Modified Gold Electrode Research Articles

Ratiometric electrochemical aptasensor for the sensitive detection of carcinoembryonic antigen based on a hairpin DNA probe and exonuclease I-assisted target recycling

A novel ratiometric electrochemical aptasensor was constructed for the detection of carcinoembryonic antigen (CEA) based on a hairpin DNA (hpDNA) probe and exonuclease Ⅰ (Exo Ⅰ)-assisted target recycling amplification strategy. A thiolated methylene blue (MB)-labeled hpDNA as the internal control element was fixed on the surface of the gold nanoparticles (AuNPs)-modified gold electrode (AuE) through Au–S bonds. A ferrocene (Fc)-modified aptamer DNA (Fc-Apt) was partially hybridized with hpDNA to form a Fc-Apt/hpDNA duplex. Due to the specific recognition of Fc-Apt to CEA, the presence of CEA caused dissociation of Fc-Apt from the duplex, and further triggered the degradation process of Exo Ⅰ and recycling of CEA. Hence, the Fc tags were released from the electrode surface and the oxidation peak current of Fc (IFc) decreased while that of MB (IMB) remained stable owing to the distance between MB tags and the electrode unchanged. A linear relationship was observed between IFc/IMB and the logarithm of CEA concentration from 10 pg mL−1 to 100 ng mL−1 with a detection limit of 1.9 pg mL−1. Moreover, the developed aptasensor had been applied to detect CEA in diluted human serum with satisfactory results, indicating its great potential in practical applications.

The Performance of Polyaniline Electropolymerization at Various Acidic Electrolytes on Gold Electrodes for Electrochemical Biosensor Application

Polyaniline (PANI), a conductive polymer, has been played a significant role as an electrode material for electrochemical biosensor development. In this study, the electrochemical properties of PANI synthesized in two different acid dopants, i.e. 1.0 M HCl and 0.50 M H2SO4using chronopotentiometry, were investigated. The surface morphologies of the PANI modified gold electrodes were observed using SEM and EDS. The PANI electrodeposition times were also considered. The electrochemical characteristics in terms of the peak-to-peak potential separations (ΔEp), the current of the oxidation (Ipa), and reversible redox properties were investigated using cyclic voltammetry. The results showed that the modified electrode with PANI electropolymerization in H2SO4 as a dopant performed significantly better electrochemically than PANI in HCl at all electrodeposition times. In particular, the PANI prepared in H2SO4 with the electrodeposition time of 120 s demonstrated the best performance in terms of electron transfer and reversible redox reaction.

Rapid Detection of Deoxynivalenol in Dry Pasta Using a Label-Free Immunosensor.

This work focused on the development and optimization of an impedimetric label-free immunosensor for detecting deoxynivalenol (DON). A monoclonal antibody for DON detection was immobilized on a modified gold electrode with a cysteamine layer and polyamidoamine (PAMAM) dendrimers. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to monitor the layer-by-layer development of the immunosensor design, while electrochemical impedance spectroscopy and differential pulse voltammetry were employed to investigate the antigen/antibody interaction. The PAMAM dendrimers, allowing to immobilize a large number of monoclonal antibodies, permitted reaching, through the DPV technique, a high sensitivity and a low limit of detection equal to 1 ppb. The evaluation of the possible reuse of the immunosensors highlighted a decrease in the analytical performances of the regenerated immunosensors. After evaluating the matrix effect, the developed immunosensor was used to quantify DON in pasta samples spiked with a known mycotoxin concentration. Taking into consideration the DON extraction procedure used for the pasta samples and the matrix effect related to the sample, the proposed immunosensor showed a limit of detection of 50 ppb, which is lower than the maximum residual limit imposed by European Regulation for DON in dry pasta (750 ppb).

