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A Label-Free Impedance Immunosensor Using Screen-Printed Interdigitated Electrodes and Magnetic Nanobeads for the Detection of E. coli O157:H7.

Wang R, Lum J, Callaway Z, Lin J, Bottje W, Li Y - Biosensors (Basel) (2015)

Bottom Line: The impedance immunosensor could detect E. coli O157:H7 at a concentration of 10(4.45) cfu·mL(-1) (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment.A linear relationship between bacteria concentration and impedance value was obtained between 10(4.45) cfu·mL(-1) and 10(7) cfu·mL(-1).The magnetic field and impedance were simulated using COMSOL Multiphysics software.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, AR 72701, USA. rwang@uark.edu.

ABSTRACT
Escherichia coli O157:H7 is one of the leading bacterial pathogens causing foodborne illness. In this study, an impedance immunosensor based on the use of magnetic nanobeads and screen-printed interdigitated electrodes was developed for the rapid detection of E. coli O157:H7. Magnetic nanobeads coated with anti-E. coli antibody were mixed with an E. coli sample and used to isolate and concentrate the bacterial cells. The sample was suspended in redox probe solution and placed onto a screen-printed interdigitated electrode. A magnetic field was applied to concentrate the cells on the surface of the electrode and the impedance was measured. The impedance immunosensor could detect E. coli O157:H7 at a concentration of 10(4.45) cfu·mL(-1) (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment. A linear relationship between bacteria concentration and impedance value was obtained between 10(4.45) cfu·mL(-1) and 10(7) cfu·mL(-1). Though impedance measurement was carried out in the presence of a redox probe, analysis of the equivalent circuit model showed that the impedance change was primarily due to two elements: Double layer capacitance and resistance due to electrode surface roughness. The magnetic field and impedance were simulated using COMSOL Multiphysics software.

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Immunomagnetic separation of E. coli O157:H7 from media using the antibody-coated nanobeads and the concentration of bacteria on the electrode surface using a magnetic field.
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biosensors-05-00791-f001: Immunomagnetic separation of E. coli O157:H7 from media using the antibody-coated nanobeads and the concentration of bacteria on the electrode surface using a magnetic field.

Mentions: Screen-printed interdigitated electrodes were cleaned using 1 M NaOH for 3 min. The electrode was then washed with deionized water and dried with nitrogen. Impedance detection of E. coli O157:H7 was done by placing a 25 μL drop of a prepared sample from immunomagnetic separation onto the electrode surface. A magnetic field with a surface intensity of ~0.4 T was applied using a permanent magnet (neodymium magnet, CMS Magnetics, Garland, TX, USA) and used to draw the bacteria/nanobead complexes to the electrode surface for 10 min before impedance measurement. The impedance was measured while the magnetic field was still being applied. The impedance of the control sample prepared in parallel with the bacterial sample was measured first to gather a baseline for detection. The impedance of each bacteria sample was compared to the control sample prepared in parallel to it. Figure 1 shows the diagrams of the immunomagnetic separation and detection protocols.


A Label-Free Impedance Immunosensor Using Screen-Printed Interdigitated Electrodes and Magnetic Nanobeads for the Detection of E. coli O157:H7.

Wang R, Lum J, Callaway Z, Lin J, Bottje W, Li Y - Biosensors (Basel) (2015)

Immunomagnetic separation of E. coli O157:H7 from media using the antibody-coated nanobeads and the concentration of bacteria on the electrode surface using a magnetic field.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697145&req=5

biosensors-05-00791-f001: Immunomagnetic separation of E. coli O157:H7 from media using the antibody-coated nanobeads and the concentration of bacteria on the electrode surface using a magnetic field.
Mentions: Screen-printed interdigitated electrodes were cleaned using 1 M NaOH for 3 min. The electrode was then washed with deionized water and dried with nitrogen. Impedance detection of E. coli O157:H7 was done by placing a 25 μL drop of a prepared sample from immunomagnetic separation onto the electrode surface. A magnetic field with a surface intensity of ~0.4 T was applied using a permanent magnet (neodymium magnet, CMS Magnetics, Garland, TX, USA) and used to draw the bacteria/nanobead complexes to the electrode surface for 10 min before impedance measurement. The impedance was measured while the magnetic field was still being applied. The impedance of the control sample prepared in parallel with the bacterial sample was measured first to gather a baseline for detection. The impedance of each bacteria sample was compared to the control sample prepared in parallel to it. Figure 1 shows the diagrams of the immunomagnetic separation and detection protocols.

Bottom Line: The impedance immunosensor could detect E. coli O157:H7 at a concentration of 10(4.45) cfu·mL(-1) (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment.A linear relationship between bacteria concentration and impedance value was obtained between 10(4.45) cfu·mL(-1) and 10(7) cfu·mL(-1).The magnetic field and impedance were simulated using COMSOL Multiphysics software.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, AR 72701, USA. rwang@uark.edu.

ABSTRACT
Escherichia coli O157:H7 is one of the leading bacterial pathogens causing foodborne illness. In this study, an impedance immunosensor based on the use of magnetic nanobeads and screen-printed interdigitated electrodes was developed for the rapid detection of E. coli O157:H7. Magnetic nanobeads coated with anti-E. coli antibody were mixed with an E. coli sample and used to isolate and concentrate the bacterial cells. The sample was suspended in redox probe solution and placed onto a screen-printed interdigitated electrode. A magnetic field was applied to concentrate the cells on the surface of the electrode and the impedance was measured. The impedance immunosensor could detect E. coli O157:H7 at a concentration of 10(4.45) cfu·mL(-1) (~1400 bacterial cells in the applied volume of 25 μL) in less than 1 h without pre-enrichment. A linear relationship between bacteria concentration and impedance value was obtained between 10(4.45) cfu·mL(-1) and 10(7) cfu·mL(-1). Though impedance measurement was carried out in the presence of a redox probe, analysis of the equivalent circuit model showed that the impedance change was primarily due to two elements: Double layer capacitance and resistance due to electrode surface roughness. The magnetic field and impedance were simulated using COMSOL Multiphysics software.

Show MeSH
Related in: MedlinePlus