Monitoring of Specific Phytoestrogens by Dedicated Electrochemical Sensors: A Review

Phytoestrogens are non-steroidal estrogens produced from plants that can bind with the human body's estrogenic receptor site and be used as a substitute for maintaining hormonal balance. They are mainly classified as flavonoids, phenolic acids, lignans, stilbenes, and coumestans; some are resocyclic acids of lactones, which are mycotoxins and not natural phytoestrogen. Phytoestrogens have many beneficial medicinal properties, making them an important part of the daily diet. Electrochemical sensors are widely used analytical tools for analysing various pharmaceuticals, chemicals, pollutants and food items. Electrochemical sensors provide an extensive platform for highly sensitive and rapid analysis. Several reviews have been published on the importance of the biological and medicinal properties of phytoestrogens. However, this review provides an overview of recent work performed through electrochemical measurements with electrochemical sensors and biosensors for all the classes of phytoestrogens done so far since 2019.

Fabrication of high-resolution, flexible, laser-induced graphene sensors via stencil masking

The advent of wearable sensing platforms capable of continuously monitoring physiological parameters indicative of health status have resulted in a paradigm shift for clinical medicine. The accessibility and adaptability of such portable, unobtrusive devices enables proactive, personalized care based on real-time physiological insights. While wearable sensing platforms exhibit powerful capabilities for continuously monitoring physiological parameters, device fabrication often requires specialized facilities and technical expertise, restricting deployment opportunities and innovation potential. The recent emergence of rapid prototyping approaches to sensor fabrication, such as laser-induced graphene (LIG), provides a pathway for circumventing these barriers through low-cost, scalable fabrication. However, inherent limitations in laser processing restrict the spatial resolution of LIG-based flexible electronic devices to the minimum laser spot size. For a CO2 laser-a commonly reported laser for device production-this corresponds to a feature size of ∼120 μm. Here, we demonstrate a facile, low-cost stencil-masking technique to reduce the minimum resolvable feature size of a LIG-based device from 120 ± 20 μm to 45 ± 3 μm when fabricated by CO2 laser. Characterization of device performance reveals this stencil-masked LIG (s-LIG) method yields a concomitant improvement in electrical properties, which we hypothesize is the result of changes in macrostructure of the patterned LIG. We showcase the performance of this fabrication method via production of common sensors including temperature and multi-electrode electrochemical sensors. We fabricate fine-line microarray electrodes not typically achievable via native CO2 laser processing, demonstrating the potential of the expanded design capabilities. Comparing microarray sensors made with and without the stencil to traditional macro LIG electrodes reveals the s-LIG sensors have significantly reduced capacitance for similar electroactive surface areas. Beyond improving sensor performance, the increased resolution enabled by this metal stencil technique expands capabilities for scalable fabrication of high-performance wearable sensors in low-resource settings without reliance on traditional fabrication pathways.

PD-L1 DNA aptamers isolated from agarose-bead SELEX

Increased expression and activity of the PD-L1/PD-1 pathway suppresses the activation of cytotoxic T cells, which is vital in anti-tumour defence, allowing tumours to rise, expand and progress. Current strategies using antibodies to target PD-1/PD-L1 have been very effective in cancer therapeutics and companion diagnostics. Aptamers are a new class of molecules that offer an alternative to antibodies. Herein, the systematic evolution of ligands by exponential enrichment (SELEX) using agarose slurry beads was conducted to isolate DNA aptamers specific to recombinant human PD-L1 (rhPD-L1). Isolated aptamers were sequenced and analysed using MEGA X and structural features were examined using mFold. Three aptamer candidates (P33, P32, and P12) were selected for evaluation of binding affinity (dissociation constant, Kd) using ELONA and specificity and competitive inhibition assessment using the potentiostat-electrochemical method. Among those three, P32 displayed the highest specificity (8 nM) against PD-L1. However, P32 competes for the same binding site with the control antibody, 28-8. This study warrants further assessment of P32 aptamer as a potential, cost-effective alternative tool for targeting PD-L1.

