Surface Of Modified Electrode Research Articles

The Conversion of Li2SnO3 Li-Ion Hybrid Supercapacitors from Pastes Containing LiCl-SnCl2 Liquid Precursors Using an Atmospheric-Pressure Plasma Jet

We fabricate lithium tin-based oxide Li2SnO3 on carbon cloth from a gel-state precursor containing LiCl and SnCl2·2H2O using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ treatment provides both a high-temperature environment for the conversion of precursor into Li2SnO3 and nitrogen plasma reactive species for electrode surface modification. Here, the best electrochemical performance for the Li2SnO3 Li-ion hybrid supercapacitors (Li–HSCs) is achieved with 480 s of APPJ processing. The areal capacity of the 480 s APPJ-processed Li2SnO3 Li–HSCs reached 46.113 mC/cm2. The results indicate that APPJ is an effective tool for the rapid conversion processing of Li2SnO3 electrodes for Li–HSCs.

Development of morphologically tunable cobalt-zeolitic framework with copper nanowires: A bifunctional catalyst for the analysis of nitrobenzene and ortho-nitrobenzaldehyde in environmental effluents

Hazardous nitroaromatic compounds are a top-priority environmental pollutant and extremely harmful to human health and ecological systems. Hence, selective and ultra-sensitive quantitative analysis of nitroaromatic target detection is highly important nowadays. In this report, we designed and successfully developed the morphologically tunable hybrid composite nature of the cobalt-zeolitic framework (CZ) with copper nanowires (CNW). The morphological structure was highly controlled by switching different weight ratios of CNW into the CZ. Morphological and spectral analysis revealed the developed system is composite with mesoporous properties. Followed by, the designed catalyst was applied to catalytic reduction and electrochemical simultaneous with sensitive sensing of nitrobenzene (NB) and ortho-nitrobenzaldehyde (ONBA). The optimized modified electrode surface exhibited first-rate catalytic activity, the ultra-sensitive limit of detection of 5.3 nM and 2.6 nM (S/N = 3) with a linear response range of 20 nM – 1 mM and 10 nM – 1.5 mM for ONBA and NB. The selectivity of the system is evaluated in the presence of twelve potentially interfering analytes (including phenols, metal ions, and biomolecules). As an added benefit, the CNWCZ/GCE was used to quantify the detection targets in real industrial water samples, with high-rate recoveries of 96.60–99.68±0.05%, and the electrochemical result was validated by standard analytical method. Furthermore, the catalytic degradation of NB and ONBA was tested and achieved more than 91.63±1.13% degradation within 10 and 15 minutes for NB and ONBA, and facile kinetic rate reactions. The developed research findings suggest that catalysts can be used to dual-analyze NB and its derivatives.

Electrochemical and quantum chemical approaches to the study of dopamine sensing using bentonite and l-cysteine modified carbon paste electrode

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 μM with a limit of detection and quantification of 0.5 μM and 1.5 μM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA–DA, DA–UA, and AA–UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations.

Gold nanosheet modified electrode with reduced impedance for electrophysiological recordings

In neurophysiological recording, reducing electrode impedance is crucial for enhancing the signal-to-noise ratio and achieving the desired spatial resolution. This study presents an approach to improve the performance of Au/Cr/glass electrodes by incorporating synthesized gold nanosheets without the need for additional adhesive material. We characterized the performance of the modified electrodes using electrochemical impedance spectroscopy and equivalent circuit analysis. Our findings showed an 81% reduction in mean impedance for the modified electrode, which was 0.85 kΩ at 1 kHz, compared to the unmodified electrode at 4.5 kΩ, an improvement attributed to the higher effective surface area of the modified electrode. Additionally, Scanning electron microscopy observations of PC12 cells cultured on the modified electrodes indicated favorable cell elongation and interaction with the rough surface. Stability studies indicated acceptable performance of the modified electrodes in solution environments. These results suggest that surface modification of electrodes with gold nanosheets could be a promising strategy for enhancing neural interface applications.

