| 1. |
- Álvarez, Jesús, et al.
(författare)
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Real time optical immunosensing with flow-through porous alumina membranes
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 202, s. 834-839
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Tidskriftsartikel (refereegranskat)abstract
- Through the presentation of analytical data from bioassay experiments, measured by polarimetry, we demonstrate for the first time a real time immunoassay within a free standing macroporous alumina membrane. The 200 nm nominal pore diameter of the membrane enables flow-through, thereby providing an ideal fluidic platform for the targeted delivery of analytes to bioreceptors immobilized on the pore walls, enabling fast sensing response times and the use of small sample volumes (<100 μL). For the immunoassay, the pore walls were first coated with the functional copolymer, copoly(DMA-NAS) using a novel coupling process, before immobilization of the allergen protein, β-lactoglobulin, by spotting. The immuno-assay then proceeded with the binding of the primary and secondary antibody cognates, rabbit anti-β-lactoglobulin and anti-rabbit IgG respectively. Through the use of streptavidin coated quantum dots as refractive index signal enhancers, a noise floor for individual measurements of 3.7 ng/mL (25 pM) was obtained, with an overall statistical, or formal assay LOD of 33.7 ng/mL (225 pM), for total assay time below 1 h.
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| 2. |
- Anderson, Henrik, et al.
(författare)
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Systematic investigation of biomolecular interactions using combined frequency and motional resistance measurements
- 2011
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 153:1, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- The resonance frequency of acoustic biosensors is today used as a label-free technique for detecting mass changes on sensor surfaces. In combination with an appropriate continuous flow system it has earlier been used for affinity and kinetic rate determination. Here, we assess the potential of a modified acoustic biosensor, monitoring also the real-time dissipation through the resistance of the sensor, to obtain additional kinetic information related to the structure and conformation of the molecules on the surface. Actual interaction studies, including an attempt to determine avidity, are presented along with thorough verification of the experimental setup utilizing true viscous load exposure together with protein and DNA immobilizations. True viscous loads show a linear relationship between resistance and frequency as expected. However, in the interaction studies between antibodies and proteins, as well as in the immobilization of DNA and proteins, higher surface concentrations of interacting molecules led to a decrease (i.e. deviation from the linear trend) in the differential resistance to frequency ratio. This is interpreted as increased surface rigidity at higher surface concentrations of immobilized molecules. Consequently, studies that aim at obtaining biological binding information, such as avidity, from real-time resistance and dissipation data should be conducted at low surface concentrations. In addition, the differential resistance to frequency relationship was found to be highly dependent on the rigidity of the preceding layer(s) of immobilized molecules. This dependence can be utilized to obtain a higher signal-to-noise ratio for resistance measurement by using low surface densities of immobilized interaction partners.
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| 3. |
- Andersson, Mike, et al.
(författare)
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New generation SiC based field effect transistor gas sensors
- 2013
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 179:SI, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- With the advances in SiC processing and high temperature packaging technology over the past few years as well as the accumulation of knowledge regarding the sensing characteristics of different gate metal/insulator material combinations for different gaseous substances SiC based field effect high temperature sensors are moving towards commercial maturity. The route towards commercialization has, however, also led to the necessity of making new considerations regarding the basic transducer design and operation. The focus of this paper is thus the investigation of some basic transducer related parameters influence on sensor device performance, e.g. sensitivity and long-term stability, and characteristics to exemplify the importance of taking design, processing and operation parameters into account when developing field effect sensor devices for commercial applications. less thanbrgreater than less thanbrgreater thanTwo different types of devices, enhancement and depletion type MISFET sensors, with different gate dimensions and two different gate metallisations, Pt and Ir, have been processed. I/V-characteristics have been obtained under exposure to various concentrations of H-2, NH3, CO and O-2 and different bias conditions and the influence of gate dimensions and bias conditions on the sensitivity and dynamic range investigated. The long-term stability has also been studied and compared between different devices and bias conditions for conceptually different gas compositions. The results show that the type of basic transducer device, its design and mode of operation has a large influence on sensor performance. Depletion type devices offer better possibilities for tuning of sensitivity and dynamic range as well as improved longterm stability properties, whereas enhancement type devices require much less control of the processing to ensure good repeatability and yield. Some results have also been verified for two possible applications of SiC based field effect sensors, ammonia slip monitoring for the control of SCR/SNCR and combustion control in domestic/district heating facilities.
