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1344 KiB

Open AccessArticle

Iterative Precise Conductivity Measurement with IDEs

by Jaromír Hubálek

Sensors 2015, 15(5), 12080-12091; https://doi.org/10.3390/s150512080 - 22 May 2015

Cited by 7 | Viewed by 6725

The paper presents a new approach in the field of precise electrolytic conductivity measurements with planar thin- and thick-film electrodes. This novel measuring method was developed for measurement with comb-like electrodes called interdigitated electrodes (IDEs). Correction characteristics over a wide range of specific [...] Read more.

The paper presents a new approach in the field of precise electrolytic conductivity measurements with planar thin- and thick-film electrodes. This novel measuring method was developed for measurement with comb-like electrodes called interdigitated electrodes (IDEs). Correction characteristics over a wide range of specific conductivities were determined from an interface impedance characterization of the thick-film IDEs. The local maximum of the capacitive part of the interface impedance is used for corrections to get linear responses. The measuring frequency was determined at a wide range of measured conductivity. An iteration mode of measurements was suggested to precisely measure the conductivity at the right frequency in order to achieve a highly accurate response. The method takes precise conductivity measurements in concentration ranges from 10⁻⁶ to 1 M without electrode cell replacement. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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2756 KiB

Open AccessArticle

A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

by Jana Vlachova, Katerina Tmejova, Pavel Kopel, Maria Korabik, Jan Zitka, David Hynek, Jindrich Kynicky, Vojtech Adam and Rene Kizek

Sensors 2015, 15(2), 2438-2452; https://doi.org/10.3390/s150202438 - 22 Jan 2015

Cited by 16 | Viewed by 7349

Abstract

Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur [...] Read more.

Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion) for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH). It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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358 KiB

Open AccessArticle

Fluorescent Cellular Assay for Screening Agents Inhibiting Pseudomonas aeruginosa Adherence

by Libuše Nosková, Božena Kubíčková, Lucie Vašková, Barbora Bláhová, Michaela Wimmerová, Marie Stiborová and Petr Hodek

Sensors 2015, 15(1), 1945-1953; https://doi.org/10.3390/s150101945 - 16 Jan 2015

Cited by 4 | Viewed by 5737

Abstract

Antibodies against Pseudomonas aeruginosa (PA) lectin, PAIIL, which is a virulence factor mediating the bacteria binding to epithelium cells, were prepared in chickens and purified from egg yolks. To examine these antibodies as a prophylactic agent preventing the adhesion of PA we developed [...] Read more.

Antibodies against Pseudomonas aeruginosa (PA) lectin, PAIIL, which is a virulence factor mediating the bacteria binding to epithelium cells, were prepared in chickens and purified from egg yolks. To examine these antibodies as a prophylactic agent preventing the adhesion of PA we developed a well plate assay based on fluorescently labeled bacteria and immortalized epithelium cell lines derived from normal and cystic fibrosis (CF) human lungs. The antibodies significantly inhibited bacteria adhesion (up to 50%) in both cell lines. In agreement with in vivo data, our plate assay showed higher susceptibility of CF cells towards the PA adhesion as compared to normal epithelium. This finding proved the reliability of the developed experimental system. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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2412 KiB

Open AccessArticle

Chemical Sensor Platform for Non-Invasive Monitoring of Activity and Dehydration

by Dmitry Solovei, Jaromír Žák, Petra Majzlíková, Jiří Sedláček and Jaromír Hubálek

Sensors 2015, 15(1), 1479-1495; https://doi.org/10.3390/s150101479 - 14 Jan 2015

Cited by 15 | Viewed by 7676

Abstract

A non-invasive solution for monitoring of the activity and dehydration of organisms is proposed in the work. For this purpose, a wireless standalone chemical sensor platform using two separate measurement techniques has been developed. The first approach for activity monitoring is based on [...] Read more.

A non-invasive solution for monitoring of the activity and dehydration of organisms is proposed in the work. For this purpose, a wireless standalone chemical sensor platform using two separate measurement techniques has been developed. The first approach for activity monitoring is based on humidity measurement. Our solution uses new humidity sensor based on a nanostructured TiO₂ surface for sweat rate monitoring. The second technique is based on monitoring of potassium concentration in urine. High level of potassium concentration denotes clear occurrence of dehydration. Furthermore, a Wireless Body Area Network (WBAN) was developed for this sensor platform to manage data transfer among devices and the internet. The WBAN coordinator controls the sensor devices and collects and stores the measured data. The collected data is particular to individuals and can be shared with physicians, emergency systems or athletes’ coaches. Long-time monitoring of activity and potassium concentration in urine can help maintain the appropriate water intake of elderly people or athletes and to send warning signals in the case of near dehydration. The created sensor system was calibrated and tested in laboratory and real conditions as well. The measurement results are discussed. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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2579 KiB

Open AccessArticle

Simultaneous Automatic Electrochemical Detection of Zinc, Cadmium, Copper and Lead Ions in Environmental Samples Using a Thin-Film Mercury Electrode and an Artificial Neural Network

by Jiri Kudr, Hoai Viet Nguyen, Jaromir Gumulec, Lukas Nejdl, Iva Blazkova, Branislav Ruttkay-Nedecky, David Hynek, Jindrich Kynicky, Vojtech Adam and Rene Kizek

Sensors 2015, 15(1), 592-610; https://doi.org/10.3390/s150100592 - 30 Dec 2014

Cited by 55 | Viewed by 8792

Abstract

In this study a device for automatic electrochemical analysis was designed. A three electrodes detection system was attached to a positioning device, which enabled us to move the electrode system from one well to another of a microtitre plate. Disposable carbon tip electrodes [...] Read more.