Spatially hierarchical nano-architecture for real time detection of Interleukin-8 cancer biomarker

In the present work we have developed two hierarchical nano-architectures based electrochemical immunosensors for the detection of interleukin-8 (IL-8) cytokine tumor biomarker. A comparative study has been performed for spatial nano-architectures and their relative sensing to establish the model for real time monitoring. With the first platform, the recognition layer consisted with immobilised IL-8 on aminothiol modified gold electrodes. In the second approach, the activated multi walled carbon nanotubes (MWCNT-COOH) were added in the functionalisation process by covalent attachment between the functionalities NH2 of aminothiol and the functionalities COOH of carbon nanotubes. The surface topology of the recognition layer has been characterised by atomic force spectroscopy (AFM) and contact angle (CA) measurements. The electrochemical response of the developed sensor was measured by electrochemical impedance spectroscopy (EIS). A side-by-side comparison showed that aminothiol/activated MWCNTs/anti-IL-8 based impedimetric immunosensor exhibits high reproducibility (The relative standard deviation (R.S.D) = 3.2%, n = 3) with high stability. The present sensor allows evaluating a lower detection limit of 0.1 pg mL−1 with a large dynamic sensitivity range from 1 pg mL−1to 1000 pg mL−1 covering the entire clinical therapeutic window. The developed MWCNTs based immunosensor has been calibrated by determining IL-8 in artificial plasma and showed a selective response to IL-8 even in the interfering environment of other cytokines such as Interleukin-1 (IL-1) and Interleukin-6 (IL-6).

Surface functionalized gold electrode by axial ligand exchanged CoIIIcorroles for accelerating electrocatalyzed hydrogen evolutions

Herein, a series of CoIIIcorroles with different meso-substituents were successfully functionalized on gold electrodes through self-assembled axial coordination with 4-(methylthio)pyridine (MTP) and 4-(4-methylthiobenzo)pyridine (MTPP). The surface modified gold electrode performed enhanced and tunable electrochemically catalyzed hydrogen evolution behaviors that demonstrates the tunable surface molecular engineering of CoIIIcorroles via self-assembled monolayer is an effective strategy for energy related small molecule activations. Additionally, the CoIIIcorrole with electron-withdrawing meso-substituents axially coordinated with expanded conjugation system, 4-(4-methylthiobenzo)pyridine (MTPP), has the best performance of electrochemically catalyzed hydrogen evolutions.

Designing of surface engineered Ytterbium oxide nanoparticles as effective electrochemical sensing platform for dopamine

The simple and well framed sensing podium for Dopamine (DA) is holding significant importance in early analysis of neurodegenerative syndromes. Here, a facile electrochemical biosensor of Ytterbium oxide nanoparticles (Yb2O3 NPs) functionalized with (3-mercaptopropyl)trimethoxysilane (MPTMS) were prepared for efficient and selective quantification of DA. The developed electrocatalytic sensor overcome the associated confronts related to selectivity, sensitivity and interference from co-existing bio-components. The fabrication of MPTMS@Yb2O3 NPs was carried out by hydrothermal route. The physiochemical, morphological and structural characterization of chosen electrocatalyst was performed HRTEM, FE-SEM, XRD, SAXS, Raman, FTIR, TGA-DTA, XPS and DSC techniques. The electrochemical investigation suggests the superior performance of MPTMS@Yb2O3 NPs modified gold electrode as compared to the individual MPTMS or Yb2O3 modified electrodes towards DA sensing. The formed sensor displayed wide linear ranges from 1 to 40 µM with lowest detection limit (LOD) of 41 nM for DA. The calculated diffusion coefficient value is 8.57 × 10−5 cm2s−1 for DA. The usability of Au/ MPTMS@Yb2O3 NPs for DA estimation was successfully checked in real samples for practical applications. The developed sensor offers a great signal recovery and reproducibility and showed enhanced prospective in clinical samples.

Electrochemical and X-ray Photoelectron Spectroscopy Surface Characterization of Interchain-Driven Self-Assembled Monolayer (SAM) Reorganization.

