Sensors

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622 KiB

Open AccessArticle

Toward a Continuous Intravascular Glucose Monitoring System

by Brooke Beier, Katherine Musick, Akira Matsumoto, Alyssa Panitch, Eric Nauman and Pedro Irazoqui

Sensors 2011, 11(1), 409-424; https://doi.org/10.3390/s110100409 - 31 Dec 2010

Cited by 10 | Viewed by 10338

Abstract

Proof-of-concept studies that display the potential of using a glucose-sensitive hydrogel as a continuous glucose sensor are presented. The swelling ratio, porosity, and diffusivity of the hydrogel increased with glucose concentration. In glucose solutions of 50, 100, 200, and 300 mg/dL, the hydrogel [...] Read more.

Proof-of-concept studies that display the potential of using a glucose-sensitive hydrogel as a continuous glucose sensor are presented. The swelling ratio, porosity, and diffusivity of the hydrogel increased with glucose concentration. In glucose solutions of 50, 100, 200, and 300 mg/dL, the hydrogel swelling ratios were 4.9, 12.3, 15.9, and 21.7, respectively, and the swelling was reversible. The impedance across the hydrogel depended solely on the thickness and had an average increase of 47 W/mm. The hydrogels exposed to a hyperglycemic solution were more porous than the hydrogels exposed to a normal glycemic solution. The diffusivity of 390 Da MW fluorescein isothiocyanate in hydrogels exposed to normal and hyperglycemic solutions was examined using fluorescence recovery after photobleaching and was found to be 9.3 × 10⁻¹⁴ and 41.4 × 10⁻¹⁴ m²/s, respectively, compared to 6.2 × 10⁻¹⁰ m²/s in glucose solution. There was no significant difference between the permeability of hydrogels in normal and hyperglycemic glucose solutions with averages being 5.26 × 10⁻¹⁷ m² and 5.80 × 10⁻¹⁷ m², respectively, which resembles 2–4% agarose gels. A prototype design is presented for continuous intravascular glucose monitoring by attaching a glucose sensor to an FDA-approved stent. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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738 KiB

Open AccessArticle

Biocatalysts Immobilized in Ultrathin Ordered Films

by Jadwiga Sołoducho and Joanna Cabaj

Sensors 2010, 10(11), 10298-10313; https://doi.org/10.3390/s101110298 - 16 Nov 2010

Cited by 6 | Viewed by 8165

Abstract

The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new [...] Read more.

The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new materials are of interest for applications as biosensors and biocatalysts. We review the growing field of oxidases immobilized onto ordered Langmiur-Blodgett and Langmuir-Schaefer films. Strategies for the preparation of solid supports and the essential properties of the resulting materials with respect to the envisaged applications are presented. Basic effects of the nature of the adsorption and various aspects of the application of these materials as biosensors, biocatalysts are discussed. Outlook of potential applications and further challenges are also provided. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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482 KiB

Open AccessArticle

Development of an Electrochemical Biosensor for the Detection of Aflatoxin M₁ in Milk

by Nathalie Paniel, Antonio Radoi and Jean-Louis Marty

Sensors 2010, 10(10), 9439-9448; https://doi.org/10.3390/s101009439 - 20 Oct 2010

Cited by 114 | Viewed by 13449

Abstract

We have developed an electrochemical immunosensor for the detection of ultratrace amounts of aflatoxin M₁ (AFM₁) in food products. The sensor was based on a competitive immunoassay using horseradish peroxidase (HRP) as a tag. Magnetic nanoparticles coated with antibody (anti-AFM [...] Read more.

