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Selected
papers from the latest issue:
Increasing sensitivity of complementary metal–oxide–semiconductor (CMOS) based fluorescence detection
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Joshua Balsam, Hugh Alan Bruck, Yordan Kostov, Avraham Rasooly
Optical technologies are important for biological analysis. Current biomedical optical analyses rely on high-cost, high-sensitivity optical detectors such as photomultipliers, avalanched photodiodes or cooled CCD. In contrast, Webcams, mobile phones and other popular consumer electronics use lower-sensitivity, lower-cost optical components such as photodiodes or CMOS. In order for consumer electronics devices to be useful for biomedical analysis, they must have increased sensitivity. We combined two strategies to increase the sensitivity of CMOS based fluorescence detector. We captured hundreds of low sensitivity images using a Webcam in video mode, instead of a single image typically used in cooled CCD devices. Then we used a computational approach, with an image stacking algorithm, to remove the noise from the many images and combine them into a single image. While video mode is widely used for dynamic scene imaging (e.g. movies or time-lapse photography), it is not used to capture still single static images, removing the images noise increased sensitivity by more than thirty fold. The portable, battery-operated Webcam-based fluorometer system developed here consists of five modules: (1) a low cost CMOS Webcam to monitor light emission, (2) a plate to perform assays, (3) filters and multi-wavelength LED illuminator for fluorophore excitation, (4) a portable computer to acquire and analyze images, and (5) image stacking software for image enhancement. The samples were various concentrations of fluorescein, ranging from 30 uM to 1000 uM, in a 36-well miniature plate. In the single frame mode, the fluorometer's limit-of-detection (LOD) for fluorescein is ∼1000 uM, which is relatively insensitive. However, when used in video mode combined with image stacking enhancement, the LOD is dramatically reduced to 30 uM, sensitivity which is similar to that of state-of-the-art ELISA plate photomultiplier based readers. Numerous medical diagnostics assays rely on optical and fluorescence readers, Our novel combination of detection technologies which is new to biodetection may enable the development of new low cost optical detectors based on an inexpensive Webcam (<$10) has the potential to form the basis of high sensitivity, low cost medical diagnostics for resource-poor settings.
Source:Sensors and Actuators B: Chemical
Joshua Balsam, Hugh Alan Bruck, Yordan Kostov, Avraham Rasooly
Optical technologies are important for biological analysis. Current biomedical optical analyses rely on high-cost, high-sensitivity optical detectors such as photomultipliers, avalanched photodiodes or cooled CCD. In contrast, Webcams, mobile phones and other popular consumer electronics use lower-sensitivity, lower-cost optical components such as photodiodes or CMOS. In order for consumer electronics devices to be useful for biomedical analysis, they must have increased sensitivity. We combined two strategies to increase the sensitivity of CMOS based fluorescence detector. We captured hundreds of low sensitivity images using a Webcam in video mode, instead of a single image typically used in cooled CCD devices. Then we used a computational approach, with an image stacking algorithm, to remove the noise from the many images and combine them into a single image. While video mode is widely used for dynamic scene imaging (e.g. movies or time-lapse photography), it is not used to capture still single static images, removing the images noise increased sensitivity by more than thirty fold. The portable, battery-operated Webcam-based fluorometer system developed here consists of five modules: (1) a low cost CMOS Webcam to monitor light emission, (2) a plate to perform assays, (3) filters and multi-wavelength LED illuminator for fluorophore excitation, (4) a portable computer to acquire and analyze images, and (5) image stacking software for image enhancement. The samples were various concentrations of fluorescein, ranging from 30 uM to 1000 uM, in a 36-well miniature plate. In the single frame mode, the fluorometer's limit-of-detection (LOD) for fluorescein is ∼1000 uM, which is relatively insensitive. However, when used in video mode combined with image stacking enhancement, the LOD is dramatically reduced to 30 uM, sensitivity which is similar to that of state-of-the-art ELISA plate photomultiplier based readers. Numerous medical diagnostics assays rely on optical and fluorescence readers, Our novel combination of detection technologies which is new to biodetection may enable the development of new low cost optical detectors based on an inexpensive Webcam (<$10) has the potential to form the basis of high sensitivity, low cost medical diagnostics for resource-poor settings.
