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Recent advances in biosensor based endotoxin detection
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): A.P. Das , P.S. Kumar , S. Swain
Endotoxins also referred to as pyrogens are chemically lipopolysaccharides habitually found in food, environment and clinical products of bacterial origin and are unavoidable ubiquitous microbiological contaminants. Pernicious issues of its contamination result in high mortality and severe morbidities. Standard traditional techniques are slow and cumbersome, highlighting the pressing need for evoking agile endotoxin detection system. The early and prompt detection of endotoxin assumes prime importance in health care, pharmacological and biomedical sectors. The unparalleled recognition abilities of LAL biosensors perched with remarkable sensitivity, high stability and reproducibility have bestowed it with persistent reliability and their possible fabrication for commercial applicability. This review paper entails an overview of various trends in current techniques available and other possible alternatives in biosensor based endotoxin detection together with its classification, epidemiological aspects, thrust areas demanding endotoxin control, commercially available detection sensors and a revolutionary unprecedented approach narrating the influence of omics for endotoxin detection.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): A.P. Das , P.S. Kumar , S. Swain
Endotoxins also referred to as pyrogens are chemically lipopolysaccharides habitually found in food, environment and clinical products of bacterial origin and are unavoidable ubiquitous microbiological contaminants. Pernicious issues of its contamination result in high mortality and severe morbidities. Standard traditional techniques are slow and cumbersome, highlighting the pressing need for evoking agile endotoxin detection system. The early and prompt detection of endotoxin assumes prime importance in health care, pharmacological and biomedical sectors. The unparalleled recognition abilities of LAL biosensors perched with remarkable sensitivity, high stability and reproducibility have bestowed it with persistent reliability and their possible fabrication for commercial applicability. This review paper entails an overview of various trends in current techniques available and other possible alternatives in biosensor based endotoxin detection together with its classification, epidemiological aspects, thrust areas demanding endotoxin control, commercially available detection sensors and a revolutionary unprecedented approach narrating the influence of omics for endotoxin detection.
Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Subash C.B. Gopinath , Thangavel Lakshmipriya , Koichi Awazu
Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Subash C.B. Gopinath , Thangavel Lakshmipriya , Koichi Awazu
Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs.
Graphical abstract
Surface stress-based biosensors
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Shengbo Sang , Yuan Zhao , Wendong Zhang , Pengwei Li , Jie Hu , Gang Li
Surface stress-based biosensors, as one kind of label-free biosensors, have attracted lots of attention in the process of information gathering and measurement for the biological, chemical and medical application with the development of technology and society. This kind of biosensors offers many advantages such as short response time (less than milliseconds) and a typical sensitivity at nanogram, picoliter, femtojoule and attomolar level. Furthermore, it simplifies sample preparation and testing procedures. In this work, progress made towards the use of surface stress-based biosensors for achieving better performance is critically reviewed, including our recent achievement, the optimally circular membrane-based biosensors and biosensor array. The further scientific and technological challenges in this field are also summarized. Critical remark and future steps towards the ultimate surface stress-based biosensors are addressed.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Shengbo Sang , Yuan Zhao , Wendong Zhang , Pengwei Li , Jie Hu , Gang Li
Surface stress-based biosensors, as one kind of label-free biosensors, have attracted lots of attention in the process of information gathering and measurement for the biological, chemical and medical application with the development of technology and society. This kind of biosensors offers many advantages such as short response time (less than milliseconds) and a typical sensitivity at nanogram, picoliter, femtojoule and attomolar level. Furthermore, it simplifies sample preparation and testing procedures. In this work, progress made towards the use of surface stress-based biosensors for achieving better performance is critically reviewed, including our recent achievement, the optimally circular membrane-based biosensors and biosensor array. The further scientific and technological challenges in this field are also summarized. Critical remark and future steps towards the ultimate surface stress-based biosensors are addressed.
