has received great research interest because of the importance of H₂O₂ in biological systems and its practical applications in other fields. In this study, a H₂O₂ electrochemical sensor was constructed based on chalcogenide molybdenum disulfide-gold-silver nanocomposite (MoS₂-Au-Ag). Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) were utilized to characterize the nanocomposites, and the electrochemical performances of the obtained sensor were assessed by two electrochemical detection methods: cyclic voltammetry and chronoamperometry. The results showed that the MoS₂-Au-Ag-modified glassy carbon electrode (GCE) has higher sensitivity (405.24 µA mM^-1 cm^-2), wider linear detection range (0.05-20 mM) and satisfactory repeatability and stability. Moreover, the prepared sensor was able to detect the H₂O₂ discharge from living tumor cells. Therefore, this study offers a platform for the early diagnosis of cancer and other applications in the fields of biology and biomedicine.

Developing a Silk Fibroin Composite Film to Scavenge and Probe H2O2 Associated with UV-Excitable Blue Fluorescence

A silk fibroin composite film that can simultaneously scavenge and probe H₂O₂ in situ was developed for possibly examining local concentrations of H₂O₂ for biomedical applications. A multi-functional composite film (GDES) that consists of graphene oxide (G), a photothermally responsive element that was blended with polydopamine (PDA, D)/horseradish peroxidase (HRP, E) (or DE complex), and then GDE microaggregates were coated with silk fibroin (SF, S), a tyrosine-containing protein. At 37 °C, the H₂O₂-scavenging ability of a GDES film in solution at approximately 7.5 × 10^-3 μmol H₂O₂/mg film was the highest compared with those of S and GS films. The intensities of UV-excitable blue fluorescence of a GDES film linearly increased with increasing H₂O₂ concentrations from 4.0 μM to 80 μM at 37 °C. Interestingly, after a GDES film scavenged H₂O₂, the UV-excitable blue fluorescent film could be qualitatively monitored by eye, making the film an eye-probe H₂O₂ sensor. A GDES film enabled to heat H₂O₂-containing samples to 37 °C or higher by the absorption of near-IR irradiation at 808 nm. The good biocompatibility of a GDES film was examined according to the requirements of ISO-10993-5. Accordingly, a GDES film was developed herein to scavenge and eye-probe H₂O₂ in situ and so it has potential for biomedical applications.

A novel hydrogen peroxide sensor based on electrodeposited copper/cuprous oxide nanocomposites

Copper/cuprous oxide nanocomposites were electrodeposited on a fluorine doped tin oxide (FTO) glass substrate for sensitive determination of hydrogen peroxide.

In situ controllable synthesis of cotton-like polyaniline nanostructures for a H2O2 sensor using an embedded three-electrode microfluidic chip

Fabrication of a thickness controllable polyaniline film based on an embedded three-electrode microfluidic chip for application as a H₂O₂ sensor.

Enzymatic oligomerization and polymerization of arylamines: state of the art and perspectives

The literature concerning the oxidative oligomerization and polymerization of various arylamines, e.g., aniline, substituted anilines, aminonaphthalene and its derivatives, catalyzed by oxidoreductases, such as laccases and peroxidases, in aqueous, organic, and mixed aqueous organic monophasic or biphasic media, is reviewed. An overview of template-free as well as template-assisted enzymatic syntheses of oligomers and polymers of arylamines is given. Special attention is paid to mechanistic aspects of these biocatalytic processes. Because of the nontoxicity of oxidoreductases and their high catalytic efficiency, as well as high selectivity of enzymatic oligomerizations/polymerizations under mild conditions-using mainly water as a solvent and often resulting in minimal byproduct formation-enzymatic oligomerizations and polymerizations of arylamines are environmentally friendly and significantly contribute to a "green" chemistry of conducting and redox-active oligomers and polymers. Current and potential future applications of enzymatic polymerization processes and enzymatically synthesized oligo/polyarylamines are discussed.

Microperoxidase-11/metal–organic framework/macroporous carbon for detecting hydrogen peroxide

Schematic illustrating of the fabrication and sensing principle of the newly develpoed H₂O₂ biosensor.

A Facile One-Pot Synthesis of Au/Cu2O Nanocomposites for Nonenzymatic Detection of Hydrogen Peroxide

Au/Cu2O nanocomposites were successfully synthesized by a facile one-pot redox reaction without additional reducing agent under room temperature. The morphologies and structures of the as-prepared products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The electrocatalytic performance of Au/Cu2O nanocomposites towards hydrogen peroxide was evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). The prepared Au/Cu2O nanocomposite electrode showed a wide linear range from 25 to 11.2 mM (R = 0.9989) with a low detection limit of 1.05 μM (S/N = 3) and high sensitivity of 292.89 mA mM(-1) cm(-2). The enhanced performance for H2O2 detection can be attributed to the introduction of Au and the synergistic effect between Au and Cu2O. It is demonstrated that the Au/Cu2O nanocomposites material could be a promising candidate for H2O2 detection.