A disposable electrochemical magnetic immunosensor for the rapid and sensitive detection of 5-formylcytosine and 5-carboxylcytosine in DNA

5-formylcytosine (5 fC) and 5-carboxylcytosine (5caC) serve as key intermediates in DNA demethylation process with significant implications for gene regulation and disease progression. In this study, we introduce a novel electrochemical sensing platform specifically designed for the sensitive and selective detection of 5 fC and 5caC in DNA. Protein A-modified magnetic beads (ProtA-MBs) coupled with specific antibodies facilitate the immunorecognition and enrichment of these modified bases. Signal amplification is achieved through several chemical reactions involving the interaction between N3-kethonaxl and guanine, copper-free click chemistry for the attachment of dibenzocyclooctyne (DBCO)-Biotin, and the subsequent recognition by streptavidin-conjugated horseradish peroxidase (SA-HRP). The assay's readout is performed on a disposable laser-induced graphene (LIG) electrode, modified with the bead-antibody-DNA complex in a magnetic field, and analyzed using differential pulse voltammetry in a system employing hydroquinone (HQ) as the redox mediator and H2O2 as the substrate. This immunosensor displayed excellent sensitivity, with detection limits of 14.8 fM for 5 fC across a 0.1-1000 pM linear range and 87.4 fM for 5caC across a 0.5-5000 pM linear range, and maintained high selectivity even in the presence of interferences from other DNA modifications. Successful application in quantifying 5 fC and 5caC in genomic DNA from cell extracts, with recovery rates between 97.7% to 102.9%, underscores its potential for clinical diagnostics. N3-kethoxal was used for the first time in an electrochemical sensor. This work not only broadens the toolkit for detecting DNA modifications but also provides a fresh impetus for the development of point-of-care testing (POCT) technologies.

Dual-mode detection of α-fetoprotein using the photothermal effect and peroxidase-like activity of Au@Cu/Cu2O-rGO

α-Fetoprotein (AFP) is widely recognized as an important marker for monitoring hepatocellular carcinoma (HCC), and its monitoring using two different transduction mechanisms is an effective way to avoid the risk of false positives or false negatives. In this paper, Au@Cu/Cu2O-rGO was used as a photothermal converter as well as an actuator to promote the decomposition of hydrogen peroxide (H2O2), which was further designed as a probe for dual-mode detection to quantitatively assess AFP. The composite nanomaterials possessed photothermal conversion efficiencies (η) of up to 54.9 % and catalytically generated signals up to 1.6 times greater, relative to a single material. Based on the generated temperature and current signals, AFP has been sensitively detected in the range of 0.01-100 ng/mL, with limits of detection (LOD) of 5.62 pg/mL and 1.23 pg/mL, respectively. The dual-mode assay combines portability with high accuracy for the detection of human health systems.

Reviewing neonicotinoid detection with electroanalytical methods

Neonicotinoids, as the fastest-growing class of insecticides, currently account for over 25% of the global pesticide market. Their effectiveness in controlling a wide range of pests that pose a threat to croplands, home yards/gardens, and golf course greens cannot be denied. However, the extensive use of neonicotinoids has resulted in significant declines in nontarget organisms such as pollinators, insects, and birds. Furthermore, the potential chronic, sublethal effects of these compounds on human health remain largely unknown. To address these pressing issues, it is crucial to explore and understand the capabilities of electrochemical sensors in detecting neonicotinoid residues. Surprisingly, despite the increasing importance of this topic, no comprehensive review article currently exists in the literature. Therefore, our proposed review aims to bridge this gap by providing a thorough analysis of the use of electrochemical methods for neonicotinoid determination. In this review article, we will delve into various aspects of electrochemical analysis, including the influence of electrode materials, employed techniques, and the different types of electrode mechanisms utilized. By synthesizing and analysing the existing research in this field, our review will offer valuable insights and guidance to researchers, scientists, and policymakers alike.