In this study a device for automatic electrochemical analysis was designed. A three electrodes detection system was attached to a positioning device, which enabled us to move the electrode system from one well to another of a microtitre plate. Disposable carbon tip electrodes were used for Cd(II), Cu(II) and Pb(II) ion quantification, while Zn(II) did not give signal in this electrode configuration. In order to detect all mentioned heavy metals simultaneously, thin-film mercury electrodes (TFME) were fabricated by electrodeposition of mercury on the surface of carbon tips. In comparison with bare electrodes the TMFEs had lower detection limits and better sensitivity. In addition to pure aqueous heavy metal solutions, the assay was also performed on mineralized rock samples, artificial blood plasma samples and samples of chicken embryo organs treated with cadmium. An artificial neural network was created to evaluate the concentrations of the mentioned heavy metals correctly in mixture samples and an excellent fit was observed (R² = 0.9933). Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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1471 KiB

Open AccessArticle

Rapid Detection of Microorganisms Based on Active and Passive Modes of QCM

by Zdeněk Farka, David Kovář and Petr Skládal

Sensors 2015, 15(1), 79-92; https://doi.org/10.3390/s150100079 - 23 Dec 2014

Cited by 37 | Viewed by 8010

Abstract

Label-free immunosensors are well suited for detection of microorganisms because of their fast response and reasonable sensitivity comparable to infection doses of common pathogens. Active (lever oscillator and frequency counter) and passive (impedance analyzer) modes of quartz crystal microbalance (QCM) were used and [...] Read more.

Label-free immunosensors are well suited for detection of microorganisms because of their fast response and reasonable sensitivity comparable to infection doses of common pathogens. Active (lever oscillator and frequency counter) and passive (impedance analyzer) modes of quartz crystal microbalance (QCM) were used and compared for rapid detection of three strains of E. coli. Different approaches for antibody immobilization were compared, the immobilization of reduced antibody using Sulfo‑SMCC was most effective achieving the limit of detection (LOD) 8 × 10⁴ CFU·mL⁻¹ in 10 min. For the passive mode, software evaluating impedance characteristics in real-time was developed and used. Almost the same results were achieved using both active and passive modes confirming that the sensor properties are not limited by the frequency evaluation method but mainly by affinity of the antibody. Furthermore, reference measurements were done using surface plasmon resonance. Effect of condition of cells on signal was observed showing that cells ruptured by ultrasonication provided slightly higher signal changes than intact microbes. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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2404 KiB

Open AccessArticle

Formation of DNA Adducts by Ellipticine and Its Micellar Form in Rats — A Comparative Study

by Marie Stiborova, Zuzana Manhartova, Petr Hodek, Vojtech Adam, Rene Kizek and Eva Frei

Sensors 2014, 14(12), 22982-22997; https://doi.org/10.3390/s141222982 - 03 Dec 2014

Cited by 9 | Viewed by 5083

Abstract

The requirements for early diagnostics as well as effective treatment of cancer diseases have increased the pressure on development of efficient methods for targeted drug delivery as well as imaging of the treatment success. One of the most recent approaches covering the drug [...] Read more.

The requirements for early diagnostics as well as effective treatment of cancer diseases have increased the pressure on development of efficient methods for targeted drug delivery as well as imaging of the treatment success. One of the most recent approaches covering the drug delivery aspects is benefitting from the unique properties of nanomaterials. Ellipticine and its derivatives are efficient anticancer compounds that function through multiple mechanisms. Formation of covalent DNA adducts after ellipticine enzymatic activation is one of the most important mechanisms of its pharmacological action. In this study, we investigated whether ellipticine might be released from its micellar (encapsulated) form to generate covalent adducts analogous to those formed by free ellipticine. The ³²P-postlabeling technique was used as a useful imaging method to detect and quantify covalent ellipticine-derived DNA adducts. We compared the efficiencies of free ellipticine and its micellar form (the poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PAGE-PEO) block copolymer, P 119 nanoparticles) to form ellipticine-DNA adducts in rats in vivo. Here, we demonstrate for the first time that treatment of rats with ellipticine in micelles resulted in formation of ellipticine-derived DNA adducts in vivo and suggest that a gradual release of ellipticine from its micellar form might produce the enhanced permeation and retention effect of this ellipticine-micellar delivery system. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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Review

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1997 KiB

Open AccessReview

Functionalized Solid Electrodes for Electrochemical Biosensing of Purine Nucleobases and Their Analogues: A Review

by Vimal Kumar Sharma, Frantisek Jelen and Libuse Trnkova

Sensors 2015, 15(1), 1564-1600; https://doi.org/10.3390/s150101564 - 14 Jan 2015

Cited by 46 | Viewed by 8584

Abstract

Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical [...] Read more.

Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications. Full article

(This article belongs to the Special Issue Selected Papers from XIV. Workshop of Physical Chemists and Electrochemists)

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