scholarly journals An Electrochemical Immunosensor Based on a Self-Assembled Monolayer Modified Electrode for Label-Free Detection of α-Synuclein

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 617 ◽  
Author(s):  
Chuang-Ye Ge ◽  
Md. Mahbubur Rahman ◽  
Wei Zhang ◽  
Nasrin Siraj Lopa ◽  
Lei Jin ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Label Free ◽  
Serum Samples ◽  
Self Assembled Monolayer ◽  
Electrochemical Impedance Spectra ◽  
Transfer Resistance ◽  
Label Free Detection ◽  
Self Assembled

This research demonstrated the development of a simple, cost-effective, and label-free immunosensor for the detection of α-synuclein (α-Syn) based on a cystamine (CYS) self-assembled monolayer (SAM) decorated fluorine-doped tin oxide (FTO) electrode. CYS-SAM was formed onto the FTO electrode by the adsorption of CYS molecules through the head sulfur groups. The free amine (–NH2) groups at the tail of the CYS-SAM enabled the immobilization of anti-α-Syn-antibody, which concurrently allowed the formation of immunocomplex by covalent bonding with α-Syn-antigen. The variation of the concentrations of the attached α-Syn at the immunosensor probe induced the alternation of the current and the charge transfer resistance (Rct) for the redox response of [Fe(CN)6]3−/4−, which displayed a linear dynamic range from 10 to 1000 ng/mL with a low detection limit (S/N = 3) of ca. 3.62 and 1.13 ng/mL in differential pulse voltammetry (DPV) and electrochemical impedance spectra (EIS) measurements, respectively. The immunosensor displayed good reproducibility, anti-interference ability, and good recoveries of α-Syn detection in diluted human serum samples. The proposed immunosensor is a promising platform to detect α-Syn for the early diagnose of Parkinson’s disease, which can be extended for the determination of other biologically important biomarkers.

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.

scholarly journals Label-Free Electrochemical Detection of S. mutans Exploiting Commercially Fabricated Printed Circuit Board Sensing Electrodes

Micromachines ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 575 ◽  
Author(s):  
Gorachand Dutta ◽  
Abdoulie A. Jallow ◽  
Debjani Paul ◽  
Despina Moschou
Keyword(s):  
Electrochemical Detection ◽  
Printed Circuit Board ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Charge Transfer Resistance ◽  
Circuit Board ◽  
Label Free ◽  
Electrochemical Impedance Spectra ◽  
Transfer Resistance ◽  
Printed Circuit

This paper reports for the first time printed-circuit-board (PCB)-based label-free electrochemical detection of bacteria. The demonstrated immunosensor was implemented on a PCB sensing platform which was designed and fabricated in a standard PCB manufacturing facility. Bacteria were directly captured on the PCB sensing surface using a specific, pre-immobilized antibody. Electrochemical impedance spectra (EIS) were recorded and used to extract the charge transfer resistance (Rct) value for the different bacteria concentrations under investigation. As a proof-of-concept, Streptococcus mutans (S. mutans) bacteria were quantified in a phosphate buffered saline (PBS) buffer, achieving a limit of detection of 103 CFU/mL. Therefore, the proposed biosensor is an attractive candidate for the development of a simple and robust point-of-care diagnostic platform for bacteria identification, exhibiting good sensitivity, high selectivity, and excellent reproducibility.

scholarly journals Microfluidic Impedance Biosensor Chips Using Sensing Layers Based on DNA-Based Self-Assembled Monolayers for Label-Free Detection of Proteins

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 80
Author(s):  
Khaled Alsabbagh ◽  
Tim Hornung ◽  
Achim Voigt ◽  
Sahba Sadir ◽  
Taleieh Rajabi ◽  
...  
Keyword(s):  
Troponin I ◽  
Electrochemical Impedance ◽  
Specific Binding ◽  
Self Assembled Monolayers ◽  
Significant Shift ◽  
Label Free ◽  
Label Free Detection ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Biosensor Chip