Functionalization of Carbon Electrode Surface Using Polyaniline and Gold Nanoparticles for Protein Immobilization

This study presents a screen-printed carbon electrode surface functionalization to immobilize proteins. The process involves the deposition of gold nanoparticles on the carbon electrode and subsequent surface modification to immobilize bovine serum albumin–fluorescein isothiocyanate conjugate (BSA-FITC). A combination of conducting polymer and gold nanoparticles was employed to enhance the electrode contact area and current transmission. The electrode surface morphology and properties were evaluated by scanning electron microscopy (SEM) and Raman spectroscopy, showing the porous polyaniline (PANI) film has been formed on the carbon electrode surface with the network of dendritic nanofibers. Gold nanoparticles were evenly distributed on the PANI film to form a nanocomposite material layer on the carbon electrode. The observed size of these gold nanoparticles was significantly smaller than those on the electrode without a PANI film. Additionally, the current transmission of this composite material layer has been verified by cyclic voltammetry (CV). The results show that the amplitude of the redox peak was doubled compared to the bare carbon electrode and gold nanoparticle-only deposited electrode. Moreover, the success of the process was verified by fluorescence and cyclic voltammetry. The fluorescent green color observed under the microscope indicated that BSA-FITC was on the electrode surface. The change of CV signal after each step verified the formation of a new layer on the electrode surface. These results are anticipated to play an important role in developing high-sensitivity immunosensors in the future.

Porous cobalt phosphide nanoflakes supported on ordered mesoporous carbon for superior electrochemical performance supercapacitor and hydrogen evolution reaction

In this study, we synthesized cobalt phosphate flake-like nanostructures anchored to the OMC matrix using a simple and cost-effective hydrothermal process followed by an environmentally friendly phosphidation process. The physicochemical characterization of the CoP@OMC composite indicated that the porous CoP nanoflakes made up of bundles of ultrathin nanosheets with an approximate thickness of 30nm are anchored on rod-like hexagonal OMC with a diameter of 110-140nm, allowing remarkable enhancement of mesoporosity and active surface area. The CoP@OMC composite was employed as a new material for modification of electrode surface used in supercapacitor and hydrogen evolution reaction (HER). Interestingly, CoP@OMC acquired a specific capacitance of 3182 Fg-1 at current density of 1Ag-1, in 6M KOH. Asymmetrical CoP@OMC//CB cell showed a capacity of 194 Fg-1 at the current density of 1Ag-1 with a maximum energy density of 77.9Whkg-1 and a power density of 17kWkg-1. CoP@OMC composite also showed an excellent HER performance with only 111mV overpotential to drive a current density of 10mAcm−2 and a low Tafel slope of 43.8mV dec−1 in 1M KOH. Therefore, CoP(OMC) as an environmentally friendly material with high efficiency and significant catalytic / electronic properties is expected to be a good candidate for future energy storage & conversion systems.

An Optimized MnO2-Ag Nanocomposite-Based Sensing Platform for Determination of 4-nitrophenol in Tomato Samples: Influences of Morphological Aspect of MnO2 Nanostructures and Synergic Effect on Electrochemical Kinetic Parameters and Analytical Performance

Abstract We have introduced potential modifiers synthesized from attached Ag nanoparticles (NPs) on MnO2 nanostructural surfaces, and fabricated an electrochemical sensor toward 4-nitrophenol (4-NP) detection. MnO2 with various morphologies (nanowires, nanorods, and nanosheets) has been prepared by hydrothermal and microwave-assisted hydrothermal methods, while AgNPs have been prepared by the simple electrochemical method. The structural characteristics and surface morphologies have been investigated via X-ray diffraction and scanning electron microscopy measurements. The effect of the change in morphology on the electrochemical behaviors and sensing performance has been investigated and discussed in detail. A parameter series involving the redox reaction of [Fe(CN)6]3-/4- and 4-NP reduction process has been calculated for each as-prepared modified electrode. Electrochemical results evidenced that benefiting from possessing outstanding electrochemical behaviors such as better conductivity, faster electron transfer ability, larger electroactive surface area, and higher charge transfer kinetics, MnO2 sheets-Ag/SPE has offered wider linear concentration range of 0.5-50 μM, LOD value as low as 0.073 µM, and high selectivity/repeatability. Furthermore, the optimization in the morphological aspect of MnO2 nanosheets and synergic effects arising from the effective combination with AgNPs make it become a model material for modifying electrode surfaces, indicating great potential for advanced electrochemical sensing applications.

Facile Synthesis of Fe-Doped, Algae Residue-Derived Carbon Aerogels for Electrochemical Dopamine Biosensors.