Thousand-fold fluorescent signal amplification for mHealth diagnostics
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Joshua Balsam , Reuven Rasooly , Hugh Alan Bruck , Avraham Rasooly
The low sensitivity of Mobile Health (mHealth) optical detectors, such as those found on mobile phones, is a limiting factor for many mHealth clinical applications. To improve sensitivity, we have combined two approaches for optical signal amplification: (1) a computational approach based on an image stacking algorithm to decrease the image noise and enhance weak signals, and (2) an optical signal amplifier utilizing a capillary tube array. These approaches were used in a detection system which includes multi-wavelength LEDs capable of exciting many fluorophores in multiple wavelengths, a mobile phone or a webcam as a detector, and capillary tube array configured with 36 capillary tubes for signal enhancement. The capillary array enables a ∼100× increase in signal sensitivity for fluorescein, reducing the limit of detection (LOD) for mobile phones and webcams from 1000nM to 10nM. Computational image stacking enables another ∼10× increase in signal sensitivity, further reducing the LOD for webcam from 10nM to 1nM. To demonstrate the feasibility of the device for the detection of disease-related biomarkers, adenovirus DNA labeled with SYBR green or fluorescein was analyzed by both our capillary array and a commercial plate reader. The LOD for the capillary array was 5ug/mL, and that of the plate reader was 1ug/mL. Similar results were obtained using DNA stained with fluorescein. The combination of the two signal amplification approaches enables a ∼1000× increase in LOD for the webcam platform. This brings it into the range of a conventional plate reader while using a smaller sample volume (10ul) than the plate reader requires (100ul). This suggests that such a device could be suitable for biosensing applications where up to 10 fold smaller sample sizes are needed. The simple optical configuration for mHealth described in this paper employing the combined capillary and image processing signal amplification is capable of measuring weak fluorescent signals without the need of dedicated laboratories. It has the potential to be used to increase sensitivity of other optically based mHealth technologies, and may increase mHealth's clinical utility, especially for telemedicine and for resource-poor settings and global health applications.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Joshua Balsam , Reuven Rasooly , Hugh Alan Bruck , Avraham Rasooly
The low sensitivity of Mobile Health (mHealth) optical detectors, such as those found on mobile phones, is a limiting factor for many mHealth clinical applications. To improve sensitivity, we have combined two approaches for optical signal amplification: (1) a computational approach based on an image stacking algorithm to decrease the image noise and enhance weak signals, and (2) an optical signal amplifier utilizing a capillary tube array. These approaches were used in a detection system which includes multi-wavelength LEDs capable of exciting many fluorophores in multiple wavelengths, a mobile phone or a webcam as a detector, and capillary tube array configured with 36 capillary tubes for signal enhancement. The capillary array enables a ∼100× increase in signal sensitivity for fluorescein, reducing the limit of detection (LOD) for mobile phones and webcams from 1000nM to 10nM. Computational image stacking enables another ∼10× increase in signal sensitivity, further reducing the LOD for webcam from 10nM to 1nM. To demonstrate the feasibility of the device for the detection of disease-related biomarkers, adenovirus DNA labeled with SYBR green or fluorescein was analyzed by both our capillary array and a commercial plate reader. The LOD for the capillary array was 5ug/mL, and that of the plate reader was 1ug/mL. Similar results were obtained using DNA stained with fluorescein. The combination of the two signal amplification approaches enables a ∼1000× increase in LOD for the webcam platform. This brings it into the range of a conventional plate reader while using a smaller sample volume (10ul) than the plate reader requires (100ul). This suggests that such a device could be suitable for biosensing applications where up to 10 fold smaller sample sizes are needed. The simple optical configuration for mHealth described in this paper employing the combined capillary and image processing signal amplification is capable of measuring weak fluorescent signals without the need of dedicated laboratories. It has the potential to be used to increase sensitivity of other optically based mHealth technologies, and may increase mHealth's clinical utility, especially for telemedicine and for resource-poor settings and global health applications.