Chitosan lecithin nanocomposite based electrochemical biosensor for glycine detection in biological matrices

Increased glycine concentrations are associated with altered metabolism of cancer cells and is reflected in the bodily fluids of the brain cancer patients. Various studies have been conducted in past to detect glycine as an imaging biomarker via NMR Spectroscopy tools. However, the use is limited because of the low concentration and different in vivo detection due to overlapping of peaks with myo-inositol in same spectral position. Alongside, little is known about the electrochemical potential of Glycine as a biomarker for brain cancer. The prime impetus of this study was to check the feasibility of glycine as non-invasive biomarker for brain cancer. A divergent approach to detect glycine "non-enzymatically" via unique chitosan lecithin nanocomposite has been utilised during this study. The electrochemical inactivity at provided potential that prevented glycine to get oxidized or reduced without mediator was compensated utilising the chitosan-lecithin nanocomposite. Thus, a redox mediator (Prussian blue) was used for high sensitivity and indirect detection of glycine. The chitosan nanoparticles-lecithin nanocomposite is used as a matrix. The electrochemical analysis of the onco-metabolomic biomarker (glycine) utilizing cyclic voltammetry in glycine spiked multi-Purpose artificial urine was performed to check distribution of glycine over physiological range of glycine. A wide linear range of response varying over the physiological range from 7 to 240 μM with a LOD 8.5 μM was obtained, showing potential of detection in biological samples. We have further evaluated our results via simulating the interaction of mediator and matrix with Glycine by HOMO-LUMO band fluctuations.

A portable magnetic electrochemical sensor for highly efficient Pb(II) detection based on bimetal composites from Fe-on-Co-MOF

The practical, sensitive, and real-time detection of heavy metal ions is an essential and difficult problem. This study presents the design of a unique magnetic electrochemical detection system that can achieve real-time field detection. To enhance the electrochemical performance of the sensor, Fe2O3@C-800, Co/CoO@/C-600, and CoFe2O4@C-600 magnetic composites were synthesized using three MOFs precursors by the solvothermal method. And the morphology structure and electrochemical properties of as-prepared magnetic composites were researched by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), specific surface area and porosity analyzer (BET) and differential pulse voltammetry (DPV). The results shown that these composites improve conductivity and stability while preserving the MOFs basic frame structure. Compared with the monometallic MOFs-derived composites, the synergistic effect of the bimetallic composite CoFe2O4@C-600 can significantly enhance the electrochemical performance of the sensor. The linear range for the detection of lead ions was 0.001-60 μM, and the detection limit was 0.0043 μM with a sensitivity of 22.22 μA μM·cm-2 by differential pulse voltammetry. The sensor has good selectivity, stability, reproducibility and can be used for actual sample testing.

Self-validating photothermal and electrochemical dual-mode sensing based on Hg2+ etching Ti3C2 MXene

Mercury ions can cause serious damage to the ecological environment, and it is necessary to develop reliable and elegant mercury ion sensors. In this protocol, a label-free photothermal/electrochemical dual-mode strategy for Hg2+ is proposed based on delaminated Ti3C2 MXene nanosheets (DL-Ti3C2 MXene). Hg2+ exists in water in the form of HgCl2, Hg(OH)2, and HgClOH, and the electron-rich elements O and Cl can specifically bind to the positively charged DL-Ti3C2 MXene at the edge, and further oxidation-reduction reaction occurs to obtain TiO2/C and Hg2Cl2. In view of the reduction activity and the performance of photothermal conversion of DL-Ti3C2 MXene itself, the electrochemical and photothermal responses decrease with the increase of the logarithm of Hg2+ concentration. The corresponding linear ranges are 50 pmol L-1-500 nmol L-1 and 1 nmol L-1-50 μmol L-1, and their detection limits calculated at 3 S/N are 17.2 pmol L-1 and 0.43 nmol L-1, respectively. DL-Ti3C2 MXene has the characteristics of a wide range of raw materials, low cost, and easy preparation. In addition, the design takes full advantage of the properties of the material itself, avoids the complex assembly and detection process of conventional sensors, and enables high selectivity and sensitivity for mercury detection. In particular, the dual-mode sensing endows self-confirmation of mercury ion detection results, thereby improving the reliability of the sensor.