We have developed an electrochemical immunosensor for the detection of ultratrace amounts of aflatoxin M₁ (AFM₁) in food products. The sensor was based on a competitive immunoassay using horseradish peroxidase (HRP) as a tag. Magnetic nanoparticles coated with antibody (anti-AFM₁) were used to separate the bound and unbound fractions. The samples containing AFM₁ were incubated with a fixed amount of antibody and tracer [AFM₁ linked to HRP (conjugate)] until the system reached equilibrium. Competition occurs between the antigen (AFM₁) and the conjugate for the antibody. Then, the mixture was deposited on the surface of screen-printed carbon electrodes, and the mediator [5-methylphenazinium methyl sulphate (MPMS)] was added. The enzymatic response was measured amperometrically. A standard range (0, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.3, 0.4 and 0.5 ppb) of AFM₁-contaminated milk from the ELISA kit was used to obtain a standard curve for AFM₁. To test the detection sensitivity of our sensor, samples of commercial milk were supplemented at 0.01, 0.025, 0.05 or 0.1 ppb with AFM₁. Our immunosensor has a low detection limit (0.01 ppb), which is under the recommended level of AFM₁ [0.05 µg L-1 (ppb)], and has good reproducibility. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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1273 KiB

Open AccessArticle

Design and Characterization of a High Resolution Microfluidic Heat Flux Sensor with Thermal Modulation

by Sung-Ki Nam, Jung-Kyun Kim, Sung-Cheon Cho and Sun-Kyu Lee

Sensors 2010, 10(7), 6594-6611; https://doi.org/10.3390/s100706594 - 9 Jul 2010

Cited by 18 | Viewed by 11505

Abstract

A complementary metal-oxide semiconductor-compatible process was used in the design and fabrication of a suspended membrane microfluidic heat flux sensor with a thermopile for the purpose of measuring the heat flow rate. The combination of a thirty-junction gold and nickel thermoelectric sensor with [...] Read more.

A complementary metal-oxide semiconductor-compatible process was used in the design and fabrication of a suspended membrane microfluidic heat flux sensor with a thermopile for the purpose of measuring the heat flow rate. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, a low pass filter, and a lock-in amplifier can yield a resolution 20 nW with a sensitivity of 461 V/W. The thermal modulation method is used to eliminate low-frequency noise from the sensor output, and various amounts of fluidic heat were applied to the sensor to investigate its suitability for microfluidic applications. For sensor design and analysis of signal output, a method of modeling and simulating electro-thermal behavior in a microfluidic heat flux sensor with an integrated electronic circuit is presented and validated. The electro-thermal domain model was constructed by using system dynamics, particularly the bond graph. The electro-thermal domain system model in which the thermal and the electrical domains are coupled expresses the heat generation of samples and converts thermal input to electrical output. The proposed electro-thermal domain system model is in good agreement with the measured output voltage response in both the transient and the steady state. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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1348 KiB

Open AccessArticle

Enzyme Immobilization Strategies and Electropolymerization Conditions to Control Sensitivity and Selectivity Parameters of a Polymer-Enzyme Composite Glucose Biosensor

by Sharon A. Rothwell, Sarah J. Killoran and Robert D. O’Neill

Sensors 2010, 10(7), 6439-6462; https://doi.org/10.3390/s100706439 - 30 Jun 2010

Cited by 62 | Viewed by 12519

Abstract

In an ongoing programme to develop characterization strategies relevant to biosensors for in-vivo monitoring, glucose biosensors were fabricated by immobilizing the enzyme glucose oxidase (GOx) on 125 µm diameter Pt cylinder wire electrodes (Pt_C), using three different methods: before, after or [...] Read more.