An abnormal level of dopamine (DA), a kind of neurotransmitter, correlates with a series of diseases, including Parkinson's disease, Willis-Ekbom disease, attention deficit hyperactivity disorder, and schizophrenia. Hence, it is imperative to achieve a precise, rapid detection method in clinical medicine. In this study, we synthesized nanocomposite carbon aerogels (CAs) doped with iron and iron carbide, based on algae residue-derived biomass materials, using Fe(NO3)3 as the iron source. The modified glassy carbon electrode (GCE) for DA detection, denoted as CAs-Fe/GCE, was prepared through surface modification with this composite material. X-ray photoelectron spectroscopy and X-ray diffraction characterization confirmed the successful doping of iron into the as-prepared CAs. Additionally, the electrochemical behavior of DA on the modified electrode surface was investigated and the results demonstrate that the addition of the CAs-Fe promoted the electron transfer rate, thereby enhancing their sensing performance. The fabricated electrochemical DA biosensor exhibits an accurate detection of DA in the concentration within the range of 0.01~200 µM, with a detection limit of 0.0033 µM. Furthermore, the proposed biosensor is validated in real samples, showing its high applicability for the detection of DA in beverages.

An electrochemiluminescent magneto-immunosensor for ultrasensitive detection of hs-cTnI on a microfluidic chip

Sensitive detection and precise quantitation of trace-level crucial biomarkers in a complex sample matrix has become an important area of research. For example, the detection of high-sensitivity cardiac troponin I (hs-cTnI) is strongly recommended in clinical guidelines for early diagnosis of acute myocardial infarction. Based on the use of an electrode modified by single-walled carbon nanotubes (SWCNTs) and a Ru(bpy)32+-doped silica nanoparticle (Ru@SiO2)/tripropylamine (TPA) system, a novel type of electrochemiluminescent (ECL) magneto-immunosensor is developed for ultrasensitive detection of hs-cTnI. In this approach, a large amount of [Ru(bpy)3]2+ is loaded in SiO2 (silica nanoparticles) as luminophores with high luminescent efficiency and SWCNTs as electrode surface modification material with excellent electrooxidation ability for TPA. Subsequently, a hierarchical micropillar array of microstructures is fabricated with a magnet placed at each end to efficiently confine a single layer of immunomagnetic microbeads on the surface of the electrode and enable 7.5-fold signal enhancement. In particular, the use of transparent SWCNTs to modify a transparent ITO electrode provides a two-order-of-magnitude ECL signal amplification. A good linear calibration curve is developed for hs-cTnI concentrations over a wide range from 10 fg/ml to 10 ng/ml, with the limit of detection calculated as 8.720 fg/ml (S/N = 3). This ultrasensitive immunosensor exhibits superior detection performance with remarkable stability, reproducibility, and selectivity. Satisfactory recoveries are obtained in the detection of hs-cTnI in human serum, providing a potential analysis protocol for clinical applications.

Dopamine modified electrodes for indirect voltammetric determination of magnesium ions

This article outlines the fabrication process of an electrochemical sensor designed for the innovative determination of magnesium ions based on the electrochemistry of dopamine. The sensor operates under voltammetric conditions, accounting for variations in the electrochemical reversibility of immobilized dopamine in the presence of magnesium ions under conditions of square-wave voltammetry. The immobilization of dopamine on the glassy carbon electrode is achieved through the electrochemical oxidation of its side amino group, leading to covalent grafting onto the electrode surface. All stages of the proposed electrode surface modification procedure were carefully optimized. The dopamine sensor exhibited a linear response in the concentration range of magnesium ions from 0.1 to 10 mmol L−1, with a limit of detection (LOD) value equal to 1.3 × 10−5 mol L−1. To validate the electroanalytical significance of the developed methodology, real food supplement samples were quantitatively analyzed, demonstrating a highly satisfactory rate of recovery. The proposed voltammetric method serves as a simple and cost-effective procedure for the indirect determination of magnesium ions. Additionally, this approach allows for the analysis of real samples without the need for time-consuming preparation steps, as the complex matrices of food supplement samples did not adversely affect the registered currents.

