scholarly journals Label-free hairpin-like aptamer and EIS-based practical, biostable sensor for acetamiprid detection

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244297
Author(s):  
Jianhui Zhen ◽  
Gang Liang ◽  
Ruichun Chen ◽  
Wenshen Jia
Keyword(s):  
Charge Transfer ◽  
Orange Juice ◽  
Electrochemical Impedance ◽  
Specific Binding ◽  
Charge Transfer Resistance ◽  
Electrochemical Sensing ◽  
Label Free ◽  
Human Beings ◽  
Potential Health ◽  
Transfer Resistance

Acetamiprid (ACE) is a kind of broad-spectrum pesticide that has potential health risk to human beings. Aptamers (Ap-DNA (1)) have a great potential as analytical tools for pesticide detection. In this work, a label-free electrochemical sensing assay for ACE determination is presented by electrochemical impedance spectroscopy (EIS). And the specific binding model between ACE and Ap-DNA (1) was further investigated for the first time. Circular dichroism (CD) spectroscopy and EIS demonstrated that the single strand AP-DNA (1) first formed a loosely secondary structure in Tris-HClO4 (20 mM, pH = 7.4), and then transformed into a more stable hairpin-like structure when incubated in binding buffer (B-buffer). The formed stem-loop bulge provides the specific capturing sites for ACE, forming ACE/AP-DNA (1) complex, and induced the RCT (charge transfer resistance) increase between the solution-based redox probe [Fe(CN)6]3−/4− and the electrode surface. The change of ΔRCT (charge transfer resistance change, ΔRCT = RCT(after)-RCT(before)) is positively related to the ACE level. As a result, the AP-DNA (1) biosensor showed a high sensitivity with the ACE concentration range spanning from 5 nM to 200 mM and a detection limit of 1 nM. The impedimetric AP-DNA (1) sensor also showed good selectivity to ACE over other selected pesticides and exhbited excellent performance in environmental water and orange juice samples analysis, with spiked recoveries in the range of 85.8% to 93.4% in lake water and 83.7% to 89.4% in orange juice. With good performance characteristics of practicality, sensitivity and selectivity, the AP-DNA (1) sensor holds a promising application for the on-site ACE detection.

scholarly journals Deciphering the Disaggregation Mechanism of Amyloid Beta Aggregate by 4-(2-Hydroxyethyl)-1-Piperazinepropanesulfonic Acid Using Electrochemical Impedance Spectroscopy

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 788
Author(s):  
Hien T. Ngoc Le ◽  
Sungbo Cho
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Specific Binding ◽  
Amyloid Β ◽  
Electrochemical Measurement ◽  
Charge Transfer Resistance ◽  
Chemical Agent ◽  
Transfer Resistance ◽  
K Value

Aggregation of amyloid-β (aβ) peptides into toxic oligomers, fibrils, and plaques is central in the molecular pathogenesis of Alzheimer’s disease (AD) and is the primary focus of AD diagnostics. Disaggregation or elimination of toxic aβ aggregates in patients is important for delaying the progression of neurodegenerative disorders in AD. Recently, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS) was introduced as a chemical agent that binds with toxic aβ aggregates and transforms them into monomers to reduce the negative effects of aβ aggregates in the brain. However, the mechanism of aβ disaggregation by EPPS has not yet been completely clarified. In this study, an electrochemical impedimetric immunosensor for aβ diagnostics was developed by immobilizing a specific anti-amyloid-β (aβ) antibody onto a self-assembled monolayer functionalized with a new interdigitated chain-shaped electrode (anti-aβ/SAM/ICE). To investigate the ability of EPPS in recognizing AD by extricating aβ aggregation, commercially available aβ aggregates (aβagg) were used. Electrochemical impedance spectroscopy was used to probe the changes in charge transfer resistance (Rct) of the immunosensor after the specific binding of biosensor with aβagg. The subsequent incubation of the aβagg complex with a specific concentration of EPPS at different time intervals divulged AD progression. The decline in the Rct of the immunosensor started at 10 min of EPPS incubation and continued to decrease gradually from 20 min, indicating that the accumulation of aβagg on the surface of the anti-aβ/SAM/ICE sensor has been extricated. Here, the kinetic disaggregation rate k value of aβagg was found to be 0.038. This innovative study using electrochemical measurement to investigate the mechanism of aβagg disaggregation by EPPS could provide a new perspective in monitoring the disaggregation periods of aβagg from oligomeric to monomeric form, and then support for the prediction and handling AD symptoms at different stages after treatment by a drug, EPPS.

