scholarly journals Rapid Determination of Ochratoxin A in Grape and Its Commodities Based on a Label-Free Impedimetric Aptasensor Constructed by Layer-by-Layer Self-Assembly

Toxins ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 71 ◽  
Author(s):  
Mina Nan ◽  
Yang Bi ◽  
Huali Xue ◽  
Sulin Xue ◽  
Haitao Long ◽  
...  
Keyword(s):  
Ochratoxin A ◽  
Self Assembly ◽  
Electrochemical Impedance ◽  
Rapid Determination ◽  
Grape Juice ◽  
High Sensitivity ◽  
Layer By Layer ◽  
Label Free ◽  
Transfer Resistance

A simple and sensitive label-free impedimetric aptasensor for rapid determination of ochratoxin A (OTA) has been developed, which was based on the combination between thiolated aptamer and gold nanoparticles by layer-by-layer self-assembly. Because of the interaction between aptamer and OTA, the relative normalized electron-transfer resistance (ΔRct) values obtained by electrochemical impedance spectroscopy (EIS) was proportional to the concentration of OTA and showed a good linear relationship from 0.1 to 10.0 ng/mL, with a lower detection limit (0.030 ng/mL) than one-step thiolated DNA aptasensor. The established method was successfully applied to detect and analyze OTA in table wine and grape juice, and the recovery was 90.56%–104.21% when PVP effective removed of phenolic substances. The label-free impedimetric aptasensor was used for rapid detection and quantitation of OTA in the inoculated grapes with the Aspergillus Nigri (H1), and the production of OTA (62.4 μg/kg, 20 μg/kg) far exceeded the maximum levels of 2 μg/kg after inoculation for three days. The developed method exhibited a good specificity, high sensitivity, time-efficient, and it could be applied to detect the OTA concentration in grape and its commodities.

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.

Determination of Ascorbic Acid Based on Gold Nanoparticles-L-Alanine/GCE

2011 ◽  
Vol 214 ◽  
pp. 498-502 ◽  
Author(s):  
Hai Yan Kuang ◽  
Jia Hong He ◽  
Qiang Xu ◽  
Zhong Rong Song
Keyword(s):  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Self Assembly ◽  
High Sensitivity ◽  
Glass Electrode ◽  
Layer By Layer ◽  
Current Time ◽  
Electrochemical Behaviors ◽  
Assembly Technology

A Gold nanoparticles-L-alanine modified glass electrode has been successfully fabricated by using layer-by-layer self-assembly technology and used for determination of ascorbic acid. First, the clean electrode was immersed into L-Alanine solution to acquire a L-Alanine film on the surface of GCE and dried at room temperature, then the gold colloid was dipped onto the L-Alanine film. The electrochemical behaviors of ascorbic acid at the modified electrode were investigated by cyclic voltammetry and current-time techniques. The results showed that the sensor produced high sensitivity and good stability to ascorbic acid and the current was linear with the concentration of ascorbic acid in the range of 1.20×10-5 to 1.60×10-4 mol/L with a detection limit of 1.00×10-5 mol/L.

Quantitative Determination of Triiodothyronine by Electrochemical Impedance Spectroscopic Biosensor Using Gold Nanoparticle-Modified Electrode

2020 ◽  
Vol 20 (11) ◽  
pp. 7163-7168
Author(s):  
Huynh Vu Nguyen ◽  
Anna Go ◽  
Min-Ho Lee
Keyword(s):  
Quantitative Determination ◽  
Gold Nanoparticle ◽  
Modified Electrode ◽  
Electrochemical Impedance ◽  
Low Cost ◽  
Charge Transfer Resistance ◽  
Impedance Change ◽  
Label Free ◽  
Transfer Resistance

A label-free electrochemical impedimetric immunosensor for the detection of Triiodothyronine—a thyroid hormone that functions as the biomarker for monitoring for thyroid dysfunction was developed. The gold nanoparticle-modified electrode was employed to achieve the sensitive determination of Triiodothyronine at a low concentration level. The gold nanoparticle layer on the gold electrode was generated by chronoamperometry method and its resulting characteristics were investigated by scanning electron microscopy. Redox probe [Fe(CN)6]3−/4− and electrochemical impedance spec-troscopy was used for both evaluation of the immobilization of anti-Triiodothyronine antibody on the electrode surface and quantitative determination of target Triiodothyronine in different concentrations. The electrode with absorbed antibodies showed significant changes in charge transfer resistance upon binding the antigen, which resulted in an increase in normalized impedance change as the addition of antigen concentrations over a dynamic linear range of 0.01–100 ng/ml. These results indicated that the proposed immunosensor could be a potential alternative method for determination of Triiodothyronine in clinics with the advantage of low cost and less time-consuming.

scholarly journals Comparison of Flow Injection-MS/MS and LC-MS/MS for the Determination of Ochratoxin A

Toxins ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 547
Author(s):  
Kai Zhang
Keyword(s):  
Ochratoxin A ◽  
Flow Injection ◽  
Internal Standard ◽  
Grape Juice ◽  
Tandem Mass ◽  
Triple Quadrupole ◽  
On Line ◽  
Red Grape Juice ◽  
Red Grape

