Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-viny... more Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-vinyl alcohol and regenerated silk fibroin, and IR was employed to provide a useful insight into the structure of the composite membrane. A methylene bluemediated sensor highly sensitive to hydrogen peroxide was constructed, which was based on the immobilization of HRP in the composite membrane. Cyclic voltammetry and amperometric measurement were utilized to demonstrate the feasibility of electron communication between immobilized HRP and a glassy carbon electrode in the bioelectrocatalytic reduction of hydrogen peroxide via methylene blue. Performance and characteristics of the sensor were evaluated with regard to response time, detection limit, selectivity, and dependence on temperature and pH as well as operating and storage stability. The sensor possesses a variety of characteristics including high sensitivity, rapid response time and a low detection limit of 0.1 amol/L.
... was weight and mixed thoroughly with 225 grams of 0.1 % peptone buffer in a Whirl-pak plastic... more ... was weight and mixed thoroughly with 225 grams of 0.1 % peptone buffer in a Whirl-pak plastic bag ... The fiber optic light guide was used to bring the light from the reaction cell to the detector. ... It was ascribed to a lot of proteins, fats and bacteria in the chicken carcass wash water ...
The structures of the blend membrane of regenerated silk fibroin and glucose oxidase were investi... more The structures of the blend membrane of regenerated silk fibroin and glucose oxidase were investigated by means of FT-IR spectra, electronic absorption spectra and SEM. The structures of the membranes were partly transferred from silk I to silk II after the membrane had been treated with ethanol. It was found that the glucose oxidase in the membrane existed in molecular aggregates and the blend membrane had an islands sea structure. p-Benzoquinone in solution was employed to speed up the electron transfer between glucose oxidase in a regenerated silk fibroin membrane and a glassy carbon electrode. The effects of pH, temperature, concentration of p-benzoquinone and applied potential on the sensor were examined. The major advantage of water dispersed regenerated silk fibroin is its ability to immobilize the enzyme without any significant loss of enzymatic activity.
An immuno-optical absorption method with immunomagnetic separation was developed for rapid detect... more An immuno-optical absorption method with immunomagnetic separation was developed for rapid detection of Salmonella typhimurium. The magnetic microbeads coated with anti-Salmonella were used to separate Salmonella from sample solutions by the speci®c antibody± antigen interaction at room temperature for 30 min. Then the``sandwich'' complexes (anti-Salmonella coated on to magnetic microbeads, Salmonella, anti-Salmonella labeled with alkaline phosphatase) were formed by binding the microbeads, which captured Salmonella from sample solution, with alkaline phosphatase-labeled anti-Salmonella at room temperature for 30 min. The``sandwich'' complexes were separated from the solution by a magnetic ®eld and incubated in p-nitrophenyl phosphate substrate at 378C for 30 min to produce pnitrophenol by the enzymatic hydrolysis. The cell number of Salmonella was detected by measuring absorbance of p-nitrophenol at 404 nm. A linear response was found between 2X2 Â 10 4 and 2X2 Â 10 6 colony forming units (CFU) ml À1. The whole detection process could be completed within 2 h.
A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia col... more A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia coli O157:H7 inoculated in ground beef, chicken carcass, and romaine lettuce samples. The biosensor consisted of a chemiluminescence reaction cell, a fiber-optic light guide, and a luminometer linked to a personal computer in conjunction with immunomagnetic separation. The samples inoculated with E. coli O157:H7 were first centrifuged and suspended in buffered peptone water and then incubated with anti-E. coli O157 antibody-coated magnetic beads and horseradish peroxidase (HRP)-labeled anti-E. coli O157 antibodies to form antibody-coated bead-bacterium-HRP-labeled antibody sandwich complexes. Finally, the sandwich complexes were separated from the samples in a magnetic field and reacted with luminol in the reaction cell. The number of E. coli O157:H7 cells was determined by collecting the HRP-catalyzed chemiluminescence signal from the bead surface through a fiber-optic light guide and meas...
Optical fiber-based moisture sensors have been developed to help detect moisture problems in buil... more Optical fiber-based moisture sensors have been developed to help detect moisture problems in building envelopes. The sensors are created with a coating on a long period grating that is written onto optical fiber. As the coating absorbs moisture from its surroundings, the refractive index of the coating changes, thereby changing the propagation of light down the fiber. In addition to
Regenerated silk fibroin prepared from waste silk was employed as immobilization matrix for perox... more Regenerated silk fibroin prepared from waste silk was employed as immobilization matrix for peroxidase and the structures of the blend membranes of regenerated silk fibroin and peroxidase were first investigated with IR and scanning electron microscopy. There was intermolecular interaction between peroxidase and regenerated silk fibroin in the immiscible state. Cyclic voltammetry and constant applied potential measurement showed that Methylene Green efficiently mediated electron transfer from oxidized horseradish peroxidase in regenerated silk fibroin membrane to a glassy carbon electrode. A sensor coupling immobilized peroxidase with Methylene Green responded rapidly to low H,O, concentration and achieved 95% of the steady-state current in less than 25 s with a detection limit of 1.0 x lop7 M H,Oz. The sensor was stable in continuous operation, indicating that peroxidase was entrapped in regenerated silk fibroin membrane and did not freely diffuse away from the sensor surface into solutions.
