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Chemosensors, Volume 2, Issue 4 (December 2014), Pages 219-286

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Research

Open AccessArticle Reproducible Design for the Optical Screening and Sensing of Hg(II) Ions
Chemosensors 2014, 2(4), 219-234; doi:10.3390/chemosensors2040219
Received: 1 April 2014 / Revised: 22 September 2014 / Accepted: 25 September 2014 / Published: 24 October 2014
Cited by 4 | PDF Full-text (1276 KB) | HTML Full-text | XML Full-text
Abstract
We fabricated silica nanotubes with hexagonally ordered mesopores (6 nm) inside a membrane disc with a uniform channel neck size of 200 nm and a longitudinal thickness of 60 μm to design an optical sensor membrane (OSM) for the screening and sensing of
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We fabricated silica nanotubes with hexagonally ordered mesopores (6 nm) inside a membrane disc with a uniform channel neck size of 200 nm and a longitudinal thickness of 60 μm to design an optical sensor membrane (OSM) for the screening and sensing of extremely toxic Hg(II) ions. The optical detection and quantitative recognition of Hg(II) ions in water were conducted even at trace concentrations without the need for sophisticated instruments. The OSM design was based on the physical interaction of a responsive organic probe with silica pore surfaces followed by strong and selective binding Hg(II)–probe interactions under specific sensing conditions, particularly at pH 5. Ultra-trace concentrations of Hg(II) ions were easily detected with the naked eye using the OSM. The remarkable ion spectral response of Hg(II) ion–OSM ensured the excellent quantification of the OSM for Hg(II) ion sensing over a wide range of concentrations with a detection limit of 1.75 × 10−9 M. This result indicated that low concentrations of Hg(II) ions can be detected with a high sensitivity. One of the key issues of OSM is the Hg(II) ion-selective workability even in the presence of high doses of competitive matrices and species. The OSM design showed significant Hg(II) ion-sensing capability despite the number of reuse/recycles using simple decomplexation. Given its high selectivity, fast response, and sensitivity, the OSM could be developed into a specific Hg(II) ion-sensing kit in aqueous solutions. Full article
(This article belongs to the Special Issue Nanosensors)
Open AccessArticle Simple and Sensitive Electrochemical Sensor-Based Three-Dimensional Porous Ni-Hemoglobin Composite Electrode
Chemosensors 2014, 2(4), 235-250; doi:10.3390/chemosensors2040235
Received: 25 November 2013 / Revised: 9 October 2014 / Accepted: 16 October 2014 / Published: 12 November 2014
Cited by 5 | PDF Full-text (574 KB) | HTML Full-text | XML Full-text
Abstract
The development of sensing systems that can detect ultra-trace amounts of hydrogen peroxide (H2O2) remains a key challenge in biological and biomedical fields. In the present study, we introduce a simple and highly sensitive enzymeless H2O2
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The development of sensing systems that can detect ultra-trace amounts of hydrogen peroxide (H2O2) remains a key challenge in biological and biomedical fields. In the present study, we introduce a simple and highly sensitive enzymeless H2O2 biosensor based on a three-dimensional open pore nickel (Ni) foam electrode functionalized with hemoglobin (Hb). Our findings revealed that the Hb maintained its biological functions and effective electronic connection even after immobilization process. The exceptional physical and intrinsic catalytic properties of the Ni foam combined with the bio-functionality and electron transport facility of the Hb robustly construct a H2O2 biosensor. The enzymeless H2O2 biosensor showed high selectivity, a quick response time, high sensitivity, a wide linear range and a low limit of detection (0.83 μM at a signal-to-noise ratio of three). Such an electrode composition with safe immobilization processes offers viability for engineering new biosensors. Full article
Open AccessCommunication Voltammetric Electronic Tongue for Discrimination of Milk Adulterated with Urea, Formaldehyde and Melamine
Chemosensors 2014, 2(4), 251-266; doi:10.3390/chemosensors2040251
Received: 29 August 2014 / Revised: 16 October 2014 / Accepted: 27 October 2014 / Published: 14 November 2014
Cited by 4 | PDF Full-text (979 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report the fabrication of a voltammetric electronic tongue for the detection and discrimination of harmful substances intentionally added to milk to increase its shelf life or imitate protein content. The electronic tongue consisted of three working electrodes composed of platinum, gold, and
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We report the fabrication of a voltammetric electronic tongue for the detection and discrimination of harmful substances intentionally added to milk to increase its shelf life or imitate protein content. The electronic tongue consisted of three working electrodes composed of platinum, gold, and copper. The measurement principles involved the extraction of information from cyclic voltammograms recorded in unadulterated and adulterated milk. The extracted data were analysed using principal component analysis and the contaminants were successfully differentiated from one another in a score plot. Electrochemical quartz crystal microbalance analysis was used to investigate the electrode response in order to understand the mechanism by which the tongue could discriminate between the samples. It was found that the electrochemical formation and dissolution of platinum and gold oxides, and the reduction of a copper-melamine ionic pair formed at the surface of the copper electrode were the main factors responsible for discrimination. In addition, the electronic tongue was capable of identifying adulterations in different types of milk (whole, skimmed, and semi-skimmed) and milk from different brands. The lowest concentration of adulterant that resulted in a good discrimination was 10.0, 4.16, and 0.95 mmol·L−1 for formaldehyde, urea, and melamine, respectively. Full article
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Open AccessArticle Effect of Cholesterol Anchoring Group on the Properties of G-Quadruplex-Based FRET Probes for Potassium Ion
Chemosensors 2014, 2(4), 267-286; doi:10.3390/chemosensors2040267
Received: 31 August 2014 / Revised: 13 October 2014 / Accepted: 15 October 2014 / Published: 21 November 2014
PDF Full-text (1311 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study we report on the spectral properties and G-quadruplex folding ability of fluorescent oligonucleotide probes modified by the attachment of a cholesterol moiety. These probes were designed and studied in order to verify their potential as potassium-sensing devices that can be
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In this study we report on the spectral properties and G-quadruplex folding ability of fluorescent oligonucleotide probes modified by the attachment of a cholesterol moiety. These probes were designed and studied in order to verify their potential as potassium-sensing devices that can be incorporated into the cellular membrane. The 19-meric guanine-rich deoxyoligonucleotide was labeled with reporter fluorescent FRET groups (FAM and TAMRA) and a cholesterol anchor was attached using different approaches. The probes exhibited abilities to fold into a quadruplex structure and to bind metal cations (Na+ and K+). In an unbound state, both termini of the oligonucleotide are separated, thus fluorophores do not interact with each other and the probe exhibits an unperturbed fluorescence spectrum. In the presence of K+, the quadruplex structure is developed such that it enables fluorophores to be arranged in close proximity, causing generation of a different fluorescence spectrum (FRET signal). Folding properties of probes and their spectral behavior were examined by recording the UV-Vis, fluorescence emission, and excitation spectra (FRET efficiency), and the temperature stability of G-quadruplex structures adopted by probes (melting profiles). Fluorescence energy transfer efficiency increased with increases in sodium or potassium ion concentrations in an aqueous solution, which indicated that the probes retained their cation-binding properties and could be promising candidates for potassium sensing at the cell membrane interface. Full article
(This article belongs to the Special Issue Nucleic Acid Probes)
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