Efficient DNA walker guided by ordered cruciform-shaped DNA track for ultrasensitive and rapid electrochemical detection of lead ion

The rational design of DNA tracks is an effective pathway to guide the autonomous movement and high-efficiency recognition in DNA walkers, showing outstanding advantages for the cascade signal amplification of electrochemical biosensors. However, the uncontrolled distance between two adjacent tracks on the electrode could increase the risk of derailment and interruption of the reaction. Hence, a novel four-way balanced cruciform-shaped DNA track (C-DNT) was designed as a structured pathway to improve the effectiveness and stability of the reaction in DNA walkers. In this work, two kinds of cruciform-shaped DNA were interconnected as a robust structure that could avoid the invalid movement of the designed DNA walker on the electrode. When hairpin H2 was introduced onto the electrode, the strand displacement reaction (SDR) effectively triggered movements of the DNA walker along the cruciform-shaped track while leaving ferrocene (Fc) on the electrode, leading to a significant enhancement of the electrochemical signal. This design enabled the walker to move in an excellent organized and controllable manner, thus enhancing the reaction speed and walking efficiency. Compared to other walkers moving on random tracks, the reaction time of the C-DNT-based DNA walker could be reduced to 20 min. Lead ion (Pb2+) was used as a model target to evaluate the analytical performance of this biosensor, which exhibited a low detection limit of 0.033 pM along with a wide detection ranging from 0.1 pM to 500 nM. This strategy presented a novel concept for designing a high-performance DNA walker-based sensing platform for the detection of contaminants.

Surface adsorption and corrosion resistance performance of modified chitosan: Gravimetric, electrochemical, and computational studies

Two novel chitosan derivatives (water soluble and acid soluble) modified with thiocarbohydrazide were produced by a quick and easy technique using formaldehyde as links. The novel compounds were synthesized and then characterized by thermogravimetric analysis, elemental analysis, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Their surface morphologies were examined using scanning electron microscopy. These chitosan derivatives could produce pH-dependent gels. The behavior of mild steel in 5 % acetic acid, including both inhibitors at various concentrations, was investigated using gravimetric and electrochemical experiments. According to the early findings, both compounds (TCFACN and TCFWCN) functioned as mixed-type metal corrosion inhibitors. Both inhibitors showed their best corrosion inhibition efficiency at 80 mg L-1. TCFACN and TCFWCN, showed approximately 92 % and 94 % corrosion inhibition, respectively, at an optimal concentration of 80 mg L-1, according to electrochemical analysis. In the corrosion test, the water contact angle of the polished MS sample at 87.90 °C was reduced to 51 °C. The water contact angles for MS inhibited by TCFACN and TCFWCN in the same electrolyte were greater, measuring 78.10 °C and 93.10 °C, respectively. The theoretical results also support the experimental findings.

Water-soluble chitosan salt as ecofriendly corrosion inhibitor for N80 pipeline steel in artificial sea water: Experimental and theoretical approach

Chitosan, as a proficient biopolymer, has enormous potential as an ecofriendly corrosion inhibitor (CI), but their limited solubility restricts practical applications. Herein, an eco-friendly and water-soluble chitosan salt (CS) was utilized as a green CI on N80 pipeline steel in artificial sea water. Several structural and surface analytical tools were engaged in describing the characteristics of novel CS polymer. The corrosion inhibition efficiencies of CS on steel at different concentrations were investigated through gravimetric, conventional and advanced electrochemical techniques along with the surface analyses. Tafel polarization tests specified that CS performed as mixed-type CI with prevalent anodic inhibition characteristics. At a concentration of 1000 ppm, CS provided an inhibition efficiency (IE) of 96.68 %, following physiochemical adsorptions of CS on N80 surface validated by fitting Langmuir adsorption isotherm. However, the reductions in the values of IE at high temperature specified that the CS is the temperature dependent CIs. Scanning electrochemical microscopic evaluation confirmed the formation of thin CS inhibitors films with high electrochemical stability on N80 steel in saline. The performed surface characterizations on inhibited surfaces validated the adsorption of CS on the N80 surface by forming thin inhibitor film to obstruct metal corrosion. The theoretical simulation studies using molecular dynamics and density functional theory corroborated the experimentally obtained results.