Herein, we report a combined strategy encompassing electrochemical and X-ray photoelectron spectroscopy (XPS) experiments to investigate self-assembled monolayer (SAM) conformational reorganization onto an electrode surface due to the application of an electrical field. In particular, 3-mercaptopriopionic acid SAM (3MPA SAM) modified gold electrodes are activated with a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHSS) (EDC-NHSS) mixture by shortening the activation time, from 2 h to 15/20 min, labelled as Protocol-A, -B and -C, respectively. This step, later followed by a deactivation process with ethanolamine (EA), plays a key role in the reaction yields (formation of N-(2-hydroxyethyl)-3-mercaptopropanamide, NMPA) but also in the conformational rearrangement observed during the application of the electrical field. This study aims at explaining the high performance (i.e., single-molecule detection at a large electrode interface) of bioelectronic devices, where the 3MPA-based SAM structure is pivotal in achieving extremely high sensing performance levels due to its interchain interaction. Cyclic voltammetry (CV) experiments performed in K4Fe(CN)6:K3Fe(CN)6 for 3MPA SAMs that are activated/deactivated show similar trends of anodic peak current (IA) over time, mainly related to the presence of interchain hydrogen bonds, driving the conformational rearrangements (tightening of SAMs structure) while applying an electrical field. In addition, XPS analysis allows correlation of the deactivation yield with electrochemical data (conformational rearrangements), identifying the best protocol in terms of high reaction yield, mainly related to the shorter reaction time, and not triggering any side reactions. Finally, Protocol-C’s SAM surface coverage, determined by CV in H2SO4 and differential pulse voltammetry (DPV) in NaOH, was 1.29 * 1013 molecules cm−2, being similar to the bioreceptor surface coverage in single-molecule detection at a large electrode interface.

DNA as a Next-Generation Biomonitoring Tool of Hospital Effluent Contamination

A DNA biosensor based on a modified gold electrode with a Au/cysteine/DNA matrix was developed for ultratrace determination of genotoxicity antibiotics. The modified Au/cysteine/DNA electrode was characterized by cyclic voltammetry and impedance spectroscopy methods. The interaction between immobilized DNA and genotoxicity antibiotics in hospital wastewater was investigated using differential pulse voltammetry (DPV) technology. Using this technique, ciprofloxacin and ofloxacin were detected in real time in the hospital wastewater (HW) of the Tunisian cities of Gabes, Tozeur, Sfax, and Gbeli. In addition, physicochemical parameters such as the chemical oxygen demand (COD), biological oxygen demand (BOD), and total organic carbon (TOC) of HW samples that may affect the nature of the samples were studied. Comet assay (single-cell gel electrophoresis) was performed to measure the capacity of xenobiotics to induce DNA damage. In our conditions, this test indicated that all tested wastewater was able to alter cell integrity and cause DNA molecular damage, and the most genotoxic effect was found in the wastewater of Gabes hospital. Results show that the concentrations of the two antibiotics reached 33 and 40 ng/mL in the hospital wastewater of Gabes and Tozeur, respectively. The DNA biosensor based on the modified gold electrode exhibited superb performance and offers a probable application for the detection of genotoxicity antibiotics in hospital wastewater. The level of genotoxicity is proportional to the concentration of antibiotics detected in hospital wastewater. We will explore the application of this model for continuous monitoring downstream of hospital discharge and wastewater treatment plants for effective control of the presence of genotoxic products.

Covalent molecularly imprinted electrochemical sensor modulated by borate ester bonds for hygromycin B detection based on the synergistic signal amplification of Cu-MOF and MXene

A molecularly imprinted electrochemical sensor (MIES) modified with Cu-MOF and Ti3C2Tx was successfully prepared for the detection of hygromycin B in food. According to the pH sensitive property of reversible borate ester bonds, a molecularly imprinted polymers (MIP) were constructed on the modified gold electrode (GE) surface by electropolymerization to realize the controllable elution and adsorption of template molecules. Cu-MOF with large specific surface area and Ti3C2Tx with excellent electrical conductivity cooperate to improve the overall analytical performance of MIES. The morphology and electrochemical performance of the sensor were evaluated. Under the optimal experimental conditions, the method showed superior selectivity to hygromycin B with a linear range of 5 × 10−9–5 × 10−6 M and a detection limit of 1.92 × 10−9 M (S/N = 3). The detection results of this method are in good agreement with HPLC-MS/MS, which proves that the method has reliable practicability and accuracy.

Elucidating Film Loss and the Role of Hydrogen Bonding of Adsorbed Redox Enzymes by Electrochemical Quartz Crystal Microbalance Analysis.

