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Sensors, Volume 7, Issue 3 (March 2007), Pages 222-419

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Research

Jump to: Review

Open AccessArticle A Fluorimetric Sensor for Detection of One Living Cell
Sensors 2007, 7(3), 222-238; doi:10.3390/s7030222
Received: 13 December 2006 / Accepted: 27 February 2007 / Published: 5 March 2007
Cited by 18 | PDF Full-text (268 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, studies of metabolic pathways and processes in living organisms cannot be easily done at the cellular level. That is why the development of a new analytical methods and approaches is needed, to allow detection of different biologically important species at very [...] Read more.
Nowadays, studies of metabolic pathways and processes in living organisms cannot be easily done at the cellular level. That is why the development of a new analytical methods and approaches is needed, to allow detection of different biologically important species at very low concentrations levels and sample volumes, especially in individual cells. In the present work, we suggested a sensor to detect units of living cells by means determination of plant esterases (PE) based on fluorimetric detection of the products of the enzymatic hydrolysis of fluorescein diacetate in plant cell cultures (BY-2 tobacco cells and early somatic embryos of Norway spruce, clone 2/32). We standardized the sensor using a readily available esterase from pig liver. The detection limits were approximately 17 to 50 amol in 2 ml (8.5 to 25 femtomolar concentrations of esterases) of the enzyme contained in BY-2 tobacco cells and spruce early somatic embryos, respectively, after re-computation on the amounts of pig liver esterases. We assumed that the optimised sensor for the determination of PE in cell extracts accomplishes all requirements for a sensitive analysis which could be usable for single cell analysis. The detection limit was 1.5 in case of analysing BY-2 tobacco cells and 0.5 in early somatic embryos. Moreover, we were able to detect single protoplasts. Full article
Open AccessArticle A Hydrogen Peroxide Sensor Prepared by Electropolymerization of Pyrrole Based on Screen-Printed Carbon Paste Electrodes
Sensors 2007, 7(3), 239-250; doi:10.3390/s7030239
Received: 5 January 2007 / Accepted: 28 February 2007 / Published: 5 March 2007
Cited by 22 | PDF Full-text (138 KB) | HTML Full-text | XML Full-text
Abstract
A disposable amperometric biosensor for commercial use to detect hydrogenperoxide has been developed. The sensor is based on screen-printed carbon paste electrodesmodified by electropolymerization of pyrrole with horseradish peroxidase (HRP) entrapped.The facture techniques of fabricating the enzyme electrodes are suitable for mass [...] Read more.
A disposable amperometric biosensor for commercial use to detect hydrogenperoxide has been developed. The sensor is based on screen-printed carbon paste electrodesmodified by electropolymerization of pyrrole with horseradish peroxidase (HRP) entrapped.The facture techniques of fabricating the enzyme electrodes are suitable for mass productionand quality control. The biosensor shows a linear amperometric response to H2O2 from 0.1to 2.0 mM, with a sensitivity of 33.24 μA mM-1 cm-2. Different operational parameters ofelectropolymerization are evaluated and optimized. Full article
Open AccessArticle Prediction-based Dynamic Energy Management in Wireless Sensor Networks
Sensors 2007, 7(3), 251-266; doi:10.3390/s7030251
Received: 28 January 2007 / Accepted: 1 March 2007 / Published: 5 March 2007
Cited by 36 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
Abstract
Energy consumption is a critical constraint in wireless sensor networks. Focusing on the energy efficiency problem of wireless sensor networks, this paper proposes a method of prediction-based dynamic energy management. A particle filter was introduced to predict a target state, which was [...] Read more.
Energy consumption is a critical constraint in wireless sensor networks. Focusing on the energy efficiency problem of wireless sensor networks, this paper proposes a method of prediction-based dynamic energy management. A particle filter was introduced to predict a target state, which was adopted to awaken wireless sensor nodes so that their sleep time was prolonged. With the distributed computing capability of nodes, an optimization approach of distributed genetic algorithm and simulated annealing was proposed to minimize the energy consumption of measurement. Considering the application of target tracking, we implemented target position prediction, node sleep scheduling and optimal sensing node selection. Moreover, a routing scheme of forwarding nodes was presented to achieve extra energy conservation. Experimental results of target tracking verified that energy-efficiency is enhanced by prediction-based dynamic energy management. Full article
Open AccessArticle Effects of the Acrylic Polyol Structure and the Selectivity of the Employed Catalyst on the Performance of Two-component Aqueous Polyurethane Coatings
Sensors 2007, 7(3), 308-318; doi:10.3390/s7030308
Received: 6 February 2007 / Accepted: 8 March 2007 / Published: 13 March 2007
Cited by 2 | PDF Full-text (144 KB) | HTML Full-text | XML Full-text
Abstract
Two kinds of aqueous acrylic polyols (single step and multi step synthesis type)have been investigated for their performance in the two-component aqueous polyurethaneapplication, by using more selective catalysts. The aliphatic polyfunctional isocyanatesbased on hexamethylen diisocyanates have been employed as suitable hardeners. Thecomplex [...] Read more.