The comparative study by Raman spectroscopy of the plastic tide in the three ports of the Mediterranean Sea

This paper summarizes the field studies on marine microplastics (MPs) carried out in the autumn season in four various localisations within three ports chosen at the Mediterranean Sea near the French Riviera and the West Coast of Italy (within the Ligurian Sea). It considers the transport problem and the fate of the MPs introduced to the sea by analysing beach debris found on the shore after the stormy weather. Monitored ports included Saint-Tropez, Portoferraio and Porto Ercole, in which two different places were monitored. The aim is to approach the plastic tide phenomena by concentrating on a selected fraction of all MPs presented on the seashore. The final identification of debris was performed using Raman spectroscopy, providing a high-resolution signal. The PE, PP and PS contents were compared as the most frequent and representative polymers. Finally, we tackle the pending issue of the compound leakage from the MPs taking the environmentally aged particles from Portoferraio for further laboratory experiments and discuss an innovative approach with a low detection limit based on the electrochemical methods.

Development of an electrochemical biosensor utilizing a combined aptamer and MIP strategy for the detection of the food allergen lysozyme

This study aims to develop a MIP-Apt-based electrochemical biosensor for the sensitive and selective determination of Lysozyme (Lyz), a food allergen. For the development of the sensor, in the first stage, modifications were made to the screen-printed electrode (SPE) surface with graphene oxide (GO) and gold nanoparticles (AuNPs) to increase conductivity and surface area. The advantages of using aptamer (Apt) and molecularly imprinted polymer (MIP) technology were combined in a single biointerface in the prepared sensing tool. Surface characterization of the biosensor was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), contact angle measurements, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). A wide linear range from 0.001 to 100 pM was obtained under optimized conditions for the determination of Lyz detection using the proposed MIP-Apt sensing strategy. The limit of detection (LOD) and limit of quantification (LOQ) for Lyz were 3.67 fM and 12 fM, respectively. This biosensor displays high selectivity, repeatability, reproducibility, and long storage stability towards Lyz detection. The results show that a sensitive and selective sensor fabrication is achieved compared with existing methods.

Revealing the solid-solution interface interference behaviors between Cu2+ and As(III) via partial peak area analysis of simulations and experiments

The mutual interference in the sensing detection of heavy metal ions (HMIs) is considerably serious and complex. Besides, the co-existed ions may change the stripping peak intensity, shape and position of the target ion, which partly makes peak current analysis inaccurate. Herein, a promising approach of partial peak area analysis was proposed firstly to research the mutual interference. The interference between two species on their electrodeposition processes was investigated by simulating different kinetics parameters, including surface coverage, electro-adsorption, -desorption rate constant, etc. It was proved that the partial peak area is sensitive and regular to these interference kinetics parameters, which is favorable for distinctly identifying different interferences. Moreover, the applicability of the partial peak area analysis was verified on the experiments of Cu2+, As(III) interference at four sensing interfaces: glassy carbon electrode, gold electrode, Co3O4, and Fe2O3 nanoparticles modified electrodes. The interference behaviors between Cu2+ and As(III) relying on solid-solution interfaces were revealed and confirmed by physicochemical characterizations and kinetics simulations. This work proposes a new descriptor (partial peak area) to recognize the interference mechanism and provides a meaningful guidance for accurate detection of HMIs in actual water environment.

Graphene/metal-organic framework nano-sandwiches derived N, P-codoped porous carbon nanosheets as robust material for electrochemical analysis