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| 4. |
- Antiochia, Riccarda, et al.
(författare)
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A new osmium-polymer modified screen-printed graphene electrode for fructose detection
- 2014
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 195, s. 287-293
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development and performance of the first fructose biosensor based on a commercial screen-printed graphene electrode (SPGE). The electrode was modified with an osmium-polymer, which allowed the efficient wiring of the enzyme fructose dehydrogenase (FDH). The immobilization of both osmium-polymer and FDH was realized in an easy way. Aliquots of 10 mu L, Os-polymer and 10 mu L, FDH were thoroughly mixed with poly(ethylene glycol) (400) diglycidyl ether (PEDGE) and deposited on the electrode surface and left there to dry overnight. The biosensor exhibits a detection limit of 0.8 mu M, a linear range between 0.1 and 8 mM, high sensitivity to fructose (2.15 mu A cm(-2)/mM), good reproducibility (RSD = 1.9%), fast response time (3 s) and a stability of 2 months when stored in the freezer. The proposed fructose biosensor was tested in real food samples and validated with a commercial spectrophotometric enzymatic kit. No significant interference was observed with the proposed biosensor. Published by Elsevier B.V.
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| 5. |
- Bai, Yunpeng, et al.
(författare)
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Interfacing picoliter droplet microfluidics with addressable microliter compartments using fluorescence activated cell sorting
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 194, s. 249-254
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Tidskriftsartikel (refereegranskat)abstract
- Droplet microfluidic platforms have, while enabling high-throughput manipulations and the assaying of single cell scale compartments, been lacking interfacing to allow macro scale access to the output from droplet microfluidic operations. Here, we present a simple and high-throughput method for individually directing cell containing droplets to an addressable and macro scale accessible microwell slide for downstream analysis. Picoliter aqueous droplets containing low gelling point agarose and eGFP expressing Escherichia coli (E. coli) are created in a microfluidic device, solidified to agarose beads and transferred into an aqueous buffer. A Fluorescence activated cell sorter (FACS) is used to sort agarose beads containing cells into microwells in which the growth and expansion of cell colonies is monitored. We demonstrate fast sorting and high accuracy positioning of sorted 15 μm gelled droplet agarose beads into microwells (14 × 48) on a 25 mm × 75 mm microscope slide format using a FACS with a 100 μm nozzle and an xy-stage. The interfacing method presented here enables the products of high-throughput or single cell scale droplet microfluidics assays to be output to a wide range of microtiter plate formats familiar to biological researchers lowering the barriers for utilization of these microfluidic platforms.
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| 6. |
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| 7. |
- Bergström, Gunnar, et al.
(författare)
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Orientation and capturing of antibody affinity ligands: Applications to surface plasmon resonance biochips
- 2011
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 158:1, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- A surface plasmon resonance (SPR) sensor chip with immobilized protein G was used for simultaneously capturing, purifying and orienting antibody ligands. The ligands were further stabilized by chemical cross-linking. This procedure of designing the sensor chip improved efficient use of the ligands and could prolong the analytical use. less thanbrgreater than less thanbrgreater thanThe procedure was evaluated on standard dextran-coated sensor chips onto which commercial semi-purified antibodies towards human serum albumin and human troponin where captured and used for analysing their antigens. less thanbrgreater than less thanbrgreater thanThe procedure demonstrates a general design approach for presenting the biorecognition element on a biosensor surface which enhances sensitivity, stability and selectivity at the same time as an impure ligand is purified.
