An Impedimetric Biosensor Based on Ionic Liquid-Modified Graphite Electrodes Developed for microRNA-34a Detection

In the present work, an impedimetric nucleic acid biosensor has been designed for the purpose of detection of microRNA (miRNA). Ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (IL))-modified chemically activated pencil graphite electrodes (PGEs) were used for the sensitive and selective detection of miRNA-34a. After covalent activation of the PGE surface using covalent agents (CAs), the ionic liquid (IL) was immobilized onto the surface of the chemically activated PGE by passive adsorption. The electrochemical and microscopic characterization of the IL/CA/PGEs was performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscopy (SEM). DNA probe concentration, miRNA target concentration, and also the hybridization time and wet adsorption time were optimized by using the EIS technique. Then, the hybridization occurred between specific DNA probes and miRNA-34a was immobilized onto the surface of the IL/CA/PGEs. The impedimetric detection of miRNA-DNA hybrid was performed by EIS. The detection limit (DL) was calculated in a linear concentration range of 2–10 µg/mL miRNA-34a target, and it was found to be 0.772 µg/mL (109 nM) in phosphate buffer solution (PBS) and 0.826 µg/mL (117 nM) in diluted fetal bovine serum (FBS). The selectivity of impedimetric biosensor for miRNA-34a was also tested against to other non-complementary miRNA sequences both in buffer media, or diluted FBS.

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Synthesis of poly-Lysine/Gold nanoparticle films and their electrocatalytic properties

Biointerface Research in Applied Chemistry ◽

10.33263/briac14.119126 ◽

2011 ◽

Vol 1 (4) ◽

pp. 119-126 ◽

Cited By ~ 4

Keyword(s):

Gold Nanoparticles ◽

Electron Transfer ◽

Glassy Carbon ◽

Electrochemical Impedance ◽

Supporting Electrolyte ◽

Phosphate Buffer Solution ◽

Modified Electrodes ◽

Buffer Solution ◽

Transfer Constant ◽

Electrocatalytic Properties

Films composed of citrate stabilized gold nanoparticles (AuNPs) and Poly-Lysine (pLys) were fabricated by electropolymerization on glassy carbon (GC) electrodes from 0.1M phosphate buffer solution at pH = 8. The films were topographically analyzed by atomic force microcopy whereas their electrocatalytic properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy in aqueous solution using 0.0005M [Fe(CN)6] 3-/4- as redox probes and 0.1M NaClO4 as supporting electrolyte. The electron transfer process proved to be more efficient at the pLys-AuNP modified electrodes containing low amounts of gold nanoparticles (500 µL, 2.5×10-4M) than at the bare glassy carbon electrode. The heterogeneous electron transfer constant increased 2 orders of magnitude at the pLys-AuNP modified electrodes proving a more efficient electron transfer than at bare GC. These new films have a great potential for DNA biosensor applications.

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Electrochemistry and Electrocatalysis of Hemoglobin Based on Graphene Quantum Dots Modified Electrode

Current Analytical Chemistry ◽

10.2174/1573411015666181128144712 ◽

2020 ◽

Vol 16 (3) ◽

pp. 308-315

Author(s):

Xiaoyan Li ◽

Hui Xie ◽

Guiling Luo ◽

Yanyan Niu ◽

Xiaobao Li ◽

...

Keyword(s):

Quantum Dots ◽

Modified Electrode ◽

Electrochemical Impedance ◽

Ph Value ◽

Catalytic Reduction ◽

Graphene Quantum Dots ◽

Phosphate Buffer Solution ◽

Buffer Solution ◽

Detection Range ◽

Electrochemical Behaviors

Background: Graphene quantum dots (GQD) is a new member of carbon nanomaterial that has attracted increasing attention owing to its better chemical inertness, low cytotoxicity, large specific surface area, cheap cost, suitable conductivity and excellent biocompatibility. Methods: Electrochemical behaviors of this modified electrode were studied by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical investigations of Nafion/Hb/GQD/ CILE were carried out with electrochemical parameters calculated. Results: In the phosphate buffer solution with a pH value of 5.0, good linear relationships between the catalytic reduction current and the concentration of substrate were got for TCA (6.0~100.0 mmol·L-1), NaNO2 (2.0~12.0 mmol·L-1) and H2O2 (6.0~30.0 mmol·L-1). The proposed method was applied to NaNO2 concentration detection in soak water from picked vegetables with satisfactory results. Conclusion: This Nafion/Hb/GQD/CILE had a good bioelectrocatalytic activity to different substrates such as trichloroacetic acid, NaNO2 and H2O2 reduction with the advantages including wide detection range, low detection limit and good stability. Therefore, the application of GQD in electrochemical sensor was extended in this paper.