A biosensor is an analytical device that responds in a direct. reversible. continuous. rapid. and... more A biosensor is an analytical device that responds in a direct. reversible. continuous. rapid. and accurate (precise) manner to changes in the concentration of chemical or biochemical species in an untreated sample. It may consist of a sensing microzone where a chemical or biochemical reaction (and. occasionally. a separation process) takes place. which is connected or integrated with an optical.
Materials and Methods: Materials. Zinc stearate (ZnSt 2 , 12.5-14% ZnO), stearic acid (SA, 95%), ... more Materials and Methods: Materials. Zinc stearate (ZnSt 2 , 12.5-14% ZnO), stearic acid (SA, 95%), selenium powder (~200 mesh, 99.999%) tetramethylammonium hydroxide (TMAH), manganese chloride (MnCl 2), dodacanethiol (DDT), and octadecylamine (ODA, 95%) were purchased from Alpha Aesar. 1-octadecene (ODE), mercaptopropionic acid (MPA), and tributyl phosphine (TBP, 95%) were purchased from Aldrich. Zinc undecylenate was purchased from Gelest. undecylenoic acid was purchased from TCI, Rhodamine 3B and Stilbene 420 dyes were purchased from Eastman. All chemicals were used without further purification.
The structural characteristics of regenerated silk fibroin were determined IR spectra. Without et... more The structural characteristics of regenerated silk fibroin were determined IR spectra. Without ethanol treatment, the membrane has the structure of silk I. When treated with ethanol, the membrane possesses a mixed structure of silk I and silk II. The structures of the blend membrane were identified as a composite of the absorption bands characteristic of both molecules. SEM showed that
A new type of in situ, remotely monitored magnetism-based sensor is presented that is comprised o... more A new type of in situ, remotely monitored magnetism-based sensor is presented that is comprised of an array of magnetically soft, magnetostatically-coupled ferromagnetic thin-film elements or particles combined with a chemically responsive material that swells or shrinks in response to the analyte of interest. As the chemically responsive material changes size the distance between the ferromagnetic elements changes, altering the inter-element magnetostatic coupling. This in turn changes the coercive force of the sensor, the amplitude of the voltage spikes detected in nearby pickup coils upon magnetization reversal and the number of higher-order harmonics generated by the flux reversal. Since the sensor is monitored through changes in magnetic flux, no physical connections such as wires or cables are needed to obtain sensor information, nor is line of sight alignment required as with laser telemetry; the sensors can be detected from within sealed, opaque or thin metallic enclosures.
An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic s... more An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic separation of the target pathogen from samples and absorbance measurement of p-nitrophenol at 400 nm from p-nitrophenyl phosphate hydrolysis by alkaline phosphatase (EC 3.1.3.1) on the ''sandwich'' structure complexes (antibodies coated onto micromagnetic beads-E. coli O157:H7-antibodies conjugated with the enzyme) formed on the microbead surface. The effects of immunoreaction time, phosphate buffer concentration, pH and temperature on the immunomagnetic separation of E. coli O157:H7 from samples were determined and the conditions used for the separation were 1-h reaction time, 1.0 Â 10 À 2 M PBS, pH 8.0 and 33 jC in this system. The effects of MgCl 2 concentration, Tris buffer concentration, pH and temperature on the activity of alkaline phosphatase conjugated on the immuno-''sandwich'' structure complexes were investigated after immunomagnetic separation of the target pathogen and the conditions used for the enzymatic amplification were 1.0 Â 10 À 4 M MgCl 2 , 1.0 M Tris buffer, pH 8.0, 28 jC and 30-min reaction time during the assay. The selectivity of the system was examined and no interference from the other pathogens including Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes was observed. Its working range was from 3.2 Â 10 2 to 3.2 Â 10 4 CFU/ml, and the relative standard deviation was 2.5-9.9%. The total detection time was less than 2 h.
We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperatu... more We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperature in noncoordinating solventoctadecene. Thiol was needed to control the reaction at a suitable nucleation and growth speed. In the early stage of the reaction, HgTe nanocrystals formed aggregates, and then the aggregates were dispersed and individual dot-shaped nanocrystals were formed with stronger photoluminescence emitting. UV-vis, photoluminescence, and TEM have been used to study the properties of as-prepared HgTe nanocrystals.
Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-viny... more Horseradish peroxidase (HRP) was effectively entrapped in a novel composite membrane of poly-vinyl alcohol and regenerated silk fibroin, and IR was employed to provide a useful insight into the structure of the composite membrane. A methylene bluemediated sensor highly sensitive to hydrogen peroxide was constructed, which was based on the immobilization of HRP in the composite membrane. Cyclic voltammetry and amperometric measurement were utilized to demonstrate the feasibility of electron communication between immobilized HRP and a glassy carbon electrode in the bioelectrocatalytic reduction of hydrogen peroxide via methylene blue. Performance and characteristics of the sensor were evaluated with regard to response time, detection limit, selectivity, and dependence on temperature and pH as well as operating and storage stability. The sensor possesses a variety of characteristics including high sensitivity, rapid response time and a low detection limit of 0.1 amol/L.
... was weight and mixed thoroughly with 225 grams of 0.1 % peptone buffer in a Whirl-pak plastic... more ... was weight and mixed thoroughly with 225 grams of 0.1 % peptone buffer in a Whirl-pak plastic bag ... The fiber optic light guide was used to bring the light from the reaction cell to the detector. ... It was ascribed to a lot of proteins, fats and bacteria in the chicken carcass wash water ...
The structures of the blend membrane of regenerated silk fibroin and glucose oxidase were investi... more The structures of the blend membrane of regenerated silk fibroin and glucose oxidase were investigated by means of FT-IR spectra, electronic absorption spectra and SEM. The structures of the membranes were partly transferred from silk I to silk II after the membrane had been treated with ethanol. It was found that the glucose oxidase in the membrane existed in molecular aggregates and the blend membrane had an islands sea structure. p-Benzoquinone in solution was employed to speed up the electron transfer between glucose oxidase in a regenerated silk fibroin membrane and a glassy carbon electrode. The effects of pH, temperature, concentration of p-benzoquinone and applied potential on the sensor were examined. The major advantage of water dispersed regenerated silk fibroin is its ability to immobilize the enzyme without any significant loss of enzymatic activity.
An immuno-optical absorption method with immunomagnetic separation was developed for rapid detect... more An immuno-optical absorption method with immunomagnetic separation was developed for rapid detection of Salmonella typhimurium. The magnetic microbeads coated with anti-Salmonella were used to separate Salmonella from sample solutions by the speci®c antibody± antigen interaction at room temperature for 30 min. Then the``sandwich'' complexes (anti-Salmonella coated on to magnetic microbeads, Salmonella, anti-Salmonella labeled with alkaline phosphatase) were formed by binding the microbeads, which captured Salmonella from sample solution, with alkaline phosphatase-labeled anti-Salmonella at room temperature for 30 min. The``sandwich'' complexes were separated from the solution by a magnetic ®eld and incubated in p-nitrophenyl phosphate substrate at 378C for 30 min to produce pnitrophenol by the enzymatic hydrolysis. The cell number of Salmonella was detected by measuring absorbance of p-nitrophenol at 404 nm. A linear response was found between 2X2 Â 10 4 and 2X2 Â 10 6 colony forming units (CFU) ml À1. The whole detection process could be completed within 2 h.
A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia col... more A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia coli O157:H7 inoculated in ground beef, chicken carcass, and romaine lettuce samples. The biosensor consisted of a chemiluminescence reaction cell, a fiber-optic light guide, and a luminometer linked to a personal computer in conjunction with immunomagnetic separation. The samples inoculated with E. coli O157:H7 were first centrifuged and suspended in buffered peptone water and then incubated with anti-E. coli O157 antibody-coated magnetic beads and horseradish peroxidase (HRP)-labeled anti-E. coli O157 antibodies to form antibody-coated bead-bacterium-HRP-labeled antibody sandwich complexes. Finally, the sandwich complexes were separated from the samples in a magnetic field and reacted with luminol in the reaction cell. The number of E. coli O157:H7 cells was determined by collecting the HRP-catalyzed chemiluminescence signal from the bead surface through a fiber-optic light guide and meas...
Optical fiber-based moisture sensors have been developed to help detect moisture problems in buil... more Optical fiber-based moisture sensors have been developed to help detect moisture problems in building envelopes. The sensors are created with a coating on a long period grating that is written onto optical fiber. As the coating absorbs moisture from its surroundings, the refractive index of the coating changes, thereby changing the propagation of light down the fiber. In addition to
Regenerated silk fibroin prepared from waste silk was employed as immobilization matrix for perox... more Regenerated silk fibroin prepared from waste silk was employed as immobilization matrix for peroxidase and the structures of the blend membranes of regenerated silk fibroin and peroxidase were first investigated with IR and scanning electron microscopy. There was intermolecular interaction between peroxidase and regenerated silk fibroin in the immiscible state. Cyclic voltammetry and constant applied potential measurement showed that Methylene Green efficiently mediated electron transfer from oxidized horseradish peroxidase in regenerated silk fibroin membrane to a glassy carbon electrode. A sensor coupling immobilized peroxidase with Methylene Green responded rapidly to low H,O, concentration and achieved 95% of the steady-state current in less than 25 s with a detection limit of 1.0 x lop7 M H,Oz. The sensor was stable in continuous operation, indicating that peroxidase was entrapped in regenerated silk fibroin membrane and did not freely diffuse away from the sensor surface into solutions.