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| 8. |
- Bora, Tanujjal, et al.
(författare)
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Controlled side coupling of light to cladding mode of ZnO nanorod coated optical fibers and its implications for chemical vapor sensing
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 202, s. 543-550
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Tidskriftsartikel (refereegranskat)abstract
- Controlled light coupling from surrounding to the cladding mode of zinc oxide (ZnO) nanorod coated multimode optical fiber induced by the light scattering properties of the nanorod coating and their applications of sensing are reported here. A dense and highly ordered array of ZnO nanorods is grown on the cladding of silica fibers by using low temperature hydrothermal process and the effect of the hydrothermal growth conditions of the nanorods on the light scattering and coupling to the optical fibers is experimentally investigated. The nanorod length and its number per unit area are found to be most crucial parameters for the optimum side coupling of light into the fibers. Maximum excitation of the cladding mode by side coupling of light is obtained with ZnO nanorods of length similar to 2.2 mu m, demonstrating average coupling efficiency of similar to 2.65%. Upon exposure to different concentrations of various chemical vapors, the nanorod coated fibers demonstrated significant enhancement in the side coupled light intensity, indicating the potential use of these ZnO nanorod coated fibers as simple, low cost and efficient optical sensors. The sensor responses to methanol, ethanol, toluene and benzene vapor were investigated and compared, while the effect of humidity in the sensing environment on the sensor performance was explored as well.
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| 9. |
- Bur, Christian, et al.
(författare)
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Selectivity enhancement of SiC-FET gas sensors by combining temperature and gate bias cycled operation using multivariate statistics
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 193, s. 931-940
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Tidskriftsartikel (refereegranskat)abstract
- In this paper temperature modulation and gate bias modulation of a gas sensitive field effect transistor based on silicon carbide (SiC-FET) are combined in order to increase the selectivity. Data evaluation based on extracted features describing the shape of the sensor response was performed using multivariate statistics, here by Linear Discriminant Analysis (LDA). It was found that both temperature cycling and gate bias cycling are suitable for quantification of different concentrations of carbon monoxide. However, combination of both approaches enhances the stability of the quantification, respectively the discrimination of the groups in the LDA scatterplot. Feature selection based on the stepwise LDA algorithm as well as selection based on the loadings plot has shown that features both from the temperature cycle and from the bias cycle are equally important for the identification of carbon monoxide, nitrogen dioxide and ammonia. In addition, the presented method allows discrimination of these gases independent of the gas concentration. Hence, the selectivity of the FET is enhanced considerably.
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| 10. |
- Chen, Bin, et al.
(författare)
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TICT based fluorescence "turn-on" hydrazine probes
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 199, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence "turn-on" probes PC3 and C3 with weak background emissions were developed for hydrazine sensing. The aldehyde and dicyanovinyl groups were used as the recognition units for PD and C3, respectively. Because of low reactivity of the aldehyde group, the fluorescence of PC3 was enhanced by only ca. 93 folds upon addition of a large amount of 1646 eq. hydrazine. In contrast, 0 exhibited fluorescence enhancement by ca. 239 folds upon addition of only 1.3 eq. hydrazine, and thus it showed high sensitivity towards hydrazine, with the detection limit of 7 ppb. In aqueous systems, it also works well with improved selectivity for hydrazine over CN-. The weak fluorescence of PC3 and 0 can be ascribed to twisted intramolecular charge transfer (TICT) processes by the combination of the bulky diphenylamino and 9-anthryl units, which were well demonstrated by theoretical calculations, viscosity dependent fluorescence, and fluorescence decay behaviour. Addition of hydrazine induced the disappearance of the TICT deactivation pathway, resulting in the observed fluorescence enhancement. It can be concluded that the combination of the bulky diphenylamino and 9-anthryl units is an effective approach for developing fluorescence turn-on hydrazine probes based on the TICT mechanism.
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