In an ongoing programme to develop characterization strategies relevant to biosensors for in-vivo monitoring, glucose biosensors were fabricated by immobilizing the enzyme glucose oxidase (GOx) on 125 µm diameter Pt cylinder wire electrodes (Pt_C), using three different methods: before, after or during the amperometric electrosynthesis of poly(ortho-phenylenediamine), PoPD, which also served as a permselective membrane. These electrodes were calibrated with H₂O₂(the biosensor enzyme signal molecule), glucose, and the archetypal interference compound ascorbic acid (AA) to determine the relevant polymer permeabilities and the apparent Michaelis-Menten parameters for glucose. A number of selectivity parameters were used to identify the most successful design in terms of the balance between substrate sensitivity and interference blocking. For biosensors electrosynthesized in neutral buffer under the present conditions, entrapment of the GOx within the PoPD layer produced the design (Pt_C/PoPD-GOx) with the highest linear sensitivity to glucose (5.0 ± 0.4 μA cm⁻² mM⁻¹), good linear range (K_M= 16 ± 2 mM) and response time (< 2 s), and the greatest AA blocking (99.8% for 1 mM AA). Further optimization showed that fabrication of Pt_C/PoPD-GOx in the absence of added background electrolyte (i.e., electropolymerization in unbuffered enzyme-monomer solution) enhanced glucose selectivity 3-fold for this one-pot fabrication protocol which provided AA-rejection levels at least equal to recent multi-step polymer bilayer biosensor designs. Interestingly, the presence of enzyme protein in the polymer layer had opposite effects on permselectivity for low and high concentrations of AA, emphasizing the value of studying the concentration dependence of interference effects which is rarely reported in the literature. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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928 KiB

Open AccessArticle

Immunosensor Incorporating Anti-His (C-term) IgG F(ab’) Fragments Attached to Gold Nanorods for Detection of His-Tagged Proteins in Culture Medium

by Michal Wąsowicz, Małgorzata Milner, Dorota Radecka, Krystyna Grzelak and Hanna Radecka

Sensors 2010, 10(6), 5409-5424; https://doi.org/10.3390/s100605409 - 1 Jun 2010

Cited by 21 | Viewed by 10676

Abstract

Immunosensors based on gold electrodes (electrochemical) or gold discs (optical) modified with 1,6-hexanedithiol, gold nanorods and Anti-His (C-term) monoclonal antibody F(ab’) fragment are described. The antigen detected by the sensing platform is a recombinant histidine-tagged silk proteinase inhibitor (rSPI2-His6). Electrochemical impedance spectroscopy (EIS) [...] Read more.

Immunosensors based on gold electrodes (electrochemical) or gold discs (optical) modified with 1,6-hexanedithiol, gold nanorods and Anti-His (C-term) monoclonal antibody F(ab’) fragment are described. The antigen detected by the sensing platform is a recombinant histidine-tagged silk proteinase inhibitor (rSPI2-His6). Electrochemical impedance spectroscopy (EIS) and surface plasmon resonance (SPR) techniques were used as methods for detection of the antigen. This approach allows to detect the antigen protein in concentration of 10 pg per mL (0.13 pM) of culture medium. The immunosensor shows good reproducibility due to covalent immobilization of F(ab’) fragments to gold nanorods layer Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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1117 KiB

Open AccessArticle

Development of a Three Dimensional Neural Sensing Device by a Stacking Method

by Chih-Wei Chang and Jin-Chern Chiou

Sensors 2010, 10(5), 4238-4252; https://doi.org/10.3390/s100504238 - 28 Apr 2010

Cited by 22 | Viewed by 11678 | Correction

Abstract

This study reports a new stacking method for assembling a 3-D microprobe array. To date, 3-D array structures have usually been assembled with vertical spacers, snap fasteners and a supporting platform. Such methods have achieved 3-D structures but suffer from complex assembly steps, [...] Read more.