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Effect of fluoride on the thickness, surface roughness and corrosion resistance of titanium anodic oxide films formed in a phosphate buffer solution at different applied potentials

Research Society and Development ◽

10.33448/rsd-v9i11.10689 ◽

2020 ◽

Vol 9 (11) ◽

pp. e95791110689

Author(s):

Gláucia Domingues ◽

Michele de Almeida Oliveira ◽

Nayne Barros Gonzaga Ferreira ◽

Bhetina Cunha Gomes ◽

Elivelton Alves Ferreira ◽

...

Keyword(s):

Surface Roughness ◽

Corrosion Resistance ◽

Oxide Film ◽

Phosphate Buffer ◽

Electrochemical Impedance ◽

Oxide Films ◽

Phosphate Buffer Solution ◽

Buffer Solution ◽

Titanium Film ◽

Small Surface

The anodizing process and anions type present in the electrolyte during anodic oxidation are important parameters to improve oxide biocompatibility. From these parameters, it is possible to control the thickness and surface roughness of the oxide film. This control is of major importance, once blood clots can be avoided when the oxide film on the metal substrate has a small surface roughness (Ra ≤ 50 nm). In this paper, the thickness, surface roughness, and corrosion resistance of the anodized titanium film were studied in a phosphate buffer solution containing fluoride anions (0.6 w.t % NaF), at 20 V, 40 V, 60 V, and 80 V, using atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy (EIS) techniques. It was observed that thickness and roughness tend to increase as the applied potential rises. For oxides grown in the solution without NaF, the growth rate is roughly 1.3 ± 0.2 nm/V. Surface roughness generally presents the same behaviour. Moreover, EIS and SE thickness measurements agree at 20 V and 60 V but disagree at 80 V. This may be associated with a possible dielectric breakdown at 80 V. The oxide film formed at 60 V showed the best corrosion resistance in relation to the other studied potentials. Globular structures were also observed using AFM on surfaces at 40 V, 60 V, and 80 V, which suggests oxide film nucleation. Oxide films formed in solution with NaF presented lower thickness, excellent corrosion resistance, and low surface roughness (Ra ≤ 50 nm).

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Corrosion Resistance Evaluation of Porous Titanium with Biomimetic Coatings

Materials Science Forum ◽

10.4028/www.scientific.net/msf.591-593.55 ◽

2008 ◽

Vol 591-593 ◽

pp. 55-60 ◽

Cited By ~ 1

Author(s):

E.P. Banczek ◽

S.L. de Assis ◽

Marize Varella de Oliveira ◽

Waléria Silva de Medeiros ◽

Luiz Carlos Pereira ◽

...

Keyword(s):

Corrosion Resistance ◽

Body Fluid ◽

Electrochemical Impedance ◽

Surface Film ◽

Phosphate Buffer Solution ◽

Porous Titanium ◽

Buffer Solution ◽

Porous Ti ◽

Potentiodynamic Polarisation ◽

Sbf Solution

In this work, porous titanium samples processed by powder metallurgy and coated with biomimetic coatings, obtained during different periods of immersion in a simulated body fluid (SBF), were tested for corrosion resistance in a phosphate buffer solution (PBS). Uncoated samples were also tested for comparison. The corrosion resistance of both types of titanium samples was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarisation curves. The electrochemical results indicated the formation of a surface film on the porous Ti samples with immersion in the SBF solution and this biomimetic film increased their corrosion resistance. This film helps osteointegration besides increasing corrosion resistance.

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Development of Novel Magneto-Biosensor for Sulfapyridine Detection

Biosensors ◽

10.3390/bios10040043 ◽

2020 ◽

Vol 10 (4) ◽

pp. 43 ◽

Cited By ~ 1

Author(s):

Talha Jamshaid ◽

Ernandes Taveira Tenório-Neto ◽

Abdoullatif Baraket ◽

Noureddine Lebaz ◽

Abdelhamid Elaissari ◽

...

Keyword(s):

Counter Electrode ◽

Electrochemical Impedance ◽

Phosphate Buffer Solution ◽

Reference Electrode ◽

Data Fitting ◽

Buffer Solution ◽

Fixed Concentration ◽

Highly Sensitive ◽

3D Architecture ◽

Micro Electromechanical System

In this work, we report the development of a highly sensitive biosensor for sulfapyridine detection based on an integrated bio micro-electromechanical system (Bio-MEMS) containing four gold working electrodes (WEs), a platinum counter electrode (CE), and a reference electrode (RE). Firstly, the cleaned WEs were modified with 4-aminophenylacetic acid (CMA). Then, (5-[4-(amino)phenylsulfonamide]-5-oxopentanoic acid (SA2BSA) was immobilized onto the transducers surface by carbodiimide chemistry. The analyte was quantified by competitive detection with SA2BSA immobilized on the WE toward a mixture of Ab155 antibody (with fixed concentration) and sulfapyridine. In order to obtain a highly sensitive biosensor, Ab155 was immobilized onto magnetic latex nanoparticles surface to create a 3D architecture (Ab-MLNp). Using electrochemical impedance spectroscopy (EIS), we investigated the influence of the Ab-MLNp on the sensitivity of our approach. The optimized system was analyzed, as competitive assay, with different concentrations of sulfapyridine (40 µM, 4 µM, and 2 nM) and with phosphate buffer solution. From data fitting calculations and graphs, it was observed that the EIS showed more linearity when Ab-MLNp was used. This result indicates that the magnetic latex nanoparticles increased the sensitivity of the biosensor.