MONITORED DEFORMATION BY POTENTIAL-INDUCED DEFECTS IN CH3(CH2)n−1SH SELF-ASSEMBLED MONOLAYERS ON GOLD: EIS STUDY OF CHAIN LENGTH EFFECT ON SUBDIFFUSION AND SAMs’ HETEROGENEITY

2019 ◽  
Vol 26 (10) ◽  
pp. 1950067 ◽  
Author(s):  
AHMED MOUGARI ◽  
MOKHTAR ZABAT ◽  
SMAIL BOUDJADAR
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance ◽  
Defect Density ◽  
Charge Transfer Resistance ◽  
Electrical Circuit ◽  
Transfer Resistance ◽  
Low Frequencies ◽  
Interface Evolution ◽  
Impedance Measurements ◽  
Self Assembled

From the defects-free self-assembled organic layers (SAMs) of CH3([Formula: see text]SH molecules with short chain lengths ([Formula: see text]) electrodeposited on the (111) surface of monocrystalline gold previously prepared, monitored defects (pinholes) were potential-induced from cyclic partial reduction of SAMs at an appropriate potential. Electrochemical impedance measurements were in-situ conducted and [Fe(CN)6][Formula: see text] ions were used as probes for mass and charge transfer. Interface evolution was modeled with an equivalent electrical circuit containing two distinct constant-phase elements (CPEs). One is a generalized semi-infinite Warburg element in series with a charge transfer resistance attributed to subdiffusion phenomenon through leaky sublayers at low frequencies; the other CPE is used for characterizing the interface heterogeneity at medium and high frequencies. At low frequencies, electrochemical impedance measurements show subdiffusion phenomenon, which depends on the remaining sublayer and its thickness. When the defect density increases, diffusion tends to be ordinary, obeying the Fick’s law.

scholarly journals Electrochemical behaviour of poly(3,4-ethylenedioxytiophene) modified glassy carbon electrodes after overoxidation − the influence of the substrate on the charge transfer resistance

2018 ◽  
Author(s):  
Dora Zalka ◽  
Soma Vesztergom ◽  
Mária Ujvári ◽  
Gyözö Láng
Keyword(s):  
Charge Transfer ◽  
Glassy Carbon ◽  
Electrochemical Impedance ◽  
Electrochemical Behaviour ◽  
Mechanistic Explanation ◽  
Time Instant ◽  
Charge Transfer Resistance ◽  
Polymer Chains ◽  
Transfer Resistance ◽  
Impedance Measurements

<p class="PaperAbstract">Time dependence of the electrochemical impedance of an overoxidized glassy carbon|poly(3,4-ethylenedioxytiophene) (PEDOT)|0.1 mol·dm<sup>-3</sup> sulfuric acid (aq.) elec­trode has been investigated. To follow the changes occurring at the film/substrate interface after the overoxidation procedure, successive impedance measurements were carried out. Although the system is intrinsically nonstationary, the charge transfer resis­tance (R<sub>ct</sub>) cor<strong>­</strong>res<strong>­</strong>ponding to different time instants could be determined by using the so-called 4-dimensional analysis method. The same post-experimental mathematic­cal/ana­lytical procedure could be used also for the estimation of the charge transfer resistance corresponding to the time instant just after overoxidation of the PEDOT film. The increase of the charge transfer resistance of the overoxidized system with respect to that of the pristine electrode suggests that during overoxidation the electrochemical activity of the film decreases and the charge transfer process at the metal/film interface beco­mes more hindered. After the overoxidation procedure, when the electrode potential was held in the “stability region” (at E = 0.4 V vs. SSCE in the present case) the R<sub>ct</sub> decre­ased continuously with experiment time to a value somewhat higher than that of the pristine electrode.<strong> </strong>By comparing the properties of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> and the Au|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrodes a possible mechanistic explanation for the observed behavior has been proposed. This is based on the assumption that in the case of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrode two processes may occur simultaneously during the impedance measurements: (a) reduction of the oxidized surface of the GC substrate, including the reduction of the oxygen-containing surface functionalities and (b) read­sorption of the polymer chains (polymer chain ends) on the surface.<strong></strong></p>