The immobilization of redox enzymes on electrodes enables the efficient and selective electrocatalysis of useful reactions such as the reversible interconversion of dihydrogen (H2) to protons (H+) and formate to carbon dioxide (CO2) with hydrogenase (H2ase) and formate dehydrogenase (FDH), respectively. However, their immobilization on electrodes to produce electroactive protein films for direct electron transfer (DET) at the protein–electrode interface is not well understood, and the reasons for their activity loss remain vague, limiting their performance often to hour timescales. Here, we report the immobilization of [NiFeSe]-H2ase and [W]-FDH from Desulfovibrio vulgaris Hildenborough on a range of charged and neutral self-assembled monolayer (SAM)-modified gold electrodes with varying hydrogen bond (H-bond) donor capabilities. The key factors dominating the activity and stability of the immobilized enzymes are determined using protein film voltammetry (PFV), chronoamperometry (CA), and electrochemical quartz crystal microbalance (E-QCM) analysis. Electrostatic and H-bonding interactions are resolved, with electrostatic interactions responsible for enzyme orientation while enzyme desorption is strongly limited when H-bonding is present at the enzyme–electrode interface. Conversely, enzyme stability is drastically reduced in the absence of H-bonding, and desorptive enzyme loss is confirmed as the main reason for activity decay by E-QCM during CA. This study provides insights into the possible reasons for the reduced activity of immobilized redox enzymes and the role of film loss, particularly H-bonding, in stabilizing bioelectrode performance, promoting avenues for future improvements in bioelectrocatalysis.

Monolayer cobalt(II)phthalocyanine functionalized gold electrode for enhanced electrocatalyzed oxygen reductions

Monolayer Co(II)phthalocyanine (Co(II)Pc) functionalized gold electrodes through self-assembled axial coordination with 4-(methylthio)pyridine (MTP) and 4-(4-methylthiobenzo)pyridine (MTPP) were prepared. The surface modified gold electrode performed electrochemically catalyzed oxygen reduction in terms of onset-potential, current density, overpotential and Tafel in the order Au < Au/Co(II)Pc < Au/MTP/CoPc(II) < Au/MTPP/Co(II)Pc that demonstrates tunable surface molecular engineering of Co(II)Pc via self-assembled monolayer is an effective strategy for molecular catalysis and device application.

Preparation of Electrochemical Supercapacitor Based on Polypyrrole/Gum Arabic Composites.

The current research focused on the super capacitive behavior of organic conducting polymer, i.e., polypyrrole (PPy) and its composites with gum arabic (GA) prepared via inverse emulsion polymerization. The synthesized composites material was analyzed by different analytical techniques, such as UV-visible, FTIR, TGA, XRD, and SEM. The UV-Vis and FTIR spectroscopy clearly show the successful insertion of GA into PPy matrix. The TGA analysis shows high thermal stability for composites than pure PPy. The XRD and SEM analysis show the crystalline and amorphous structures and overall morphology of the composites is more compact and mesoporous as compared to the pure PPy. The electrochemical properties of modified solid state supercapacitors established on pure polypyrrole (PPy), polypyrrole/gum arabic (PPy/GA) based composites were investigated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD). The specific capacitance of the PPy modified gold electrode is impressive (~168 F/g). The specific capacitance of PPy/GA 1 electrode has been increased to 368 F/g with a high energy density and power density (~73 Wh/kg), and (~599 W/kg) respectively.

Highly sensitive electrochemical detection of biotin-avidin interaction on gold electrode modified with silver nanoparticles through bilayer assembly

The trifunctional l-cysteine containing carboxylic acid, amine and thiol is chemisorbed on the gold electrode surface via the thiol groups to form the self-assembled monolayer. Then the bilayer is assembled stepwise on the cysteine modified gold electrode. A layer of 3-marcaptopropionic acid functionalized silver nanoparticles is covalently coupled with amine group of cysteine and other layer of amine functional group containing biotin or avidin molecules is covalently coupled with carboxylic acid functional groups of cysteine. The improvement of electrochemical properties are noted for the cysteine modified gold electrode coupled with biomolecules first followed by coupling with the functionalized silver nanoparticles. This modified gold electrode is used to study the electrochemical sensing response of respective complementary biomolecule immobilized gold electrode towards the biotin or avidin. As revealed the avidin modified electrode is found to have better sensing performances toward biotin in terms of sensitivity and detection limit over the other one. The sensitivity of 1.243 Ω (ng)-1 L mm-2 and detection limit of 1.4 × 10−3 ng/L is observed for avidin sensing on biotin layer. For biotin sensing on avidin layer a sensitivity of 6.143 Ω (ng)-1 L mm-2 and detection limit of 1.2 × 10−5 ng/L is obtained from the calibration plot.