A novel biosensor based on Hafnium oxide: Application for early stage detection of human interleukin-10
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Michael Lee, Nadia Zine, Abdellatif Baraket, Miguel Zabala, Francesca Campabadal, Raffaele Caruso, Maria Giovanna Trivella, Nicole Jaffrezic-Renault, Abdelhamid Errachid
Measurement of interleukin-10 (IL-10) has subsequently become a crucial tool to identify end-stage heart failure (ESHF) patients prone to adverse outcomes during the early phase of left ventricular assisted device (LVAD) implantation. In this context, label-free detection using a novel substrate based on Hafnium oxide (HfO2) grown by Atomic Layer Deposition (ALD) on silicon was applied. Here, we studied the interaction between recombinant human (rh) IL-10 with the corresponding monoclonal antibody (mAb) for early cytokine detection of an anti-inflammatory response due to LVAD implantation. For this purpose, HfO2 has been functionalized using an aldehyde-silane ((11-(Triethoxysilyl) undecanal (TESUD)) self-assembled monolayer (SAMs), to directly immobilize the anti-human IL-10 mAb by covalent bonding. The interaction between the antibody-antigen (Ab-Ag) was characterized by fluorescence patterning and electrochemical impedance spectroscopy (EIS). Confirmation for the bio-recognition of the protein was achieved by fluorescence patterning, while Nyquist plots have shown a stepwise variation due to the polarization resistance (Rp) between the Ab activated surfaces with the detection of the protein. For early expression monitoring, commercial proteins of rh IL-10 were analyzed between 0.1pg/mL to 50ng/mL. Protein concentrations within the linear range of 0.1–20pg/mL were detected, and these values formulated a sensitivity of 0.49 (ng/mL)−1. These preliminary results demonstrated that the developed biosensor was sensitive to the detection of rh IL-10, and the measured limit of 0.1pg/mL in phosphate buffered saline (PBS) was clearly detectable, which displays the high sensitivity of EIS. On analysis of an interference attributable to non-specific binding of other cytokine biomarkers; tumour necrosis factor-α (TNF-α), and IL-1β were analyzed without causing an interference to the IL-10 mAb. This established that selective sensitivity was responsive only to rh IL-10. To our knowledge, this is the first biosensor that has been based on HfO2 for Ag detection by EIS. In time, the HfO2 insulator will be incorporated into the gate of silicon-based ion-sensitive field-effect transistors (ISFETs) and developed as a portable real time detection system for the IL family of biomarkers in human serum.
Source:Sensors and Actuators B: Chemical
Michael Lee, Nadia Zine, Abdellatif Baraket, Miguel Zabala, Francesca Campabadal, Raffaele Caruso, Maria Giovanna Trivella, Nicole Jaffrezic-Renault, Abdelhamid Errachid
Measurement of interleukin-10 (IL-10) has subsequently become a crucial tool to identify end-stage heart failure (ESHF) patients prone to adverse outcomes during the early phase of left ventricular assisted device (LVAD) implantation. In this context, label-free detection using a novel substrate based on Hafnium oxide (HfO2) grown by Atomic Layer Deposition (ALD) on silicon was applied. Here, we studied the interaction between recombinant human (rh) IL-10 with the corresponding monoclonal antibody (mAb) for early cytokine detection of an anti-inflammatory response due to LVAD implantation. For this purpose, HfO2 has been functionalized using an aldehyde-silane ((11-(Triethoxysilyl) undecanal (TESUD)) self-assembled monolayer (SAMs), to directly immobilize the anti-human IL-10 mAb by covalent bonding. The interaction between the antibody-antigen (Ab-Ag) was characterized by fluorescence patterning and electrochemical impedance spectroscopy (EIS). Confirmation for the bio-recognition of the protein was achieved by fluorescence patterning, while Nyquist plots have shown a stepwise variation due to the polarization resistance (Rp) between the Ab activated surfaces with the detection of the protein. For early expression monitoring, commercial proteins of rh IL-10 were analyzed between 0.1pg/mL to 50ng/mL. Protein concentrations within the linear range of 0.1–20pg/mL were detected, and these values formulated a sensitivity of 0.49 (ng/mL)−1. These preliminary results demonstrated that the developed biosensor was sensitive to the detection of rh IL-10, and the measured limit of 0.1pg/mL in phosphate buffered saline (PBS) was clearly detectable, which displays the high sensitivity of EIS. On analysis of an interference attributable to non-specific binding of other cytokine biomarkers; tumour necrosis factor-α (TNF-α), and IL-1β were analyzed without causing an interference to the IL-10 mAb. This established that selective sensitivity was responsive only to rh IL-10. To our knowledge, this is the first biosensor that has been based on HfO2 for Ag detection by EIS. In time, the HfO2 insulator will be incorporated into the gate of silicon-based ion-sensitive field-effect transistors (ISFETs) and developed as a portable real time detection system for the IL family of biomarkers in human serum.