Fluorescence correlation spectroscopy analysis for accurate determination of proportion of doubly labeled DNA in fluorescent DNA pool for quantitative biochemical assays
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Sen Hou , Lili Sun , Stefan A. Wieczorek , Tomasz Kalwarczyk , Tomasz S. Kaminski , Robert Holyst
Fluorescent double-stranded DNA (dsDNA) molecules labeled at both ends are commonly produced by annealing of complementary single-stranded DNA (ssDNA) molecules, labeled with fluorescent dyes at the same (3′ or 5′) end. Because the labeling efficiency of ssDNA is smaller than 100%, the resulting dsDNA have two, one or are without a dye. Existing methods are insufficient to measure the percentage of the doubly-labeled dsDNA component in the fluorescent DNA sample and it is even difficult to distinguish the doubly-labeled DNA component from the singly-labeled component. Accurate measurement of the percentage of such doubly labeled dsDNA component is a critical prerequisite for quantitative biochemical measurements, which has puzzled scientists for decades. We established a fluorescence correlation spectroscopy (FCS) system to measure the percentage of doubly labeled dsDNA (PDL) in the total fluorescent dsDNA pool. The method is based on comparative analysis of the given sample and a reference dsDNA sample prepared by adding certain amount of unlabeled ssDNA into the original ssDNA solution. From FCS autocorrelation functions, we obtain the number of fluorescent dsDNA molecules in the focal volume of the confocal microscope and PDL. We also calculate the labeling efficiency of ssDNA. The method requires minimal amount of material. The samples have the concentration of DNA in the nano-molar/L range and the volume of tens of microliters. We verify our method by using restriction enzyme Hind III to cleave the fluorescent dsDNA. The kinetics of the reaction depends strongly on PDL, a critical parameter for quantitative biochemical measurements.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Sen Hou , Lili Sun , Stefan A. Wieczorek , Tomasz Kalwarczyk , Tomasz S. Kaminski , Robert Holyst
Fluorescent double-stranded DNA (dsDNA) molecules labeled at both ends are commonly produced by annealing of complementary single-stranded DNA (ssDNA) molecules, labeled with fluorescent dyes at the same (3′ or 5′) end. Because the labeling efficiency of ssDNA is smaller than 100%, the resulting dsDNA have two, one or are without a dye. Existing methods are insufficient to measure the percentage of the doubly-labeled dsDNA component in the fluorescent DNA sample and it is even difficult to distinguish the doubly-labeled DNA component from the singly-labeled component. Accurate measurement of the percentage of such doubly labeled dsDNA component is a critical prerequisite for quantitative biochemical measurements, which has puzzled scientists for decades. We established a fluorescence correlation spectroscopy (FCS) system to measure the percentage of doubly labeled dsDNA (PDL) in the total fluorescent dsDNA pool. The method is based on comparative analysis of the given sample and a reference dsDNA sample prepared by adding certain amount of unlabeled ssDNA into the original ssDNA solution. From FCS autocorrelation functions, we obtain the number of fluorescent dsDNA molecules in the focal volume of the confocal microscope and PDL. We also calculate the labeling efficiency of ssDNA. The method requires minimal amount of material. The samples have the concentration of DNA in the nano-molar/L range and the volume of tens of microliters. We verify our method by using restriction enzyme Hind III to cleave the fluorescent dsDNA. The kinetics of the reaction depends strongly on PDL, a critical parameter for quantitative biochemical measurements.