A biosensor is an analytical device that responds in a direct. reversible. continuous. rapid. and... more A biosensor is an analytical device that responds in a direct. reversible. continuous. rapid. and accurate (precise) manner to changes in the concentration of chemical or biochemical species in an untreated sample. It may consist of a sensing microzone where a chemical or biochemical reaction (and. occasionally. a separation process) takes place. which is connected or integrated with an optical.
Materials and Methods: Materials. Zinc stearate (ZnSt 2 , 12.5-14% ZnO), stearic acid (SA, 95%), ... more Materials and Methods: Materials. Zinc stearate (ZnSt 2 , 12.5-14% ZnO), stearic acid (SA, 95%), selenium powder (~200 mesh, 99.999%) tetramethylammonium hydroxide (TMAH), manganese chloride (MnCl 2), dodacanethiol (DDT), and octadecylamine (ODA, 95%) were purchased from Alpha Aesar. 1-octadecene (ODE), mercaptopropionic acid (MPA), and tributyl phosphine (TBP, 95%) were purchased from Aldrich. Zinc undecylenate was purchased from Gelest. undecylenoic acid was purchased from TCI, Rhodamine 3B and Stilbene 420 dyes were purchased from Eastman. All chemicals were used without further purification.
The structural characteristics of regenerated silk fibroin were determined IR spectra. Without et... more The structural characteristics of regenerated silk fibroin were determined IR spectra. Without ethanol treatment, the membrane has the structure of silk I. When treated with ethanol, the membrane possesses a mixed structure of silk I and silk II. The structures of the blend membrane were identified as a composite of the absorption bands characteristic of both molecules. SEM showed that
A new type of in situ, remotely monitored magnetism-based sensor is presented that is comprised o... more A new type of in situ, remotely monitored magnetism-based sensor is presented that is comprised of an array of magnetically soft, magnetostatically-coupled ferromagnetic thin-film elements or particles combined with a chemically responsive material that swells or shrinks in response to the analyte of interest. As the chemically responsive material changes size the distance between the ferromagnetic elements changes, altering the inter-element magnetostatic coupling. This in turn changes the coercive force of the sensor, the amplitude of the voltage spikes detected in nearby pickup coils upon magnetization reversal and the number of higher-order harmonics generated by the flux reversal. Since the sensor is monitored through changes in magnetic flux, no physical connections such as wires or cables are needed to obtain sensor information, nor is line of sight alignment required as with laser telemetry; the sensors can be detected from within sealed, opaque or thin metallic enclosures.
An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic s... more An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic separation of the target pathogen from samples and absorbance measurement of p-nitrophenol at 400 nm from p-nitrophenyl phosphate hydrolysis by alkaline phosphatase (EC 3.1.3.1) on the ''sandwich'' structure complexes (antibodies coated onto micromagnetic beads-E. coli O157:H7-antibodies conjugated with the enzyme) formed on the microbead surface. The effects of immunoreaction time, phosphate buffer concentration, pH and temperature on the immunomagnetic separation of E. coli O157:H7 from samples were determined and the conditions used for the separation were 1-h reaction time, 1.0 Â 10 À 2 M PBS, pH 8.0 and 33 jC in this system. The effects of MgCl 2 concentration, Tris buffer concentration, pH and temperature on the activity of alkaline phosphatase conjugated on the immuno-''sandwich'' structure complexes were investigated after immunomagnetic separation of the target pathogen and the conditions used for the enzymatic amplification were 1.0 Â 10 À 4 M MgCl 2 , 1.0 M Tris buffer, pH 8.0, 28 jC and 30-min reaction time during the assay. The selectivity of the system was examined and no interference from the other pathogens including Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes was observed. Its working range was from 3.2 Â 10 2 to 3.2 Â 10 4 CFU/ml, and the relative standard deviation was 2.5-9.9%. The total detection time was less than 2 h.
We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperatu... more We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperature in noncoordinating solventoctadecene. Thiol was needed to control the reaction at a suitable nucleation and growth speed. In the early stage of the reaction, HgTe nanocrystals formed aggregates, and then the aggregates were dispersed and individual dot-shaped nanocrystals were formed with stronger photoluminescence emitting. UV-vis, photoluminescence, and TEM have been used to study the properties of as-prepared HgTe nanocrystals.
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