Temperature-Modulated Differential Scanning Calorimetry in a MEMS Device
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Bin Wang, Qiao Lin
We present a MEMS-based approach to temperature-modulated differential scanning calorimetry (AC-DSC) for biomolecular characterization. Based on a MEMS device integrating microfluidic handling with highly sensitive thermoelectric detection as well as on-chip AC heating and temperature sensing, we perform, for the first time, MEMS-based AC-DSC detection of liquid biological samples, demonstrated by the measurements of protein unfolding. The specific heat capacity and the melting temperature of the protein during the unfolding process are obtained and found to be consistent with published data. This MEMS AC-DSC approach has potential applications to label-free characterization of biomolecules.
Source:Sensors and Actuators B: Chemical
Bin Wang, Qiao Lin
We present a MEMS-based approach to temperature-modulated differential scanning calorimetry (AC-DSC) for biomolecular characterization. Based on a MEMS device integrating microfluidic handling with highly sensitive thermoelectric detection as well as on-chip AC heating and temperature sensing, we perform, for the first time, MEMS-based AC-DSC detection of liquid biological samples, demonstrated by the measurements of protein unfolding. The specific heat capacity and the melting temperature of the protein during the unfolding process are obtained and found to be consistent with published data. This MEMS AC-DSC approach has potential applications to label-free characterization of biomolecules.
Influences of Al, Pd and Pt additives on the conduction mechanism as well as the surface and bulk properties of SnO2 based polycrystalline thick film gas sensors
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
M. Hübner, N. Bârsan, U. Weimar
The reasons of the effect of Pd, Pt and Al additives on the sensing and conduction mechanism of SnO2 based thick film porous gas sensing layers are studied by a combination of DC-resistance, work function changes and catalytic conversion measurements. This is done by analyzing the dependence of the DC resistance on the corresponding band bending changes over a large range and the use of previously reported conduction models. The gained information deals with the surface band bending in the absence of ambient atmosphere oxygen, the position of the Fermi level, the concentration of free charge carriers, the Debye length and the width of the surface charge layer in various ambient conditions. Very interestingly, we found that in all cases the “doping” had an impact on both surface and bulk properties even if the additives and the technology of “doping” were targeted towards surface activation, in the case of Pt and Pd, and bulk compensation of donors, in the case of Al. Besides that, the catalytic conversion experiments indicated that the presence of Pt is associated with the reduction of the material in the absence of ambient atmosphere oxygen.
Source:Sensors and Actuators B: Chemical
M. Hübner, N. Bârsan, U. Weimar
The reasons of the effect of Pd, Pt and Al additives on the sensing and conduction mechanism of SnO2 based thick film porous gas sensing layers are studied by a combination of DC-resistance, work function changes and catalytic conversion measurements. This is done by analyzing the dependence of the DC resistance on the corresponding band bending changes over a large range and the use of previously reported conduction models. The gained information deals with the surface band bending in the absence of ambient atmosphere oxygen, the position of the Fermi level, the concentration of free charge carriers, the Debye length and the width of the surface charge layer in various ambient conditions. Very interestingly, we found that in all cases the “doping” had an impact on both surface and bulk properties even if the additives and the technology of “doping” were targeted towards surface activation, in the case of Pt and Pd, and bulk compensation of donors, in the case of Al. Besides that, the catalytic conversion experiments indicated that the presence of Pt is associated with the reduction of the material in the absence of ambient atmosphere oxygen.
Development of gas sensors coatings by polyaniline using pressurized fluid
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Clarice Steffens, Marcos L. Corazza, Elton Franceschi, Fernanda Castilhos, Paulo S.P. Herrmann,Jr, J. Vladimir Oliveira
The objective of this work was to develop gas sensors using three different techniques for the deposition of polyaniline film: a) precipitation of polyaniline particles doped with dodecylbenzenesulfonic acid (DBSA) using supercritical carbon dioxide (SC-CO2), b) rapid expansion with SC-CO2 (modified RESS) of polyaniline doped with DBSA, and c) in-situ polymerization polyaniline doped with chloridric acid. The sensors responses were evaluated at moisture and volatile organic compounds (VOCs). All of the sensors presented a satisfactory sensitivity and reversibility when exposed to VOCs. The films morphology was characterized by scanning electronic microscopy for field emission (FE-SEM). Results showed a difference regarding phase formation and behavior for the sensors obtained using SC-CO2 coatings with polyaniline and by in-situ polymerization, indicating that techniques the use of supercritical fluid techniques are promising in manufacturing such electronic devices.
