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Biosensors, Volume 4, Issue 3 (September 2014), Pages 189-328

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Research

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Open AccessArticle Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives
Biosensors 2014, 4(3), 189-203; doi:10.3390/bios4030189
Received: 21 April 2014 / Revised: 10 June 2014 / Accepted: 23 June 2014 / Published: 4 July 2014
Cited by 3 | PDF Full-text (1471 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that
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This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. Full article
(This article belongs to the Special Issue Magnetic Biosensors)
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Open AccessArticle An Inexpensive, Fast and Sensitive Quantitative Lateral Flow Magneto-Immunoassay for Total Prostate Specific Antigen
Biosensors 2014, 4(3), 204-220; doi:10.3390/bios4030204
Received: 8 April 2014 / Revised: 9 June 2014 / Accepted: 13 June 2014 / Published: 8 July 2014
Cited by 11 | PDF Full-text (635 KB) | HTML Full-text | XML Full-text
Abstract
We describe the detection characteristics of a device the Resonant Coil Magnetometer (RCM) to quantify paramagnetic particles (PMPs) in immunochromatographic (lateral flow) assays. Lateral flow assays were developed using PMPs for the measurement of total prostate specific antigen (PSA) in serum samples. A
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We describe the detection characteristics of a device the Resonant Coil Magnetometer (RCM) to quantify paramagnetic particles (PMPs) in immunochromatographic (lateral flow) assays. Lateral flow assays were developed using PMPs for the measurement of total prostate specific antigen (PSA) in serum samples. A detection limit of 0.8 ng/mL was achieved for total PSA using the RCM and is at clinically significant concentrations. Comparison of data obtained in a pilot study from the analysis of serum samples with commercially available immunoassays shows good agreement. The development of a quantitative magneto-immunoassay in lateral flow format for total PSA suggests the potential of the RCM to operate with many immunoassay formats. The RCM has the potential to be modified to quantify multiple analytes in this format. This research shows promise for the development of an inexpensive device capable of quantifying multiple analytes at the point-of-care using a magneto-immunoassay in lateral flow format. Full article
(This article belongs to the Special Issue Magnetic Biosensors)
Open AccessArticle Study of Paclitaxel-Treated HeLa Cells by Differential Electrical Impedance Flow Cytometry
Biosensors 2014, 4(3), 257-272; doi:10.3390/bios4030257
Received: 20 May 2014 / Revised: 5 August 2014 / Accepted: 8 August 2014 / Published: 13 August 2014
Cited by 2 | PDF Full-text (1487 KB) | HTML Full-text | XML Full-text
Abstract
This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes in electrical
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This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes in electrical properties compared with non-treated cells. We found that our microfluidic system was able to distinguish between treated and non-treated cells. Furthermore, we utilize a model for electrical impedance spectroscopy in order to perform a theoretical study to clarify our results. This study focuses on investigating the changes in the electrical properties of the cell membrane caused by the effect of paclitaxel. We observe good agreement between the model and the obtained results. This establishes the proof-of-concept for the application in cell drug therapy. Full article
(This article belongs to the Special Issue Label-Free Biosensors: Exploring the Field)
Open AccessCommunication Microelectrode Arrays and the Use of PEG-Functionalized Diblock Copolymer Coatings
Biosensors 2014, 4(3), 318-328; doi:10.3390/bios4030318
Received: 29 July 2014 / Revised: 28 August 2014 / Accepted: 5 September 2014 / Published: 11 September 2014
Cited by 4 | PDF Full-text (346 KB) | HTML Full-text | XML Full-text
Abstract
PEG-modified diblock copolymer surfaces have been examined for their compatibility with microelectrode array based analytical methods. The use of PEG-modified polymer surfaces on the arrays was initially problematic because the redox couples used in the experiments were adsorbed by the polymer. This led
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PEG-modified diblock copolymer surfaces have been examined for their compatibility with microelectrode array based analytical methods. The use of PEG-modified polymer surfaces on the arrays was initially problematic because the redox couples used in the experiments were adsorbed by the polymer. This led the current measured by cyclic voltammetry for the redox couple to be unstable and increase with time. However, two key findings allow the experiments to be successful. First, after multiple cyclic voltammograms the current associated with the redox couple does stabilize so that a good baseline current can be established. Second, the rate at which the current stabilizes is consistent every time a particular coated array is used. Hence, multiple analytical experiments can be conducted on an array coated with a PEG-modified diblock copolymer and the data obtained is comparable as long as the data for each experiment is collected at a consistent time point. Full article
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Review