Real-time and non-invasive impedimetric monitoring of cell proliferation and chemosensitivity in a perfusion 3D cell culture microfluidic chip
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Kin Fong Lei , Min-Hsien Wu , Che-Wei Hsu , Yi-Dao Chen
A perfusion three-dimensional (3D) cell culture microfluidic chip has been developed for real-time and non-invasive impedimetric monitoring of cell proliferation and chemosensitivity. In this study, human oral cancer cells (OEC-M1) were encapsulated in 3D agarose scaffold and cultured in a miniaturized chamber under perfusion of tested substance. This setting provides a more in vitro physiologically relevant microenvironment to better mimic the complex in vivo microenvironment. A pair of vertical electrodes was embedded at the opposite sidewalls of the culture chamber for the on-site impedance measurement. Cell density in the 3D construct was shown to be proportional to the impedance magnitude of the entire construct. Therefore, perfusion 3D cell culture was performed for up to 5 days and cell proliferation can be monitored by the impedimetric analysis. Moreover, real-time impedimetric monitoring of cell viability under the perfusion of anti-cancer drug in different concentrations was conducted and the impedance magnitude was directly correlated with the cell viability. From the confirmation of the endpoint cell viability assays, a concentration-dependent effect was shown; however, the response of cell viability during the drug treatment was able to be traced by the impedance measurement. The experimental results showed that cell proliferation and chemosensitivity in 3D cell culture format can be monitored by impedance measurement. This microfluidic chip has a high potential to develop a powerful analytical platform for cancer research.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Kin Fong Lei , Min-Hsien Wu , Che-Wei Hsu , Yi-Dao Chen
A perfusion three-dimensional (3D) cell culture microfluidic chip has been developed for real-time and non-invasive impedimetric monitoring of cell proliferation and chemosensitivity. In this study, human oral cancer cells (OEC-M1) were encapsulated in 3D agarose scaffold and cultured in a miniaturized chamber under perfusion of tested substance. This setting provides a more in vitro physiologically relevant microenvironment to better mimic the complex in vivo microenvironment. A pair of vertical electrodes was embedded at the opposite sidewalls of the culture chamber for the on-site impedance measurement. Cell density in the 3D construct was shown to be proportional to the impedance magnitude of the entire construct. Therefore, perfusion 3D cell culture was performed for up to 5 days and cell proliferation can be monitored by the impedimetric analysis. Moreover, real-time impedimetric monitoring of cell viability under the perfusion of anti-cancer drug in different concentrations was conducted and the impedance magnitude was directly correlated with the cell viability. From the confirmation of the endpoint cell viability assays, a concentration-dependent effect was shown; however, the response of cell viability during the drug treatment was able to be traced by the impedance measurement. The experimental results showed that cell proliferation and chemosensitivity in 3D cell culture format can be monitored by impedance measurement. This microfluidic chip has a high potential to develop a powerful analytical platform for cancer research.
Electrochemical sensing interfaces with tunable porosity for nonenzymatic glucose detection: A Cu foam case
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Xiangheng Niu , Yuxiu Li , Jie Tang , Yangliao Hu , Hongli Zhao , Minbo Lan
It is widely thought in electro-biochemical analysis that the sensing interfaces play a key role in the enzymeless detection of biomolecules like glucose, ascorbic acid, dopamine and uric acid. On the way to maximize the anti-poisoning sensitivity of nonenzymatic electrochemical glucose sensors as well as achieve favorable selectivity, we propose here a porous interface fabricated by a facile but effective approach for glucose monitoring in alkaline media containing dissolved oxygen. The sensing interface based on porous Cu foams is directly formed on a homemade disposable screen-printed carbon electrode (SPCE) substrate by electrodeposition assisted with hydrogen evolution simultaneously, and its porosity can be easily tailored through adjusting deposition conditions for the optimal electrocatalytic oxidation of glucose molecules. SEM and BET studies show that the generated Cu foam possesses robust hierarchical porous architectures with greatly enhanced surface area and pore volume, beneficial for the unimpeded mobility of glucose and reaction