Electrochemical Nonseparation Binding/Immunoassays Based

On Solid-State Reversible Polyion Selective Sensors

Katy FordyceDepartment of Chemistry

Corvallis, OR 97330Mentor: Dr. Alexey Shvarev

Electrodes (ISEs)

~ Conduct current through a cell

~ Used to detect specific species

~ Applying new method

Advantages Over Old Methods

~ Nondestructive

~ Noncontaminating

~ Short response time

~ Can be designed for selectivity

~ Unaffected by color or turbidity

Species of Interest

1. Protamine

~ Avg. charge = +20

~ Peptide

~ Arginine Rich

O

NHNH

ONH

O

NH NH2+

NH2

(CH2 )3

NH NH2+

NH2

(CH2 )3

NH NH2+

NH2

(CH2 )3

2. Trypsin

~ Peptidase

~ Specific for Arginine

How Trypsin Is Used

= Protamine

= Trypsin

= Other Species

•For more information about Cystic Fibrosis, please visit www.cff.org

Basic SCE Design

• PVC body

• Graphite core

• Conducting polymer~PEDOT

• Ion selective membrane

~Hydrophobic

Cross Section View:

Membrane Composition: Important!

• Selectivity = Ion exchanger (DNNS+)

Membrane

H+ DNNS-TDDA+

SO3

-

C9H19

C9H19

N

+

C12H25

C12H25C12H25

C12H25

Tetradodecylammonium Dinonylnaphthalenesulfonate

How Do Reversible SCE’s Work?

1. Constant Current

SCE

= Protamine ions

= Na+ ions

SCE

= Protamine ions

= Na+ ions

2. Stripping Current

How Do Reversible SCE’s Work?

Question:Can the method described earlier be used to

detect the enzyme activity of trypsin?

Research Goals:1. Construct electrodes which are

selective for protamine

2. Test the electrodes in a trypsin solution to monitor enzyme activity

Data Collection

Note: Both graphs share the same x-axis!

Measuring Trypsin Response

0 100 200 300 400 500 600-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

E,

V

Time, s

Units / mL 0 10 30 50

Baseline

Protamine

Trypsin

Calculating Trypsin’s Activity

Step 2. The slope will equal the k, the reaction rate

Step 1. Convert potential Concentration

EXAMPLE

0

2

4

6

0 2 4 6

Time

ln(A

/A0)

k

In Summary

Membrane

DNNS-TDDA+

Acknowledgements

~ Dr. Alexey Shvarev

~ Hasini Perera

~ Dr. Kevin Ahern

~ Group 4

~ The Howard Hughes Medical Institute