A microfluidic chip for electrochemical impedance spectroscopy (EIS) is presented as bio-sensor for label-free detection of proteins by using the example of cardiac troponin I. Troponin I is one of the most specific diagnostic serum biomarkers for myocardial infarction. The microfluidic impedance biosensor chip presented here consists of a microscope glass slide serving as base plate, sputtered electrodes, and a polydimethylsiloxane (PDMS) microchannel. Electrode functionalization protocols were developed considering a possible charge transfer through the sensing layer, in addition to analyte-specific binding by corresponding antibodies and reduction of nonspecific protein adsorption to prevent false-positive signals. Reagents tested for self-assembled monolayers (SAMs) on gold electrodes included thiolated hydrocarbons and thiolated oligonucleotides, where SAMs based on the latter showed a better performance. The corresponding antibody was covalently coupled on the SAM using carbodiimide chemistry. Sampling and measurement took only a few minutes. Application of a human serum albumin (HSA) sample, 1000 ng/mL, led to negligible impedance changes, while application of a troponin I sample, 1 ng/mL, led to a significant shift in the Nyquist plot. The results are promising regarding specific detection of clinically relevant concentrations of biomarkers, such as cardiac markers, with the newly developed microfluidic impedance biosensor chip.

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 Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5560 ◽  
Author(s):  
Somasekhar R. Chinnadayyala ◽  
Jinsoo Park ◽  
Young Hyo Kim ◽  
Seong Hye Choi ◽  
Sang-Myung Lee ◽  
...  
Keyword(s):  
Human Serum ◽  
Electrochemical Impedance ◽  
Electrode Array ◽  
C Reactive Protein ◽  
Self Assembled Monolayer ◽  
X Ray ◽  
Reactive Protein ◽  
Relative Standard ◽  
Label Free Detection ◽  
Self Assembled

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01–10,000 ng mL−1. The electrode showed detection limits of 0.025 ng mL−1 and 0.23 ng mL−1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

In-Vitro Allergy Detection Using a Silver Nanoparticle Modified Nanostructured Biosensor

2012 ◽  
Author(s):  
Gou-Jen Wang ◽  
Yi-Fen Liu ◽  
Chia-Che Wu
Keyword(s):  
Blood Serum ◽  
Immunoglobulin E ◽  
Electrochemical Impedance ◽  
Asthma Patient ◽  
Charge Transfer Resistance ◽  
Nyquist Plot ◽  
Serum Samples ◽  
Transfer Resistance ◽  
Der P2

IgE (Immunoglobulin E) in the serum of an asthma patient is a useful index for allergy diseases. In this study, a nanostructured biosensor having uniformly deposited gold nanoparticles (GNPs) as the sensing electrode was used for fast and low serum consuming detection of the IgE in allergy patients’ serum. To enhance the charge transferring efficiency of the biosensor, silver nanoparticles (SNPs) were deposited on the GNP layer. The group 2 allergen, Der p2, was used as the probe to detect IgE. To ensure the specificity of detection, the affinity purified goat anti-Human IgE antibody was further immobilized to the IgE. After immobilizing the anti-IgE on the sensor, the electrochemical impedance spectroscopy (EIS) analysis was implemented to examine the concentration of the target IgE in terms of a Nyquist plot. Blood serum samples with known allergy levels detected by the commercially available ImmunoCAP were used for the verification of the sensor. It is observed that the difference of the charge transfer resistance (ΔRet) between the Der p2 immobilized electrode and the anti-IgE bonded electrode for each individual serum sample closely correlates to its ImmunoCAP class. The blood serum detection results indicate that the presented nanostructured biosensor is able to detect a patient’s allergy level with low sample consumption, short sample preparation time, and quick processing.

Synthesis and Electrochemical Properties of Y-Doped SnO2/C Composite Materials for Lithium-Ion Battery

2011 ◽  
Vol 197-198 ◽  
pp. 1157-1162 ◽  
Author(s):  
Sheng Kui Zhong ◽  
You Wang ◽  
Chang Jiu Liu ◽  
Yan Wei Li ◽  
Yan Hong Li
Keyword(s):  
Particle Size ◽  
Electrochemical Impedance ◽  
Electronic Conductivity ◽  
Lithium Ion ◽  
Charge Transfer Resistance ◽  
Precipitation Method ◽  
Cyclic Voltammograms ◽  
Sem Images ◽  
Electrochemical Impedance Spectra ◽  
Transfer Resistance