products. Cyclic voltammetric tests indicate that a diffusion-controlled glucose electro-oxidation reaction occurs at the Cu foam electrode at around +0.35V vs. Ag/AgCl in 0.1M NaOH. Chronoamperometric results obtained under optimized conditions reveal that the proposed sensor exhibits desired poison resistance ability in the presence of chloride ions and significant selectivity to glucose, providing fascinating sensitivities of 2.57 and 1.81mAcm−2 mM−1 for glucose in the linear concentration ranges of 2–80μM and 0.1–5mM, respectively. The limit of detection is calculated to be as low as 0.98μM according to the signal-to-noise ratio of three. In addition, the fabricated sensing interface shows attractive reproducibility (RSD of 5.1% and 7.0% for 15 repeated measurements on a sensor and for measurements on 15 prepared sensors, respectively) and outstanding long-term stability (less than 5% loss in sensitivity over 1 month) for glucose detection. The application of the Cu foam based sensor for monitoring glucose in practical samples is also successfully demonstrated.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Xiangheng Niu , Yuxiu Li , Jie Tang , Yangliao Hu , Hongli Zhao , Minbo Lan
It is widely thought in electro-biochemical analysis that the sensing interfaces play a key role in the enzymeless detection of biomolecules like glucose, ascorbic acid, dopamine and uric acid. On the way to maximize the anti-poisoning sensitivity of nonenzymatic electrochemical glucose sensors as well as achieve favorable selectivity, we propose here a porous interface fabricated by a facile but effective approach for glucose monitoring in alkaline media containing dissolved oxygen. The sensing interface based on porous Cu foams is directly formed on a homemade disposable screen-printed carbon electrode (SPCE) substrate by electrodeposition assisted with hydrogen evolution simultaneously, and its porosity can be easily tailored through adjusting deposition conditions for the optimal electrocatalytic oxidation of glucose molecules. SEM and BET studies show that the generated Cu foam possesses robust hierarchical porous architectures with greatly enhanced surface area and pore volume, beneficial for the unimpeded mobility of glucose and reaction products. Cyclic voltammetric tests indicate that a diffusion-controlled glucose electro-oxidation reaction occurs at the Cu foam electrode at around +0.35V vs. Ag/AgCl in 0.1M NaOH. Chronoamperometric results obtained under optimized conditions reveal that the proposed sensor exhibits desired poison resistance ability in the presence of chloride ions and significant selectivity to glucose, providing fascinating sensitivities of 2.57 and 1.81mAcm−2 mM−1 for glucose in the linear concentration ranges of 2–80μM and 0.1–5mM, respectively. The limit of detection is calculated to be as low as 0.98μM according to the signal-to-noise ratio of three. In addition, the fabricated sensing interface shows attractive reproducibility (RSD of 5.1% and 7.0% for 15 repeated measurements on a sensor and for measurements on 15 prepared sensors, respectively) and outstanding long-term stability (less than 5% loss in sensitivity over 1 month) for glucose detection. The application of the Cu foam based sensor for monitoring glucose in practical samples is also successfully demonstrated.
Lanthanide-labeled immunochromatographic strips for the rapid detection of Pantoea stewartii subsp. stewartii
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Fan Zhang , Mingqiang Zou , Yan Chen , Jinfeng Li , Yanfei Wang , Xiaohua Qi , Qiang Xue
The lateral flow immunoassay is used in commercial pregnancy detection, and is an accepted point-of-care testing technique. The most widely used format for lateral flow immunochromatographic strips uses gold nanoparticles for colorimetric detection. However, this method often suffers from poor quantitative discrimination and low analytical sensitivity. To address these limitations, lanthanide chelate-loaded silica nanoparticles have been used as fluorescent labels. The fluorescent nanoparticles can easily bind to antibodies, with dextran as a linker. The strip reader described here was based on a sandwich immunoreaction performed on a strip, using lanthanide-labeled antibodies that served as signal vehicles for the fluorescent readout. The strip reader was used as a quantitative test system. In this work, Pantoea stewartii subsp. stewartii (Pss) was used as a model analyte to demonstrate the use of the strip reader. Under optimal conditions, the detection limit was determined as 103 cfu/mL. The quantification limit was calculated to be 104 cfu/mL. The detection limit for Pss was 100 times lower than those displayed by colloidal gold-labeled strips or ELISAs. No cross-reactions were observed with the other nine strains, indicating the good specificity of the Pss strip. This strip showed good stability in repeated tests. The tests using the fluorescence immunochromatographic strip were easy to perform, rapid, and sensitive. Methods using fluorescence strips and a strip reader have the potential to be a powerful tool for the quantification of bacteria.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Fan Zhang , Mingqiang Zou , Yan Chen , Jinfeng Li , Yanfei Wang , Xiaohua Qi , Qiang Xue