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A comparison of corrosion behaviors of additive manufacturing cobalt-chromium alloy in different solutions

Metallurgical Research & Technology ◽

10.1051/metal/2019005 ◽

2019 ◽

Vol 116 (3) ◽

pp. 311

Author(s):

Liyan Ma ◽

Jia Niu

Keyword(s):

Potentiodynamic Polarization ◽

Electrochemical Impedance ◽

Artificial Saliva ◽

Phosphate Buffer Solution ◽

Open Circuit ◽

Chromium Alloy ◽

Cobalt Chromium ◽

Buffer Solution ◽

Cocr Alloy ◽

Superior Corrosion Resistance

The corrosion behavior of selective laser melted CoCr alloy in 0.9% NaCl, phosphate buffer solution (PBS) and artificial saliva (AS) solutions were studied by using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. The potentiodynamic polarization tests were shown the lowest current density of the CoCr alloy in 0.9% NaCl, while the highest one was measured in PBS solution. CoCr alloys were passivation in all solutions, and the protective scale formed on CoCr alloy in 0.9% NaCl solution possessed the superior corrosion resistance according to EIS results.

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Cobalt Phthalocyanine-Ionic Liquid Composite Modified Electrodes for the Voltammetric Detection of DNA Hybridization Related to Hepatitis B Virus

Micromachines ◽

10.3390/mi12070753 ◽

2021 ◽

Vol 12 (7) ◽

pp. 753

Author(s):

Ece Yaralı ◽

Arzum Erdem

Keyword(s):

Ionic Liquid ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Dna Sequences ◽

Dna Hybridization ◽

Electrochemical Impedance ◽

Phosphate Buffer Solution ◽

Cobalt Phthalocyanine ◽

Voltammetric Detection ◽

B Virus

In this study, cobalt phthalocyanine (CoPc) and ionic liquid (IL) modified pencil graphite electrodes (PGEs) were designed and implemented to detect sequence-selective DNA hybridization related to the Hepatitis B virus (HBV). The surface characterization of CoPc-IL-PGEs was investigated by scanning electron microscopy (SEM), and the electrochemical behavior of electrodes were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The voltammetric detection of hybridization was investigated by evaluating the guanine oxidation signal, measured by differential pulse voltammetry (DPV) technique. The implementation of our biosensor to serum samples was also examined using fetal bovine serum (FBS). The detection limit was established as 0.19 µg/mL in phosphate buffer solution (PBS) (pH 7.40) and 2.48 µg/mL in FBS medium. The selectivity of our assay regarding HBV DNA hybridization in FBS medium was tested in the presence of other DNA sequences. With this aim, the hybridization of DNA probe with non-complementary (NC) or mismatched DNA sequence (MM), or in the presence of mixture samples containing DNA target NC (1:1) or DNA target MM (1:1), was studied based on the changes in guanine signal.

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Selective Binding of Nucleobases and its Electrochemical Behavior at Glassy Carbon Electrode in PBS at pH 7.4

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.328 ◽

2011 ◽

Vol 239-242 ◽

pp. 328-333

Author(s):

Jing Jie Cui ◽

De Hui Sun ◽

Hong Liu ◽

Guan Cong Wang ◽

Hong Shi Zhao ◽

...

Keyword(s):