The layered Y-doped SnO2/C anode materials were prepared by a co-precipitation method. The physical properties of the Y-doped SnO2/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that the Y-doped SnO2/C has the same layered structure as the undoped SnO2/C. The SEM images exhibited that the particle size of Y-doped SnO2/C is smaller than that of the undoped SnO2/C and the smallest particle size is only about 1µm. The Y-doped SnO2/C samples were investigated on the Lithium extraction/insertion performances by charge/discharge, cyclic voltammograms (CV), and electrochemical impedance spectra (EIS). The results showed that the optimal doping content of Y was that x=0.07 and 2% content of carbon nanotubes samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility and electronic conductivity were enhanced, and the charge transfer resistance was decreased through Y-doping.

Study of Insulating Properties of Alkanethiol Self-Assembled Monolayers Formed Under Prolonged Incubation Using Electrochemical Impedance Spectroscopy

2012 ◽  
Vol 3 (3) ◽  
Author(s):  
Damena D. Agonafer ◽  
Edward Chainani ◽  
Muhammed E. Oruc ◽  
Ki Sung Lee ◽  
Mark A. Shannon
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Critical Voltage ◽  
Transfer Resistance ◽  
Low Frequencies ◽  
Prolonged Incubation ◽  
Voltage Range ◽  
Self Assembled

The electrochemical interfacial properties of a well-ordered self-assembled monolayer (SAM) of 1-undecanethiol (UDT) on evaporated gold surface have been investigated by electrochemical impedance spectroscopy (EIS) in electrolytes without a redox couple. Using a constant-phase element (CPE) series resistance model, prolonged incubation times (up to 120 h) show decreasing monolayer capacitance approaching the theoretical value for 1-undecanethiol. Using the CPE exponent α as a measure of ideality, it was found that the monolayer approaches an ideal dielectric (α = 0.992) under prolonged incubation, which is attributed to the reduction of pinholes and defects in the monolayer during coalescence and annealing of SAM chains. The SAMs behave as insulators until a critical potential, Vc, is exceeded in both cathodic and anodic regimes, where electrolyte ions are believed to penetrate the monolayers. Using a Randles circuit model for these cases, the variation of the capacitance and charge transfer resistance with applied dc potential shows decreased permeability to ionic species with prolonged incubation time. The EIS data show that UDT (methylene chain length n = 10), incubated for 120 h, forms a monolayer whose critical voltage range extends from −0.3 to 0.5 V versus Ag/AgCl, previously attained only for alkanethiol at n = 15. At low frequencies where ion diffusion occurs, almost pure capacitive phase (−89 deg) was attained with lengthy incubation.

scholarly journals Label-Free Assay of Protein Kinase A Activity and Inhibition Using a Peptide-Based Electrochemical Sensor

Biomedicines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 423
Author(s):  
Hyunju Cho ◽  
Chang-Seuk Lee ◽  
Tae Hyun Kim
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Self Assembly ◽  
Dynamic Range ◽  
Electrochemical Impedance ◽  
Protein Kinase Activity ◽  
Label Free ◽  
Transfer Resistance ◽  
Substrate Peptide ◽  
Kinase A

We propose a simple label-free electrochemical biosensor for monitoring protein kinase activity and inhibition using a peptide-modified electrode. The biosensor employs cys-kemptide (CLRRASLG) as a substrate peptide which was immobilized on the surface of a gold electrode via the self-assembly of the thiol terminals in cysteine (C) residues. The interaction between protein kinase A (PKA) and adenosine 5′-triphosphate (ATP) on the cys-kemptide immobilized electrode can cause the transfer of ATP terminal phosphates to the peptide substrates at serine (S) residues, which alters the surface charge of the electrode, thus enabling monitoring of the PKA activity via measuring the interfacial electron transfer resistance with electrochemical impedance spectroscopy. The proposed sensor showed reliable, sensitive, and selective detection of PKA activity with a wide dynamic range of 0.1–100 U/mL and a detection limit of 56 mU/mL. The sensor also exhibited high selectivity, rendering it possible to screen PKA inhibitors. Moreover, the sensor can be employed to evaluate the activity and inhibition of PKA in real samples.

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