The lateral flow immunoassay is used in commercial pregnancy detection, and is an accepted point-of-care testing technique. The most widely used format for lateral flow immunochromatographic strips uses gold nanoparticles for colorimetric detection. However, this method often suffers from poor quantitative discrimination and low analytical sensitivity. To address these limitations, lanthanide chelate-loaded silica nanoparticles have been used as fluorescent labels. The fluorescent nanoparticles can easily bind to antibodies, with dextran as a linker. The strip reader described here was based on a sandwich immunoreaction performed on a strip, using lanthanide-labeled antibodies that served as signal vehicles for the fluorescent readout. The strip reader was used as a quantitative test system. In this work, Pantoea stewartii subsp. stewartii (Pss) was used as a model analyte to demonstrate the use of the strip reader. Under optimal conditions, the detection limit was determined as 103 cfu/mL. The quantification limit was calculated to be 104 cfu/mL. The detection limit for Pss was 100 times lower than those displayed by colloidal gold-labeled strips or ELISAs. No cross-reactions were observed with the other nine strains, indicating the good specificity of the Pss strip. This strip showed good stability in repeated tests. The tests using the fluorescence immunochromatographic strip were easy to perform, rapid, and sensitive. Methods using fluorescence strips and a strip reader have the potential to be a powerful tool for the quantification of bacteria.
Hairpin DNA probe with 5′-TCC/CCC-3′ overhangs for the creation of silver nanoclusters and miRNA assay
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Xiaodong Xia , Yuanqiang Hao , Shengqiang Hu , Jianxiu Wang
A facile strategy for the assay of target miRNA using fluorescent silver nanoclusters (AgNCs) has been described. Due to the preferable interaction between cytosine residues and Ag+, a short cytosine-rich oligonucleotide (ODN) with only six bases 5′-TCCCCC-3′ served as an efficient scaffold for the creation of the AgNCs. The AgNCs displayed a bright red emission when excited at 545nm. Such ODN base-stabilized AgNCs have been exploited for miRNA sensing. Overhangs of TCC at the 5′ end (5′-TCC) and CCC at the 3′ end (CCC-3′) (denoted as 5′-TCC/CCC-3′) appended to the hairpin ODN probe which also contains recognition sequences for target miRNA were included. Interestingly, the AgNCs/hairpin ODN probe showed similar spectral properties as that templated by 5′-TCCCCC-3′. The formation of the hairpin ODN probe/miRNA duplex separated the 5′-TCC/CCC-3′ overhangs, thus disturbing the optical property or structure of the AgNCs. As a result, fluorescence quenching of the AgNCs/hairpin ODN probe was obtained, which allows for facile determination of target miRNA. The proposed method is simple and cost-effective, holding great promise for clinical applications.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Xiaodong Xia , Yuanqiang Hao , Shengqiang Hu , Jianxiu Wang
A facile strategy for the assay of target miRNA using fluorescent silver nanoclusters (AgNCs) has been described. Due to the preferable interaction between cytosine residues and Ag+, a short cytosine-rich oligonucleotide (ODN) with only six bases 5′-TCCCCC-3′ served as an efficient scaffold for the creation of the AgNCs. The AgNCs displayed a bright red emission when excited at 545nm. Such ODN base-stabilized AgNCs have been exploited for miRNA sensing. Overhangs of TCC at the 5′ end (5′-TCC) and CCC at the 3′ end (CCC-3′) (denoted as 5′-TCC/CCC-3′) appended to the hairpin ODN probe which also contains recognition sequences for target miRNA were included. Interestingly, the AgNCs/hairpin ODN probe showed similar spectral properties as that templated by 5′-TCCCCC-3′. The formation of the hairpin ODN probe/miRNA duplex separated the 5′-TCC/CCC-3′ overhangs, thus disturbing the optical property or structure of the AgNCs. As a result, fluorescence quenching of the AgNCs/hairpin ODN probe was obtained, which allows for facile determination of target miRNA. The proposed method is simple and cost-effective, holding great promise for clinical applications.