Electrochemical sensing of biotin-avidin interaction on gold electrode modified by silver nanoparticles through covalent co-assembling

Electrochemical sensing of biotin-avidin interaction was investigated on gold electrode modified with 3-mercaptopropanoic acid (MPA) successively co-assembled with cysteamine functionalized silver nanoparticles and biotin or avidin. The stable aqueous colloid of cysteamine functionalized silver nanoparticles was synthesized successfully by well-known citric acid reduction method. Gold electrode was first modified with a monolayer of MPA by self-assembly technique. Then, cysteamine functionalized silver nanoparticles and biotin or avidin was co-assembled on the MPA modified gold electrode through an amide linkage. The stepwise modification process was optimized in terms of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurement in [Fe (CN)6]3−/4− redox system by varying the ratio of functionalized silver nanoparticles and biotin or avidin, viz., 1:2, 1:1, 2:1. Based on obtained results, the electrochemical sensing performances of 1:1 silver nanoparticle and biotin or avidin co-assembled gold electrode was performed by CV and EIS for varying concentration of complementary bio-affinity molecules in the same redox system. Both the CV and EIS measurements were found to have good response by resistive and capacitive changes due to coupling with a complementary biomolecule on co-assembled gold electrode. The use of avidin assembled gold electrode had led to much better response towards varying concentration of biotin over that of the biotin assembled gold electrode towards avidin.

Electrochemical immunosensor for detection of Plasmodium vivax lactate dehydrogenase.

BACKGROUND Malaria is a disease that affects many tropical and subtropical countries, including Brazil. The use of tests for malaria detection is one of the fundamental strategies recommended by the World Health Organization for the control and eradication of the disease. The lack of diagnostic tests leads to an increase in transmission and non-reporting cases.OBJECTIVES This work described an electrochemical immunosensor for detecting Plasmodium vivax lactate dehydrogenase antigen (Ag-PvLDH).METHODS The device has developed by immobilising egg yolk IgY antibodies (Ab-PvLDH) on a gold electrode surface using cysteamine as linker. The immunosensor fabrication was followed by differential pulse voltammetry, and contact angle measurements were performed to characterise the modified gold electrode surface.FINDINGS The results for Ag-PvLDH determination exhibit a linear response at 10-50 µg mL-1 concentration range, with a limit of detection of 455 ng mL-1. The excellent selectivity of the device was confirmed.MAIN CONCLUSIONS The developed immunosensor showed a good performance, therefore, it can be considered an alternative test to detect malaria caused by P. vivax.

Self-Assisted Sensing of Spermine by Controlled Dissolution of Polysulfide Modified Gold Electrode

Self-Assisted Sensing of Spermine by Controlled Dissolution of Polysulfide Modified Gold Electrode

Potentiometric aptasensing of Escherichia coli based on electrogenerated chemiluminescence as a highly sensitive readout

We introduce here a versatile approach to read out potentiometric aptasensors by electrogenerated chemiluminescence (ECL), which can amplify the small potential changes induced by the bacterial concentrations via ECL signals. In the present system, the electrode modified with single-walled carbon nanotubes (SWCNTs) and aptamer molecules acts as the reference electrode and is placed in the sample solution for sensing the bacterial concentration changes, while the Ru(bpy)32+ modified gold electrode serves as the working electrode for generating ECL signals and is placed in the detection solution containing tripropylamine (TPA) spatially separated from the sample solution by a salt bridge. Ru(bpy)32+ is immobilized on the gold electrode's surface for enhancement of luminous efficiency and reduction of reagent consumption. A moving-part-free fluid flowing system is introduced to promote the mass transport of TPA from the detection solution to the surface of the ECL generating electrode. When a constant potential is imposed between the working and reference electrodes, the potential changes at the SWCNTs-aptamer modified electrode induced by the bacterial concentrations can modulate the potentials at the Ru(bpy)32+ modified electrode, thus generating the ECL signals. The developed sensing strategy shows a highly sensitive response to E. coli O157: H7 in the linear range of 5–1000 CFU mL−1 with a low detection limit of 2 CFU mL−1. We believe that the proposed approach is promising to develop aptasensors for sensitive detection of bacterial cells.