Source:Sensors and Actuators B: Chemical
Clarice Steffens, Marcos L. Corazza, Elton Franceschi, Fernanda Castilhos, Paulo S.P. Herrmann,Jr, J. Vladimir Oliveira
The objective of this work was to develop gas sensors using three different techniques for the deposition of polyaniline film: a) precipitation of polyaniline particles doped with dodecylbenzenesulfonic acid (DBSA) using supercritical carbon dioxide (SC-CO2), b) rapid expansion with SC-CO2 (modified RESS) of polyaniline doped with DBSA, and c) in-situ polymerization polyaniline doped with chloridric acid. The sensors responses were evaluated at moisture and volatile organic compounds (VOCs). All of the sensors presented a satisfactory sensitivity and reversibility when exposed to VOCs. The films morphology was characterized by scanning electronic microscopy for field emission (FE-SEM). Results showed a difference regarding phase formation and behavior for the sensors obtained using SC-CO2 coatings with polyaniline and by in-situ polymerization, indicating that techniques the use of supercritical fluid techniques are promising in manufacturing such electronic devices.
Impedance-activated microseparator based on amplitude modulation sensing and dielectrophoretic switching methods
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Song-I Han, Young-Don Joo, Ki-Ho Han
We present an impedance-activated microseparator that can detect and isolate microparticles according to size. Using the amplitude modulation sensing method, the impedance-activated microseparator precisely detected the size of 5-, 8-, and 10-μm polystyrene beads. To obtain high sensitivity, sensing electrodes were designed in a parallel overlap electrode structure, including two excitation electrodes patterned on the roof and a sensing electrode patterned on the bottom floor. The peak output voltage was proportionally correlated with particle volume; thus, the measured peak output values were used both to calculate microparticle size and to count the number of microparticles. Experimental results showed that volume resolution of the impedance-activated microseparator is less than 30μm3 and the minimum detectable particle size is approximately 2μm in diameter. By using the dielectrophoresis-based track switching method, the proposed impedance-activated microseparator could isolate microparticles according to their size with greater than 90% separation efficiency. Consequently, the proposed impedance-activated microseparator may facilitate the identification and separation of microparticles according to size from a heterogeneous admixture.
Source:Sensors and Actuators B: Chemical
Song-I Han, Young-Don Joo, Ki-Ho Han
We present an impedance-activated microseparator that can detect and isolate microparticles according to size. Using the amplitude modulation sensing method, the impedance-activated microseparator precisely detected the size of 5-, 8-, and 10-μm polystyrene beads. To obtain high sensitivity, sensing electrodes were designed in a parallel overlap electrode structure, including two excitation electrodes patterned on the roof and a sensing electrode patterned on the bottom floor. The peak output voltage was proportionally correlated with particle volume; thus, the measured peak output values were used both to calculate microparticle size and to count the number of microparticles. Experimental results showed that volume resolution of the impedance-activated microseparator is less than 30μm3 and the minimum detectable particle size is approximately 2μm in diameter. By using the dielectrophoresis-based track switching method, the proposed impedance-activated microseparator could isolate microparticles according to their size with greater than 90% separation efficiency. Consequently, the proposed impedance-activated microseparator may facilitate the identification and separation of microparticles according to size from a heterogeneous admixture.
Theoretical optimizations of acoustic wave gas sensors with high conductivity sensitivities
23 May 2012,
09:24:28
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Li Fan, Shu-yi Zhang, Huan Ge, Hui Zhang
The frequency shift and electric loss induced by the variation of the surface conductivity caused by the sorbed matter in the acoustic wave (AW) gas sensor are evaluated with the transfer matrix method. It is found that the high conductivity sensitivity is always accompanied by the high electric loss, which increases the insert losses and the minimum detectable masses of the sensors. However, with the same electric perturbation, the AW sensors with longer operating wavelengths have smaller electric losses, which provides the opportunities to achieve the high conductivity sensitivity and reduce the minimum detectable mass simultaneously in the gas sensor.
Source:Sensors and Actuators B: Chemical
Li Fan, Shu-yi Zhang, Huan Ge, Hui Zhang
The frequency shift and electric loss induced by the variation of the surface conductivity caused by the sorbed matter in the acoustic wave (AW) gas sensor are evaluated with the transfer matrix method. It is found that the high conductivity sensitivity is always accompanied by the high electric loss, which increases the insert losses and the minimum detectable masses of the sensors. However, with the same electric perturbation, the AW sensors with longer operating wavelengths have smaller electric losses, which provides the opportunities to achieve the high conductivity sensitivity and reduce the minimum detectable mass simultaneously in the gas sensor.
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