Microfabricated Interdigitated Microelectrodes-Based ...

IBE Annual Meeting, March IBE Annual Meeting, March 66--9, 2008. Chapel Hill, NC9, 2008. Chapel Hill, NC 11

MicrofabricatedMicrofabricated InterdigitatedInterdigitatedMicroelectrodesMicroelectrodes--Based Based

Electrical/Electrochemical Impedance for Electrical/Electrochemical Impedance for Biological Detection Biological Detection

LijuLiju YangYang

BiomanufacturingBiomanufacturing Research Institute & Research Institute & Technology Enterprise (BRITE), Technology Enterprise (BRITE),

Department of Pharmaceutical Science, Department of Pharmaceutical Science, North Carolina Central University, Durham, NC North Carolina Central University, Durham, NC

2770727707


Impedance is a measurement of the ability of a circuit or electrical element to resist the flow of AC electrical current.

Solution

Impedance analyzer

Electrode


Conductive property change in the solution

Conductive property change at the interface of the electrodes

Impedance Change

1. Biological events occur in the solution.

2. Biological events occur at the interface of the electrodes


Interdigitated Array (IDA) Microelectrodes

Two-electrode systemMultiple electrode pairsProgressively shorter electrode distanceLarge electrode surface area

Low ohmic dropHigh signal-to-noise ratio Rapid attained steady stateImproved sensitivitySmall testing volumeReproducible fabrication


Chamber (50 µl)

Interdigitatedmicroelectrodes

Silicone rubber

Contact pads

Silicon substrate

AC signal generator

(a)

(b)

Van Gerwen P, et al. Sens. Actuators B, 1998; 49, 73-80


Impedance of biological cells

The cell membrane consists of a lipid bilayercontaining many proteins. It is highly insulating. The conductivity is around 10 -7 S/m.

The inside of a cell contains many dissolved charged molecules. The conductivity of the interior of a cell can be as high as 1 S/m.


(i) Making use of the metabolic activity of biological cells. This is represented by impedance microbiology, which is based on the measurements of the change in electric impedance in a medium or a reactant solution resulting from the bacterial metabolism.

Mechanisms for impedance detection of biological cells

(ii) Making use of the insulating properties of the cell membrane. –Label free biosensor.

(iii) Making use of the highly ionic cytoplasmof the cells. – cell lysis or ion release


180

200

220

240

260

280

0 2 4 6 8 10 12 14 16 18 20Time / h

Med

ium

Res

ista

nce

/ Ω No cell

9.3 x 103 CFU/ml 6.5 x 105 CFU/ml

7.6 x 101 CFU/ml

Conventional E at 1MHz

16

20

24

28

32

36

0 2 4 6 8 10 12 14 16 18

Growth time / h

Impe

danc

e / kΩ

0

104 103

102

101100105

IDA E at 10 Hz

0

2

4

6

8

10

12

14

16

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5 1.0E+6

Concentration of Salmonella ( Log cfu/ml)

Det

ectio

n tim

e (h

)

Interdigitatedmicroelectrode

ConventionalElectrode

(i) Impedance detection based on bacterial metabolism


CdlCdl

Rsol

Cdi

Equivalent Circuit of the Microelectrode Systems

CdlCdl Rsol

Cdi

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E-01 1.E+01 1.E+03 1.E+05 1.E+07Frequency / Hz

Impe

danc

e / Ω

MeasurementFitting

Cdl

RsolCdi

Cdl / nF Rs / Ω Cdi / pF

Before bacterial growth 397.2 ± 33.2 349.6 ± 16.0 45.3 ± 1.7After bacterial growth 528.2 ± 73.7 365.1 ± 25.2 44.6 ± 2.8