Construction of novel two-dimensional porous carbon nanosheets with superior electrochemical activity is of great challenge. Here, graphene/ZIF-8 nano-sandwiches derived N, P-codoped porous carbon nanosheets (N, P-codoped PCN) was easily obtained by sequential room temperature self-assembly and high-temperature carbonization method. Relative to the widely used physically exfoliated graphene nanosheets (GN) and graphene/ZIF-8 derived N-doped porous carbon nanosheets (N-doped PCN), N, P-codoped PCN displayed larger active surface, faster electron transport ability and stronger physical adsorption ability, which can be ascribed to the dual doping effect of heteroatoms N and P. As a result, N, P-codoped PCN exhibited remarkable oxidation signal enhancement for tumor marker (8-hydroxy-2'-deoxyguanosine), analgesic and antipyretic drug (acetaminophen) and organic pesticide (benomyl). Besides, the limits of detection were measured as low as 1.58 nM, 7.50 nM and 2.10 nM with sensitivity of 270.00 μA μM-1 cm-2, 757.14 μA μM-1 cm-2 and 272.86 μA μM-1 cm-2 for 8-hydroxy-2'-deoxyguanosine, acetaminophen and benomyl, respectively. Basing on this, a novel and highly sensitive electrochemical sensing platform was developed. It is believed that the reported two-dimensional N, P-codoped PCN with unique structure and composition is highly valuable for the development of carbon-based electrochemical sensors.

TiO2-guanine as a new amalgamation compound for fabrication of a disposable biosensor with high sensitivity and rapid detection of H1N1 swine flu virus

A TiO2-guanine nanocomposite (TG NC)-based electrochemical biosensor was immobilized with hemagglutinin (HA) gene specific probe with 5' NH2 group on screen-printed gold electrode (probe(ss)DNA-TG-SPGE). The modified biosensor was examined for H1N1 swine flu virus. TG NCs along with precursors were characterized spectroscopically and morphologically by employing several approaches. Electrochemical investigations were performed with the help of cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer saline (PBS; pH 7.4) with 1 µM methylene blue (MB) redox indicator. For better detection of single-stranded virus DNA, the modified electrode was optimized at various concentrations, pH, and scan rates. The modified biosensor showed high sensitivity (40.32 μA/ng.cm2), low LOD (0.00024 ng/6 µL), and broad linear range 0.0002-20 ng/6µL with coefficient of determination of R2=0.9981 for H1N1 virus detection. The HA gene-modified biosensor presented decent stability and specificity against different infectious pathogens including H3N2 virus and human DNA with negative response. Furthermore, the modified biosensor also responded well for real sample target DNA detection with a recovery of >96%. The simply designed HA gene-modified biosensor transduces decreased current response towards target-specific (ss)DNA binding and could be used as a rapid detection tool for H1N1 swine flu virus diagnosis.

Tailoring diamondised nanocarbon-loaded poly(lactic acid) composites for highly electroactive surfaces: extrusion and characterisation of filaments for improved 3D-printed surfaces

A new 3D-printable composite has been developed dedicated to electroanalytical applications. Two types of diamondised nanocarbons - detonation nanodiamonds (DNDs) and boron-doped carbon nanowalls (BCNWs) - were added as fillers in poly(lactic acid) (PLA)-based composites to extrude 3D filaments. Carbon black served as a primary filler to reach high composite conductivity at low diamondised nanocarbon concentrations (0.01 to 0.2 S/cm, depending on the type and amount of filler). The aim was to thoroughly describe and understand the interactions between the composite components and how they affect the rheological, mechanical and thermal properties, and electrochemical characteristics of filaments and material extrusion printouts. The electrocatalytic properties of composite-based electrodes, fabricated with a simple 3D pen, were evaluated using multiple electrochemical techniques (cyclic and differential pulse voltammetry and electrochemical impedance spectroscopy). The results showed that the addition of 5 wt% of any of the diamond-rich nanocarbons fillers significantly enhanced the redox process kinetics, leading to lower redox activation overpotentials compared with carbon black-loaded PLA. The detection of dopamine was successfully achieved through fabricated composite electrodes, exhibiting lower limits of detection (0.12 μM for DND and 0.18 μM for BCNW) compared with the reference CB-PLA electrodes (0.48 μM). The thermogravimetric results demonstrated that both DND and BCNW powders can accelerate thermal degradation. The presence of diamondised nanocarbons, regardless of their type, resulted in a decrease in the decomposition temperature of the composite. The study provides insight into the interactions between composite components and their impact on the electrochemical properties of 3D-printed surfaces, suggesting electroanalytic potential.