Designing and evaluation of a novel electrochemical biosensor based on carbon quantum dots and gold core-shell to detect and measure Human T-lymphotropic Virus-1 (HTLV-1) in clinical samples

The objective of this investigation is to introduce an innovative electrochemical biosensor that can swiftly detect HTLV-1 DNA targets without the need for nucleic acid amplification. The biosensor is equipped with a highly precise antisense DNA oligonucleotide. Additionally, we introduce a new core–shell material, CQDs@AuNPs, for the surface modification of glassy carbon electrodes. L-Cysteine is utilized as a conductive bridge to enhance the binding capabilities, electron transfer efficiency, and conductivity. The biosensor incorporates methylene blue (MB) as an electrochemical indicator with differential pulse voltammetry (DPV) technique, facilitating swift detection within a mere 20 min. Furthermore, it has been able to attain a detection limit of 0.7 aM and quantitation limit of 6 copies/µL with an impressive linear range spanning from 10 aM to 100 nM that displays a positive slope along with exhibiting a remarkably high correlation coefficient measuring at approximately 0.99.We tested the biosensor using 40 HTLV-1 DNA real clinical samples, comprising 30 positive and 10 negative samples, as determined by standard RT-PCR. The biosensor demonstrated a specificity of 96.67% and an exceptional sensitivity of 100%. Rigorous quantitative analysis and statistical techniques, including t-tests, cutoff value determination, receiver operating characteristic curves, and box diagrams, clearly differentiated between the positive and negative groups. These findings underscore the potential of our innovative biosensor as a rapid, precise, and cost-effective tool for early detection of HTLV-1, which holds promise for efficient management and control of the virus.

Electrodeposited Silver Dendrites on Laser‐Induced Graphene for Electrochemical Detection of Nitrate with Tunable Sensor Properties

AbstractLaser‐induced graphene (LIG) is a promising technology enabling cost‐effective, scalable, and high surface area 3D‐porous graphene electrodes for electrochemical applications. Nitrate in water bodies is a harmful contaminant to humans and the ecosystems. Its detection by electrochemical sensors is challenging due to the interference from nitrite. Herein, for the first time, a LIG‐based electrochemical sensor modified with electrodeposited silver dendrites (EdAg/LIG) without using surfactants is proposed for the detection of nitrate with tunable selectivity and sensitivity. The modified electrode surface is extensively characterized by spectroscopic and electrochemical methods and the underlying mechanism for the formation of dendrites is substantiated. The developed EdAg dendrites/LIG electrode shows excellent sensing properties for the detection of nitrate at pH 2. The interference with nitrite in acidic media is eliminated by implementing a novel strategy to shift the working pH of the electrode to 7. The achieved sensor properties at both pH values surpass other LIG‐based sensors with limit of detection of 0.46 at pH 2 and 5.53 µm at pH 7. The developed sensor also shows good recovery characteristics in mineral, tap, and groundwater across a wide range of concentrations and also demonstrates good stability under temperature fluctuations and deformations.

A Surfactant-Electropolymer modified dual sensor for the monitoring of norepinephrine at nanomolar levels in biological samples and pharmaceutical formulations

This paper focuses on the surface modification of a Glassy carbon electrode (GCE) using poly-terephthalic acid and poly-4-amino-3-hydroxy-1-naphthalenesulfonic acid (poly-(TERE-AHNSA)/GCE) by simultaneous electropolymerization of respective monomers for the first time from the best of our knowledge, which is a simple and cost-effective method. FTIR, AFM, and SEM-EDX examinations were used to confirm the developed electrode. The adapted electrode is then used for the monitoring and determination of clinically significant norepinephrine (NE) using electroanalytical techniques such as differential pulse and cyclic voltammetry. The electrooxidation of NE on poly-(TERE-AHNSA)/GCE occurred at a potential of +0.216 V in phosphate buffer solution (PB) of pH 6.0 and showed a higher current response compared to electrodes developed with separate electropolymers. This enhanced response is likely due to the synergistic effect of both polymer layers obtained through electropolymerization, which increases the surface area. The developed sensor exhibits favorable characteristics, including a lowest detection limit (LOD) of 2.08 nM, a linear range spanning from 5.0 nM to 1600.0 μM which is the widest range ever reported, as well as improved sensitivity and selectivity, surpassing previous reports. The linearity analysis was also performed utilizing a screen-printed electrode (SPE), yielding linear ranges of 100.0 nM–600.0 μM. With a recovery rate ranging from 98 to 105%, the developed sensor shows great potential as a reliable tool for electroanalysis of NE in blood, urine, and pharmaceutical samples.

Metal-Based Nanomaterials for the Sensing of NSAIDS.