scholarly journals Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO4/Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4507 ◽  
Author(s):  
Yusuke Abe ◽  
Natsuki Hori ◽  
Seiji Kumagai
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Specific Capacity ◽  
Lithium Ion ◽  
Performance Degradation ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Charge Discharge

Lithium-ion batteries (LIBs) using a LiFePO4 cathode and graphite anode were assembled in coin cell form and subjected to 1000 charge-discharge cycles at 1, 2, and 5 C at 25 °C. The performance degradation of the LIB cells under different C-rates was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. The most severe degradation occurred at 2 C while degradation was mitigated at the highest C-rate of 5 C. EIS data of the equivalent circuit model provided information on the changes in the internal resistance. The charge-transfer resistance within all the cells increased after the cycle test, with the cell cycled at 2 C presenting the greatest increment in the charge-transfer resistance. Agglomerates were observed on the graphite anodes of the cells cycled at 2 and 5 C; these were more abundantly produced in the former cell. The lower degradation of the cell cycled at 5 C was attributed to the lowered capacity utilization of the anode. The larger cell voltage drop caused by the increased C-rate reduced the electrode potential variation allocated to the net electrochemical reactions, contributing to the charge-discharge specific capacity of the cells.

Breast cancer detection using charge sensors coupled to DNA monolayer

2015 ◽  
Vol 1793 ◽  
pp. 19-26
Author(s):  
Marina R. Batistuti ◽  
Marcelo Mulato ◽  
Paulo R. Bueno
Keyword(s):  
Breast Cancer ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Electrochemical Impedance ◽  
Redox System ◽  
Charge Transfer Resistance ◽  
Label Free ◽  
Self Assembled Monolayer ◽  
Transfer Resistance ◽  
Complementary Dna

ABSTRACTWe report the development of a label-free biosensors based on DNA hybridization, using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This study uses DNA sequences based on microRNA related with breast cancer. The biosensor was fabricated by immobilizing a self-assembled monolayer of single-stranded 23-mer oligonucleotide (ssDNA) via a thiol linker on gold work electrodes. Residual binding places were filled with 6 -mercaptohexanol (MCH). The electrode was electrochemicaly characterized in the presence of a redox system ferri/ferrocyanide. Different concentrations of complementary DNA sequence for hybridization were incubated; an increase of charge transfer resistance (Rct) was observed, used as sensor parameter and correlated with concentrations of complementary DNA sequence. A debate was presented on the effect of the MgCl2 influence on ssDNA immobilization solution.

Engineering the ABIO-BIO interface of neurostimulation electrodes using polypyrrole and bioactive hydrogels

2020 ◽  
Vol 92 (6) ◽  
pp. 897-907 ◽  
Author(s):  
Ankita Bhat ◽  
Alexa R. Graham ◽  
Hemang Trivedi ◽  
Matthew K. Hogan ◽  
Philip J. Horner ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Density ◽  
Electrochemical Impedance ◽  
Inverse Correlation ◽  
Membrane Resistance ◽  
Charge Transfer Resistance ◽  
Foreign Body Response ◽  
Transfer Resistance ◽  
Cord Injury ◽  
Interfacial Impedance