Evaluating the inhibitory activity of ferrocenyl Schiff bases derivatives on 5-lipoxygenase: Computational and biological studies

In the search for new 5-LOX inhibitors, two ferrocenyl Schiff base complexes functionalized with catechol ((ƞ5-(E)-C5H4-NCH-3,4-benzodiol)Fe(ƞ5-C5H5) (3a)) and vanillin ((ƞ5-(E)-C5H4-NCH-3-methoxy-4-phenol)Fe(ƞ5-C5H5) (3b)) were obtained. Complexes 3a and 3b were biologically evaluated as 5-LOX inhibitors showed potent inhibition compared to their organic analogs (2a and 2b) and known commercial inhibitors, with IC50 = 0.17 ± 0.05 μM for (3a) and 0.73 ± 0.06 μM for (3b) demonstrated a highly inhibitory and potent effect against 5-LOX due to the incorporation of the ferrocenyl fragment. Molecular dynamic studies showed a preferential orientation of the ferrocenyl fragment toward the non-heme iron of 5-LOX, which, together with electrochemical and in-vitro studies, allowed us to propose a competitive redox deactivation mechanism mediated by water, where Fe(III)-enzyme can be reduced by the ferrocenyl fragment. An Epa/IC50 relationship was observed, and the stability of the Schiff bases was evaluated by SWV in the biological medium, observing that the hydrolysis does not affect the high potency of the complexes, making them interesting alternatives for pharmacological applications.

A low-fouling electrochemical biosensor for biomarker detection in serum based on designed α/β-peptides with anti-enzymolysis and antifouling capabilities

The zwitterionic peptides, especially those composed of glutamic (E) and lysine (K) groups have drawn enormous attention as antifouling biomaterials owing to their strong hydration capability and biocompatibility. However, the susceptibility of α-amino acid K to the proteolytic enzymes in human serum limited the broad application of such peptides in biological media. Herein, a new multifunctional peptide with favorable stability in human serum was designed, and it was composed of three sections with immobilizing, recognizing and antifouling capabilities, respectively. The antifouling section was composed of alternating E and K amino acids, but the enzymolysis-susceptive amino acid α-K was replaced by the unnatural β-K. Compared with the conventional peptide composed of all α-amino acids, the α/β-peptide exhibited significantly enhanced stability and longer antifouling performance in human serum and blood. The electrochemical biosensor based on the α/β-peptide showed a favorable sensitivity to its target IgG, with a quite wide linear range from 100 pg mL^-1 to 10 μg mL^-1 and a low detection limit (33.7 pg mL^-1, S/N = 3), and it was promising for the detection of IgG in complex human serum. The tactic of designing antifouling α/β-peptides offered an efficient way to develop low-fouling biosensors with robust operation in complex body fluids.

Lanthanum nickelate spheres embedded acid functionalized carbon nanofiber composite: An efficient electrocatalyst for electrochemical detection of food additive vanillin

Contemporary food marketing is ruined by flavor enhancers rather than emphasizing the nutritional value of food. Vanillin is an overexploited flavor enhancer added to food items, thereby necessitating its detection. In this study, an electrochemical sensor was designed using a modified electrode made up of La₂NiO₄ functionalized carbon nanofiber (f-CNF) to effectively detect vanillin in food samples. To confirm the successful formation of La₂NiO₄/f-CNF, structural and morphological studies were performed using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Further electrochemical analysis was performed using cyclic voltammetry and differential pulse voltammetry techniques, which resulted in high sensitivity (0.2899 µA·μM^-1·cm^-2) and low limit of detection (LOD) (6 nM). This modified electrode material was tested in food samples, which showed an excellent response with recovery percentage and is a promising electrocatalyst for vanillin detection.