Cadmium sulfide and zinc oxide nanoparticles were prepared, characterized and used as electrode modifiers for the sensing of two non-steroidal anti-inflammatory drugs (NSAIDs): naproxen and mobic. The structural and morphological characterization of the synthesized nanoparticles was carried out by XRD, UV-Vis spectroscopy, FTIR and scanning electron microscopy. The electrode's enhanced surface area facilitated the signal amplification of the selected NSAIDs. The CdS-modified glassy carbon electrode (GCE) enhanced the electro-oxidation signals of naproxen to four times that of the bare GCE, while the ZnO-modified GCE led to a two-fold enhancement in the electro-oxidation signals of mobic. The oxidation of both NSAIDs occurred in a pH-dependent manner, suggesting the involvement of protons in their electron transfer reactions. The experimental conditions for the sensing of naproxen and mobic were optimized and, under optimized conditions, the modified electrode surface demonstrated the qualities of sensitivity and selectivity, and a fast responsiveness to the target NSAIDs.

Anthraquinone/activated carbon electrochemical sensor and its application in acetaminophen analysis.

Acetaminophen (AC) can inhibit the synthesis of prostaglandins in the body, and has antipyretic and analgesic effects. In this paper, a two-step microwave impregnation method was used to prepare anthraquinone (AQ)-doped carbon composite, which were applied to the surface modification of glassy carbon electrodes (GCE) for the determination of acetaminophen (AC) using differential pulse voltammetry (DPV). The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and Fourier infrared spectroscopy (FT-IR). The results showed that anthraquinone was successfully modified on the surface of activated carbon. The peak current of AC increased with its concentration in the range of 0.1μM to 700μM (R2 = 0.998) and a detection limit of 0.05μM was obtained with 20%AQ doped carbon electrochemical sensor (20%AQ-C/GCE). Electrochemical Impedance Spectroscopy (EIS) test results indicated that the charge transfer resistance (Rct) of 20%AQ-C/GCE is only the one-fourth of that of bare GCE. The proposed 20%AQ-C/GCE sensor has good stability, reproducibility and selectivity for the detection of AC. The sensor is also suitable for the detection of real samples, indicating its good practicality.

Surface Modification of Screen-Printed Carbon Electrode through Oxygen Plasma to Enhance Biosensor Sensitivity.

The screen-printed carbon electrode (SPCE) is a useful technology that has been widely used in the practical application of biosensors oriented to point-of-care testing (POCT) due to its characteristics of cost-effectiveness, disposability, miniaturization, wide potential window, and simple electrode design. Compared with gold or platinum electrodes, surface modification is difficult because the carbon surface is chemically or physically stable. Oxygen plasma (O2) can easily produce carboxyl groups on the carbon surface, which act as scaffolds for covalent bonds. However, the effect of O2-plasma treatment on electrode performance remains to be investigated from an electrochemical perspective, and sensor performance can be improved by clarifying the surface conditions of plasma-treated biosensors. In this research, we compared antibody modification by plasma treatment and physical adsorption, using our novel immunosensor based on gold nanoparticles (AuNPs). Consequently, the O2-plasma treatment produced carboxyl groups on the electrode surface that changed the electrochemical properties owing to electrostatic interactions. In this study, we compared the following four cases of SPCE modification: O2-plasma-treated electrode/covalent-bonded antibody (a); O2-plasma-treated electrode/physical adsorbed antibody (b); bare electrode/covalent-bonded antibody (c); and bare electrode/physical absorbed antibody (d). The limits of detection (LOD) were 0.50 ng/mL (a), 9.7 ng/mL (b), 0.54 ng/mL (c), and 1.2 ng/mL (d). The slopes of the linear response range were 0.039, 0.029, 0.014, and 0.022. The LOD of (a) was 2.4 times higher than the conventional condition (d), The slope of (a) showed higher sensitivity than other cases (b~d). This is because the plasma treatment generated many carboxyl groups and increased the number of antibody adsorption sites. In summary, the O2-plasma treatment was found to modify the electrode surface conditions and improve the amount of antibody modifications. In the future, O2-plasma treatment could be used as a simple method for modifying various molecular recognition elements on printed carbon electrodes.

Electrochemical Monitoring in Anticoagulation Therapy.

The process of blood coagulation, wherein circulating blood transforms into a clot in response to an internal or external injury, is a critical physiological mechanism. Monitoring this coagulation process is vital to ensure that blood clotting neither occurs too rapidly nor too slowly. Anticoagulants, a category of medications designed to prevent and treat blood clots, require meticulous monitoring to optimise dosage, enhance clinical outcomes, and minimise adverse effects. This review article delves into the various stages of blood coagulation, explores commonly used anticoagulants and their targets within the coagulation enzyme system, and emphasises the electrochemical methods employed in anticoagulant testing. Electrochemical sensors for anticoagulant monitoring are categorised into two types. The first type focuses on assays measuring thrombin activity via electrochemical techniques. The second type involves modified electrode surfaces that either directly measure the redox behaviours of anticoagulants or monitor the responses of standard redox probes in the presence of these drugs. This review comprehensively lists different electrode compositions and their detection and quantification limits. Additionally, it discusses the potential of employing a universal calibration plot to replace individual drug-specific calibrations. The presented insights are anticipated to significantly contribute to the sensor community's efforts in this field.

