Microfabricated Interdigitated Microelectrodes-Based Electrical/Electrochemical Impedance for Biological Detection

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Microfabricated Interdigitated Microelectrodes-Based Electrical/Electrochemical Impedance for Biological Detection Liju Yang Biomanufacturing Research

1 Microfabricated Interdigitated Microelectrodes-Based Electrical/Electrochemical Impedance for Biological Detection Liju Yang Biomanufacturing Research Institute & Technology Enterprise (BRITE), Department of Pharmaceutical Science, North Carolina Central University, Durham, NC , Chapel Hill, NC 1

2 Impedance is a measurement of the ability of a circuit or electrical element to resist the flow of AC electrical current. Electrode Solution Impedance analyzer 6-9, Chapel Hill, NC 2

3 Conductive property change in the solution 1. Biological events occur in the solution. Impedance Change Conductive property change at the interface of the electrodes 2. Biological events occur at the interface of the electrodes 6-9, Chapel Hill, NC 3

Reproducible fabrication Two-electrode system Multiple electrode pairs

4 Interdigitated Array (IDA) Microelectrodes Low ohmic drop High signal-to-noise ratio Rapid attained steady state Improved sensitivity Small testing volume Reproducible fabrication Two-electrode system Multiple electrode pairs Progressively shorter electrode distance Large electrode surface area 6-9, Chapel Hill, NC 4

5 (a) Chamber (50 µl) Silicone rubber Interdigitated microelectrodes Contact pads Silicon substrate AC signal generator (b) Van Gerwen P, et al. Sens. Actuators B, 1998; 49, , Chapel Hill, NC 5

6 Impedance of biological cells The cell membrane consists of a lipid bilayer containing 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. 6-9, Chapel Hill, NC 6

7 Mechanisms for impedance detection of biological cells (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. (ii) Making use of the insulating properties of the cell membrane. Label free biosensor. (iii) Making use of the highly ionic cytoplasm of the cells. cell lysis or ion release 6-9, Chapel Hill, NC 7

8 (i) Impedance detection based on bacterial metabolism 280 Conventional E at 1MHz Medium Resistance / Ω x 10 5 CFU/ml 9.3 x 10 3 CFU/ml 7.6 x 10 1 CFU/ml Impedance / kω No cell Time / h Detection time (h) IDA E at 10 Hz Growth time / h 1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5 1.0E+6 6-9, Chapel Hill, NC Concentration of Salmonella ( Log cfu/ml) Interdigitated microelectrode Conventional Electrode

9 Equivalent Circuit of the Microelectrode Systems R sol 1.E+07 1.E+06 Measurement Fitting C dl C di C dl Impedance / Ω 1.E+05 1.E+04 C dl R sol C di C dl R sol C dl 1.E+03 1.E+02 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 Frequency / Hz C di C dl / nf R s / Ω C di / pf Before bacterial growth ± ± ± 1.7 After bacterial growth ± ± ± 2.8 Change 33% 4.4% 1.5% 6-9, Chapel Hill, NC 9

10 (ii) Label-free impedance biosensor i c C dl C dl i W R s W R et R et i f Imaginary impedance / Ω b a c d e (a) antibodie s (b) 4.14x10 5 (c) 4.14x10 6 (d) 4.14x10 7 (e) 4.14x10 8 CFU/ml Real impedance / Ω 6-9, Chapel Hill, NC 10

11 IDA electrodes size effect Imaginary Impedance ( Ω ) e-5um e-10um e-15um e-20um Real Impedance (Ω ) Ret um um um Concentration of Fe(CN)6 Impedance ( Ω ) 6.0E+2 5.0E+2 4.0E+2 3.0E+2 2.0E+2 bare-5um bare-10um bare-15 bare-20um impedance at 1 Hz um 10um 15um 1.0E E E+1 1.0E+2 1.0E+3 1.0E+4 1.0E Frequency (Hz) Cncentration of Fe(CN)6 6-9, Chapel Hill, NC 11

12 Manipulating bacterial cells on sensor surfaces electrode electrode electrode No DEP Positive DEP at 500 khz and 3 Vpp Negative DEP at 200 Hz and 3 Vpp 6-9, Chapel Hill, NC 12

High throughput E-plates for label free cell-based drug screening cell index 1.8 1.6 1.4 1.2 1 0.8 500nM 100nM 20nM 0.2nM control 0.

13 High throughput E-plates for label free cell-based drug screening cell index nM 100nM 20nM 0.2nM control time (h) Oxytocin Dose-Dependent Response CHO Cells Over-Expressed Oxytocin Receptor - Oxytocin Treatment Cell Index 6.00E E E E E E E Control Oxy Con (nm) 6-9, Chapel Hill, NC 13

14 (iii) Impedance detection based on ion release from bacterial cells Glass cover Cells in suspension Silicone rubber Glass substrate Interdigitated microelectrodes for impedance measurements Silicone rubber Electrode contact pads Impedance analyzer Impedance (Ω ) 1.0E+6 1.0E+5 1.0E+4 1.0E+3 (A) In DI water Measured data Fitting data C dl C dl R s w w Impedance (Ω ) 1.0E+6 1.0E+5 1.0E+4 1.0E+3 (B) In PBS) C dl R C s dl Measured data Fitting data R et R et 1.0E+2 1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5 Frequency (Hz) 1.0E+2 1.0E+0 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5 Frequency (Hz) 6-9, Chapel Hill, NC 14

1.0E+5 (A) 10 7 cfu/ml Impedance (Ω ) 1.0E+4 1.

cells/ml 10 8 cells/ml 10 9 cells/ml 1.0E+0 1.0E+1 1.

0E+5 10 8 cfu/ml 1.0E+5 (B) Impedance (Ω ) 1.

cells/ml 10 8 cells/ml 10 9 cells/ml 10 9 cfu/ml 1.

15 1.0E+5 (A) 10 7 cfu/ml Impedance (Ω ) 1.0E+4 1.0E+3 water 10 4 cells/ml 10 5 cells/ml 10 6 cells/ml 10 7 cells/ml 10 8 cells/ml 10 9 cells/ml 1.0E+0 1.0E+1 1.0E+2 1 khz Frequency (Hz) 1.0E+3 1.0E+4 1.0E cfu/ml 1.0E+5 (B) Impedance (Ω ) 1.0E+4 PBS 10 4 cells/ml 10 5 cells/ml 10 6 cells/ml 10 7 cells/ml 10 8 cells/ml 10 9 cells/ml 10 9 cfu/ml 1.0E+3 IBE Annual Meeting, 1.0E+0 March 1.0E+1 1.0E+2 1.0E+3 1.0E+4 1.0E+5 6-9, Chapel Hill, NC 15 Frequency (Hz)

16 1.0E+5 40 Impedance (Ω) 1.0E water Impedance at 1 khz (kω) y = Log (x) R 2 = 0.98 Water 1.0E Time (min) 0 1.0E E+8 1.0E+6 1.0E+4 1.0E+2 Bacterial Concentration (cells/20µl) 1.0E+0 5 percentage of impedance change (%) , Chapel Hill, NC 16 Time (h) PBS PBS w ith cells Water Water w ith cells

17 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. 6-9, Chapel Hill, NC 17

Biopotential Electrodes

Biomedical Instrumentation Prof. Dr. Nizamettin AYDIN naydin@yildiz.edu.tr naydin@ieee.org http://www.yildiz.edu.tr/~naydin Biopotential Electrodes 1 2 Electrode electrolyte interface The current crosses