A Critical Review on Orthosilicate Li2MSiO4 (M= Fe, Mn) Electrode Materials for Li Ion Batteries

The development of novel electrode materials with good electrochemical performances is necessary for the expanded and varied applications of lithium-ion batteries, and this development heavily relies on cathode materials. Due to excellent thermal stability, abundance, low cost, and environmental friendliness, orthosilicate cathode materials Li2MSiO4 (M= Fe, Mn) has received a lot of attention recently. The present review article gives a glimpse into the characteristics, advantages, and recent progress of orthosilicate cathode materials. This review starts with a brief history and working mechanism of batteries, the advantages of cathode materials followed by types of cathode materials, various synthesis methods, and different techniques used for their characterization. The most current initiatives to enhance orthosilicate Li2MSiO4 type electrochemical performances were introduced in this review. We provide a critical assessment of the efficient modification techniques for the orthosilicate Li2MSiO4 type cathode materials in particular. These potential cathode materials' synthesis, structure, morphologies, and particularly electrochemical performances have been thoroughly examined. This evaluation, we hope, will clarify the sustained advancement of high-efficiency and reasonably priced Li-ion batteries&#xD.

Kappa-carrageenan for benign preparation of CdSeNPs enhancing the electrochemical measurement of AC symmetric supercapacitor device based on neutral aqueous electrolyte

This study presents the development of an electrochemical supercapacitor with a cadmium selenide nanoparticles (CdSeNPs) electrode utilizing a straightforward and economical method based on kappa-carrageenan (κ-CGN). The structural, morphological, and optical characteristics of CdSeNPs were assessed. Activated carbon (AC) and green-prepared CdSeNPs were easily mixed to achieve excellent electrochemical properties. The nanoelectrode (AC@CdSe) was tested in an aqueous electrolyte of sodium sulfate (Na₂SO₄) with a concentration of 1 Molar. Specific capacitance (Csp) for the AC electrode and the AC@CdSe electrode at 1 A g^-1 was calculated to be 103 and 480 F g^-1, respectively. Besides, the symmetric supercapacitor AC@CdSe/AC@CdSe device has a high specific energy of 52 Wh kg^-1 and a maximum specific power of 2880 W kg^-1, with a specific capacitance of 115.5 F g^-1. With a coulombic efficiency of between 82 % and 100 %, the device continues to maintain excellent capacitance after 10.000 cycles.

Highly-efficient peroxydisulfate activation by polyaniline-polypyrrole copolymers derived pyrolytic carbon for 2,4-dichlorophenol removal in water: Coupling mechanism of singlet oxygen and electron transfer

Carbonization of N-containing aromatic polymers is a promising route to prepare N-doped carbon materials with low cost, easy regulation, and no external N source. However, there are relatively few studies applying these materials for persulfate activation, and the catalytic mechanisms of the existing reaction systems are divergent. In this paper, a series of N-doped carbon materials were prepared by carbonizing polyaniline (PANI), polypyrrole (PPy), and PANI-PPy copolymers. The copolymer-derived carbon materials exhibit superior peroxydisulfate (PDS) catalytic activity compared to some commercially available and reported carbon materials. Combing quenching experiments, EPR analysis, chemical probe analysis, and various electrochemical analysis methods identified the singlet oxygen (¹O₂) and electron transfer as the main reaction pathways of all systems, but the contribution of each pathway was influenced by the types of precursors. The structure-activity relationship indicated that the carbonyl group (CO) was the main active site for the ¹O₂ pathway, while the electron transfer ability of the reaction system and the potential of the complex formed by catalyst and PDS jointly determined the electron transfer pathway. This paper provides a new strategy for obtaining excellent N-doped carbon-based persulfate activators and deepens the insight into the mechanism of PDS activation by N-doped carbon materials.

Electrochemical reactions of highly active nitroxyl radicals with thiol compounds

Nitroxyl radicals are known to electrochemically oxidize thiols as well as alcohols and amines. In this study, a preliminary investigation of the electrochemical reaction of thiols with 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO), 2-azaadamantane N-oxyl (AZADO), and nortropine N-oxyl (NNO), which are highly active due to their bicyclo structures, for use in electrochemical analysis was performed and the results were compared with those for a typical nitroxyl radical compound, 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO). Mercaptopropane sulfonic acid (MPS) was used as a model compound to investigate the electrochemical response in aqueous solution. In addition, electrochemical detection of glutathione, a biological thiol molecule, was performed.