Manganese porphyrin-double stranded DNA complex guided in situ deposition of polyaniline for electrochemical thrombin detection

In this work, we proposed a novel electrochemical strategy for sensitive detection of thrombin (TB) based on in situ generation of polyaniline (PANI) as a redox mediator by using a manganese porphyrin-double stranded DNA (MnTMPyP-dsDNA) peroxidase-like artificial enzyme mimic as a powerful catalyst and template.

Fabrication of water-dispersible and highly conductive PSS-doped PANI/graphene nanocomposites using a high-molecular weight PSS dopant and their application in H2S detection

This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 10(6) was synthesized using low-temperature free-radical polymerization. The PSS was used as both a doping agent and a binding agent for the polymerization of aniline monomers in a biphasic system (water-chloroform) at -50 °C. The high Mw of PSS resulted in relatively large particle sizes and smooth surfaces of the PSS-doped PANI. These physical characteristics, in turn, resulted in low interparticle resistance and high conductivity. In addition, the PSS allowed homogeneous dispersion of reduced graphene sheets through electrostatic repulsion. The prepared PSS-doped PANI/graphene solutions showed good compatibility with flexible poly(ethylene terephthalate) (PET) substrates, making them suitable for flexible sensor electrodes. Changes in the charge-transport properties, such as protonation level, conjugation length, crystalline structure, and charge-transfer resistance, of the electrode materials were the main factors influencing the electrical and sensor performance of the PSS-doped PANI-based electrodes. PSS-doped PANI/graphene composites containing 30 wt% graphene showed the highest conductivity (168.4 S cm(-1)) and the lowest minimum detection level (MDL) for H2S gas (1 ppm). This result is consistent with the observed improvements in charge transport in the electrode materials via strong π-π stacking interactions between the PANI and the graphene sheets.

Biosensor based on tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode for detection of epinephrine

A biosensor comprising tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode has been developed. The sensitive element, ie, tyrosinase, was immobilized using a drop-and-dry method followed by cross-linking. Tyrosinase maintained high bioactivity on this nanomaterial, catalyzing the oxidation of epinephrine to epinephrine-quinone, which was electrochemically reduced (−0.07 V versus Ag/AgCl) on the biosensor surface. Under optimum conditions, the biosensor showed a linear response in the range of 10–110 μM. The limit of detection was calculated to be 2.54 μM with a correlation coefficient of 0.977. The repeatability, expressed as the relative standard deviation for five consecutive determinations of 10⁻⁵ M epinephrine solution was 3.4%. A good correlation was obtained between results obtained by the biosensor and those obtained by ultraviolet spectrophotometric methods.

Magnetic silver hybrid nanoparticles for surface-enhanced resonance Raman spectroscopic detection and decontamination of small toxic molecules

Magnetic hybrid assemblies of Ag and Fe3O4 nanoparticles with biocompatibly immobilized myoglobin (Mb) were designed to detect and capture toxic targets (NO2-, CN-, and H2O2). Mb was covalently attached to chitosan-coated magnetic silver hybrid nanoparticles (M-Ag-C) via glutaraldehyde that serves as a linker for the amine groups of Mb and chitosan. As verified by surface-enhanced resonance Raman (SERR) spectroscopy, this immobilization strategy preserves the native structure of the bound Mb as well as the binding affinity for small molecules. On the basis of characteristic spectral markers, binding of NO2-, CN-, and H2O2 could be monitored and quantified, demonstrating the high sensitivity of this approach with detection limits of 1 nM for nitrite, 0.2 μM for cyanide, and 10 nM for H2O2. Owing to the magnetic properties, these particles were collected by an external magnet to achieve an efficient decontamination of the solutions as demonstrated by SERR spectroscopy. Thus, the present approach combines the highly sensitive analytical potential of SERR spectroscopy with an easy approach for decontamination of aqueous solutions with potential applications in food and in environmental and medical safety control.

Prospects of Organic Conducting Polymer Modified Electrodes: Enzymosensors

Organic conducting polymer modified electrodes (OCPMEs) have emerged as potential candidates for electrochemical biosensors due to their easy preparation methods along with unique properties, like stability in air and being compatible with biological molecules in a neutral aqueous solution. OCPMEs are playing an important role in the improvement of public health and environment for the detection of desired analytes with high sensitivity and specificity. In this paper, we highlight the prospects of OCMEs-based electrochemical enzymosensors.