A novel core-satellite CdTe/Silica/Au NCs hybrid sphere as dual-emission ratiometric fluorescent probe for Cu2+
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Yan-Qin Wang , Tong Zhao , Xi-Wen He , Wen-You Li , Yu-Kui Zhang
Herein, we synthesized a novel core-satellite CdTe/Silica/Au NCs hybrid sphere by covalently linking the separately synthesized highly fluorescent bovine serum albumin (BSA) stabilized gold nanoclusters (Au@BSA NCs) to the surface of the amino functionalized CdTe@SiO2 spheres by using the EDC chemistry. Numerous “satellites” of Au NCs were linked on the surface of the CdTe@SiO2 by the way of amide bonding. The synthesized dual-emission hybrid spheres were further characterized by the transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), UV–vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), etc. Finally, the CdTe/Silica/Au NCs hybrid spheres were developed as ratiometric fluorescence probe for the determination of Cu2+ with high sensitivity and selectivity. The fluorescence intensity ratio (F 545nm/F 655nm) of the probe against the concentration of Cu2+ showed a good linear relationship from 6.0×10−7 molL−1 to 100.0×10−7 molL−1. It showed an excellent reproducibility (0.67% relative standard deviation for 10 replicate measurements of Cu2+ at 40.0×10−7 molL−1) and low detection limit (4.1×10−7 molL−1). Furthermore, the ratiometric fluorescent probe was successfully applied in the determination of Cu2+ in vegetable samples with satisfactory results.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Yan-Qin Wang , Tong Zhao , Xi-Wen He , Wen-You Li , Yu-Kui Zhang
Herein, we synthesized a novel core-satellite CdTe/Silica/Au NCs hybrid sphere by covalently linking the separately synthesized highly fluorescent bovine serum albumin (BSA) stabilized gold nanoclusters (Au@BSA NCs) to the surface of the amino functionalized CdTe@SiO2 spheres by using the EDC chemistry. Numerous “satellites” of Au NCs were linked on the surface of the CdTe@SiO2 by the way of amide bonding. The synthesized dual-emission hybrid spheres were further characterized by the transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), UV–vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), etc. Finally, the CdTe/Silica/Au NCs hybrid spheres were developed as ratiometric fluorescence probe for the determination of Cu2+ with high sensitivity and selectivity. The fluorescence intensity ratio (F 545nm/F 655nm) of the probe against the concentration of Cu2+ showed a good linear relationship from 6.0×10−7 molL−1 to 100.0×10−7 molL−1. It showed an excellent reproducibility (0.67% relative standard deviation for 10 replicate measurements of Cu2+ at 40.0×10−7 molL−1) and low detection limit (4.1×10−7 molL−1). Furthermore, the ratiometric fluorescent probe was successfully applied in the determination of Cu2+ in vegetable samples with satisfactory results.