AbstractFollowing spinal cord injury, the use of electrodes for neurostimulation in animal models has been shown to stimulate muscle movement, however, the efficacy of such treatment is impaired by increased interfacial impedance caused by fibrous encapsulation of the electrode. Sputter-deposited gold-on-polyimide electrodes were modified by potentiostatic electrodeposition of poly(pyrrole-co-3-pyrrolylbutyrate-conj-aminoethylmethacrylate): sulfopropyl methacrylate [P(Py-co-PyBA-conj-AEMA):SPMA] to various charge densities (0–100 mC/cm2) to address interfacial impedance and coated with a phosphoryl choline containing bioactive hydrogel to address biocompatibility at the ABIO-BIO interface. Electrodes were characterized with scanning electron microscopy (surface morphology), multiple-scan rate cyclic voltammetry (peak current and electroactive area), and electrochemical impedance spectroscopy (charge transfer resistance and membrane resistance). SEM analysis and electroactive area calculations identified films fabricated with a charge density of 50 mC/cm2 as well suited for neurostimulation electrodes. Charge transfer resistance demonstrated a strong inverse correlation (−0.83) with charge density of electrodeposition. On average, the addition of polypyrrole and hydrogel to neurostimulation electrodes decreased charge transfer resistance by 82 %. These results support the use of interfacial engineering techniques to mitigate high interfacial impedance and combat the foreign body response towards epidurally implanted neurostimulation electrodes.

Thermal transitions in hydrated layer-by-layer assemblies observed using electrochemical impedance spectroscopy

Soft Matter ◽  
2014 ◽  
Vol 10 (34) ◽  
pp. 6467-6476 ◽  
Author(s):  
Choonghyun Sung ◽  
Katelin Hearn ◽  
Jodie Lutkenhaus
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Thermal Transition ◽  
Layer By Layer ◽  
Thermal Transitions ◽  
Transfer Resistance ◽  
Hydrated Layer

Layer-by-layer assemblies exhibit increased conductivity and decreased charge transfer resistance upon heating through the thermal transition.

BENIGN APPROACH OF CANTHIUM PARVIFLORUM AS A BIOINHIBITOR FOR MILD STEEL CORROSION IN 0.5 M H2SO4 MEDIUM

2020 ◽  
Vol 27 (09) ◽  
pp. 1950208
Author(s):  
K. A. KARTHICK ◽  
D. S. BHUVANESHWARI ◽  
D. UMAPATHI ◽  
PANDIAN BOTHI RAJA
Keyword(s):  
Charge Transfer ◽  
Mild Steel ◽  
Electrochemical Impedance ◽  
Measurement Techniques ◽  
Charge Transfer Resistance ◽  
Effect Of Temperature ◽  
Adsorption Model ◽  
Free Energy Of Adsorption ◽  
Transfer Resistance ◽  
Vis Spectroscopy

Canthium parviflorum leaf extract (CPLE) was utilized for corrosion prevention against mild steel (MS) in 0.5[Formula: see text]mol[Formula: see text]L[Formula: see text] H2SO4 test medium. Standard corrosion measurement techniques (gravimetric and electrochemical) were employed for this purpose. Gravimetric tests clearly confirmed that the prepared CPLE efficiently performs as corrosion inhibitor. Potentiodynamic polarization measurements (PPM) and electrochemical impedance spectroscopy (EIS) measurements were performed in order to analyze the charge transfer process of CPLE. Polarization curves indicate that CPLE acts through mixed mode inhibition. Impedance study reveals that the CPLE additives enhances the charge transfer resistance values and conversely decreases values of double layer capacitance. Scanning electron microscopy (SEM), Ultraviolet-Visible (UV-Vis) spectroscopy analysis and Fourier-Transform Infrared spectroscopy (FTIR) were done to confirm the Fe-CPLE complex formation on MS. The effect of temperature reveals that the inhibition efficiency increases with decrease in temperature and increase in concentration of CPLE (maximum of 4[Formula: see text]mg[Formula: see text]L[Formula: see text]). The adsorption of CPLE shows that it obeys Langmuir’s isotherm model with free energy of adsorption, [Formula: see text][Formula: see text]kJ mol[Formula: see text]. A suitable adsorption model is also proposed.

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