This study reports a new stacking method for assembling a 3-D microprobe array. To date, 3-D array structures have usually been assembled with vertical spacers, snap fasteners and a supporting platform. Such methods have achieved 3-D structures but suffer from complex assembly steps, vertical interconnection for 3-D signal transmission, low structure strength and large implantable opening. By applying the proposed stacking method, the previous techniques could be replaced by 2-D wire bonding. In this way, supporting platforms with slots and vertical spacers were no longer needed. Furthermore, ASIC chips can be substituted for the spacers in the stacked arrays to achieve system integration, design flexibility and volume usage efficiency. To avoid overflow of the adhesive fluid during assembly, an anti-overflow design which made use of capillary action force was applied in the stacking method as well. Moreover, presented stacking procedure consumes only 35 minutes in average for a 4 × 4 3-D microprobe array without requiring other specially made assembly tools. To summarize, the advantages of the proposed stacking method for 3-D array assembly include simplified assembly process, high structure strength, smaller opening area and integration ability with active circuits. This stacking assembly technique allows an alternative method to create 3-D structures from planar components. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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Review

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792 KiB

Open AccessReview

Nitrite Biosensing via Selective Enzymes—A Long but Promising Route

by M. Gabriela Almeida, Alexandra Serra, Celia M. Silveira and Jose J.G. Moura

Sensors 2010, 10(12), 11530-11555; https://doi.org/10.3390/s101211530 - 15 Dec 2010

Cited by 48 | Viewed by 15443

Abstract

The last decades have witnessed a steady increase of the social and political awareness for the need of monitoring and controlling environmental and industrial processes. In the case of nitrite ion, due to its potential toxicity for human health, the European Union has [...] Read more.

The last decades have witnessed a steady increase of the social and political awareness for the need of monitoring and controlling environmental and industrial processes. In the case of nitrite ion, due to its potential toxicity for human health, the European Union has recently implemented a number of rules to restrict its level in drinking waters and food products. Although several analytical protocols have been proposed for nitrite quantification, none of them enable a reliable and quick analysis of complex samples. An alternative approach relies on the construction of biosensing devices using stable enzymes, with both high activity and specificity for nitrite. In this paper we review the current state-of-the-art in the field of electrochemical and optical biosensors using nitrite reducing enzymes as biorecognition elements and discuss the opportunities and challenges in this emerging market. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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2436 KiB

Open AccessReview

Optical Oxygen Sensors for Applications in Microfluidic Cell Culture

by Samantha M. Grist, Lukas Chrostowski and Karen C. Cheung

Sensors 2010, 10(10), 9286-9316; https://doi.org/10.3390/s101009286 - 15 Oct 2010

Cited by 155 | Viewed by 25620

Abstract

The presence and concentration of oxygen in biological systems has a large impact on the behavior and viability of many types of cells, including the differentiation of stem cells or the growth of tumor cells. As a result, the integration of oxygen sensors [...] Read more.

The presence and concentration of oxygen in biological systems has a large impact on the behavior and viability of many types of cells, including the differentiation of stem cells or the growth of tumor cells. As a result, the integration of oxygen sensors within cell culture environments presents a powerful tool for quantifying the effects of oxygen concentrations on cell behavior, cell viability, and drug effectiveness. Because microfluidic cell culture environments are a promising alternative to traditional cell culture platforms, there is recent interest in integrating oxygen-sensing mechanisms with microfluidics for cell culture applications. Optical, luminescence-based oxygen sensors, in particular, show great promise in their ability to be integrated with microfluidics and cell culture systems. These sensors can be highly sensitive and do not consume oxygen or generate toxic byproducts in their sensing process. This paper presents a review of previously proposed optical oxygen sensor types, materials and formats most applicable to microfluidic cell culture, and analyzes their suitability for this and other in vitro applications. Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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30 KiB

Open AccessCorrection

Correction: Chang, C.W., et al. Development of a Three Dimensional Neural Sensing Device by a Stacking Method. Sensors 2010, 10, 4238-4252

by Chih-Wei Chang and Jin-Chern Chiou

Sensors 2010, 10(5), 4716; https://doi.org/10.3390/s100504716 - 7 May 2010

Viewed by 8052

Abstract

The authors would like to correct the affiliations and acknowledgement of this paper [1] as follows: [...] Full article

(This article belongs to the Special Issue Bio-devices and Materials)

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