Development of antibiotic selection kit towards veterinary applications using glycine passivated magnetic particles
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Kaliyaperumal Viswanathan , Gopal Dhinakar Raj , V.Senthil Vadivoo , Kathaperumal Kumanan , Rajamanickam Prabakaran
Glycine functionalized (Gly/Fe3O4) and non-functionalized (Fe3O4) magnetic particles were synthesized in an autoclave and characterized by transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), X-ray diffraction patterns (XRD) and zeta potential. The size of the both these particles were in the range of 220–230nm but the shape of the Gly/Fe3O4 particles was hexagonal in contrast to the spherical shape of Fe3O4 particles. The particle characterization tests confirmed that glycine was functionalized on the Gly/Fe3O4 particles, they were positively charged and possessed strong magnetic property. These particles possessed the ability to bind to bacteria such as Escherichia coli, Streptococcus and Staphylococcus in the range of 72−90%. They were used to entrap bacteria from clinical mastitic milk samples from cows. The entrapped bacteria of the above species from these samples were isolated and used individually in the conventional disc-diffusion method of antibiotic susceptibility determination. The results were compared with that of the bacterial species isolated directly from the mastitic milk samples and were found to be 100% concordant (n=25). The developed portable antibiotic selection kit was tested with twenty five samples of mastitic milk. The results indicated that, antibiotic resistant bacteria turned the methylene blue in to white color while the bacteria that were killed (sensitive) retained the blue color of the dye. Thus the right choice of the antibiotic to treat cows with mastitis could be determined based on the naked eye. In conclusion, the kit gave quicker results, was easy to assay and read and can be ‘farm-gate’ applicable than the presently available conventional method.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Kaliyaperumal Viswanathan , Gopal Dhinakar Raj , V.Senthil Vadivoo , Kathaperumal Kumanan , Rajamanickam Prabakaran
Glycine functionalized (Gly/Fe3O4) and non-functionalized (Fe3O4) magnetic particles were synthesized in an autoclave and characterized by transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), X-ray diffraction patterns (XRD) and zeta potential. The size of the both these particles were in the range of 220–230nm but the shape of the Gly/Fe3O4 particles was hexagonal in contrast to the spherical shape of Fe3O4 particles. The particle characterization tests confirmed that glycine was functionalized on the Gly/Fe3O4 particles, they were positively charged and possessed strong magnetic property. These particles possessed the ability to bind to bacteria such as Escherichia coli, Streptococcus and Staphylococcus in the range of 72−90%. They were used to entrap bacteria from clinical mastitic milk samples from cows. The entrapped bacteria of the above species from these samples were isolated and used individually in the conventional disc-diffusion method of antibiotic susceptibility determination. The results were compared with that of the bacterial species isolated directly from the mastitic milk samples and were found to be 100% concordant (n=25). The developed portable antibiotic selection kit was tested with twenty five samples of mastitic milk. The results indicated that, antibiotic resistant bacteria turned the methylene blue in to white color while the bacteria that were killed (sensitive) retained the blue color of the dye. Thus the right choice of the antibiotic to treat cows with mastitis could be determined based on the naked eye. In conclusion, the kit gave quicker results, was easy to assay and read and can be ‘farm-gate’ applicable than the presently available conventional method.
Graphical abstract
Flow-through sensor array applied to cytotoxicity assessment in cell cultures for drug-testing purposes
29 August 2013,
19:29:09
Publication date: 15 January
2014
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Emilia Witkowska Nery , Elżbieta Jastrzębska , Kamil Żukowski , Wojciech Wróblewski , Michał Chudy , Patrycja Ciosek
The viability of cells cultured in microsystems for drug screening purposes is usually tested with a variety of colorimetric/fluorescent methods. In this work we propose an alternative way of assessing cell viability—flow-through sensor array that can be connected in series with cell microbioreactors as compatible detection system. It is shown, that the presented device is capable of cytotoxic effect detection and estimation of cell viability after treatment with 1,4-dioxane and 5-fluorouracil, which proves that it can be used for truly non-invasive, fast, reliable, continuous cell culture monitoring in microscale.
Source:Biosensors and Bioelectronics, Volume 51
Author(s): Emilia Witkowska Nery , Elżbieta Jastrzębska , Kamil Żukowski , Wojciech Wróblewski , Michał Chudy , Patrycja Ciosek
The viability of cells cultured in microsystems for drug screening purposes is usually tested with a variety of colorimetric/fluorescent methods. In this work we propose an alternative way of assessing cell viability—flow-through sensor array that can be connected in series with cell microbioreactors as compatible detection system. It is shown, that the presented device is capable of cytotoxic effect detection and estimation of cell viability after treatment with 1,4-dioxane and 5-fluorouracil, which proves that it can be used for truly non-invasive, fast, reliable, continuous cell culture monitoring in microscale.
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