Two kinds of aqueous acrylic polyols (single step and multi step synthesis type)have been investigated for their performance in the two-component aqueous polyurethaneapplication, by using more selective catalysts. The aliphatic polyfunctional isocyanatesbased on hexamethylen diisocyanates have been employed as suitable hardeners. Thecomplex of zirconium, commercially known as K-KAT®XC-6212, and manganese (III)complexes with mixed ligands based on the derivative of maleic acid have been used ascatalysts in this study. Both of the aqueous polyols give good results, in terms of applicationand hardness, when elevated temperatures and more selective catalysts are applied. A moreselective catalyst promotes the reaction between the isocyanate and polyol component. Thisincreases the percentage of urethane bonds and the degree of hardness in the films formedfrom the two components of aqueous polyurethane lacquers. The polyol based on the singlestep synthesis route is favourable concerning potlife and hardness. The obtained resultsshow that the performance of the two-component aqueous polyurethane coatings depends onthe polymer structure of the polyols as well as on the selectivity of the employed catalyst. Full article
Open AccessArticle Rapid Characterization of Monoclonal Antibodies using the Piezoelectric Immunosensor
Sensors 2007, 7(3), 341-353; doi:10.3390/s7030341
Received: 22 February 2007 / Accepted: 15 March 2007 / Published: 20 March 2007
Cited by 17 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
Monoclonal antibodies with specificity against the Francisella tularensis outerlipopolysaccharide (LPS) membrane were prepared and characterized using the piezoelectricimmunosensor with immobilized LPS antigen from F. tularensis. Signals obtained by theimmunosensor were compared with ELISA and similar sensitivity was noticed. Signal ofnegative controls obtained [...] Read more.
Monoclonal antibodies with specificity against the Francisella tularensis outerlipopolysaccharide (LPS) membrane were prepared and characterized using the piezoelectricimmunosensor with immobilized LPS antigen from F. tularensis. Signals obtained by theimmunosensor were compared with ELISA and similar sensitivity was noticed. Signal ofnegative controls obtained using the biosensor was below 0.5% of the signal obtained for theselected specific antibody clone 4H3B9D3. Testing of cross reactivity based on the sensorswith immobilized LPS from Escherichia coli and Bacillus subtilis confirmed selectivity ofthis antibody. Furthermore, the 4H3B9D3 antibody was successfully isotypized as IgM usingthe piezoelectric sensors with secondary antibodies. Kinetics parameters of antibody wereevaluated in the flow-through arrangement. The kinetic rate constants for the antibody4H3B9D3 were ka = (2.31 ± 0.20)·105 l mol-1s-1 (association) and kd = (0.0010 ±0.00062) s-1(dissociation) indicating very good affinity to the LPS antigen. Full article
Open AccessArticle An Improved Co-evolutionary Particle Swarm Optimization for Wireless Sensor Networks with Dynamic Deployment
Sensors 2007, 7(3), 354-370; doi:10.3390/s7030354
Received: 6 March 2007 / Accepted: 20 March 2007 / Published: 22 March 2007
Cited by 73 | PDF Full-text (390 KB) | HTML Full-text | XML Full-text
Abstract
The effectiveness of wireless sensor networks (WSNs) depends on the coverage and target detection probability provided by dynamic deployment, which is usually supported by the virtual force (VF) algorithm. However, in the VF algorithm, the virtual force exerted by stationary sensor nodes [...] Read more.
The effectiveness of wireless sensor networks (WSNs) depends on the coverage and target detection probability provided by dynamic deployment, which is usually supported by the virtual force (VF) algorithm. However, in the VF algorithm, the virtual force exerted by stationary sensor nodes will hinder the movement of mobile sensor nodes. Particle swarm optimization (PSO) is introduced as another dynamic deployment algorithm, but in this case the computation time required is the big bottleneck. This paper proposes a dynamic deployment algorithm which is named “virtual force directed co-evolutionary particle swarm optimization” (VFCPSO), since this algorithm combines the co-evolutionary particle swarm optimization (CPSO) with the VF algorithm, whereby the CPSO uses multiple swarms to optimize different components of the solution vectors for dynamic deployment cooperatively and the velocity of each particle is updated according to not only the historical local and global optimal solutions, but also the virtual forces of sensor nodes. Simulation results demonstrate that the proposed VFCPSO is competent for dynamic deployment in WSNs and has better performance with respect to computation time and effectiveness than the VF, PSO and VFPSO algorithms. Full article
Open AccessArticle SDS-PAGE Analysis of Soluble Proteins in Reconstituted Milk Exposed to Different Heat Treatments
Sensors 2007, 7(3), 371-383; doi:10.3390/s7030371
Received: 26 February 2007 / Accepted: 15 March 2006 / Published: 23 March 2007
Cited by 24 | PDF Full-text (563 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with the investigation of the impact of the heat treatment of reconstituted skim milk conducted at different temperatures, and the adding of demineralized whey on the protein solubility, soluble protein composition and interactions involved between proteins in a chemical [...] Read more.
This paper deals with the investigation of the impact of the heat treatment of reconstituted skim milk conducted at different temperatures, and the adding of demineralized whey on the protein solubility, soluble protein composition and interactions involved between proteins in a chemical complex. Commercial skim milk has been reconstituted and heat treated at 75°C, 85°C and 90°C for 20 minutes. Demineralized whey has been added in concentrations of 0.5%, 1.0 and 2.0%. The soluble protein composition has been determined by the polyacrilamide gel electrophoresis (SDS-PAGE) and by the densitometric analysis. Due to the different changes occurred during treatments at different temperatures, proteins of heat-treated samples containing added demineralized whey have had significantly different solubility. At lower temperatures (75°C and 85°C) the adding of demineralized whey decreased the protein solubility by 5.28%-26.41%, while the addition of demineralized whey performed at 90°C increased the soluble protein content by 5.61%- 28.89%. Heat treatments, as well as the addition of demineralized whey, have induced high molecular weight complex formation. β-Lg, α-La and κ-casein are involved in high molecular weight complexes. The disulfide interactions between denatured molecules of these proteins are mostly responsible for the formation of coaggregates. The level of their interactions and the soluble protein composition are determined by the degree of temperature. Full article