Two methods for measuring ochratoxin A in corn, oat, and grape juice were developed and compared. Flow injection (FI) and on-line liquid chromatography (LC) performances were evaluated separately, with both methods using a triple quadrupole tandem mass spectrometer (MS/MS) for quantitation. Samples were fortified with 13C uniformly labeled ochratoxin A as the internal standard (13C-IS) and prepared by dilution and filtration, followed by FI- and LC-MS/MS analysis. For the LC-MS/MS method, which had a 10 min run time/sample, recoveries of ochratoxin A fortified at 1, 5, 20, and 100 ppb in corn, oat, red grape juice, and white grape juice ranged from 100% to 117% with RSDs < 9%. The analysis time of the FI-MS/MS method was <60 s/sample, however, the method could not detect ochratoxin A at the lowest fortification concentration, 1 ppb, in all tested matrix sources. At 5, 20, and 100 ppb, recoveries by FI-MS/MS ranged from 79 to 117% with RSDs < 15%. The FI-MS/MS method also had ~5× higher solvent and matrix-dependent instrument detection limits (0.12–0.35 ppb) compared to the LC-MS/MS method (0.02–0.06 ppb). In the analysis of incurred corn and oat samples, both methods generated comparable results within ±20% of reference values, however, the FI-MS/MS method failed to determine ochratoxin A in two incurred wheat flour samples due to co-eluted interferences due to the lack of chromatographic separation.

scholarly journals Capacitive Field-effect (bio-)chemical Sensors Based on Nanocrystalline Diamond Films

2009 ◽  
Vol 1203 ◽  
Author(s):  
Matthias Bäcker ◽  
Arshak Poghossian ◽  
Maryam H. Abouzar ◽  
Sylvia Wenmackers ◽  
Stoffel D. Janssens ◽  
...  
Keyword(s):  
Thin Films ◽  
Field Effect ◽  
High Sensitivity ◽  
Ph Sensitive ◽  
Nanocrystalline Diamond ◽  
Penicillin G ◽  
Layer By Layer ◽  
Label Free ◽  
High Coverage ◽  
Layer Adsorption

AbstractCapacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structures with O-terminated nanocrystalline diamond (NCD) as sensitive gate material have been realized and investigated for the detection of pH, penicillin concentration, and layer-by-layer adsorption of polyelectrolytes. The surface oxidizing procedure of NCD thin films as well as the seeding and NCD growth process on a Si-SiO2 substrate have been improved to provide high pH-sensitive, non-porous thin films without damage of the underlying SiO2 layer and with a high coverage of O-terminated sites. The NCD surface topography, roughness, and coverage of the surface groups have been characterized by SEM, AFM and XPS methods. The EDIS sensors with O-terminated NCD film treated in oxidizing boiling mixture for 45 min show a pH sensitivity of about 50 mV/pH. The pH-sensitive properties of the NCD have been used to develop an EDIS-based penicillin biosensor with high sensitivity (65-70 mV/decade in the concentration range of 0.25-2.5 mM penicillin G) and low detection limit (5 μM). The results of label-free electrical detection of layer-by-layer adsorption of charged polyelectrolytes are presented, too.

Layer-by-layer self-assembly of 2D graphene nanosheets, 3D copper oxide nanoflowers and 0D gold nanoparticles for ultrasensitive electrochemical detection of alpha fetoprotein

RSC Advances ◽  
2015 ◽  
Vol 5 (70) ◽  
pp. 56583-56589 ◽  
Author(s):  
Yulan Wang ◽  
Dan Wu ◽  
Yong Zhang ◽  
Xiang Ren ◽  
Yaoguang Wang ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Copper Oxide ◽  
Electrochemical Detection ◽  
Self Assembly ◽  
Graphene Nanosheets ◽  
Electrochemical Immunosensor ◽  
Alpha Fetoprotein ◽  
Quantitative Detection ◽  
Layer By Layer ◽  
Label Free

In this work, a novel and ultrasensitive label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP).

Preparation of yolk–shell structured Ag@Cu particles and their application in high performance electrochemical sensing of p-aminobenzoic acid

2019 ◽  
Vol 97 (2) ◽  
pp. 140-146
Author(s):  
Tian Gan ◽  
Zhikai Wang ◽  
Mengru Chen ◽  
Wanqiu Fu ◽  
Haibo Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Performance ◽  
Electrochemical Impedance ◽  
High Sensitivity ◽  
Differential Pulse ◽  
Electrochemical Sensing ◽  
High Catalytic Activity ◽  
Aminobenzoic Acid ◽  
Transmission Electron

In this work, the Ag@Cu particles with yolk–shell nanostructure was prepared by facile solvothermal method, which was modified on glassy carbon electrode (GCE) to fabricate electrochemical sensor for the convenient and fast determination of p-aminobenzoic acid (PABA). The surface morphology and electrochemical properties of the as-prepared Ag@Cu nanocomposite modified electrode were characterized by scanning electron microscopy, transmission electron microscopy, chronocoulometry, and electrochemical impedance spectroscopy. Further, the electrochemical sensing of PABA was performed on the Ag@Cu/GCE using cyclic voltammetry and differential pulse voltammetry techniques, showing high catalytic activity. Under the optimal conditions, the sensor exhibited a wide linear range, high sensitivity, and low detection limit of 0.315 μmol/L for PABA. The developed sensor was also successfully applied for PABA detection in anesthetic and cosmetics with satisfactory results.

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