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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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Related in: MedlinePlus

A typical Bode plot of the measured impedance data of the control and E. coli O157:H7 at a concentration of 107 cfu/mL. (a) Impedance magnitude and (b) Phase angle. The frequency range was 10 Hz to 100 kHz. The amplitude of voltage applied was 50 mV.
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biosensors-05-00791-f002: A typical Bode plot of the measured impedance data of the control and E. coli O157:H7 at a concentration of 107 cfu/mL. (a) Impedance magnitude and (b) Phase angle. The frequency range was 10 Hz to 100 kHz. The amplitude of voltage applied was 50 mV.

Mentions: Impedance magnitudes and phase angles for the detection of a sample containing 107 cfu·mL−1E. coli O157:H7 and a negative control sample are shown in Figure 2. The presence of bacteria resulted in a decrease in impedance magnitude and the maximum decrease occurred at 100 Hz. The phase angle describes the contribution of the resistance and capacitance elements to the impedance value. A current passing through a capacitor is phase shifted by −90° with respect to the voltage while a current passing through a resistor is in phase with the voltage, therefore having a phase angle of 0°. A phase angle between −90° and 0° indicates that the impedance value is affected by a combination of resistance and capacitive elements. The phase angles for both the bacterial and control samples decreased in the middle frequency around 500 Hz to 1 kHz and in the high frequency range nearing 100 kHz. In the higher frequency range between 10 kHz and 30 kHz the phase angle for both samples increased, though the bacterial sample phase angle was lower than the control sample’s. At the lower frequency range (10 Hz to 500 Hz), the phase angle of the bacterial sample was higher than the control sample’s. The phase angle data suggests that the presence of bacteria disrupted a capacitance element at the higher frequencies while creating a capacitance element in the low frequency range. An equivalent circuit model was built and evaluated to better understand the impedance spectrum data.


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)

A typical Bode plot of the measured impedance data of the control and E. coli O157:H7 at a concentration of 107 cfu/mL. (a) Impedance magnitude and (b) Phase angle. The frequency range was 10 Hz to 100 kHz. The amplitude of voltage applied was 50 mV.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-05-00791-f002: A typical Bode plot of the measured impedance data of the control and E. coli O157:H7 at a concentration of 107 cfu/mL. (a) Impedance magnitude and (b) Phase angle. The frequency range was 10 Hz to 100 kHz. The amplitude of voltage applied was 50 mV.
Mentions: Impedance magnitudes and phase angles for the detection of a sample containing 107 cfu·mL−1E. coli O157:H7 and a negative control sample are shown in Figure 2. The presence of bacteria resulted in a decrease in impedance magnitude and the maximum decrease occurred at 100 Hz. The phase angle describes the contribution of the resistance and capacitance elements to the impedance value. A current passing through a capacitor is phase shifted by −90° with respect to the voltage while a current passing through a resistor is in phase with the voltage, therefore having a phase angle of 0°. A phase angle between −90° and 0° indicates that the impedance value is affected by a combination of resistance and capacitive elements. The phase angles for both the bacterial and control samples decreased in the middle frequency around 500 Hz to 1 kHz and in the high frequency range nearing 100 kHz. In the higher frequency range between 10 kHz and 30 kHz the phase angle for both samples increased, though the bacterial sample phase angle was lower than the control sample’s. At the lower frequency range (10 Hz to 500 Hz), the phase angle of the bacterial sample was higher than the control sample’s. The phase angle data suggests that the presence of bacteria disrupted a capacitance element at the higher frequencies while creating a capacitance element in the low frequency range. An equivalent circuit model was built and evaluated to better understand the impedance spectrum data.

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