Open AccessArticle Intelligent Fiber Optic Sensor for Estimating the Concentration of a Mixture-Design and Working Principle
Sensors 2007, 7(3), 384-399; doi:10.3390/s7030384
Received: 20 February 2007 / Accepted: 22 March 2007 / Published: 26 March 2007
Cited by 15 | PDF Full-text (597 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the construction and working principles of an intelligent fiber-optic intensity sensor used for examining the concentration of a mixture in conjunction with water. It can find applications e.g. in waste-water treatment plant for selection of a treatment process. The [...] Read more.
This paper presents the construction and working principles of an intelligent fiber-optic intensity sensor used for examining the concentration of a mixture in conjunction with water. It can find applications e.g. in waste-water treatment plant for selection of a treatment process. The sensor head is the end of a large core polymer optical fiber, which constitutes one arm of an asymmetrical coupler. The head works on the reflection intensity basis. The reflected signal level depends on the Fresnel reflection from the air and from the mixture examined when the head is immersed in it. The sensor head is mounted on a lift. For detection purposes the signal can be measured on head submerging, submersion, emerging and emergence. Therefore, the measured signal depends on the surface tension, viscosity, turbidity and refraction coefficient of the solution. The signal coming from the head is processed electrically in an opto-electronic interface. Then it is fed to a neural network. The novelty of the proposed sensor lies in that it contains an asymmetrical coupler and a neural network that works in the generalization mode. The sensor resolution depends on the efficiency of the asymmetrical coupler, the precision of the opto-electronic signal conversion and the learning accuracy of the neural network. Therefore, the number and quality of the points used for the learning process is very important. By way of example, the paper describes a sensor intended for examining the concentration of liquid soap in water. Full article
(This article belongs to the Special Issue Intelligent Sensors)
Open AccessArticle A New Tiapride Selective Electrode and Its Clinical Application
Sensors 2007, 7(3), 400-409; doi:10.3390/s7030400
Received: 29 January 2007 / Accepted: 19 March 2007 / Published: 27 March 2007
Cited by 8 | PDF Full-text (78 KB) | HTML Full-text | XML Full-text
Abstract
The construction and electrochemical response characteristics of a poly(vinylchloride) (PVC) membrane selective electrode for the determination of tiapride (TPD) are described. The sensing membrane comprised an ion-pair formed between the protonated drug and tetraphenylborate (TPB-) in a plasticized PVC matrix. The influence of membrane composition on the electrode response was studied. The electrode showed a fast, stable and Nernstian response over a wide tiapride concentration range (1x10-5-1x10-2 M) with a slope of 57.5±0.2 mV dec-1 of concentration, a detection limit of 4.3x10-6±2.5x10-7 M, a wide working pH range (2-8) and a fast response time (< 5 s). The electrode showed good selectivity towards tiapride with respect to some inorganic and organic compounds. The electrode has been applied to the determination of tiapride in human urine and iontophoresis solution. Full article
Open AccessArticle Colorimetric and Fluorescent Sensing of SCN- Based on meso-Tetraphenylporphyrin/meso-Tetraphenylporphyrin Cobalt(II) System
Sensors 2007, 7(3), 410-419; doi:10.3390/s7030410
Received: 27 February 2007 / Accepted: 22 March 2007 / Published: 30 March 2007
Cited by 13 | PDF Full-text (166 KB) | HTML Full-text | XML Full-text
Abstract
An approach for colorimetric and fluorescent sensing of thiocyanate (SCN-) hasbeen proposed based on the competitive-displacement strategy betweenmeso-tetraphenylporphyrin (TPP) and meso-tetraphenylporphyrin cobalt(II) (CoTPP). InTHF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence wasquenched stepwise by CoTPP, and then restored [...] Read more.
An approach for colorimetric and fluorescent sensing of thiocyanate (SCN-) hasbeen proposed based on the competitive-displacement strategy betweenmeso-tetraphenylporphyrin (TPP) and meso-tetraphenylporphyrin cobalt(II) (CoTPP). InTHF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence wasquenched stepwise by CoTPP, and then restored by SCN-, the detection limit is 6.0 × 10-4 M.The recognition of SCN- could also be easily achieved by visual way since the assemblysystem showed significant color change by the anion. Both the fluorescence and the colorchange of the system exhibits remarkably high selectivity to SCN- over a large series ofanions. The interaction mechanisms among TPP, CoTPP and SCN- were primarilyinvestigated by fluorescence lifetime. The quenching of TPP fluorescence is attributed to theformation of TPP/CoTPP aggregates, and the fluorescence restoration is due to the binding ofCoTPP with SCN-, releasing the free TPP. This simple system has the potential to be used asa latent fluorescent sensing approach for SCN- for environmental analysis. Full article
(This article belongs to the Special Issue Physiological Sensing)