Novel fluoride selective voltammetric sensing method by amino phenylboronic acid-zirconium oxide nanoparticles modified gold electrode

A novel fluoride selective voltammetric method has been developed by using the 3-amino phenylboronic acid (APBA)-zirconium oxide (ZrO2) nanoparticles modified gold (APBA-ZrO2-NPs/Au) electrode for sensitive detection of F− at trace levels in water and toothpaste. A co-precipitation approach was applied to synthesize ZrO2 nanoparticles (ZrO2-NPs) using Salvadora oleoides leaves extract and characterized by UV–Visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-Ray Diffraction (XRD) for morphological and structural analysis. The APBA-ZrO2-NPs/Au electrode was fabricated by coated of ZrO2-NPs on the surface of Au electrode by drop costing method followed by electrochemical polymerization of APBA. The reduction response of peak current of potassium ferricyanide was achieved by the interaction of the phenylboronic acid with F−to produce the boronate anions. Thus, the method was optimized in detailed for successive electrochemical detection of F−. Two linear relations were observed in reduction peak current and logarithm of F− concentration in the range of 1.0 × 10–9 – 3.0 × 10–4 M and 3.0 × 10–4 – 1.0 × 10–2M, respectively. The limits of detection (LOD) and limit of quantification (LOQ) were calculated as 3.0 × 10–10 and 1.0 × 10–9 M, respectively. Interference of other competing anions, including chloride, bromide, iodide, acetate, sulphate, carbonate, and nitrate, was also investigated. Furthermore, the developed APBA-ZrO2-NPs/Au was employed to the fast detection, wide range of response, and high selectivity of F− in water and toothpaste samples.

Electrochemical biosensor for serogroup specific diagnosis of leptospirosis

A problem with the current leptospirosis diagnostic methods is the low sensitivity and specificity during the acute phase of illness. Rapid point-of-care (POC) assays with minimal sample utilization and low cost are desired in clinical practice. Here, we report for the first time lipopolysaccharide (LPS) based electrochemical biosensor that offers a rapid, highly sensitive, serogroup specific diagnosis of leptospirosis during the acute stage of infection and also to distinguish from other flu like infections. The proposed sensor is fabricated by the immobilization of LPS onto dodecanethiol (DT) modified gold electrode. Monolayer of DT is attached through covalent bond (Au-S) interaction onto the gold electrode. Thus, leptospiral antibodies from the human serum samples bind to the LPS present on self-assembled monolayer (SAM) of DT and showed a higher RCT value compared to SAM. The detection limit of the developed LPS sensor is estimated to be 100 nM. This biosensor is the first electrochemical sensing platform used for detection of LPS from Leptospira spp. This method is completely a solution-based diagnostic method and therefore it is rapid, simple, and sensitive; thus establishing a key technology towards a useful POC diagnostic strategy in serogroup level and hence an alternative to MAT.

Preparation a novel 1-pyreneacetic acid functionalized graphene/self-assembled monolayer modified gold electrode to immobilize and study interfacial electron transfer of cytochrome c by electrochemical approaches

A new hybrid of favorable orientated cytochrome c (cyt c) and a 1-Pyreneacetic acid (PA) functionalized graphene (Gr) on Au electrode (AuE) was prepared. In the hybrid system, Gr was functionalized with (PA) molecule through π-π interaction (PA-Gr). Afterward the PA-Gr attached to the AuE via Thionalide self-assembled monolayer (SAM), then conjugated with cyt c. The AuE/SAM/PA-Gr/cyt c hybrid system was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques. SECM approach curves were applied to measure the standard tunneling electron transfer (ET) and bimolecular rate constants which were 56.6 s−1 and 1 × 109cm3mol−1 s−1, respectively.