Change 33% 4.4% 1.5%


(ii) Label-free impedance biosensor

Rs

Ret

Cdl

W

ic

if

iW

Ret

Cdl

-1200

-1000

-800

-600

-400

-200

00 500 1000 1500 2000 2500 3000

Real impedance / Ω

Imag

inar

y im

peda

nce

/ Ωb

e

d

ca

(a) antibodies

(b) 4.14x105

(c) 4.14x106

(d) 4.14x107

(e) 4.14x108

CFU/ml


-180

-160

-140

-120

-100

-80

-60

-40

-20

00 100 200 300 400 500 600

Real Impedance (Ω )

Imag

inar

y Im

peda

nce

(Ω

)e-5um

e-10um

e-15um

e-20um

0.0E+0

1.0E+2

2.0E+2

3.0E+2

4.0E+2

5.0E+2

6.0E+2

1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)

bare-5um

bare-10um

bare-15

bare-20um

10

210

410

610

810

1010

1210

10 20 30 40 50 60

Concentration of Fe(CN)6

Ret

5um

10um

15um

100

300

500

700

900

1100

1300

1500

1700

0 10 20 30 40 50 60

Cncentration of Fe(CN)6

impe

danc

e at

1 H

z

5um

10um

15um

IDA electrodes size effect


Manipulating bacterial cells on sensor surfaces

No DEP

electrode

Negative DEP at 200 Hz and 3 Vpp

electrode

Positive DEP at 500 kHz and 3 Vpp

electrode


0.6

0.8

1

1.2

1.4

1.6

1.8

17 19 21 23 25time (h)

cell

inde

x

500nM100nM20nM0.2nMcontrol

Oxytocin Dose-Dependent Response

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

500 100 20 0.2 Control

Oxy Con (nM)

Cel

l Ind

ex

High throughput E-plates for label free cell-based drug screening

CHO Cells Over-Expressed OxytocinReceptor - Oxytocin Treatment


(iii) Impedance detection based on ion release frombacterial cells

Glass substrate

Siliconerubber

Siliconerubber Impedance

analyzer

Interdigitated microelectrodesfor impedance measurements

Glass cover Cells in suspension

Electrode contact pads

1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)

Measured dataFitting data

1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)


Cdl RsCdl

CdlRs

Cdl

w wRet Ret

(A) In DI water (B) In PBS)

1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)


1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)


1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)


1.0E+2

1.0E+3

1.0E+4

1.0E+5

1.0E+6

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)


Cdl RsCdlCdl RsCdl

CdlRs

Cdl

w wRet Ret

CdlRs

Cdl

w wRet Ret

(A) In DI water (B) In PBS)


1.0E+3

1.0E+4

1.0E+5

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

)w ater104 cells/ml105 cells/ml106 cells/ml107 cells/ml108 cells/ml109 cells/ml 1 kHz

(A)

1.0E+3

1.0E+4

1.0E+5

1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5

Frequency (Hz)

Impe

danc

e ( Ω

) PBS104 cells/ml105 cells/ml106 cells/ml107 cells/ml108 cells/ml109 cells/ml

(B)

109 cfu/ml

107 cfu/ml

108 cfu/ml


1.0E+3

1.0E+4

1.0E+5

0 20 40 60 80 100Time (min)

Impe

danc

e ( Ω

)

109

103106

107105 104 102

108

water

y = -2.06 Log (x) + 5.23R2 = 0.98

0

5

10

15

20

25

30

35

40

1.0E+01.0E+21.0E+41.0E+61.0E+81.0E+10

Bacterial Concentration (cells/20µl)

Impe

danc

e at

1 k

Hz

(kΩ

)

Water

-25

-20

-15

-10

-5

0

5

0 5 10 15 20 25 30 35Time (h)

perc

enta

ge o

f im

peda

nce

chan

ge

(%)

PBS

PBS w ith cells

Water

Water w ith cells


Acknowledgement Funding from Golden LEAF Foundation and the State of North Carolina through the Biomanufacturing Research Institute & Technology Enterprise (BRITE) Center for Excellence at North Carolina Central University.

Microfabricated Interdigitated Microelectrodes-Based ...

Documents

Transcript of Microfabricated Interdigitated Microelectrodes-Based ...