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Open AccessReview Sensing Magnetic Directions in Birds: Radical Pair Processes Involving Cryptochrome
Biosensors 2014, 4(3), 221-242; doi:10.3390/bios4030221
Received: 30 April 2014 / Revised: 14 July 2014 / Accepted: 18 July 2014 / Published: 24 July 2014
Cited by 13 | PDF Full-text (824 KB) | HTML Full-text | XML Full-text
Abstract
Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can
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Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an “inclination compass”, not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green. The Radical Pair-Model of magnetoreception can explain these properties by proposing spin-chemical processes in photopigments as underlying mechanism. Applying radio frequency fields, a diagnostic tool for radical pair processes, supports an involvement of a radical pair mechanism in avian magnetoreception: added to the geomagnetic field, they disrupted orientation, presumably by interfering with the receptive processes. Cryptochromes have been suggested as receptor molecules. Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins. Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds. Full article
(This article belongs to the Special Issue Magnetic Biosensors)
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Open AccessReview Electrochemical Biosensors Based on Ferroceneboronic Acid and Its Derivatives: A Review
Biosensors 2014, 4(3), 243-256; doi:10.3390/bios4030243
Received: 9 June 2014 / Revised: 3 July 2014 / Accepted: 25 July 2014 / Published: 30 July 2014
Cited by 6 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
Abstract
We review recent progress in the development of electrochemical biosensors based on ferroceneboronic acid (FcBA) and ferrocene (Fc)-modified boronic acids. These compounds can be used to construct electrochemical biosensors because they consist of a binding site (i.e., a boronic acid moiety)
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We review recent progress in the development of electrochemical biosensors based on ferroceneboronic acid (FcBA) and ferrocene (Fc)-modified boronic acids. These compounds can be used to construct electrochemical biosensors because they consist of a binding site (i.e., a boronic acid moiety) and an electrochemically active part (i.e., an Fc residue). By taking advantage of the unique properties of FcBA and its derivatives, electrochemical sensors sensitive to sugars, glycated hemoglobin (HbA1c), fluoride (F) ions, and so forth have been widely studied. FcBA-based sugar sensors rely on the selective binding of FcBA to 1,2- or 1,3-diol residues of sugars through the formation of cyclic boronate ester bonds. The redox properties of FcBA-sugar adduct differ from those of free FcBA, which forms the basis of the electrochemical determination of sugars. Thus, non-enzymatic glucose sensors are now being actively studied using FcBA and Fc-modified boronic acids as redox markers. Using a similar principle, HbA1c can be detected by FcBA-based electrochemical systems because it contains hydrocarbon chains on the polypeptide chain. HbA1c sensors are useful for monitoring blood glucose levels over the preceding 8–12 weeks. In addition, FcBA and Fc-modified boronic acids have been used for the detection of F ions due to the selective binding of boronic acid to F ions. F-ion sensors may be useful alternatives to conventional ion-selective electrodes sensitive to F ion. Furthermore, FcBA derivatives have been studied to construct lectin; steroids; nucleotides; salicylic acid; and bacteria sensors. One of the limitations of FcBA-based sensors comes from the fact that FcBA derivatives are added in sample solutions as reagents. FcBA derivatives should be immobilized on the surface of electrodes for developing reagentless sensors. Full article
(This article belongs to the Special Issue Electrochemical and Biomedical Sensors)
Open AccessReview Biosensors with Built-In Biomolecular Logic Gates for Practical Applications
Biosensors 2014, 4(3), 273-300; doi:10.3390/bios4030273
Received: 3 July 2014 / Revised: 15 August 2014 / Accepted: 22 August 2014 / Published: 27 August 2014
Cited by 7 | PDF Full-text (1297 KB) | HTML Full-text | XML Full-text
Abstract
Molecular logic gates, designs constructed with biological and chemical molecules, have emerged as an alternative computing approach to silicon-based logic operations. These molecular computers are capable of receiving and integrating multiple stimuli of biochemical significance to generate a definitive output, opening a new
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Molecular logic gates, designs constructed with biological and chemical molecules, have emerged as an alternative computing approach to silicon-based logic operations. These molecular computers are capable of receiving and integrating multiple stimuli of biochemical significance to generate a definitive output, opening a new research avenue to advanced diagnostics and therapeutics which demand handling of complex factors and precise control. In molecularly gated devices, Boolean logic computations can be activated by specific inputs and accurately processed via bio-recognition, bio-catalysis, and selective chemical reactions. In this review, we survey recent advances of the molecular logic approaches to practical applications of biosensors, including designs constructed with proteins, enzymes, nucleic acids, nanomaterials, and organic compounds, as well as the research avenues for future development of digitally operating “sense and act” schemes that logically process biochemical signals through networked circuits to implement intelligent control systems. Full article
(This article belongs to the Special Issue Electrochemical and Biomedical Sensors)
Open AccessReview Piezoelectric Biosensors for Organophosphate and Carbamate Pesticides: A Review
Biosensors 2014, 4(3), 301-317; doi:10.3390/bios4030301
Received: 12 May 2014 / Revised: 28 July 2014 / Accepted: 7 August 2014 / Published: 9 September 2014
Cited by 9 | PDF Full-text (454 KB) | HTML Full-text | XML Full-text
Abstract
Due to the great amount of pesticides currently being used, there is an increased interest for developing biosensors for their detection. Among all the physical transducers, piezoelectric systems have emerged as the most attractive due to their simplicity, low instrumentation costs, possibility for
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Due to the great amount of pesticides currently being used, there is an increased interest for developing biosensors for their detection. Among all the physical transducers, piezoelectric systems have emerged as the most attractive due to their simplicity, low instrumentation costs, possibility for real-time and label-free detection and generally high sensitivity. This paper presents an overview of biosensors based on the quartz crystal microbalance, which have been reported in the literature for organophosphate and carbamate pesticide analysis. Full article
(This article belongs to the Special Issue Piezoelectric Biosensors)
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