Review

Jump to: Research

Open AccessReview Gas Sensors Based on Conducting Polymers
Sensors 2007, 7(3), 267-307; doi:10.3390/s7030267
Received: 30 October 2006 / Accepted: 2 March 2007 / Published: 7 March 2007
Cited by 494 | PDF Full-text (514 KB) | HTML Full-text | XML Full-text
Abstract
The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances [...] Read more.
The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessReview Studying the Effect of Deposition Conditions on the Performance and Reliability of MEMS Gas Sensors
Sensors 2007, 7(3), 319-340; doi:10.3390/s7030319
Received: 8 October 2006 / Accepted: 16 February 2007 / Published: 14 March 2007
Cited by 5 | PDF Full-text (4803 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the reliability of a micro-electro-mechanical system (MEMS)-based gas sensor has been investigated using Three Dimensional (3D) coupled multiphysics Finite Element (FE) analysis. The coupled field analysis involved a two-way sequential electro- thermal fields coupling and a one-way sequential thermal-structural [...] Read more.
In this paper, the reliability of a micro-electro-mechanical system (MEMS)-based gas sensor has been investigated using Three Dimensional (3D) coupled multiphysics Finite Element (FE) analysis. The coupled field analysis involved a two-way sequential electro- thermal fields coupling and a one-way sequential thermal-structural fields coupling. An automated substructuring code was developed to reduce the computational cost involved in simulating this complicated coupled multiphysics FE analysis by up to 76 percent. The substructured multiphysics model was then used to conduct a parametric study of the MEMS-based gas sensor performance in response to the variations expected in the thermal and mechanical characteristics of thin films layers composing the sensing MEMS device generated at various stages of the microfabrication process. Whenever possible, the appropriate deposition variables were correlated in the current work to the design parameters, with good accuracy, for optimum operation conditions of the gas sensor. This is used to establish a set of design rules, using linear and nonlinear empirical relations, which can be utilized in real-time at the design and development decision-making stages of similar gas sensors to enable the microfabrication of these sensors with reliable operation. Full article
(This article belongs to the Special Issue Gas Sensors)

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