A novel split-type photoelectrochemical biosensor based on liposome-induced in situ formation of Bi2S3@BiOI/Ag2S heterojunction for the sensitive detection of CEA

A novel split-type photoelectrochemical (PEC) biosensor was constructed for the sensitive detection of carcinoembryonic antigen (CEA) based on the Ag+-liposome (ALL) signal amplification strategy and Bi2S3@BiOI heterojunction as the substrate material. The split-type sensing mode effectively avoids the complex fixation of biomolecules on the electrode surface and preserves the activity of biomolecules. The sandwich complex was formed between CEA and aptamer-anchored streptavidin-functionalized magnetic beads (SMB-Apt) and ALL-labeled aptamer (ALL-Apt). After the methanol was added, a large amount of Ag+ was released from the liposome. The released Ag+ was transferred to the Bi2S3@BiOI modified electrode surface for incubation and then soaked in Na2S solution to form a narrow band gap photosensitive material Ag2S on the electrode surface. Bi2S3@BiOI/Ag2S ternary heterojunction in situ was formed due to the band gap matching relationship between Ag2S and the Bi2S3@BiOI heterojunction, which effectively expanded the light absorption range and enhanced the photocurrent signal. Under the optimal experimental conditions, the constructed PEC sensing platform exhibited good analytical performance for CEA with a linear range of 0.005 ∼ 50 ng mL−1 and a detection limit of 1.21 pg mL−1. Additionally, the PEC sensor had good selectivity, reproducibility, and stability, which provided a new research idea for the detection of clinical tumor biomarkers.

Sensitive electrochemical biosensor for Ustilaginoidea Virens short-stranded DNA segment via higher-ordered G-quadruplex multimerization induced by LAMP/H+-responsive i-motif folding

By using variable loop-mediated isothermal amplification byproduct H+ ions (vLAMP/H+) as signal transducer, exploring the electrochemical assay of short-stranded DNA segment related to U. virens (uDNA, 21-nt) is intriguing. Herein, we report the first design of a sensitive electrochemical biosensor for uDNA as targeting input promoter of vLAMP, for which a discernible template hairpin and a precursor hairpin are well-designed. The specific recognition and complementary hybridization among them form a double-dumbbell DNA structure tethering two stem-loop motifs that is served as template precursor to operate vLAMP for DNA+1 polymerization via nucleotide incorporation, generating vLAMP/H+ to modulate pH-responsive i-motif folding of a C-rich strand. A ferrocene-tagged G-rich strand is dehybridized and incubated in modified electrode surface including an amino-labeled G-rich strand that adopts compact G-quadruplex (G4) conformation. This G4, as an initiator, guides the ‘head-to-tail’ π-π stacking of electroactive tags for developing higher-ordered wire-like G4 multimers (G4W), which are stably held together via interquadruplex multimerization. No involving additional nucleic acid amplifiers, numerous electroactive mediators are repetitively cascaded, thereby significantly amplifying the current readout signal and achieving sensitive electrochemical detection of U. virens. Benefited from simple and rapid vLAMP/H+-G4W route, our assay strategy would provide a new paradigm to create applicable electrochemical biosensors for diverse short-stranded DNA biomarkers by altering LAMP operation modes readily.

Nickel oxide electroplating and electrode surface modification for electrochemical detection of glutamate

The electrochemical behavior and catalytic properties of nickel oxide (NiOx) are enhanced through cathodic electroplating and subsequent electrochemical activation in an alkaline aqueous electrolyte. The electrochemical detection of ʟ-glutamate becomes feasible by introducing an amine group through immobilizing APTES ((3-aminopropyl)triethoxysilane) on the NiOx surface, resulting in a positive charge. The synergistic effect of electrochemically activated electroplated NiOx and the APTES-modified surface facilitates the effective electrochemical detection of trace ʟ-glutamate. The APTES-activated NiOx electrode exhibits a linear detection range of 0.2 nM to 2 mM for glutamate. This relatively wide concentration range is promising for the analysis of human biological fluids.