Glassy Carbon Electrode ◽

Glassy Carbon ◽

Electrochemical Behavior ◽

Electrochemical Impedance ◽

Electrochemical Behaviour ◽

Phosphate Buffer Solution ◽

Carbon Electrode ◽

Oxidation Peak ◽

Buffer Solution ◽

Selective Binding

The electrochemical behavior of nucleobases has been studied in 0.1 M phosphate buffer solution (PBS), pH 7.4 without removing oxygen, using glassy carbon electrode (GCE). Cyclic voltammetry (CV), electrochemical impedance experiment (EIS) and square wave voltammetry (SWV) were employed in the measurements of the nucleobases electrochemical signals at GCEs. Guanine (G) and adenine (A) produced well-defined oxidation peaks at about +0.66 and +0.96 V under the CV sweep at 100 mV/s, respectively. SWV was particularly useful in investigating the electrochemical behaviour of pyrimidine bases. In the SWV detection, thymine (T) clearly appeared an oxidation peak at 1.1 V, while cytosine (C) and uracil (U) did a complex oxidation peak at 1.3 V. Nucleobases possess an irreversible and adsorption-controlled electrochemical process at GCEs in 0.1 M PBS (pH 7.4). The average surface concentrations (Γ) of G and A on the surface of the GCE were estimated to be about 1.6515×10−10and 8.8232×10−11mol/cm2, respectively. Due to the selective interactions of nucleobases with each other, the nucleobase oxidation peaks shift and new oxidation peaks appeared. The new oxidation peaks at +1.62 and 1.55 V may correspond to the oxidation of GC pairs and AT pairs, respectively. The detection of the electrochemical behaviour and selective binding of nucleobases in a physiological PBS at pH 7.4 is of particular interest for electrochemical sensor applications in physiological media.

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Modified graphite electrodes as potential cathodic electrocatalysts for microbial electrolysis cells

Bulgarian Chemical Communications ◽

10.34049/bcc.51.2.5154 ◽

2019 ◽

Vol 51 (2) ◽

pp. 284-288

Author(s):

E. Chorbadzhiyska ◽

I. Bardarov ◽

Y. Hubenova ◽

M. Mitov

Keyword(s):

Phosphate Buffer Solution ◽

Modified Electrodes ◽

Linear Sweep Voltammetry ◽

Cost Effective ◽

Innovative Technology ◽

Electrolysis Cell ◽

High Catalytic Activity ◽

Buffer Solution ◽

Graphite Electrodes ◽

Microbial Electrolysis

Microbial electrolysis cell (MEC) is an ecologically clean and innovative technology for hydrogen production. The development of cost-effective cathodes with high catalytic activity for hydrogen evolution reaction (HER) in nearneutral electrolytes is the most critical challenge for the practical application of MEC technology. In this study, graphite electrodes, functionalized with non-noble metal oxides, were produced and after electrochemical pre-treatment investigated as potential cathodes for MEC. The morphology of the developed materials was analyzed by scanning electron microscopy (SEM). Their electrochemical performance in neutral phosphate buffer solution (PBS) was explored by means of linear sweep voltammetry (LSV) and chronoamperometry (CA). The results from both methods show that all modified electrodes exhibit higher electrocatalytic activity towards HER than that of bare graphite, which is a prerequisite for further evaluation of these materials as cathodes in real MEC.

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Voltammetric Approach for Pharmaceutical Samples Analysis; Simultaneous Quantitative Determination of Resorcinol and Hydroquinone

10.21203/rs.3.rs-1106870/v1 ◽

2021 ◽

Author(s):

Ebrahim Nabatian ◽

Mahdi Mousavi ◽

Mostafa Pournamdari ◽

Saeid Ahmadzadeh

Keyword(s):

Simultaneous Determination ◽

Electrochemical Impedance ◽

Limit Of Detection ◽

Phosphate Buffer Solution ◽

Regression Equations ◽

Carbon Paste ◽

Buffer Solution ◽

Solution Ph ◽

Pharmaceutical Samples

Abstract A simple and precise analytical approach developed for single and simultaneous determination of resorcinol (RC) and hydroquinone (HQ) in pharmaceutical samples using carbon paste electrode (CPE) modified with 1-Ethyl-3-methylimidazolium tetrafluoroborate as ionic liquid and ZnFe2O4 nanoparticle. A significant enhancement in the peak current and sensitivity of the proposed sensor observed by using modifiers in the composition of working electrode compared to bare CPE which is in accordance with the results obtained from electrochemical impedance spectroscopy investigations. Electrochemical investigations revealed a well-defined irreversible oxidation peak for RC over a wide concentration range from 3.0 µM to 500 µM in 0.1 M phosphate buffer solution (pH 6.0) with the linear regression equations of Ip (µA) = 0.0276 CRC (µM) + 0.5508 (R2 = 0.997). The limit of detection and quantification for RC analysis were found to be 1.46 µM and 4.88 µM, respectively. However, the obtained SW voltammograms for simultaneous determination of RC and HQ exhibited a desirable peak separation of about 360 mV potential difference and a satisfactory linear response over the range of 50-700 µM and 5-350 µM with the favorable correlation coefficient of 0.991 and 0.995, respectively. The diffusion coefficient (D) of RC and the electron transfer coefficient (α) at the surface of ZnFe2O4/NPs/IL/CPE estimated to be 2.83×10−4 cm s−1 and 0.76. The proposed sensor as a promising and low-cost method successfully applied for determination of RC in commercial pharmaceutical formulations such as the resorcinol cream of 2% O/W emulsion available on the market with the recovery of 98.47±0.04.

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